Is it the infamous hot soak......

So I drove home from work last night (10 miles), got home turned the van off and went into the house to get ready to take the girlfriend to dinner....20 minutes or so).... As we get in the car and start it up, it would crank, start and then die. So, I start it and give it some gas and hold steady at 2-3k...... then it was ok.

What does that sound like it could be? I just took it to a mechanic friend of mine to go through it and it checked out great. Curious if it's the hot soak problem ive heard about and if so what is that and how do i cure it?

P.S. this is the first time it has happened.

You could either replace the fuel pressure regulator for a 1989 Toyota Van regulator, or put up with it. I chose to just put up with it for now. Won't hurt anything. They, supposedly solved the hot soak issues in the 1989 models by using a higher pressure regulator.

Oh, OK. So basically it's not hurting anything?

What is causing this and does my vans symptoms even sound like a hot soak problem or something else?

Thanks guys!

It sounds like it. There is a sequence of events and certain conditions that lead up to hot soak. It's hard to accurately duplicate these conditions for testing, so chasing down and proving the problem can be difficult.

I will attempt to explain the issue as I understand it. Since the van is a mid-engine vehicle the engine compartment cannot be vented on top (smoke and noxious fumes in the passenger compartment isn't a good thing). So as a result the engine is sitting under a sealed metal dome. When you shut off the engine, since the cooling fan is run by the water pump, the coolant circulation and the air ventilation go away. Since heat rises it gets trapped there in the dome and cannot escape. If it's a hot day and/or if you've been driving it hard (like going up a steep hill or freeway driving) then there's even more heat getting trapped there. To complicate things, the fuel rail, injectors, pulsation damper, and FPR (Fuel Pressure Regulator) sit right above the exhaust manifold and are covered by the upper half of the intake manifold.

The extreme heat that's trapped there soaks into the fuel rail and depending on the quality of gasoline and the pressure in the rail, the gasoline may boil. The result is expansion and vaporization.......otherwise known as a vapor lock condition. Since there is still pressure in the fuel rail, the regulator will not allow more fuel into the rail until pressure is reduced. The only way vapor/pressure can escape is through the injectors (when you are trying to start). Of course vapor isn't dense like liquid, so there's not enough energy being delivered for your engine to start or run correctly. As the vapor/pressure escapes into the manifold new fuel trickles into the hot rail and immediately vaporizes. When vaporization occurs, volume increases exponentially (expansion) and that keeps the pressure up. This in turn prevents sufficient amounts of fuel from entering the rail. Once started, keeping the engine RPM's up helps because the injectors will vent vapor/pressure faster and allow more new gas to enter the rail. The faster the cool gas flows into the rail, the quicker the rail cools. Once the rail is cool enough to hold liquid gasoline the problem disappears and the van runs normal again.

Because this involves boiling and vaporization, there is a direct correlation between the quality of gasoline and this problem. Back in the 80s this wasn't such an issue because gasoline had a higher boiling temp. Todays gasoline has lots of additives (such as ethanol) and this can significantly lower the boiling point. You can minimize this problem by staying away from the gas that says it has a high percentage of alcohol/ethanol but this option may not be available. It's my belief that gasoline is becoming standardized and brand name doesn't matter much anymore.

So this leaves you 2 other options:

1. Increase fuel pressure in the fuel rail (higher pressure = higher boiling temp)

2. Provide ventilation to your engine compartment after shut-down

I'm not crazy about option #1 because increased pressure = more stress on injectors and other fuel system components (IMO this is more of a safety issue). If and when a fuel system leak occurs, more fuel will leak and your fire danger goes up. That being said, there is an easy way to automatically increase your fuel pressure for only a couple of minutes after start-up. IMO, the benefit of this is questionable because you will only be increasing pressure AFTER the fuel has been boiled. In other words this will minimize the effects of hot soak, but will not prevent it from happening.

There is also a way to permanently increase pressure in the fuel rail, and this makes more sense to me because it's more likely to prevent the problem from occurring. Of course this benefit is off-set by decreased safety.......and that's not to be taken lightly. Fuel leaks in the fuel rail area are not uncommon and several vans have gone up in smoke (sometimes taking other property with them).

Before changes are made, one should understand how the system works. Our FPRs (Fuel Pressure Regulators) have 2 output pressures. When vacuum is applied to the FPR diaphragm it will put out around 30 psi. When no vacuum is present, it will put out around 40 psi. There is a temperature switch on the engine coolant filler neck (vans that came with factory AC). This is a simple on/off switch that's triggered by coolant temp. The switch is normally open but when coolant temp hits 230 deg F it closes and grounds the wire going to it. That wire is attached to the ECU (Electronic Controlled Unit). Each time the van is started, the ECU monitors that circuit and if it detects a ground condition it activates the EFI VSV (Electronic Fuel Injection Vacuum Switching Valve) for a period of about 2 minutes. When the EFI VSV is activated, it shuts off vacuum to the FPR and vents the FPR diaphragm to atmosphere. With no vacuum, the FPR holds pressure at around 40 psi. After about 2 minutes, the ECU turns off the EFI VSV, vacuum returns to the FPR, and pressure returns to around 30 psi.

The existence of this system tells me that Toyota realized the potential for heat soak, but miscalculated the activation temp (of course the changing fuel market is partly to blame). Later on when heat soak became a bigger issue Toyota issued a service bulletin (TSB #E020). Part of that bulletin requires mechanics to replace the 230 deg F switch with a much much lower temp 140 deg F switch. The lower temp switches were only available for this service bulletin campaign (see PDF file attached to this post) and are now NLA (No Longer Available).

If you think about it, the normal operating temp of the engine is about 185° - 210° F so this means the new switch will activate the "pressure up" mode of the fuel injection system almost every time the van is started (unless the van has had over an hr to cool). Because of this, I think it's reasonable to assume it wouldn't hurt for the "pressure up" mode to be activated on every start (including cold ones). This can be easily achieved by simply cutting the wire off of this sensor and attaching it to ground.

To permanently increase pressure, there are several ways this can be done, but probably the simplest method would be to disconnect the vacuum line from the FPR and plug it to prevent a vacuum leak. I wouldn't put a cap on the FPR port because you'd want the diaphragm in there to breath. Again, I don't recommend this, but I'm providing the info to help create a better understanding of these issues.

Personally, the remedy I like best is the "ventilation after shut-down" method. I'm using this method (and this method only) on my van and I've been happy with it. A side benefit to this ventilation is increased life span of rubber seals, rubber hoses, and other sensitive parts (due to reduced temps in the engine compartment). I've heard other guys talk about opening their hoods each time they stop or using computer fans and ducts to ventilate small amounts of cool air into this area, and I don't disagree with the success of such methods, but who wants to have a super heated and/or smelly cabin on a hot day? As for the small fans and ducts, there's already limited space here and access to key areas is already tough enough. That's why I chose to install electric cooling fans on my radiator. I built a shroud and installed (2) 10" high output electric fans on the back-side (engine side) of my radiator. I rigged them up to be thermostatically controlled and wired direct to the battery (so they have power all the time). I got an adjustable t-stat with a submersible probe, put the probe into the extra 16mm port near the front of the head, and set the t-stat to come on at 200 deg F. Now whenever the coolant temp is 200 deg F or above, the fans will run (doesn't matter if the ignition is on or off). This has worked out great for me and completely solved the heat soak issue.

The fans do come on and run (on and off for about 20 - 30 min after shut down), but they eventually stop and I've always been able to restart the van easily.

I just realized this is a pretty long winded post so I'll stop here. If anybody is interested in pictures or more details, please ask and I'll be happy to answer questions and/or post pics/schematics. Tim

PS: Installing an 89 FPR will help, but only slightly. I probably wouldn't replace an earlier version just for this benefit, but if it needed replacement anyhow, I'd definitely go with the 89 FPR. FWIW, normal operating pressure of the earlier FPR's is 27-31 psi and the "pressure-up" mode is 33-38 psi. 89 FPR's normal operating pressure is 30-33 psi & "pressure-up" mode is 38-44 psi.

This thread has a bit more related information: http://www.toyotavantech.com/forum/s...tached-diagram

WOW...... Now that was a response!!! :clap:

Very very useful info Tim and definitely helped me understand what "heat soak" is. However, one last question.... Can "heat soak" hurt your engine?

It has only happened once and I run 91 octane from either chevron or shell.

Thanks as always guys!:drunk:

Lol, I'm surprised you made it through all that. Sometimes I get started and just can't stop :lol:. Heat soak is hard on your starter and embarrassing when witnessed by others......other than that it's just a nuisance. Over time, the excessive heat in the engine compartment will harden rubber and plastic parts. Tim

BTW, high octane gas won't help. If your engine doesn't ping on the 87 octane stuff, then more octane is just a waste of money.

Quote:

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Originally Posted by timsrv

BTW, high octane gas won't help. If your engine doesn't ping on the 87 octane stuff, then more octane is just a waste of money.

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Holy crap balls!! I thought I read somewhere that your van will run better and get better gas mileage on 91? Please tell me I haven't been wasting my money..... :doh:

Octane ratings effect pre-detonation, which can be an issue on high performance engines.............but we're talking about boiling points here. So unless you've done something to effect compression ratios, 87 octane should be fine for your van. I'd be a little weary of the no-name discount gas..........especially if has ethanol. Usually they will display a sign that says 10% ethanol or whatever. If you can run it and have no problems, then fine. If however you get heat soak issues more on one gas then another I'd avoid the gas that gives you problems. I'd also monitor gas mileage and avoid fuel that consistently gives you poor MPGs. Tim

Awesome, looks like im back to 87 :yes:

Thanks Tim!

hey, I've tried both the solutions that Tim "detailed". Grounding the temp sensor heloed a little but didn't completely solve the problem. Ventilation solved the problem. I kept the stock cooling fan and fan clutch and installed an additional fan on the front of the radiator and hooked up a thermostat probe to the (return) fuel line right above the fuel rail. Set the thermostat to activate the fan at a temperautre such that the fan does not run during engine operation (except under extreme conditions like very slow ascent or idling in very hot conditions) but kicks on after shut down when the temperature climbs in the engine compartment. This was a relatively simple modification and worked awesome:clap:

If someone could post photos of the fan install I would appreciate it.

well I should really try to take some pictures - maybe next weekend?

Here's a bunch of pics of my fan set-up. I plan on writing a detailed article but haven't gotten around to it yet.

The shroud is made of 22 ga galvanized sheet metal and soldered at the seams with 50/50 solder. It is made to perfectly fit (2) 10" electric fans.
http://i8.photobucket.com/albums/a23...m/shroud-1.jpg

http://i8.photobucket.com/albums/a23.../shroud3-1.jpg

http://i8.photobucket.com/albums/a23.../shroud4-1.jpg

http://i8.photobucket.com/albums/a23...hroudcut-1.jpg

http://i8.photobucket.com/albums/a23...roudfans-1.jpg

http://i8.photobucket.com/albums/a23...oudfans1-1.jpg


The adjustable thermostat I'm using to make my fans turn off and on is a capillary type with a 1/4" sensor probe on the end. To make the transition from the 1/4" sensor to 16mm X 1.5 pitch threads (the size of the extra unused port), I purchased a brass adaptor at the local hardware store. It originally was 3/8"mpt on one end and 1/4" compression on the other (these are readily available). I also purchased a 16mm X 1.5 die and simply chased the slightly larger 3/8" threads to convert to metric. The larger size 3/8 pipe thread was almost too big to chase without turning in a lathe, but with a little effort and patience this can be done by hand with only a vice and hand threading tools. After chasing, the new metric threads are perfect. You cannot even tell it was ever a standard 3/8 pipe thread . See the t-stat and modified brass adaptor below:
http://i8.photobucket.com/albums/a23...m/t-stat-1.jpg

http://i8.photobucket.com/albums/a23...IMG_8970-1.jpg

http://i8.photobucket.com/albums/a23...IMG_8968-1.jpg

http://i8.photobucket.com/albums/a23...IMG_8971-1.jpg

Here's some links to thermostats controls: http://www.amazon.com/Flex---lite-31...3160624&sr=8-6 http://www.amazon.com/Flex---lite-31...3160624&sr=8-1

The one in the black box is basically the same thermostat but it has a relay and some diodes added. I like this one because the relay protects the t-stat. The other cool part is it gives you multiple options for triggering fans. One of the posts hooks to your AC and turns the fans on anytime you're running AC, another post is for a manual override switch on the dash. I have this control installed on one of my vans and it's easier and cleaner than building one from individual components.

I see that Flex-A-Lite now has a variable speed fan control that uses a thermistor type probe with wires. It is a metal probe and could most likely be immersed in the coolant (most accurate way to trigger fans). Tim

Suddenly I have heat soak issues (vapour lock) on my 89 4wd. My experience with VW and Porsche tells me pressure has gone down in the fuel rail which allows the gas to boil. Given that 89 FPRs are higher pressure and somewhat free of this issue I am going to assume my FPR is bad. On the German cars the problem was almost always a bad fuel check valve (often part of the fuel pump). We had work arounds for Porsche 911s with their really high pressure and metal lines involving an in-line check valve unit (cheap) to avoid fuel pump replacement (costly). Do our vans have a check valve that might be the culprit or is it just the FPR that keeps the pressure up when the engine is off? I can open the engine hatch and bleed heat when I park etc but I think a new FPR is the way to go - right? Unless there is a check valve trick someone knows about?????

Yes, it could be low fuel pressure, but it could also be the result of cheap gasoline. I'm not sure about where you're at, but in some places they introduce a "winter blend" gasoline around this time of year. This "winter blend" often has an even lower boiling point than the "summer" gasoline and could be at least partly to blame for your problem. I would recommend testing your fuel system with a pressure gauge before spending time and money on a fuel pressure regulator. FWIW, I have replaced the FPR on a 4wd van before and I can tell you that job really sucks. 2wd vans are manageable but the 4wd vans are very challenging. I'm a seasoned mechanic and I had to use about every trick and swear word in my vocabulary :(:.

Here's a write-up I just posted on Testing the fuel system / Replacing fuel pressure regulator. Tim

Thanks Tim.
I guess this is just another darn job I should have done when I did the injectors and had the intake manifold off.
Man, I missed the boat on that one and left the hose of death, the TPS and the FPR untouched.
I deserve a beating!
Chevron Gas. Canada. West Coast near Bellingham Washington.

Living in Texas, I'm looking to make my van Hot Soak proof. It seems an Electric Fan setup is the only reliable way & the extra cooling capabilities might help a bit during summer (which is year round here) too.

I did a general Google search & there are plenty of other classic vehicles that are struggling with modern ethanol gasoline too. Likewise, electric fan setups appear to be the standard practice.

Tim did a write-up on his thermostat set-up before but I've yet to see where & how y'all are putting your electric fans.

Tim did mention that the thermostats are a bit dodgy & need to be replaced every few years. Has anyone found an ultra reliable Thermostat?

Does anyone have any photos, part numbers, wiring diagrams, etc... I don't want to be the guy who can't start his vehicle on the Ferry this summer.

:wave1:

I ran the set-up shown above for about 5 years & it worked great. The only bad part was this style thermostat seems to fail every 2 or 3 years. I had thermostat failure twice & both times resulted in an overheat :pissed: (before I realized what was happening and turned on the manual override switch). The 1st time it happened I thought it was a fluke, but the 2nd time really annoyed me so I replaced with a Flex-a-Lite #31165 variable speed control. The thermistor sense probe used with this controller is also 1/4" diameter so it fits using the same adapter I used before. I was very happy with the performance of the variable speed control but my van was put out of commission by a reckless/uninsured/unlicensed motorist before I had a chance to test long term reliability.

I plan on fixing this van, so eventually it will be back on the road for more testing. Here's some pics of the installed Flex-a-Lite control:

http://i8.photobucket.com/albums/a23...ps543b05e3.jpg

http://i8.photobucket.com/albums/a23...ps41087d50.jpg

Although not directly related to the fan shroud/fans, here is another add-on/upgrade that helps direct air flow up and into the radiator/engine compartment when cruising. I made this "scoop" out of galvanized sheet metal flashing. There is a noticeable improvement in cooling when cruising at highway speeds with the AC on:

http://i8.photobucket.com/albums/a23...ps86c795cd.jpg

http://i8.photobucket.com/albums/a23...ps408649fe.jpg

http://i8.photobucket.com/albums/a23...ps26f6b42a.jpg

http://i8.photobucket.com/albums/a23...psc3c1e687.jpg

http://i8.photobucket.com/albums/a23...ps1e578c72.jpg

http://i8.photobucket.com/albums/a23...psdb89be3d.jpg

http://i8.photobucket.com/albums/a23...ps4dd28c4d.jpg

http://i8.photobucket.com/albums/a23...pse0f8f23f.jpg

Hi Tim,
I am really interested in your awsome repair for the heat soak problem. After a hilarious scene at the local country club where I picked up my son, trying to restart on a hill with a car parked close to my front bumper, I had to back up the hill to get out. Spinning tires, a roaring engine, in lots of looks of disapproval had my son and I in stitches of laughter for a half hour after! But, I guess I need to see if I can cool the engine better so I'd like to create your setup. Did you make measurements or does it have to be a custom creation? This is my DD so I would need to turn it around fairly quickly. I would be happy to make a donation, etc, for plan's or guidance.
Thanks,
John

The scoop was something I "threw" together in an afternoon with materials I already had on hand. I just cut it with tin-snips then bent it over itself for strength. Basically I just bent a little, held it up to the van, bent & cut some more, held it up to the van & repeated until I was satisfied. The shroud took more time as I soldered at the joints and used a heavier sheet metal. I didn't write down any dimensions, I just used an old radiator I had laying around and simply made the shroud to fit.

Any sheet metal shop could do this pretty quick. Just take them your radiator and print some pics from this thread for them. In hind sight I made mine more complicated than it needed to be. I wouldn't have had to make a relief for the transmission cooling hose if I had not made the shroud so deep. Trestlehed (member here) had one made that is thinner and simpler. I would guess it works as good as mine. He probably has pics posted somewhere. Tim

Thanks Tim,
found his thread and have all the part numbers etc.
J

Cirrus - You may want to make note that Tim's set-up, while a good design in theory, left him with two blown engines. Its one of the first things he mentions in regards to the design.

I think when I finally install an electric fan I won't be removing the clutch fan. It is way too efficient at cooling the engine. Others have installed a smaller auxiliary fan, in addition to the clutch fan, to just deal with the hot soak. If the thermostat fails then you're not out an engine... you only have to deal with hot soak. I realize the clutch fans have their problems too & failed units have been the cause of many engine deaths as well.

Also, so you know, there are companies out there that will build you a shroud when you order the fan. I don't have any of this information collected at the moment but I know out in San Diego you can very easily find someone to take care of this for you if you don't have the tools, material, or motivation.

One last thing that I pondered, in regards to Tim's experience with his thermostats - I know there are units that hook-up into the radiator hose. Perhaps these thermostat's - while not as 'clean' in design - are more reliable. I'm not sure, but its something that I wondered.

Good luck, & let us know what you decide to do & inform us of the results.

Thanks Foreverly,
previous owner said cooling was not and issue and that seems to be the case so far, but my hot soak issue is bad. So far Ive settled on pumping the gas paddle 3 to 5 times and then try to start. Starts after 3 tries or so then I give throttle until it smooths out after a minute or so. I am having a hard time finding a mechanic who works on them but I PM'd Trestlehed to get his guy as we live very close to each other I think. I am going in for an oil change on Tuesday and will ask them too about adding a fan but I don't think they are very familiar with TV's. Also, I have to smog it so I am thinking of waiting until I see how I do at that first! I have my fingers crossed! Thanks for the heads up. I will search for the aux fan threads.
john

John, you might want to read through some of the Hot Soak & Electric Fan threads over at TVP. If your hot soak is that bad you might want to try some of the other remedies until you get yourself a fan.

Instead of going to a regular mechanic you might want to find a classic car guy as Hot Soak is a problem on many late model vehicles. I helped my friend restore his 1943 Ford that his grandpa bought brand new. He had hot soak problems all the time with that car here in Austin.

Some of the coastal towns in TX have gas stations that stock ethanol free gas. Have you checked your area for ethanol free gas stations? There is a website out there that lists them all by state.

Quote:

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Originally Posted by foreverly

Cirrus - You may want to make note that Tim's set-up, while a good design in theory, left him with two blown engines. Its one of the first things he mentions in regards to the design.....................

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Who said anything about blowing engines? When my thermostats failed it did lead to overheat conditions (both times) but these were not severe overheats, just enough to get my attention, annoy me, and leave me with a confidence problem with the capillary style t-stat design. The flex-a-lite variable speed electronic t-stat I'm trying now gives me that "warm fuzzy" feeling, but only time will tell if it's going to last. That being said, foreverly's position does have merit. I go back & forth in my head when it comes to clutch fan vs electric. There are pros and cons to either way you go. A correctly functioning clutch fan will move more air at high RPMs, but the engine also works harder generating more heat while doing that. The beauty of the electric fan set-up is it will cool at maximum rate while your engine is at rest. To me that's the clincher that sells me on electric. Of course there's a down-side. An electric fan set-up will increase the load on an already fragile alternator.........and if the alternator fails.........battery goes dead quickly...........and no more electric fan.........or anything else (bad). It sucks when that happens.

Of course the other advantage to electric is it can be used to combat the heat soak issue (clutch cannot). If you aren't ready to give up your clutch fan, an alternative could be installing a pusher fan to the front of the radiator (or AC condenser if you have one of those in front of the radiator). The t-stat could be set up the same as mine or it could be put through the fins in the radiator. FWIW, initially I ran my t-stat by putting the probe in the radiator fins. It worked okay but I didn't like the response time. Heat transfer was delayed and performance was poor (thermostat would not consistently kick in until van was already running too hot). Submersing t-stat probe directly in the coolant was the answer. Direct contact with coolant gives instant response and fans come on predictably every time. Tim

Thank you for correcting me. My memory is sometimes warm & fuzzy too, I apologize. :redface: For some reason I was in the understanding that you blew head gaskets before you realized the fans weren't working properly.

Thank you for the additional information regarding T-Stat placement.

I thought I'd comment on a work-around, if someone hasn't gotten around to upgrading the fans/cooling. I've experienced the hot-soak occasionally. When I feel that there is potential for the problem, I would let the starter run on for a couple of seconds more than a "normal" starting duration. There is the "intuitional" turn the key and quit when the engine starts, that you do every morning or after a considerable cool-down. By adding maybe a second or two, to that interval, with the starter assisiting in getting the fuel moving through has worked for me.

I'm citing this from memory, though, as I don't really seem to experience the issue much/at all any more. I'm not sure if it is coincidental, or not, but the problem seemed to clear up after I replaced the thermostat with an OEM Toyota thermostat (coolant, not fan control). I know I've heard Tim (and others) specify using that OEM thermostat and wonder if it is intended to help with this? It is constructed much differently than a Napa (or other) aftermarket thermostat.

Anyway, my $.02

Hey Cirrus, I just replied to your PM so check your inbox.
In the mean time, here is a thread concerning a "Cheap and Easy" heat-soak remedy.

Just prop your engine lid open after driving to vent the engine bay. Keeping the windows cracked about an inch or so is a good idea so when you get back to your van it's not an oven inside:

http://www.toyotavantech.com/forum/s...ng-some-parts!

Well that link goes to the thread about making the engine lid / seat holder out of bulk wire, but I think what we are all beating around the bush about is you may want to cut & ground the temp. switch wire.

Tim mentions it in his blog post about hot soak. It is the switch that has one scrawny wire going to it below the radiator cap.

I haven't tried it - it may help a bit but from what I've gleaned its not going to fix the hot soak problem. I wish I could get my hands on one of those updated fuel pressure regulators though.

I was really hoping to hear from Arp on this thread. His posts at TVP indicate he has been through the gamut but in the end installed an aux. fan, keeping the clutch fan. I'm really curious about his setup.

Oh, I just found his contact info, but he sold his van...

ok I'm back by special request:rol:

I did sell my van with a fully functional hot soak fix which had been working nicely for about two years. I tried to keep it simple, kept the stock fan clutch setup and added a single pusher fan to the front of the radiator. Don't have the van or details but here's what I remember.

I went to the local Schucks (now O'Reilleys) and asked for a single aux. radiator fan of the correct size to fit on the front of the radiator (Thinline fan or something like that, there's not much room up there), and a thermostat kit to hook it up to. The adjustable thermostat unit had a metal probe maybe half the dimensions of a pencil which I zip-tied to a return fuel line right above the fuel rail (where I assumed the fuel vaporization ocurrs). Very simple, didn't submerge in coolant or anything like that. The fan had these attachments (rod like I think) that went through the radiator fins and a disk went over them on the other side and held the fan on. I attached the thermostat to the firewall right above the air element and hooked it up to unswitched power at the little + electrical connector box near the engine/air cleaner box (I believe there was a fuse in line here).

I set the adjustable thermostat so that it generally did not come on when the vehicle was operating (except once - see below). But usually, especially on hot days it would come on a few minutes after shutting the engine down as heat built up in the engine compartment. Depending on how hot the day/engine was it would cycle on and off for up to half an hour after engine shut down. I told people the elves were vacuuming in the van. Never had a problem with hot soak after this. Of course you need to make sure you keep a good battery in the vehicle with this set-up, although I never had a problem with that either.

Seriously, this was one of the easiest jobs I ever did on the van, only took a few hours I think (usually anything I did on the van stretched towards midnight if not the next day), and the results were spectacular. The hardest part was getting to the bolts holding the radiator on so I could rock it backwards and install the fan on the front of it (no need to remove it completely or disconnect hoses). I went through all the other ideas for a fix and all were unscuccessful until this one.

One advantage to this approach is you now have both kinds of cooling systems, if one fails you can fall back on the other at least temporarilly. My replacement vehicle (2004 Dodge Dakota crew cab) has both the fan clutch and aux. fan stock, though the needle has never strayed far from the 1/3rd spot :) and I've never heard the aux. fan come on. It may be overkill on this vehicle unless you're towing a load.

One summer after the fix I had a fully loaded van (for camping with the family) and the family, car top carrier the whole bit, pulling the grade out of Zion canyon in stop and go traffic, maybe 30 mph when moving. It was around 110 -115 F outside. AC full on. The worst possible conditions on Earth for overheating! My attention was riveted to the temperature guage. A few miles before the tunnel the needle got to 3/4's with the fan clutch already fully engaged, and I started sweating bullets. Then I heard the electric fan kick on and the guage maintained until we made it to safety (cooler temps) in the tunnel. I'm convinced the electric fan kept me from an overheat on that day.

Good luck Y'all!

Thanks to everyone who has replied on this thread......... ARP, thats sounds like a winner. I have an Oreillys right near work so I will pop in there tomorrow. I have AC so that may hamper things a bit but I am sure I will figure something out. Thanks again to everyone for pitching in with ideas. I will fully document what I do and post pics. etc.
Cirrus

I think I set the thermostat to trigger at 185 F, and that was real close to resulting in operation as described above. Each van might require a little different setting.

I had AC also but not rear air where I think there's a condensor on the front of the radiator? The front of my radiator was clear.

Thank you Arp - this fix might be easier than the original TSB.

Cirrus - be sure to measure the gap before the radiator so you know how thick of a fan will fit in that space.

After a few other projects I'll be right behind you on this one, so let me know what fan & t-stat you end-up with.

I started using my 86 van again after 13 years of it sitting in the black berries. I remember 1 or 2 times I had heat soak issues back in the 90's but nothing like now. As stated earlier I believe this is due to changes in the gasoline market over the past few years (lower boiling temperatures). Anyhow, even this time of year it's been giving me fits so I put my mind to finding a cure. I didn't want to spend a bunch of money and time with electric fans, shrouds, thermostats, etc so I came up with a compromise. I've been running/testing this for about a week now & it's been working flawlessly.

I had an old 11" electric fan laying around & decided to use it. I took my fan shroud off & took some measurements. I found there was more than enough room to install the fan directly to the engine side of the radiator so I put it there :dance2:.

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Since my intent is only to ventilate the engine compartment after shut down I don't need to worry about a custom shroud or a thermostat. I decided running the fan for 15 minutes after shut down would be sufficient, so I purchased a 12V "delay off" timer. The timer I chose was the Durite #0-740-57 programmed for 15 minutes. This relay was way overpriced, but I liked it due to the type of trigger it uses & because it fits into a standard Bosch relay harness. Coupled with a standard Bosch relay, a capacitor, & a diode I was able to construct a circuit that would activate the fan for 15 minutes every time the van engine is shut off (see PDF file attached to this post). Here's what it looks like:

http://i8.photobucket.com/albums/a23...ps3583aa3b.jpg

Due to space and ease of installation I decided to put it behind the glove box. My van is pre-wired for an ice-maker but doesn't have one, so I'm using the ice maker harness to supply 12V ignition switched power source (this circuit is only activated when the key is in the "run" position). Also lot's of good places here to tap ground.

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I put the override switch down by my right knee. This switch will activate fan only when key is in "Run" position. I probably won't use this, but it might come in handy during the summer while I'm using my AC :thmbup:.

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It's pretty cool to have this thing come on and go off based on time. My other van with the thermostat control will switch the fans on/off for about 20 min after shut down. I like the constant 15 minutes of fan much better than the on/off, on/off of the thermostat set-up, so now I'm thinking of adding this delay to my other van with the t-stat control. Tim

Awesome Tim! :thmbup: I'm glad to see that you are experimenting with Aux fans. Where did that fan come from or where could one find a similar fan?

I think the override switch is a great idea. Does the switch have an 'off' setting too? There doesn't seem to be a reason to run the system during the winter. & even sometimes during the summer, I think I would want to have quiet moments.

I didn't wire an off switch into the system but I also was thinking it would be nice. I had to move the van a couple times this weekend (just a few feet), but then the fan runs for 15 min. :doh:. It would be easy to do, but then easy to forget it's off. I may incorporate a temperature switch so it only activates when the engine compartment is over 200 deg. It's still awesome the way it is (compared to heat soak). I was experiencing start problems almost every time the van was warm. Since I put this in it hasn't happened once :thmbup:. Tim

Quote:

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Originally Posted by foreverly

Where did that fan come from or where could one find a similar fan?

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If I remember right I think I pulled it from something in a salvage yard years ago. Here's a similar one on eBay: http://www.ebay.com/itm/New-Turbo-Sw...4edc82&vxp=mtr

I did some research / cross referencing & came up with a temperature switch that activates (closes contacts) at 170 deg F. Since I have my thermal switch for the "pressure-up" disconnected & grounded, I'm going to put this switch into that port on my filler neck. The switch I found is AIRTEX Part # 1S4382. It has M16 X 1.5 threads (same as our sensor ports). Other numbers that came up in the cross reference are: 21595M4960, 21595M4961, 88923732, & SW542. I'm going to wire it in series with the ignition coil side of the timer so the 15 minutes of automatic fan will only occur after the ignition has been turned on/off & engine coolant temperature is above 170 deg F. It was a bit expensive, I found it on www.rockauto.com for $49.79. I suspect if I would have searched a bit more I could have done better. I'll post pics of it installed & report back on performance. Here's a file picture I found of the switch:


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I installed the temperature switch tonight & wired it into the circuit. The over-ride switch will still work like before, but the automatic 15 minutes of fan after shut-down won't occur unless the coolant temperature is over 170 deg F. The only "hiccup" was the probe end of the switch was too big diameter to fit into the bore of the "pressure-up" switch. So I took the filler neck off and drilled the bore out to 1/2" and then it fit fine.

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The bore was smaller for the old switch because Toyota uses the smaller bore to seal against the shoulder of the brass switch. Since this switch doesn't have a shoulder I'm using a copper crush washer to seal the new switch.

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Here's the switch after I've installed and wired it.

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Here's the path I chose for the wire run. Note: To protect from chaffing I'm using a piece of pex tubing where the wire passes through the body.

http://i8.photobucket.com/albums/a23...ps431c77fc.jpg

I wired this switch in series with the coil side of the timer relay. Here's a PDF file to show how the switch is wired into the timer circuit. Tim

Very Cool. This is better than having an off switch.

But I love what would have made this impossible for me is just a little hiccup for you. Congratulations on sticking with your idea & seeing it through. :thmbup: