Possible thermostat issues.

[mbc]

The last few days, the Van has been running a little hotter than I'm comfortable with. After 10 minutes of trouble shooting, here's what I've determined so far.

I'm fairly certain that there are:
No leaks.
No coolant loss.
No bubbling.
Water pump shaft has no play.
Belt is okay and not loose/ slipping.
Ign timing within specs.

It's possible that:
There's blockage within the (original) radiator.
The thermostat is faulty.

However,the upper radiator hose is hot and the lower hose is warm (not cold).

I looked for the Bill Maley manual to determine the direction of coolant flow, but it's now gone. My logic and experience tell me that the Van has a sticking T-stat based on the symptoms, but the reversal of hot and cold hoses has led me to post here.

Can anyone confirm the direction of coolant flow? Has anyone here experienced these symptoms?

[llamavan]

The coolant flow direction is located here.

What you describe sounds normal (that is, hot upper, warm lower). Because the lower hose isn't cold, I'd suspect the thermostat first. If a new Toyota t-stat doesn't do the trick, I'd be all over the radiator next. Even partially clogged radiators noticeably compromise our vans' cooling.

Gwen

[NEC]

x2

[mbc]

cool thanks,

I totally forgot to look up your thread.

The T-stat is from Napa (170*)and is about four years old. I read all of the threads regarding the use of OEM T-stats, but mine was already in and I haven't had any issues with any Napa T-stats.

I wonder if Toyota sells 180* T-stats for the Van (attn NEC). I had a 195* one in the Van years ago, and the temp gauge was constantly above the half-way mark. Too high for me.

I'll take a closer look and report back.

P.S. I still haven't had the time to remove the rear heater either. I'm not one to turn down work.

It will have to wait until the weekend anyway, fortunately, I'm very busy with work.

[llamavan]

My experience with the NAPA t-stats is:

• they tend to run slightly warmer than OEM
• they don't last as long as OEM
• when they fail, they fail closed (OEM have gone both ways for me)

T-stat time!

Gwen

[mbc]

After thinking about it some more, I surely hope that it is indeed the T-stat. I'd hate for it to be a clogged / worn out radiator or...

I neglected to add that the Van only seems to heat up under a heavy load, or occasionally after shut down. the temp gauge never goes into the red, or even that space before, but hot enough to cause alarm. Oh yeah, the fan clutch roars like a lion...it's been my Van's saving grace.

I'll get a Toyota T-stat in the morning (fingers crossed).

[NEC]

The oem only makes one temperature range tstat for our vans. Mine never gets past 50% on the dial no matter how hot it is outside or how hard I push it. If you still have issues after you rule out the thermostat and you are sure your fan clutch is working I would suggest getting your radiator re-cored.

[mbc]

I figured I'd give a quick update.

I've found that the existing thermostat works fine. I could tell when it was opening during last week's cooling system flush. With the radiator petcock removed and the engine running, there was good water flow through the system too. I used a garden hose (with low water flow) inserted into the filler neck while running the engine and both heaters. Each time I revved the engine a little, the volume of water leaving the system increased indicating decent flow.

No longer running hot... for now.

[Cornato]

My thermostat has the opposite problem. It won't go past the quarter mark no matter how long I drive. Stuck open? And if it is, is that such a bad thing?

[timsrv]

It's not terrible. With a working 180 deg t-stat and a good working cooling system the engine will run at about about 180-205 deg F (if measured from the same spot as your stock temperature sending unit). Assuming your gauge is reading accurately, 200 deg F is about the middle of the scale.

Regardless of where the needle lives, If you heater is working good and the engine is not overheating then I'd assume the thermostat is working fine. If this is the case and your needle is not in the middle, then perhaps your temp gauge is just a little off (might just be normal for your van). On the other hand, if the heater only blows luke warm then I'd recommend replacing the t-stat. Just keep in mind that more internal engine wear occurs at temp ranges outside of the norm. It's not such a big a deal on an old engine with lots of miles, but having a good working cabin heater this time of year would be enough motivation for me. Tim

[Cornato]

Well, the heater works just fine I just would like to replace anything faulty on the van. I'm also having problems with it kicking into overdrive and I talked to a local toyota mechanic and he said, the thermo is stuck open so the engine is abnormally cold not allowing the temperature sensor to register right, which has to be a certain temperature to allow the overdrive switch engage.

So I blocked off almost all of the radiator from receiving any air flow and drove pretty far on a decent day (mid 70's), and no change. What does this indicate?

[timsrv]

It indicates a problem with your overdrive system (not your cooling system) I responded to your OD related question HERE. Tim

[skibum]

I would like to reaffirm the choice of the Toyota thermostat as opposed to Napa. I have replaced my thermostat with the Napa one a few times and have always has widely varied temperatures (1/3 to 7/8 on the guage). I drive in the mountains and have to grab second gear on steeper grades, both for the power and the cooling.

I just had an overheating episode that either started with, or caused the water pump to go out. I replaced the water pump, so I can't say for sure, but I also replaced the thermostat with a genuine Toyota and now I run at about 1/4 on the guage and only up to about 1/2 when it's working. I've had the van for close to 75,000 miles, so I believe that the change was the thermo, not the pump.

FWIW,
Scott

[MonTex]

My '89 4WD/automatic seems to run on the hot side, above the half-scale on the temperature gauge. I have taken my radiator to the radiator shop to have it gone through, which was returned to me with a clean bill of health after about $60 for the cleaning/flushing, rodding-out job. I was told that it 'wasn't in bad condition' by the radiator shop personnel.

I have also installed the following new Toyota parts: thermostat/O-ring gasket/water pump/water temperature sensor/radiator (coolant) cap/upper & lower radiator hoses and new timing gears chain. I also recently installed a new head gasket and had the head gone through by a very competent machine shop. The head was in good condition, but had it gone through anyway. I have verified that my timing and timing advance is correct. I also squeezed my lower radiator hose several times, after warm-up, with the coolant cap off to ensure that no air bubbles existed in my coolant system.

On a warm 70 -75 degree day, without my A/C running, my temperature gauge reads a bit above half-scale - about a needle's width above half scale to half-way between half-scale and the upper-end of the 'white/normal' part of the scale. I reference that my engine is running 'hot' after reading many posts on this forum whereby reports of normal operating temperature reports seem to be between 1/4-scale to 1/2-scale on the water temp gauge. I tried running with my front heater on, which does blow warm air, but this does not seem to lower my operating temperature. I have also verified that my fan clutch is working OK, as I can hear it rev up and down as it should.

However, I have noticed that if I top-off my coolant to the top of the filler neck, and verify that my coolant level in the coolant reservoir is at the high mark, after driving around for a few miles, I am losing a bit of coolant. When I check my coolant reservoir, it remains at the high mark. I have not replaced the hose from the coolant reservoir to the coolant filler neck (but perhaps I should do so).

Given that I live in the Los Angeles area, where it gets quite warm in the summer, with lots of stop-n-go traffic, I am really trying to keep my operating temperature at a more 'normal' temperature - not to exceed half-scale on my water temp scale.

I have read of people re-coring their radiator with a (the) larger more-efficient core that is available at a Yuba City, CA radiator shop, which by-the-way is also available at the radiator shop that I visited when I had my existing radiator gone through. The owner of my local radiator shop told me that there is some risk with using the larger radiator core with an extra row, in that the larger radiator core cannot accept 'enough' solder where the radiator side tanks meet the core, and thereby the risk of the tanks leaking because of the reduced amount of solder that can be used with this larger than stock radiator core.

I am reaching-out to forum members for any additional comments/help. Is there anything that I am missing here?

Thanks in advance for your comments and advice.

[timsrv]

It sounds like you have addressed everything. I wish I could offer an easy remedy, but I've been here too. With these vans I've found cooling issues are typically easy to remedy with few exceptions. Unfortunately it sounds like you may have one of those exceptions . Before doing any more, I would recommend installing an accurate temperature gauge with numbers so you can monitor/compare with the stock gauge. My 2wd cargo van had a problem that wasn't so easy to diagnose/repair. After replacing several stock parts with no joy, I installed a custom radiator with a high efficiency core. Yes it helped, but didn't completely solve the problem. Next I put in electric fans & a homemade shroud.......that helped too, but at times (typically when air conditioning was running) it would still run hot. Next I installed a heater core from a Previa behind the vent holes on my front bumper (tied into my cooling system) and this helped too. After that the problem was almost gone except when driving up steep grades on hot days with my AC on. Next I fabricated & installed an air scoop and installed down low in front of my radiator. This helps direct air up and into the radiator/engine area when I'm driving. I haven't been in a situation yet since installing the scoop to see if the problem has been completely solved. To this day I still haven't figured out why this particular van has been so difficult to keep cool. Yes I haul around a lot of weight (almost 3,000 lbs) but I've done this with other vans with stock cooling system components and had no problems. Tim

[MonTex]

It sounds like you have addressed everything. I wish I could offer an easy remedy, but I've been here too. With these vans I've found cooling issues are typically easy to remedy with few exceptions. Unfortunately it sounds like you may have one of those exceptions . Before doing any more, I would recommend installing an accurate temperature gauge with numbers so you can monitor/compare with the stock gauge. My 2wd cargo van had a problem that wasn't so easy to diagnose/repair. After replacing several stock parts with no joy, I installed a custom radiator with a high efficiency core. Yes it helped, but didn't completely solve the problem. Next I put in electric fans & a homemade shroud.......that helped too, but at times (typically when air conditioning was running) it would still run hot. Next I installed a heater core from a Previa behind the vent holes on my front bumper (tied into my cooling system) and this helped too. After that the problem was almost gone except when driving up steep grades on hot days with my AC on. Next I fabricated & installed an air scoop and installed down low in front of my radiator. This helps direct air up and into the radiator/engine area when I'm driving. I haven't been in a situation yet since installing the scoop to see if the problem has been completely solved. To this day I still haven't figured out why this particular van has been so difficult to keep cool. Yes I haul around a lot of weight (almost 3,000 lbs) but I've done this with other vans with stock cooling system components and had no problems. Tim

Thanks, Tim:

After re-reading the head gasket issues thread, I too am losing a cup or two of coolant out of my engine - yet not from out of my coolant reservior. I'm now on the hunt for coolant leaks around the engine compartment and elsewhere. I have ordered a new coolant reservoir cap to filler-neck hose just in case...it seemes a but too soft for my liking. I'll share what I may discover, leak-wise. Nothing is quite obvious at this writing.

Regarding air inlets to cool the engine area, there are a variety of aircraft fuselage air inlet scoops available at the URL below. Might be an interesting custom look to mount one or more of these on the LF and/or RF quarter panels of our vans!

http://www.aircraftspruce.com/catego...ts_inlets.html

- Carl

[timsrv]

I would like to reaffirm the choice of the Toyota thermostat as opposed to Napa. I have replaced my thermostat with the Napa one a few times and have always has widely varied temperatures (1/3 to 7/8 on the guage). I drive in the mountains and have to grab second gear on steeper grades, both for the power and the cooling.

I just had an overheating episode that either started with, or caused the water pump to go out. I replaced the water pump, so I can't say for sure, but I also replaced the thermostat with a genuine Toyota and now I run at about 1/4 on the guage and only up to about 1/2 when it's working. I've had the van for close to 75,000 miles, so I believe that the change was the thermo, not the pump.

FWIW,
Scott

I can confirm it was definitely the thermostat. My 86 van was having an issue with super long warm-up times so I pulled the thermostat & found it stuck open. After looking through my boxes of parts I couldn't find my extra Toyota thermostats (6 months after moving finding stuff still sucks). Anyhow, after about an hr of looking I gave up and called Napa. I asked for their most premium thermostat and got a Tama Enterprises Co. Part #154-2403 "made in Japan". It looked pretty good & even had a jiggle valve. I compared to the Toyota thermostat and although a bit different it looked to be the same depth & travel. Long story short I installed it and immediately started having the same problem as Scott. My new fan clutch (which I know to be adjusted correctly) would only run sometimes even though the gauge was getting up to 3/4 (this means the radiator temp was already cool but the system was lacking circulation).

This weekend I picked up a Toyota thermostat part #90916-03046 (was actually a couple bucks cheaper than the Napa one) and that completely solved the problem. Now my temperature gauge stays rock solid at 1/4 - 3/8 of the scale. It was warm today and I even ran my AC for a while. Tim

[EdCrono]

Hi Tim. I got stuck in traffic today in the hot (85f/h) part of the day (1:30 PM-2:00 PM). And my temp started slowly going up. I got to my destination and was I was idling, waiting for this parking spot to open and my gauge got a little higher than 3/4 of the way, then I shut the engine off untill the parking spot got open so I could park my Van.

Next I raised my seat to check on the engine and bubbling water was coming out the reservoir tank. I left it parked there until almost sunset and then put some water in the radiator. I started the engine so the water could flow and I could pour some more in but it didn't take anymore, and for some reason I felt Like I didn't put enough. Anyways, when the engine was warm enough I put the radiator cap back on and put water in the reservoir tank to "full" line. Then I drove home 15 miles away and it did not heat up. Of course, weather temperature was a lot cooler (68f/h), but I noticed the temp gauge in my van dancing at the halfway marc when it is usually at 3/4 of the way.

My van has been sitting for a while and today I moved it...

I'm planing on getting a new tmstat from the dealer in the morning. Do you think that could be he problem? may be a closed tmstat? Any inputs would be helpful as I'm trying to do this the right way.

Thanks!

[timsrv]

Replacing the thermostat is a good 1st step when chasing cooling issues. It's a moving part & one of the most likely to fail. It's also cheap and fairly easy to change. It may not solve the problem but if nothing else you can rule it out and feel confident with it for at least a few more years.

Were you running AC when this happened?

[MonTex]

Replacing the thermostat is a good 1st step when chasing cooling issues. It's a moving part & one of the most likely to fail. It's also cheap and fairly easy to change. It may not solve the problem but if nothing else you can rule it out and feel confident with it for at least a few more years.

Were you running AC when this happened?

I too have had cooling system problems with my '89 4x4 van (automatic). The original radiator has been 'rodded-out'/checked and tested at a local, reputable radiator shop, and was given a good bill of health. It was re-installed, along with a new Toyota thermostat (P/N 90916-03046), new Toyota Upper/Lower radiator hoses, new Toyota water pump, new Toyota fan clutch. The water temp sensor is the original one. The radiator fan clutch operates as it should. New (Prestone-Green) coolant level remains constant in the system. No leaks detected after long warmup times.

My water temp on the factory gauge reads 3/4-scale (with the A/C off), on the "white" part of the scale, with outside ambient air temps around 80-90 Deg. F. (here in Southern California). I'm wondering if my gauge could be off, or the water temp sensor may be out of spec. The fan shroud is complete, intact, and on correctly.

Thoughts?

Who reading this has placed a 4-row core into their van? If so, was it beneficial? My radiator shop can retrofit a high-efficiency 4-row core onto my original radiator tanks, but I was told (cautioned) that a larger 4-row core would accommodate less solder at the tanks than the original 3-row core
has. This may result in the radiator being less reliable over time.

Thoughts?