Temperature sensor and sender

I've been collecting parts to update and swap out on my 4wd Van to help with the heat soak/vapor lock issues that I've been having during the summer months. I ordered the Fuel pulsation damper and I thought the coolant temperature sensor needed to be changed as well? I looked at the Toyota bulletin that Tim posted on the Heat Soak tread but when I tried the part number it said the part has been discontinued. I found this part number and was wondering if it's just the updated/replaced part number?--

Genuine Toyota 89428-28030 Coolant Temperature Sensor

http://www.amazon.com/Genuine-Toyota...ype=automotive

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Originally Posted by timsrv

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 195-205 deg F (in the switch location), 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.

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This is a temperature switch (not sensor). The original temp switch (the one you ordered) is still available, but it's activation temp of 230 deg makes it next to worthless. If you wanted a 140 deg one (like what they used in that service bulletin campaign), you could probably get one designed for a different application, but IMO it's not worth wasting a sensor port for. Just cut the wire going to that switch and ground it (the wire). This will activate the "pressure-up" VSV and temporarily increase fuel pressure (about 2 minutes) every time you start the van.

Tim,

thank you I cancelled the order on the switch. I was hoping to replace all the parts that was associated with the heat soak thread. This is the picture that I had copied a while back and saved cause I knew I was going to need to address this. I think this is the right picture.

That picture is super awesome and the person who added the tags did a super nice job. There are however some minor terminology errors. I haven't checked part numbers to verify, but I assume they are correct.

So just to complicate things here, where exactly is the temperature sensor located? And, what is its part #?
Is it down on the head on the left side adjacent to the distributor?

If you're talking about the temperature sensor for the ECU (not the sender for the gauge), it's the one in the picture JDM VANMAN posted above labeled "Airtex Wells #551492). Whoever marked up that picture did a beautiful job, but they improperly called it a "Temperature Switch". This is NOT a switch, it's a sensor. To be more technical, it's a "thermistor" (a resistor that changes resistance with temperature). In order for the ECU to calculate correct fuel mix, it needs to know temperature of the engine. This sensor is what gives the ECU that information (in the form of resistance). This is one of the more important sensors and the van will not run good if this one fails.

BTW, I assume whoever marked up that picture put the correct part number there, but I have not verified that. So far I've only used Napa part #TS5520 (around $15) and the OEM Toyota part #89422-12010 (around $80) here. In my experience, the Napa sensor has worked fine. I've been running the $15 Napa one on my 86 LE for the last 40k miles and that van runs sweet. Tim

I was looking for the part # of the sensor that is attached to the gauge on the instrument panel. I kind of figured if the van is running good and I have replaced EVERYTHING else in the system, I should start with a new sending unit as well. It's just hard for me to nail all of these sensors and switches down. :wnk: Thanks for your help

Toyota calls that one a "sender" Here's a post that has that information in it: http://www.toyotavantech.com/forum/s...1483#post11483

Good post, but I'm still confused after reading it 3 times. Which sensor effects the temp gauge?

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Originally Posted by scotty

Good post, but I'm still confused after reading it 3 times. Which sensor effects the temp gauge?

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http://www.toyotavantech.com/forum/s...1966#post11966

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Originally Posted by timsrv

http://www.toyotavantech.com/forum/s...1966#post11966

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Figured I'd piggy back here - as this may be a silly question. But... do I need to drain any coolant prior to installing the digital temp gauge in the extra / unused port?

Thank you! Amazingly helpful info on this site!

No, it's pretty high up so you will only lose a couple cups of coolant. If you want to minimize that you can drain a couple cups worth out of the radiator petcock prior. The block drain would be a better place to drain, but Toyota put it in such a bad place it's hardly worth the effort. Personally I'd just pre-prep the new fitting/sender with teflon tape and pipe dope so it's ready for a quick swap. If you move fast you'll likely only lose an ounce or 2.

FYI, That plug in the unused port is usually extremely tight and you'll probably need some good leverage to get it out. I've removed several and I'd give you about a 50/50 chance of it coming out without extreme measures (the Allen socket will likely strip). If that happens there are still ways to remove, but those become more challenging when the Allen socket is stripped.

I learned after the 1st couple that it's best to (carefully) apply heat to that plug with a torch before trying, then success is almost guaranteed. Propane probably won't get it hot enough, and other types of gas can cause damaged to the aluminum head, so try to focus the heat in the center of the plug. If you don't have a torch and/or don't have the confidence you may want to look at a different place to put the sender. If it's an automatic with AC, then all the other ports are in use, however the overdrive temp switch and the "Idle-up Temperature Switch" (as labeled in the picture, post #3 above) are not important and should be easy to remove. If the van is a manual without factory AC, then both those ports will be plugged. Not sure how tight the OD sensor port plug would be, but the one on the fill neck would likely be much easier to remove. Tim

Many thanks as always Tim! It is a 5 speed, so from the photos, it looks like either the port under the sender or the extra port would be options. Great tip about the heat. Will be attempting this pretty soon, fingers crossed it comes out OK!

Installing a new temperature sensor (Napa Part #TS5520) today. Would you recommend a thread SEALER or thread LOCKER on there? The new sensor comes with a copper crush washer and I thought that might be sufficient but am now second guessing myself... The old sensor did not have anything on it and did not appear to be leaking.

Some of these sensors use crush washers and others don't. It's been too long since I did this one to remember, but if it came with a crush washer and the hole it goes into has a smooth outer surface, then use the crush. If it leaks you can always take it back out and apply Teflon. Tim