replaced thermostat, but temp sensor still reads low - Toyota Nation Forum : Toyota Car and Truck Forums

nogard · 03-09-2007, 07:10 PM

All of my other Toyotas, the temp sensor gauge read straight up and down in the center. I had a problem with a sticking thermostat on my '88 wagon 3S-FE. The temp of air coming out of the vents wasn't that hot, and the gauge read low, I also had a lower gas mileage in colder weather.

So I just replaced the thermostat with a Stant Super Stat. The car doesn't warm up any faster, but it feels like it puts out more heat. The engine also feels hotter when I open the hood. But the gauge is still reading low, no different than before. How do I fit that? Is it a bad temp gauge sensor?

Also what is the advantage/disadvantage of a hotter or colder thermostat. I put in the OEM temp of 180, but I know they offered a 192, and I forget the colder one.

***HomeGrown*** · 03-09-2007, 07:25 PM

Sounds like maybe your sensor might be going bad, or perhaps there's a lot of corrosion on it, essentially insulating it from the true temp (just a longshot).

I know in a lot of performance applications, the tend to run cooler t-stats and cooler range of plugs to help reduce engine heat. That seems to be the norm on a turbocharged engine anyway.

Cam-Shaft · 03-09-2007, 08:31 PM

Hey nogard.

If you replaced the thermostat, and it is still not heating up, ...your gauge probably has a short in it somewhere.

Something you could do, to find out the real temp of your engine, is to find someone who has a temperature gun( or if you have one), to see the actual temp of your engine.
Just aim it at the cylinder head, that should work fine. (This is while the car is running, and has been warmed up for a while.)

If you dont have one of those, just use a regular thermometer (a household one) and you can just check the temp of the coolant that way.

A good way to tell if your engine is getting warm enough is if your fans turn on, since they are electric (just while sitting and idling.)
If the temp of the coolant is at spec, you have a shortened gauge. If not, then its another problem.
Process of elimination

Best of luck to ya.

***toyomoho*** · 03-10-2007, 01:56 AM

Fan should kick in about 192F. With engine cold remove the radiator cap, put in a thermometer and see how the temp corresponds to the dash gage. Temp should be about 185Fish.

The car should run fine with the 180F thermostat.

You can download the service info at the link below then do an ohms resistance test on the coolant sender.

http://oregonstate.edu/~tongt/camry

nogard · 03-11-2007, 08:08 PM

Well the fans are kicking in. I made sure of that after I replaced the thermostat. I started it up, bleed the air out of the cooling system and made sure the engine got hot enough to turn the fans on. Since it was running hot before fixing, I also wanted to make sure the fans were turning on, and it wasn't overheating due to a relay or fan motor failure.

I do have a non-contact IR thermometer, I did check out the engine temp and it checks out. I'm positive the engine is at the right temp and the thermostat is working. I know the fans, etc. work. I think it is my temp gauge sending unit, I will definetly check out the resistance of the sender, I think that is the problem.

Homegrown,

Yes they do run colder plugs, etc. on turbo/super charger applications. When boosting an engine it is more likely to predetonate. Usually this is also combated by using a higher octane fuel, and retarding timing.

Thanks for all the help.

***HomeGrown*** · 03-11-2007, 09:10 PM

I boosted a 2000 S-10 pickup and went thru all that. I feel the need for another turbo project.

Cam-Shaft mentioned somethingn about the gauge being shorted. My (very limited) experience with malfunctioning gauges is that there is usually an "open" as opposed to a "short", which would cause the gauge to read dead-cold. Something as serious as a "short" probably wouldn't result in the gauge reading only slightly off.

marc780 · 03-11-2007, 10:57 PM

The ONLY POSSIBLE thing that can make an engine run cooler than it's supposed to is a thermostat stuck open. And since you changed it that too is probably not the problem. Lacking any other info beyond what you write, maybe the problem is...winter?

Quote:

Also what is the advantage/disadvantage of a hotter or colder thermostat. I put in the OEM temp of 180, but I know they offered a 192, and I forget the colder one.

I'd stick with the exact thermostat Toyota recommends, and that's probably the hotter one - if you bought the recommended one thats what you got. If you are still not convinced just get a genuine Toyota part and put that in and that ought to remove all doubt (along with another 5 or 10 bucks from your wallet).

fredk · 03-12-2007, 12:52 PM

wheres the gage at when the fans come on?

nogard · 03-12-2007, 08:54 PM

The gauge is at about 3 gauge widths to the left (cold) from direct center. I did double check the temp of the engine with a non contact thermometer today. I got home so the car was warm, and took the thermometer to it. I had 160 deg on the lower hose and 180 on the upper, when the thermostat was closed. The is would heat up equally on both hoses. The upper hose would get to about 203, and the lower hose would get to 183, then the temp would start to drop on the lower and upper hoses, that is when I would say the thermostat opened. At the same time both fans would come on for about a minute, and shut off. Then it would take a few minutes, didn't time exactly, for everything to warm up and go through the cycle again.

I confident that the thermostat is working great. I'm not sure about the fans, I got the impression that one is supposed to turn on when it is warm, and the two when it is hot. I haven't really checked into this yet.

I know winter isn't the problem. I'm in Wisconsin, and it is cold here right now, but today we had a taste of spring, it was at least 50 deg on the way home today. The gauge read the same in warmer weather with the new thermostat, as it did in about 10 deg weather with a wind chill with the old junk thermostat.

I'm not totally sold on buying factory toyota parts. They have someone else make most of the parts for them, to there spec on course. But if you shop around and don't buy the cheapest thing out there. Chances are you are getting a quality part. I did buy the Super Stat which is chrome plated (won't corrode as easy), will fail open, and has a larger wax pellet to operate the larger spring. It is a $12 part.

nogard · 03-12-2007, 08:58 PM

Homegrown didn't realize you turboed a s-10, fasinating in its own right,

two thumbs up, something different with a little more power, and something that could be a budget build I would imagine.

proj87c · 03-16-2007, 12:20 AM

im having a similar problem it reads dead cold but after 5 mins or so it suddenly jumps to the middle, then it goes higher..dun think this applies to u but my frd said the previous owner put like half a tube of silicone on the thermostat..

Kyle1! · 02-24-2010, 02:34 AM

I have an 88 camry 4 cyl 82k on JDM. The cooling system was working as it should; temp guage at the right level, fresh coolant, heat is hot and fans would come on as they should. The radiator developed a leak and I replaced it.

After replacement the temp guage stays about 1/3 instead of slightly below 1/2 mark on the gauge and the lower rad hose was cool even after driving for some distance. The fans have not come on when idling like before. The car also doesn't seem to have as much pep. Because of the cool hose I replaced the T'stat and bled the air out. The changing of the T'stat did not improve the situation. Temp gauge is still at 1/3 and the lower hose is still cool (a tad warmer then before replacement) but what is

me is I have nice hot heat. These things normally don't go hand and hand Replace the rad cap? I'm out of ideas

Thanks for your help.

Brian

white90dx · 02-24-2010, 01:54 PM

You probably should have started a new thread... but whatever.

The lower radiator hose should generally not be too hot - that is the cool outlet side of the radiator. That means your radiator is doing its job! The top hose to the radiator should be hot after driving a bit though.

Not sure about the low-reading temp gauge though...

-Charlie

Mike Gerber · 02-24-2010, 04:42 PM

Check the actual sending unit that feeds the gage on the dash. It is independent of the engine coolant temperature sensor that feeds the main engine computer. The one for the dash may not be showing the right reading and your engine/cooling system may be operating normally. Either that or stop by a shop that has a point and shoot digital thermometer and have them measure the temperature of the radiator. That should take about 15 seconds, if they have the right tool. I say this because you said "but what is me is I have nice hot heat."

Mike