Infrared thermo on T-stat housing (1 Viewer)

[Dozer18]

Fellas,

Been going through some overheating/leaking problems but getting it worked out. Want to run something by you guys to make sure I'm not going crazy. Recently replaced my water pump, and while I was at it replaced the belts, hoses, and coolant temp sensor. After burping the system, etc, it's running hot -- about 80% of the way up the gauge towards the red.

So today I take an infrared thermo and hold it on the T-stat housing, while running, at normal operating temp. I watched while the temp showed 207, then the t-stat opened and it dropped to about 187. Held for a few seconds, t-stat closed, and it rose again until the t-stat opened. Never got higher than 207-208.

You guys think I got a bad sensor from CCOT? Hate to use the name, but I've read a few posts from others implying the same thing. Am I missing something in the temp readings? Any advice is much appreciated. Have a great weekend!

Dozer

 

[lovetoski]

If you have a reputable infared thermo, and have the emissivity setting correct for the t-stat housing, then I would believe that number. Since you just replaced the temp sender...it does seem likely that it is the culprit. Every vendor has product problems from time to time though, so it seems like a call to them would be the next step.

 

[Tinker]

If you believe the infrared thermometer, the tstat is opening too late. It should open at 180 & stay open while the engine is running unless you're in Colorado where it's been below freezing for most of a month.

 

[loeky]

i went through a similar process during last year. don't want to be an alarmist, but went through the whole cooling system only to find out it was a leaking head gasket and cracked head that were causing VERY similar symptoms to what you describe.

i would install a manual gauge and get some numbers inside.

 

[IH8Wood]

Wouldn't you expect your tstat housing to be the same temp as the rating of your tstat( i.e. 180 degrees). Remove the tstat and see what happens.

 

[haryv]

I sold my thermal infrared tool. Now I wish I still had it as I am having problems with my t-stat. Dozer18, good idea to use it without breaking open the housing.

 

[Dozer18]

Lots of great feedback, which I love. First, I think the thermo is reputable; it's a Craftsman, which I trust. Now, as for the temps: as I understand it, the temp should fluctuate. The t-stat doesn't hold a temp within a couple of degrees. From research on this site, I expect to see max coolant temps up to 220, with the lower temps within the t-stat around 180-190. Again, I'm fairly new to the FJ82, so I really hope to hear from some more experienced folks.

Please, sound off if you have some thoughts here, for better or for worse.

Thanks again for ALL the input,

Dozer

 

[Dozer18]

A couple bottles of wine deep; I meant to say FJ62. Persecute me at your will....

 

[Dozer18]

Loekey,

I don't really have any of the other standard blown head gasket symptoms: no white smoke, no water out of the exhaust, no moisture in the filler cap, no milky oil on the dipstick; that said, if I'm missing something, please tell me.

There's a very good chance that I'm in denial about a blown head gasket. I keep telling myself that I don't have that problem, and the thermo on the t-stat supports it on the surface. That said, I'm all ears.

Dozer

 

[Dozer18]

I'm hijacking my own thread -- wine will do that to you. Do y'all recommend I replace the t-stat and see what happens?

 

[Tinker]

There's a test available at better shops that checks the "air" in your cooling system & indicates whether it contains exhaust. Did it on my '98 Vortec to find out it had the typical intake manifold gasket leak.

 

[Landpimp]

taking the temp at the block is a better place IMOP, t-stat housing will be hotter than the actaully block temp(which is what really matters IMOP)

 

[loeky]

Loekey,

I don't really have any of the other standard blown head gasket symptoms: no white smoke, no water out of the exhaust, no moisture in the filler cap, no milky oil on the dipstick; that said, if I'm missing something, please tell me.

There's a very good chance that I'm in denial about a blown head gasket. I keep telling myself that I don't have that problem, and the thermo on the t-stat supports it on the surface. That said, I'm all ears.

Dozer

crappy thing is, neither did i. only after knowing it was running hot for a while and still running hot after going through the whole cooling system did it finally let go of the gasket in Las Vegas at the Mandalay Bay valet parking.

if you end up replacing everything that really needs it and you still have an overheating problem, it's going to be the gasket and/or head.

i might've had the cracked head there for a long time and never knew, it was really the gasket that told the tale. only when they checked the head did they find a crack.

good luck and hopefully other more minor fixes take care of the problem.

 

[Dozer18]

Got It!!

Well, the overheating problem is fixed! Turns out it was a bad temp sensor that I got from a popular vendor. Ordered the part along with a new OEM water pump, belts, and hoses, and replaced the sensor while I had everything out. Truck had never run hot before. After reading a few other posts, I saw where some others had had that problem, so I picked up an OEM TSU from my local Toyota dealer. Put it in today and the temp holds exactly where it should. I don't want to call the dealer out in public, but PM me if you want to know where I got it. I'll be posting a warning thread as well. Thanks much to everyone who tried to help me out! It's much appreciated. Dozer