Engine running hot

if the bottom of the radiator or hose is cold after warmup, that's a pretty good indicator of a thermostat problem or a water pump.

 

Ok update we did a leak down check to make sure there were no leaks from the combustion chambers. There were none. So we replaced the radiator, burped the system, did another leak down check. The engine is still running hot. I'm perplexed all components have been checked. I'm about to take it to Toyota and let them figure it out if any one else has another idea let me know.

 

I say replace the thermostat or at least check it again,

 

Where do you live Daniel? I am in Marion and do a lot of work on the Alabama member's trucks from time to time. If you are not too far of a drive I can take a look at it and see what we can find out.

 

Like I suggested previously, run it without the thermostat and see how it does. Depending on the air temperature, it may not warm up all the way, but that will still tell you that everything else is working OK.

I still think it's the thermostat. I guess another possibility is that the temperature sending unit is jacked up and it's really not running as hot as your gauge say it is. But I don't know how they behave when they go bad. If the part is cheap and easy to replace I would just do it. Imagine if it has been lying to you this whole time and everything has been working fine!

 

I live in Scottsboro Bill. I also don't think the sensor is out if it were then everything else would be normal including the lower hose warming up and the bottom of the radiator not being cold. I will try running the truck with no thermostat.

 

OK, that is up there by Huntsville. You may want to find the Alabama thread on here and ask for help. Lots of guys up in that area that may be willing to help you.

You will find us here:

http://www.tacomaworld.com/forum/south-east/37848-alabama.html

 

Yea bout an hour east of Huntsville 2 hours north of Birmingham. The truck is actually at the shop my brother in law works at we work on the truck on the weekends. He's been a certified mechanic since before I was born and he's just as confused as I am. We're going to try to do a vacuum test on it or something like that I'm not sure what he was talking about.

 

You guys are probably right about the sending unit, as that wouldn't explain the cold lower hose. But then again, nothing is actually making sense at this point. When things are really weird, I typically take the low-hanging fruit and the sending unit might qualify.

If the thermostat had an opening temperature of around 230°F, that would explain the running temperature, but it still wouldn't explain the cold lower hose. If the thermostat were stuck closed, the engine would go past 230°F and eventually overheat but that would explain the cold lower hose. I can't think of a condition that would cause a cold lower hose but not cause you to overheat, unless it was a closed thermostat, cold out and you ran the heat at full blast in the truck and essentially used the heater core (a mini radiator) to cool the engine.

So what's left? A bad clutch fan would cause you to run hot when you're not moving and still get the lower hose hot.

One more question, does the analog gauge (and the digital, for that matter) start out really low when the engine is really cold and climb at a steady rate to 230 and just stay there?

 

Another question: Do you get heat and is it very hot?

 

Yes both gauges gradually increase. I have hot heat and cold A/C. The clutch fan has also been replaced and is working as it should. In my opinion it does seem to go back to the thermostat even though I did test it and it works. This weekend i'll be removing the thermostat and running the engine to see what happens. The Vacuum test we will be doing could help some since there may just be a large air pocket in the system somewhere.

 

It is not beyond the realm of possibility that your thermostat, even though it is new3, is having a problem. Please don't take this as anything other than a "I've done it myself in my younger days" but is there a chance you accidentally installed the thermostat backwards, or crooked?

 

The thermostat you installed is it OEM or a STANT one. It could be a higher temp rating

 

While I agree it could be a higher temp rating, the radiator and lower hose should not be cold after the engine has been running as long as his has.

A bad water pump, or faulty thermostat are the most likely conditions. A restricted radiator could cause a reduced flow in the radiator, but I would think that his engine would overheat, and the lower hose would be warmer.

 

Ok it's been awhile since i posted, the truck recently got a new frame. I still have not figured out why it is running hot and have resorted to driving without a thermostat.

 

I got a head gasket job done, picked it up from mechanic and within 10min of driving, temp gauge was pegged! Radiator and top hose was hot to touch, bottom hose was cool (not circulating) how can I fix this? Mechanic said to burp it, so we tried, installed a new thermostat (so when fluid gets hot again it will flow), took truck for a spin again and was pegged again, rad & top hose still hot, bottom one still cool to touch.

 

check to see how the thermostat was installed. Jiggle valve in the upward position would cause hotter temps because on the 3.4L its supposed to be in the downward 6:00 position. My ultra guage was reading my engine temps to be in the 210 degree range. After checking the thermostat I saw that the jiggle valve was placed upward, so I rotated it to be in the 6:00 position and now my engine temps are 20 degrees cooler and are in the 188-192 range. I was skeptical of the "jiggle Valve" mod but it did make a big difference. Wouldn't hurt to try.