I've got an issue with my 90 22R Pickup that has me completely perplexed.

My truck is running hot. Thankfully it hasn't gone into the red yet and I don't want it to.

I've done the following:

* replaced radiator
* replaced coolant temp sensor
* replaced thermostat (twice)
* replaced water pump
* replaced radiator cap
* replaced clutch fan

I've had the truck in a shop and they did a test to see if there were fumes in the coolant and it came up negative. Oil looks fine.

When I run the truck without the thermostat it barely gets warm - as expected.

As soon as I put in a thermostat - 190 or 180 - it gets hot.

The heat works fine.

The system has been burped multiple times throughout this process.

I'm starting to think it could be some sort of blockage in the motor because the previous coolant before all of this started was really brown/rusty. Could the thermostat impede the water flow just enough and if there is a slight blockage cause this issue? I've never seen anything like this before.

Any thoughts or comments are welcomed.

Thanks for reading.

 

Factory temp gauges are not the most accurate of instruments. You are lucky that yours actually moves.

Have you verified what actual temps are at the upper water outlet using a decent IR temp gun??

May be that your problem is one of false indication, rather than one of reality.

 

I have. With the thermostat in the lower hose is A LOT cooler than the top. With the thermostat out both are warm as they should be.

I've used a IR temp gun and with the thermostat in the temp is very high compared to 70 at the bottom hose.

I really suspected the gauge and I agree - I do not like not knowing the actual temp. However, I have to believe it is OK or at least somewhat accurate based on my testing.

I do plan - once all of this is over - to install a real manual temp gauge as well as an oil gauge.

 

'A lot hotter' ' very high'???????

If you have used an instrument, What did it read????

It is VERY unlikely that a cooling system completely full of coolant and circulating that does not expel coolant from over-pressure can cause overheating damage.

 

Yes, what I mean by a lot hotter is 3/4 up the gauge. Normally, on all of my previous 22R and RE trucks it is at 1/4. I have an instant read thermometer (don't judge - I don't have a lot of $$) that I put in the coolant and it read 197. The IR gun shows the top of the radiator at 200+ and in the low 70s when the thermostat is in. With the thermostat out it the temps are consistent using the IR gun when I check both hoses. The lower is slightly cooler than the top.

Thanks again for the reply. I feel like something is clogged in the motor but not sure how to deal with it.

 

197'F is not too hot with a 190 thermo in place. If the system does not expel coolant, I still think that the dash guage just reads a bit high.

 

Thanks. Do you happen to have a manual water temp gauge on your 4Runner? If so, which did you go with?

 

I use the factory gauges on both my Runners. Both read differently, even though both have the same temp thermostats installed

They start cold at the bottom of the temp scale and move higher with heat.

I have verified coolant temps at the highest they climb and I'm satisfied that I can see trouble if, and when it might occur.

I know that the actual reading on the gauge means little; only its movement into uncharted territory might mean trouble.

 

What do you use to measure the temp?

 

I have a Fluke 561 IR thermo gun that I have tested against more expensive instruments.

Sadly, it is of chinese origin and that grinds me; but I do trust it.

I like to think that a Fluke instrument is built to higher standards than cheap Harbor freight goods, but I'm probably just kidding myself.

I really try not to purchase any goods that do not come from countries that have a high standard of living for workers.

 

The Fluke's that fail get sent to harbor freight...

Kidding of course.. The last time a saw a fluke teardown it atleast had protection devices in place.

 

Took a look at the Fluke today. Looks very nice.

 

When I run the truck without the thermostat it barely gets warm - as expected.

As soon as I put in a thermostat - 190 or 180 - it gets hot.
This means the thermostat isn't working...

 

Yep, but I've tried a total of 3 thermostats. All new and from different manufacturers. I've also tested each one and they all open.

This whole thing has me baffled.

 

Eventually you will become reconciled to the fact that your truck is not actually running too hot.

 

So the thermostat is in the right way around? Not sure if this could be something, but I'm out of ideas In reality I think dudes are right, your gauge is off. Possibly you have GND issue or something? I have had my RPMs read incorrectly - but stable, have had jumping needles and I think at one time my temp gauge was always a bit above horizontal.

 

any of them an OEM one?

 

Which temp sensor did you change?

Did you clean up the housing in goes in?

Ten degrees over the thermostat temp is in the ball park if it's consistent, does it stay around 190 with the 180 thermostat? If it still wants to run at 200 then it might be an issue.

Also consider your thermometer might not be very accurate.

 

No, I have not been able to get my hands on an OEM.

 

the coolant temperature sensor .

I get that the stock gauge probably isn't accurate. I'm going to find a better way to take the trucks temp. The IR gun I used yesterday (a SnapOn) showed it was a lot hotter (head was 200+ in spots) vs when the thermostat was out.

Does the heather core come into play with any of this with regards to coolant flow? I wouldn't think so but again this thing is odd to me a others that have looked at this.