Running warm - multiple bad OEM t-stats??

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MrWrench
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Running warm - multiple bad OEM t-stats??

Post by MrWrench »

Hey all, battling a strange issue. Current outside temps are 30-45 degrees Fahrenheit.
Spud, my 85 has been running a little bit warm lately. It'll be near the top end of the center of the temp gauge.

Initially I was using a Toyota thermostat I purchased new on eBay. I used the dealerships p# and bought one on eBay to save some $$$. It worked great for several years but lately seemingly has failed because the lower coolant hose will be stone cold. The upper hose will start bulging out from running warm.

I coughed up the $$$ and purchased an OEM one from Toyota themselves. Installed it a few days ago (with the little hole facing upwards) and found the lower hose was still stone cold.
The rad cap is cold to the touch. So I decided to change the rad cap with another Stant. No change again. New cap is cold to the touch when running.
I decided to purchase a Aisin one off Rockauto and installed that today. Lo and behold? Lower hose is still stone cold and the car is running warm.
Before returning the OEM one, I did drop it in some boiling water and it opened up... Which means something is funny going on with my car.
I'm at a loss as to what's next. The radiator is 3 years old, the water pump is a little over 4 years old. (I installed a new one after the engine and head we're rebuilt) The hoses are fairly new. There's no leaks in the system... What am I missing? Why are none of my thermostats opening up?
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NWMO
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Re: Running warm - multiple bad OEM t-stats??

Post by NWMO »

Hey Luke,

You’re better wrenching than me, but I would suspect low coolant levels or an air pocket. If nothing else, pull the thermostat and see how it does. Not ideal, but might help trouble shoot.

I noticed my gauge runs “hotter” when I’m running the heat/blower, but it’s an electric issue I suspect.

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MrWrench
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Re: Running warm - multiple bad OEM t-stats??

Post by MrWrench »

I am positive it's bled of air bubbles. I ran it on an incline with a coolant funnel and squeezed the coolant hoses while it was running.

I have noticed the same thing. It runs a bit hotter with the heat on. My other T4s haven't done this. But I am still troubled by the fact that my lower coolant hose is stone cold, even after a 20 minute drive on the interstate. :|
1984 SR5. winter driver rescue
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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Nordical25
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Re: Running warm - multiple bad OEM t-stats??

Post by Nordical25 »

Have you checked that you have water on engine coolant reservoir? My Tercel was leaking from heater core and it emptied the engine coolant reservoir first and then radiator. When it got to radiator, I noticed that already from temp gauge.

It is connected to radiator by a small rubber hose. There are correct levels stamped on reservoir. Could it be that? Other more unlikely reasons might be ineffective spare part water pump, worn out radiator or failing head gasket. But I suspect reservoir if engine temperature gets back to correct level again.
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Re: Running warm - multiple bad OEM t-stats??

Post by Nordical25 »

There is a way also to verify condition of your thermostat. You put it in a pot full of water and start cooking water + thermostat. Then you inspect thermostat and measure temperature of the water when it opens. If the thermostat won't open before the water boils, you have a thermostat problem. It should be ok if it opens in correct temperature somewhere between 82-90 Celsius (180F-194F).
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Re: Running warm - multiple bad OEM t-stats??

Post by MrWrench »

The coolant overflow bottle is full. I initially looked at that when I first started noticing it was running warm. I was driving through a massive snowstorm and it was running hot.


I did test the most recent thermostat in water. I dropped it in just before it was boiling and it opened up. I didn't check the temp but it was right around where it should have been. I can reverify this and make sure the temp is correct, but I'm 3 t-stats into this and there's been zero changes.

I am hoping it isn't the radiator but a Civic radiator will be in order if that is the case.
1984 SR5. winter driver rescue
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Re: Running warm - multiple bad OEM t-stats??

Post by SirFoxx »

your tstat installed in the right direction? im not sure if its possible to do on the tercels...but on my mercedes, as well as a friends mighty max, we were having the same issue. running warm, bottom hose was ice cold. turns out in both our cases the PO had installed the tstat backwards.

as a last resort, you could remove the tstat, run CLR through the engine for 1-2 hours, drain, rinse several times, and put new coolant in it. or, if that scares you, do water + citric acid. mercedes sells their own branded citric acid for such events lol. if you could park your wagon inside where you work, id do that and let it sit to let the acid work, and to prevent the water from freezing, then change it before leaving your work.
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Re: Running warm - multiple bad OEM t-stats??

Post by Nordical25 »

In that case it sounds to me that your cooling circuit is clogged somehow or has low coolant flow.

You could test that water flows freely through radiator, hoses and that your water pump pumps water. Your thermostat can open also very little, which has same end result. So you could indeed double verify that thermostat opens fully too in right temperature.

Radiator cap should be anyway hot if radiator just cannot cool enough. So I would test that whole cooling cirquit has free water flow and that water pump works. I had once partially failed water pump in Kadett C. It was nearly overheating only in low speeds, because air flow cooled engine in higher speeds.

Small coolant leak could also generate issues to cooling system but if your car does not lose coolant, this may not be the case neither.
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Re: Running warm - multiple bad OEM t-stats??

Post by dlb »

Here are a few old threads on using vinegar and water hammer-style tools to breathe some new life into old radiators:

viewtopic.php?p=105983

viewtopic.php?t=9589

I have the Viper flush tool and it has worked wonders for me over in the past. I will actually be using it on my latest al25 in the near future because it is also having some running hot issues.
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Re: Running warm - multiple bad OEM t-stats??

Post by MrWrench »

SirFoxx wrote: Mon Dec 05, 2022 5:46 am your tstat installed in the right direction?
It is in the correct direction. They (thankfully) are not able to be installed backwards. The engine was rebuilt a few years ago and the block was hot tanked and very thoroughly rinsed out. The pipe on the cylinder head was cleaned out well and the head was washed and machined by a local machine shop.
I wouldn't imagine I'd have much of anything for builds up in the block/head. I have only used distilled water if I bought coolant that wasn't pre-mixed.


I just checked my rockauto purchase history and the water pump I ordered back in early 2019 before the engine rebuild was an ACDelco brand. It has over 40,000 on it so it's possible it's getting weak.
One thing I have noticed is that the car is running warmer as I'm driving it. So maybe that checks out with a weak/failing waterpump and low coolant flow like you mentioned Nordical25?
I am positive I'm not losing coolant anywhere. The last few times when I was finishing up the thermostat replacement I would pump my radiator pressure tester up to 15 PSI and there was zero leaks after that and a long test drive.

I think I might start with a new waterpump this weekend and then do a CLR flush if that doesn't fix the problem. I did test the waterpump belt tension and that was plenty tight..

I appreciate all your responses!
1984 SR5. winter driver rescue
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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MrWrench
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Re: Running warm - multiple bad OEM t-stats??

Post by MrWrench »

dlb wrote: Mon Dec 05, 2022 8:43 am Here are a few old threads on using vinegar and water hammer-style tools to breathe some new life into old radiators:

viewtopic.php?p=105983

viewtopic.php?t=9589

I have the Viper flush tool and it has worked wonders for me over in the past. I will actually be using it on my latest al25 in the near future because it is also having some running hot issues.
Looking at that second link. It seems a lot of people have made some great progress with that tool.
Is this something similar to it?
Screenshot_20221205-203307.png
If so, that seems like a worthwhile investment to clean my heater core as well. The heat in this car is fairly marginal. I used some CLR and vinegar in years past and brought the temps up to 140 but I have another tercel that absolutely cooks me alive in the winter.

Lisle also makes one with a port for an air compressor to pulsate the air.
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1984 SR5. winter driver rescue
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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Re: Running warm - multiple bad OEM t-stats??

Post by dlb »

The viper and gates ones hook up to compressed air, which I like because it rapidly pulses/hammers the system. But the one you posted the image of has lots of good reviews so it can't be that bad.

The viper one I have has a large rubber tip that seals against all sizes of outlets. I like that more than the long stepped nozzle on the one in the image you posted. But again, probably not a big deal if it works well for so many people.
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Re: Running warm - multiple bad OEM t-stats??

Post by Nordical25 »

The previous heater core cleanup threads are really good tip from you dlb. My Tercel is not warm on winter so I need to swap heater core. I could try also one of these methods to clean my old core. I could start with vinegar tip after swapping heater core and getting old "cold" core into my hands.
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Re: Running warm - multiple bad OEM t-stats??

Post by dlb »

Nordical25 wrote: Mon Dec 05, 2022 11:48 pm The previous heater core cleanup threads are really good tip from you dlb. My Tercel is not warm on winter so I need to swap heater core. I could try also one of these methods to clean my old core. I could start with vinegar tip after swapping heater core and getting old "cold" core into my hands.
I tried various vinegar and chemical flushes but didn't notice much, if any, improvement with any of them. The viper tool was game-changing though. One car I had went from zero heat to incredible heat. I'm a big fan of the tool.
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Re: Running warm - multiple bad OEM t-stats??

Post by Nordical25 »

dlb wrote: Tue Dec 06, 2022 9:54 am
Nordical25 wrote: Mon Dec 05, 2022 11:48 pm The previous heater core cleanup threads are really good tip from you dlb. My Tercel is not warm on winter so I need to swap heater core. I could try also one of these methods to clean my old core. I could start with vinegar tip after swapping heater core and getting old "cold" core into my hands.
I tried various vinegar and chemical flushes but didn't notice much, if any, improvement with any of them. The viper tool was game-changing though. One car I had went from zero heat to incredible heat. I'm a big fan of the tool.
Ok, then I need to look after such a tool during summer months. Is viper tool still available? Gates one was around 1000€ so that one definitely is not the cheapest alternative. Or maybe Amazon flush tool if someone verifies it working flawlessly.
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