Hey guys, I have a 97 Camry 4 banger that was leaking some oil. I thought it was from the head gasket, come to find out it was the oil sending unit. ANYWAY. After changing out the HG it started to overheat and I can't figure out why for the life of me. I'll try to run down a list of everything I've already done, determined and checked:

1. T-Stat is new

2. Radiator was flushed and seems to flow very well

3. Drivers side fan is hard wired to run when key is on

4. The heater work great and it will also cool down the car when it starts to get hot. This means that it's not plugged right?
4a. Wouldn't this also mean that the coolant is flowing threw it? So the pump is good?

5. I took the rad cap off and put a digital thermometer in it and it ran at 198 when the engine showed hot.
this made me think the temp gauge sending unit was bad so I replaced that... still overheating. After thinking about it (and figuring out that the coolant flows the opposite way I thought) this actually made sense. The coolant is coming out of the engine hot, going past the temp sensor then going into the radiator past the constantly running fan before getting to my thermometer.

6. Now all of this started to happen right after the HG was replaced so now I'm thinking something is clogging a coolant port? I proceeded to flush the system.
I drained all the coolant
Took out the T-stat
Unhooked the bottom radiator hose from the T-Stat housing
Unhooked the Top radiator hose from the radiator

Then I blew the garden hose through the top hose so it started to come out of the T-stat housing.

I figured the majority of the water was probably going through the bypass pipe in the front so I made a circle out of the heater core pipe back into where the bypass hose goes. I know that can not make sense lol. I should have taken a picture I guess. Basically the water comes out of the engine and goes three places, the heater core, the bypass valve and the radiator. I essentially blocked of the bypass and heater core. So now I'm blowing water into the upper radiator hose and it HAS to be going through the engine and it is sure enough coming out the T-Stat housing. I must have put 30 gallons through it. Hooked everything back up the way it should be. Filled it with 50/50 and burped it. STILL overheating! and quick too. It was dead cold after having all that water go through it and it overheated in 5 min.

Sorry this is so long but I figured I'd get the whole back story out there all at once. Any help with be greatly appreciated. Thanks

 

Did you do the HG replacement?

Any other symptoms besides a high temp gauge indication? Is coolant back flowing out the filler port in the radiator?

Was the T-stat in stalled correctly?

Did you leave any rags, etc inside the coolant holes, ports, etc?

Feel the bottom and top hoses. Is one cold, the other hot, both about the same temp?

The fan being constantly on may cause more problems then it solves. The fan is slow speed driving, stop and go, idling not hwy.

Coolant flows into the top of the radiator and out the bottom.

By-passing the bypass and heater core should not be necessary. The T-stat side with the spring has device that is exposed to water inside the engine. As the water heats up the device opens the T-stat allowing water to circulate through the engine.

 

Yes I did it myself and I was sure I got everything out but I'm doubting it now.

No other symptoms at all. The top hose will get really hot if I let it get close to the red line and the bottom one will be warm enough for me to still hold in my hand. Coolant does not bubble, does not come up into the overflow tank and very little will come out of the radiator cap if I leave it off, even when hot. I believe the radiator is cooling very well.

Yes the T-Stat went in the correct way, however I did get an aftermarket one without the jiggle hole. Should I drill a hole in the new one?

I may very well hook the fan back up correctly once I solve the bigger problem here but for now I think it's helping the situation.

I only bypassed the heater core and bypass tube in order to attempt to flush out the head. When I first did the flush I think the majority of the water was going straight through the bypass. Everything is hooked back up correctly now. I never actually had it running like that.

Thank you for your response I really appreciate your help.

 

If the coolant temp is 198F the lower hose should be too hot to hold. Too hot to hold is about 155F.

When engine is hot are upper and lower radiator hoses rock hard or compliant (can squeeze them)?

Did you ever run the engine with the old T-stat in place? You can test the T-stat by heating it in water. Should start to open around 180F and be 3/10 of inch open at 203F. If the old T-stat is good swap it out. Or drill a hole in the new one in the same location as the jiggle pin or hole in the old one. Orient the T-stat with the hole at the top.

 

The temp at the radiator cap was 198 and I could hold the lower hose. Maybe it was still cooling down before it made it down to the hose?

I am able to squeeze both hoses at all times to include when it's running hot.

I did run it with the old T-Stat in there. It was acting exactly the same thing. I also did test the old one in water to see if it opened up and it did. I didn't have the thermometer at that point so I don't know when it opened. I'll test that out and if it's good I'll just throw that one back in there.

I think I'm about ready to take the head off again and check for something being clogged up.

 

How did you flush the radiator, did you use chemicals? If so these can cause the radiator to plug up. If you place a garden hose at full flow into the upper radiator hose port, it should flow out the bottom port without backing up.

Try removing the T-stat which should over cool the engine.

 

I was told that I shouldn't run it without the T-Stat. If I do remove it then what is this going to tell me if
A) it still overheats?
B) it does not overheat?

And no I have not flushed either the radiator or engine with chemicals. I flushed the radiator just the way you suggested and it did flow perfectly with no backup at all.

 

Perhaps the cooling system has a problem.

You stated using the heater helped cool the engine down, the heater is just another radiator.

Removing the T-stat will allow maximum coolant flow and may compensate for other issues with the cooling system.

Removing the head take a lot of work. Best to check out all other possible problems. Suppose it is possible to have put the head gasket on wrong causing the engines internal coolant passages to be blocked. The head could be warped resulting in exhaust gas getting into the coolant and raising the temperature.

 

I realize that it may compensate for some other issue in the cooling system but I want to find and fix that other issue, not just get around it. Tearing the head off is a lot of work but it doesn't bother me to the point that I would rather just work around it. I would much rather have it fixed correctly.
So my point is, I don't see the point in running it without the T-Stat. If it still overheats then there is still a bigger problem. If it stops overheating then it just means that it's able to cool down faster then the problem heats it up. In either case there is still a problem. And I don't think that gets me any closer to solving it.

I'm almost certain that exhaust gas is NOT getting in the coolant. I know this for 2 reasons,
1) the compression is really good
2) and more accurately, I have done the "sniff" test found here:
How To Tell If Your Head Gasket Is Blown - YouTube
This test came up negative.

We've got some bad weather down here in South Florida but I think Im gonna open the head up on Tuesday.

 

Sounds good.

Please post back with findings.