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Hey all. I have a 97 EX (D16y8) that warms up quite a bit while stopped. About 3/4 of the temp gauge. Now I have tested the fan, motor, relay and all are working. I replaced the radiator about a year ago and just replaced the rad. cap. Now ive noticed that my coolant in the overflow boils, so i replaced the rad cap. Still "overheats". So what else could it be? Coolant is also just over a year old. Thanks in advance guys!!

 
Rep Power: 188

You've probably checked this but the thermostat?

Maybe air bubbles can cause this, not sure.

 
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Ok, I did test the T-stat. It does open and close. It appears to open around 180 degrees. Does that sound about right, because on the T-stat its self it says 78 degrees Celsius which is about 172 degrees F. Also oil is not milky, I just checked it this morning. I guess maybe the only other cause could be air in the cooling system??

 
Rep Power: 518

180 is fine.


That doesn't rule out anything.
And how would 'air' get in there?

 
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check for a bad head gasket

 
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Headgasket is all good. The coolant in my overflow boils after a drive. So i think I am loosing pressure somewhere. Radiator cap was replaced 2 weeks ago. So loose hose maybe?

 
Rep Power: 518

What did you do to test this?

 
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No test. I heard it so i opened te hood and saw coolant boiling in the overflow

 
Rep Power: 518

So you are just assuming the head gasket is good then?

 
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It was replaced a year ago. Plus oil isnt milky or anything. My bad thought you were talking about overflow

 
Rep Power: 518

That doesn't mean it's good.
Not a typical symptom for that engine.

A head gasket can fail in any of a dozen different ways.


What I think you are seeing in the overflow is not boiling.
There isn't enough heat in the reservoir to boil water.

You are seeing the venting of excess pressure from the radiator into the reservoir. The issue is that it is not venting liquid, but "air". How low is the radiator?

It could be the result of boiling within the pressurized cooling system, or you might be seeing the venting of excess pressure caused by combustion leakage from a head gasket leak.

That's 2 possibilities.
You have to figure out what it really is, and why.

HTH

 
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Sounds almost exactly like what happened to my car when I had a bad headgasket. Try taking the rad cap off while its cold, then start the car. Give it some gas and see if it shoots coolant out of the radiator. If it does then it probably a crack in the gasket allowing combustion gasses into the coolant.

 
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Thanks, I will give that a shot