3.8 overheating randomly

[jwhisl]

Hey guys I really need some help here. My 95 3.8 has been giving me cooling issues off and on for the last 2 years. The radiator was new when I bought it and I have since replaced the water pump, thermostat, and radiator cap. I'll be driving along just fine with the temp gauge usually pointing at R or M and all of a sudden it will go just past L without making it to the red line on the right. Within 15 to 30 seconds it will go back to M. On the highway it will run fine at 70-80mph even if I have to drive 50 miles but as soon as I get off the highway the temp spikes. Usually I will have to pull over and let it cool off for 10 or 15 minutes and its fine after that. Last night I was on my way home on the highway and the temp gauge went all the way to red. I immediately pulled over and found antifreeze all over my battery, engine, fan, belt, and all over the hood. The over flow jug had filled up completely and had been spewing from the cap. I didn't try to open the radiator because I could hear it boiling and I had topped it off that morning. After 20 minutes of sitting on the side of the road I checked again and the overflow jug was empty. Started up the car and drove the last 8 miles home without any issues.......WTF!?

Please help me figure this out before I wind up damaging this engine or blow a gasket. BTW there was also new silicone around the lower intake when I got it so someone had at least replaced the intake gaskets.

 

[jwhisl]

Anybody? I really need some help here. I did a flush on the radiator 2 weeks ago

 

[GT Rob]

Is there air in the radiator and check the fan it might seem like its working but it might not pulling enough air . My car did the same thing I change everything and even thought I blow a head gasket and it truned out to be my fan. Good luck

 

[copmagnet]

your car doesn't use the fan when your over 25MPH because it has enough airflow over the radiator. when you flushed the coolant did you burp the system to get the air bubbles out?

 

[KillNThrill24]

It sounds like you have air in the system and it's hitting an air pocket at the temp sensor which is why it's sending the temp gauge sky rocketing. Just my guess... 1st make sure you have enough coolant. Then run it with the coolant tank cap off, IIRC that will remove any air in the system. And that should fix your problem. Fortunately coolant systems are fairly easy to diagnose for the most part because there aren't many things it could be lol. And being you replaced the thermostat and radiator that rules them out, and it's working most of the time so the water pump is working.. Which leads me to believe an air pocket. OR your thermostat is opening really late, which could be an issue even with a new thermostat. Those are my 2 guesses

EDIT: I suppose the fan could be an issue too. Not kicking on when it's supposed to. But that would have to be in line with the temp sens I'd have to think. Start with the rad cap. Get the air, if any, out of it and move on from there.

 

[jwhisl]

Ok I will try burping it... That at least gives me a place to start. I'm also going to replace the rad cap and thermostat again just in case they are failing. Thanks guys it does sound like there is air in the system

 

[copmagnet]

IIRC you have to pump the return hose a couple times too. when I burped my 96 after my head swap thats what the guide said to do anyways..

 

[jwhisl]

Thanks everyone! That seems to have helped but now I need to look into the fan and some other non related issues. Alot of air came up out of the radiator when I burped it

 

[jwhisl]

Just wanted to let everyone know that all the bubbles I was getting in my coolant were exhaust bubbles. Apparently when I overheated on the highway I blew a headgasket

 

[full force]

The head gasket was the issue before, I gurantee it, 3.8 is known for it, make sure you mill heads and USE NEW BOLTS.... the fan don't matter once your rolling as stated, aside from that its almost always a head gasket issue in a 3.8....

 

[jwhisl]

Yeah I was quoted 750 ish to fix it. Then a guy offered me a 4.6 for 500 so I think im going that route

 

[full force]

Fix it yourself.....

a 4.6 swap gonna cost way more by the one you buy all parts needed gonna have 2000 plus into it exhaust.... Trans....wiring completed and all that...

 

[jwhisl]

Mechanic tore into the v6... 3 burnt valves and a cracked head.... no happy but it is what it is

 

[daltonduree]

alright buddy. i might be a little late. but test the resistance of your coolant temp sensor. your pump can work all it wants if you cant cool off the radiator if your fan doesnt know to turn on.

 

[MustangChris]

Mechanic tore into the v6... 3 burnt valves and a cracked head.... no happy but it is what it is

sorry to hear that man. ouch

 

[daltonduree]

think of it this way... CONGRATS ON THE GT SWAP!

 

[jwhisl]

think of it this way... CONGRATS ON THE GT SWAP!

I've given up on the gt swap for now. The guy raised the price on the engine when he found out I needed the trans too. I found a set of reman heads for $150 a piece plus core so fixing the car is still a cheaper way out