I havent posted on this site in years, but I have a 2004 blk supercharged ss with only 72,000 miles on it. I bought it in 07 with only 13,000 miles on it. I put high flow cats, deleted the resonator, ubend delete and put new mufflers on it back in august of 07. I have a check engine light on because i never got the car tuned, but the car has been running great. I get oil changes every 3,000 miles and only put 93 in the car so I take very good care of it.

A couple of weeks ago while it was still very cold here in Cleveland I noticed that my heat was not working. Instead of heat it was cold air blowing out the vents and my engine gauge would jump all the way to 260 and I would get "HOT COOLANT TEMP" in my message center. I checked it and there was no coolant in there. I went to the part store and bought some DEX COOL and my car started to have heat again.

I checked for any leaks and there is no leaking on to the ground. I took it to my mechanic and he pressure tested it and he said there was no leaks when he pressure tested it. I am low on coolant again and will take my car to his engine guy tomorrow. I know its going somewhere, and I know its not supposed to just evaporate, so what could the problem be? It also just stopped on me in the middle of the road today and everything just locked up, but it started right back up.

I know some of u are very knowledgeable here so I thought I would ask for some general answers or ideas to what may be going on. I am hoping that my engine is not about to blow or something like that so hopefully someone here can chime in for me.

 

I'm by far no expert, but I'm wondering if it's the same old issues with the catalytic converter going bad on you, causing the engine to run hot and making it just die on you because of a bad cat and also making it overheat??????? I wish I could be more helpful on this, hopefully you'll get better answers from the rest of the forum, goodluck!

 

Ok, none of the parts on my car is not stainless steel. The parts are cheap and I have to change them out every other year. U might be right about my catalytic converter. Also something under my car has been rattling lately, but I dont know what it is. When I take my car to the shop tomorrow, I will have them look under there, and that may be the problem because I think it has been about 2 years since the last time I changed the catalytic converter. Thanks

 

I'm a little concerned about the coolant loss. A bad cat can explain hot temps and such, but if the coolant system is working right, it should not be going empty to easily (it's a closed system, tough for it to evaporate anywhere).

Since the mechanic pressure tested it, the coolant system is sealed outside the car.... Check your oil (via the dip stick and removing the oil cap and looking in the valve cover and underside of the cap). See if the oil looks milky AND if it's way past full. I'm wondering if you have a bad head gasket letting coolant into the oil.... Or, you could have a failing lower intake gasket allowing it in as well...

 

Just talked to my mechanic & I have BLOWN HEAD GASKETS!!!!!!!!!!!!!!!!!

 

That's what I was afraid was going on. I've never done head gaskets on any 3800, but given how far I've had my L36 ripped apart, going to the heads does not seem like it would be that much of a chore.
I've done 3100/3400's and those are fairly easy.

How ever you go about having this done (DIY or a mechanic), buy the Fel-Pro aluminum lower intake gaskets to use during re-assembly.

My guess as a DIY, it would be a full 1-2 day project (cramming it in one day for a first timer, in my opinion from what I've seen of the job, is rough, but possible).