About every 4 months or so (this has happened twice), my car's (1998 3.8 A4 Camaro) temperature gauge goes crazy, up and down like it's overheating. I check the coolant, which gets very low, fill it up, and it's fine for another 4 months. Well, week ago this happened for the second time and I decided to bring it to a shop for checks because my SES light is on now too. It's throwing two codes, both for P0147 (HO2S Heater Circuit Bank 1 Sensor 3 - Post Converter). Well we figured it might be a head gasket, so after getting it tested with a pretty insufficient test, they said yes.

Well I brought it somewhere else and after over 4 hours of testing, they cannot find any leaks anywhere... not the radiator, gaskets... anywhere. Now I'm ****ting bricks because I don't know what's going on. You guys have any suggestions?

 

where are the drips coming from? Have u checked the oil to see if it might be in it?... i dunno

 

any white smoke comming out the tail pipe? Pretty tale tale sign of and intake manifold/head gasket going bad. And what kind of test did the first shop do to determin that the head gaskets are gone? Don't worry I feel for ya I blieve I have either an intake manifold leaking or heads possibly. Tomarrow I"m going to pull all my plugs and do compression test and see whats going on there. I"m also going to replace the plugs if they are fouled out. Whitch I think they are. And I'm also going to do a block test on it and if non of that gives me any further leads I'm going to put a vacume gague and see what the top of the engine is doing. After that I'm all out of ideas so if it comes to that then I'm going to hand if over to the lead tech of my shop and have him tell me whats wrong.

 

Try starting with checking your entire cooling system, from the radiator to the fans to the water pump and so on. More than likely if theres no dripping or the dye crap they run through your motor then its probably when the temp gets to high it kicks it out the overflow. Could be your fans not kicking on, your water pump not performing the way it should or your thermostat going out. Or like your OBDII said, could be in your electrical.

 

There are no apparent external leaks or drips...

 

I had a similiar issue on my 1994 camaro, eventually starting losing coolant faster and faster, I am 95% sure it was the head gasket. I suggest some Bars leak as a temporary solution.

 

I had this same problem. Couldnt find out where it was coming from. It turned out to be the water pump. There is a weep hole that is designed to fail when the pump starts becoming ineffecient and old, and the hole unplugs itself and starts draining coolant when you are stopped. It only will drain it sometimes, and different amounts each time. Water pumps are about $20 to replace and take like 15 minutes to do yourself. You need the water pump and some RTV sealant. Easiest way to tell is to check to see if there is a puddle of coolant (small puddle) right under the water pump in the block area.

 

Like.. on the ground? There's no leaks on the ground. And would a pressure test show that the water pump is faulty?

 

uhhh... Check the timing cover/water pump housing Got mirrors and a pressure tester? Damn, I wish I knew where chesterfield was I'd try to take a look for you.

 

My coolant seems to disappear also and actually got low enough to throw a code one time. I see no leaks also from anywhere or any puddles. Its like it just vaporizes lol. Oil looks fine and no smoke either.

 

Just curious, how can you possibly have no leaks on the ground but your coolant is constantly low?

Look for a puddle in the block, like i said, under the water pump. Also, your timing cover MAY be cracked or something, which is behind the water pump.

I dont know if a pressure test would pick it up.

 

It would. And if it didnt you dont have a leak - lol. Pressure test your coolant system. Trust me

 

I never checked underneath my water pump though, so thats something I'm going to have to look at next time.

 

It may be leaking as you *drive* hence no apparent leak puddles. My water pump had a leak in it, but I don't remember if they said it would leak as you were driving or idling. It got pretty bad eventually and leaked coolant everywhere. And a pressure test should tell you if it is the water pump.