every once and a while sitting still it would get hot, the fan would come on but it would still get hot. so I figured the thermo was getting stuck. So I changed it and added more fluid...everything was fine for about 20 minutes. I'm at a light and notice it getting hot, then it goes back down. So I drive home, its no problem, in boost theres no problem.

I get home and it gets hot again, fan is on...its just getting hotter and hotter. so I turn the heat on, it goes down but comes back up....its going up and down up and down, only when I'm stopped. Fan is definately working...and I have a big fan too.

So what's left? the headgasket isn't blown, no white smoke, plus it would be hot all the time if the head gasket was blown, not just sitting still.

May there be an air pocket in the system? I didn't really bleed it after I refilled it...ran out of time I changed all the crap in a parking lot cause it happened while driving far from home...so I got back home and its late so I said screw it. but I'm guessing it needs another flushing or theres an air pocket?

 

A bad T stat usually makes it so the fans don't come on. The fact that yours do tells me that's fine. It could be that the cooling system is losing pressure some where. Usually from the cap. Have you tried having the cap and cooling system pressure tested? I've also heard that boosted B18's need a better than stock radiator, so don't rule that out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pushinlsteg &raquo;</TD></TR><TR><TD CLASS="quote">
May there be an air pocket in the system? I didn't really bleed it after I refilled it...ran out of time I changed all the crap in a parking lot cause it happened while driving far from home...so I got back home and its late so I said screw it. but I'm guessing it needs another flushing or theres an air pocket?</TD></TR></TABLE>
yeah... u should do that, let ur car run idle for like 5-10 minutes w/ the radiator cap off.

 

A small leak in the system could cause your syptoms, and refilling without bleeding can cause air pockets in the head that could cause your fan switch to not ground your fan circuit. A small leak could be in one of the little hoses under your intake manifold or somewhere else that gradually cause you to loose coolant until you begin to overheat. I had a similar situation and it was one of the little hoses under my IM. Good luck finding the problem.

 

Did you replaced the radiator cap when you did the thermostat?, could be that the cap is bad and you are loosing pressure. Pressure is what helps the water pump make a good coolant flow.

 

quick way to tell if its the cap... listen to the car after it gets crazy hot. once it reaches its peak temp. (maybe around 200*) cut the engine off and see if you hear boiling. if you do, the cap is crap . you raise the boiling temp. 3 degrees for every 1psi you put on the coolant. 18psi cap = 54 degrees. good random check i found works quite often another thing you may want to check is whether or not you have the right thermostat.. too quick of a flow or too much flow through the system will cause overcooling... meaning the coolant isnt in the block and head long enough to make any heat transfer happen. meaning coolant stays cool, engine gets hot as hell.... it also may cause the fluctuating in temps. you were talking about

 

I bled the system and everything. Its been good for a few days now...
Last night after stoppin at a conveinence store, I turned the key on, but didnt start it yet. the fan was on and the temp gauge was less than half way up.

I start the car the temp gauge shoots over towards the red, then flies back down, then continues to go back up, so I turn the car off and turn the key back to the ON position, the gauge is back at a normal temp, fan finally goes off.

I start it up it jumps up again, I start driving and it goes back down, I get home and leave the car running, it never once gets hot. I look under the hood and my over-flow tank is completely full... I had it half full, and now it was completely full and looked like a little had came out.

While at the store I didn't hear any boiling like you usually do on a over-heated car. So..... you think the gauge could be bad.

I'm going to get a real water temp gauge with actual numbers on it so I can see whats going on cause this is gettin annoying.

Could the water-pump be bad? I dont think it would...
still no signs of white smoke-IE headgasket.