I just drove my car to work and did a full 4th gear pull "120mph" and quick 5th gear pull "140mph". Looked down to check my speed and noticed temp gauge went up to about 3/4. Drove for a few seconds and it did not go down so I turned the heat on and it went down. After it cooled down I turned the heat off and it stayed in the middle for a few seconds then gradually started going back up. Heat on again went down. Turned heat back off and it went back up. pulled into work and sat there for a minute with the heat on and it went down to normal again. Then it started going back up after about 20-30 seconds. Please help me. Car is a tuned stock ls on 12.5psi. A/f are good. There is no signs of any leaking. Checked under the car after I pulled into work. Also went back out and let it run and looked around again with a flashlight. No wet spots on the ground or on the motor that I can see. Did notice the overflow has about an inch more in it then normal. Pulled the cap and checked fluid in the radiator and it was low. I added about 1 full overflow tank worth to get it back up to full. Fan comes on. Upper hose gets really hot and the lower not really any more then warm. Any possible ideas. water pump --- thermostat --- head gasket --- ?
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Do a cold start with the heater off. As it warms up check both coolant hoses for temp (mind you being careful as it gets hot) One hose should be fairly cooler than the other until near the time the fan comes on. If the fan comes on and the hoses are not close to the same feeling(very hot to touch) replace thermostat and recheck.

 

Just let it run for about 10 minutes. both hoses were warm. The upper was a bit warmer then the lower. temp gauge in car never went past normal operating temp but the fan never kicked on. I might not of let it run long enough though.

 

Considering the way you described the symptoms, I would still say t-stat.

 

Yeah I think your right. I just went back out and let it run some more. The upper hose got pretty damn hot and the lower was kind of warm at best. Then fan kicked on and the upper stayed hot but the lower was like luke warm and the temp gauge in the car was still rising at a slow rate up to around 3/4 then I shut it off. My guess is the same as yours. I'll pick up a new one from advance auto in the morning and swap it out. I just hope it's not a head gasket problem.
Motor only has about 95k on it and been boosted/tuned for 1.5 months. None of this happened earlier while driving around just started on the way to work.

 

If it ONLY got hot under load, maybe hg. You have a bad t-stat. Only if your coolant is basically acid, the water pump would be the only other suspect.

 

It gets hot sitting at idle. Water pump is basically new. About 6-8k on it.

 

Bump

 

I just drove it home about 12-15 miles. All normal driving until the last 1/2 mile. I did 2 4th gear pulls back to back. The temp gauge didn't budge but I popped the hood when I pulled in the driveway. Overflow was full and you could clearly tell some came out. Fan kicked on and upper hose was hot and lower was warm. They were firm feeling. the gauge then moved up just slightly after sitting there for a minute or two. Also were my log manifold connects to my turbo was glowing red. "that might be normal I've never popped the hood in the dark after a hard pull"

 

Is this still happening after replacing the t-stat?

 

headgasket/head lift.

 

I just replaced the thermostat and lower rad hose. Also took the oem rad cap from my friends s2k. I took the car out and beat on it. Temp gauge never went up but when I came back the resorvoir was full. Upper and lower hoses both hot. No oil in coolant when I drained it. No coolant on dipstick. No smoking out the exhaust. Wouldn't I be able to tell if the hg was blown. Obvious signs

 

obvious signs are the coolant tank overflowing. you have a blown headgasket but not enough to mix oil and coolant.

 

Gotcha I've never blown one before so I'm in the dark about it. Just was always told that you would know 100%. Clouds of white smoke,coolant smell,oil and coolant mixing,car running badly.

So on to my next question if I'm replacing the head gasket I'm gonna buy arp studs while I'm at it but what head gasket should I get? I figured just an oem replacement would be fine. Anything better out there for a boosted ls.

 

i dont think you are having a hg problem. you replaced the thermostat and the overheating went away. sounds like problem solved to me.

your overflow tank should be full (but not overflowing) when the engine is warm. as the system builds pressure the rad cap opens and allows coolant to escape into the overflow increasing the coolant level. as the engine cools off the coolant gets pulled back into the rad, decreasing the coolant level in the overflow.

 

I've never had an overflow tank fill up until now. Was always filled to the min line and stayed there. Now it's filling up and taking it out of the radiator.
Also if you read my post I drove home last night with no overheating issues and that was with the old thermostat. Thanks for the suggestion though.

 

Did leak down test after work tonight. Cylinder 1 @ tdc and once pressure was applied I could here gurgling in the radiator. So now I'm going to install arp studs and new head gasket. My question is should I just get another oem one or is there something better out there? Also from what I'm finding the head gaskets are different from 90-95 and 96-01. Can anyone please confirm this for me. The only oem I found on ebay was for 90-95. It's from a dealer for $71 shipped. Thanks for all the input everyone.

 

Sorry to hear about the HG letting go man. I am pretty sure the top end gasket sets are different from the pr4 to the p75 (90-95 and 96-01 respectively.) On the hg only, I'm not sure, entirely possible. Maybe someone will chime in. Good luck the car!

 

Bought the head gasket yesterday and ordered arp studs yesterday. Arp stuff came today so now it's on to the fun part lol. Anyone have the sequence for loosing/tightening the head bolts also for the cam caps. Thanks

They have different part numbers from honda. Also different part numbers looking online at advance auto but on the package from advance it says that it replaces the "older" one.
So they are all the same. No differences except part number.