I put on some new pulleys last week and in order to do so more easily, I pulled the radiator. I also put on a dp at the same time and haven't replaced the turbo heat shield yet. I was going to cut it to shape and install it tonight.

Anyways. I put in 2 gallons of coolant/water back. Everything seemed to be ok for a few days, but last night I got some mild overheating and it got me worried. The temp gauge went up a bit. Never got over the higher hashmark though. I noticed that the temp would go up and down with how hard I was on the turbo. Cruising with a few psi would cause the needle to creep up a bit, and then off the gas cruising would lower it back to normal. Also idling, the needle was completely normal.

I was thinking that this *might* have something to do with the heat shield being off the turbo, but I didnt think the car would be that finicky with just that missing. The coolant level is perfect in both the overflow tank as well as the tank with the cap. I also used about 30/70 coolant/water.

Any ideas?
-Tom

 

I ran without my heatshield for a couple months. I really couldn't really tell any performance loss, but if you drive, then feel the intercooler, it is waaaayy hotter than it gets with the heat shield on. I'm no expert or anything, but your intercooler can't work nearly as well when it is absorbing all that excess heat from the turbo.

 

another thing to think about for those of you running without your turbo heatshield, the turbo and dp are very close to the passenger side cv boot, and the excess heat can cause the boot to go bad and crack. not only did I reinstall the shield when I installed my dp, but I wrapped the turbo outlet and dp with thermal wrap to insulate that area even further.

i've read that wrapping the dp reduces its effectiveness, that never made any sense to me, so I went through some of my old heat transfer and thermo textbooks from college and never found any evidence to support that theory

and keeping my boot away from heat is more important to me then losing a hp or 2 from wrapping the dp.

just a suggestion for those of you 'going commando' with your turbos.

 

Could it have to do with the mixture? I thought that Subaru recomended a 50/50 mix? Hmm. Just a thought.

 

Well I cooled the car down. I opened the cap and tried squeezing the radiator hose. All that would happen was the level of the coolant would go up. No bubbles. Then I turned the heat on all the way and ran the car for 5-6 mins with the cap open. No bubbles. All that happened was the coolant would rise a bit as the engine got warmer.

Everything was fine about 90% of the way to work and then the needle hopped up to the send hash mark again. As soon as I stopped for a stoplight it went right back to normal.

Any other ideas?
-Tom

 

A few things to do along with stealth wrx's comments...

Fill it up, let it warm up until the thermostat opens, keep the cap off and fill as the level drops, also, start the heater on full hot as there may be air pockets in there as well that might get filled later on and drop the level...

As for the water temp gauge, it's far far from being linear... The needle will stay in the 'ok' zone through a very wide temperature range, if it does get hotter, only a few degrees will send it to the top.. you need to worry if it reaches the "HOT" zone with a double line (it's got a double line on the gauge in my GC8), then you need to figure out what happens.

If you get the needle going up and down when you hammer it, it could be a few other things as well... Air pockets for one... your water temp sensor is in the water pipe between the two heads, if there's air in the system it'll go through there and the gauge will measure the air temp, not the coolant, that is until the air pocket reaches the filler tank.

The other thing to look for is bubbles in your expansion tank. If you drive your car hard and have done some turbo upgrades and you go hot after mushing it, you might be leaking pressure into your cooling system... The best way to tell is if you get a lot of air in your expansion tank to the point where it fills up with coolant and it starts puking out... in that case, you need to either turn down the boost or get a new headgasket!