Well I was running the car hard today and boosted it a few times to 8500 when I noticed my water temperature go up about 3 lines past 1/2. I let it sit for awhile and it ran at that level for a little bit and then my cooling fan came on and regulated the temperature back down. It only does this when I boost it past 8500. It goes a little past the 1/2 way mark. This just doesn't seem normal to me. The car seems to be running just fine, that just caught my attention. Once I get the car moving the temperature will go down.

I will boost it hard, temp goes up, and then I just drive it normal temp goes down. I boost it hard then let the car idle the needle just goes up a little more, then goes back down after the cooling fan comes on.

 

temp increases with boost are 100% normal. yours sounds somewhat excessive though. make sure you have enough fluid in your radiator for starters.
sam

 

my car did that till i put a mugen thermostat and fan switch in
before i put those in my autometer would go to almost 230
now i cruise at 180 and when in boost it goes to 195

 

you running a block gaurd or anything???

Is there any noticable smoking while running or on startup???

Coolant level OK???

Has it always done this???

When your car heats up under stress like boost and then you just drive it normal the temp will drop back down fairly quickly b/c you are running the pump faster and you are getting air through the rad. this is normal.

 

Humm, I'm not sure what your cooling system is capable of but IMO that is not normal. My friends turbo crx does not heat up when boosting, and my DSM sure does not. After boosting, see if their is air bubbling in your overflow tank. This is a sure sign of a blown heagasket. Air from the combustiong chamber enters teh coolant under boost and since air doesn't cool so well, you over heat. Its something I would definatley check.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ebp 99 si &raquo;</TD></TR><TR><TD CLASS="quote">my car did that till i put a mugen thermostat and fan switch in
before i put those in my autometer would go to almost 230
now i cruise at 180 and when in boost it goes to 195</TD></TR></TABLE>

Yeah, the thermostat and switch help a ton. So does the High pressure radiator cap.
You can also run more water than coolant. This will also help. I run 65% water 35% coolant in my car. I don't get over 190 no matter what I am boosting or how hard I drive it. This is even in 90 degree heat.

Now that it is cold, I can barely get 175 to tune my hondata.

 

I had some air in my system. Seems to be just fine now.

 

To do a quick check, just look under your oil cap and see if any milky stuff is under there......

If it were just an air pocket, you would over heat all the time. Even at idle. When you say overheating at boost only, that automatically makes me think of headgasket/dropped sleeve/stretching headbolts. Ive been though tons of overheating issues in the past with my old motors. Not to jinx you or anything.

 

wrong. coolant has a higher boiling point then water. Read the label on the coolant container.