[phoenix96]

Hi everyone.

For the last year and a half I've been having some periodic heat problems in my SVX. For some history of the car:

It is a 1992 SVX LS-L, now up to 145,000 miles. It's on the original transmission (a transmission cooler was added sometime prior to 114,000 miles when I acquired the car). The radiator, water pump, steering rack, and timing belt were replaced at 125,000 miles (the radiator was cracked and no longer held pressure, the water pump bearing was showing signs of going out, and the steering rack was leaking). Other than both rear wheel bearings being replaced and the front right CV joint being replaced, that's pretty much the extent of the mechanical work that's been done (beyond normal maintenance). The only performance modification is the ECUTune Stage 1 chip, which was installed in August of this year.

The car drives perfectly most of the time. In normal operation, the needle in my temperature gauge stays just below the halfway point. My A/C compressor is not functional (it doesn't even have a belt on it right now) so it is never run, although a lot of the time I will have the climate control system set to "Vent". I've seen no signs of oil leaks anywhere.

Here's a chronology of the problems I've had:

August 2003: After 4 hours of highway driving in 100 degree weather, I reached a mountainous area and was driving uphill. I decided to stop to get a bite to eat, and as I pulled onto the offramp and slowed down, the needle in the temperature gauge started to rise. I found the nearest parking lot and stopped the car before the needle hit the red. After letting it cool off for half an hour and checking the coolant level (which was fine at that point) I hit the road again. I drove another two hours with no problems (it was evening by this time so it wasn't quite as hot out).

September 2003: Driving hard up a 7% grade in 100 degree weather, the needle in the temperature gauge began to rise. It hit around the 3/4 point (halfway between the thermostat icon and the red) before I slowed down and dropped the RPMs to ~2500, and the temperature began to drop again. It returned to normal once I was over the hill and didn't rise again.

September 2004: Driving up that same 7% grade mentioned above, in similar weather, the needle began to rise again. I kept the RPMs between 2500 and 3000 and made it over the hill.

At this point, I was convinced that the problem was because of a combination of high ambient temperature and heavy load on the engine (going uphill). The next time I had a problem changed that idea though:

November 2004: I got an oil change (at which time my radiator cap was also replaced - I checked the new cap, it is rated at the proper pressure level for the SVX) and immediately afterwards set out on a driving trip. After four hours of highway driving (the weather being in the mid-60s most of the time), I reached a city. After a bit of city traffic, I was stopped at a red light. When the light turned green and I began to accelerate, the needle in the temperature gauge quickly started to rise. I increased my speed up to the speed limit (~35) and the temperature returned to normal again. I had no more problems that day.
The next morning, I did about 20 minutes of city driving and found that I was having a constant heat problem. Every time I started to accelerate from a stop, the temperature would rise. Once I had reached around 30mph, it would return to normal again. I set out for home again, and had no trouble during the four hours of highway driving. About a half mile from my house, going up a very slight incline on a residential street, I had to make a complete stop for some deer crossing the road. When I gave the car some gas to get moving again, the temperature quickly shot up all the way to the red. I pulled off the road and stopped the car as quickly as I could. After about 15 minutes with the hood open (with the engine not running), the temperature had returned to normal and I started the car again. At idle it didn't seem to have any problems, so I accelerated and quickly got back up to 35mph, and thereafter had no troubles.

Since that last incident, I've made several 100 mile round trips with some city driving in between and had no temperature problems.
It has made me very wary of driving the car when I don't have to, however, and I'd really like to get this issue resolved. I've begun to become concerned that it may be a head gasket issue.

If anyone has any insight, I'd be very grateful.

Edit: For a bit more information, I've never lost coolant. I've never seen steam come out from under the hood or anything like that either.