Engine Cooling

Overheating, Results of

Overheating, Results of

I was enjoying a fine summer afternoon on I-95 last week and glanced down at my gauges just in time to see my temp needle go stratospheric and set off the warning light. I immediately got into the right lane, over in the shoulder and coasted to a stop, where I shut the engine off. (It probably was in the red for a total of ten seconds or less.) When I got to a complete shutdown, the overflow valve on the reserve tank was shooting antifreeze on the inside of my hood. I let it cool down, started it up again after all the drama was over, and watched the needle creep back up. Otherwise the car ran fine. It turns out that my water pump failed, but what I would like to know is: what kind of damage can you expect from being in an overheat situation for that long? If the car runs fine at cool temps, can it be assumed that no permanent damage (other than the pump) occured?

Thanks in Advance

You're probably fine. Head gaskets and other hoses/fittings can start seeping after such an occurence, but if it was only 10 secs, you may have reacted soon enough.

Keep a watchful eye on the whole system to see if stresses cause any problems, and check your rad cap too (on the fill reservoir), often the most overlooked seal in the system. Don't forget to do the timing belt (new, not those used ones on EBay) and check the rollers and tensioner after the anti-freeze shower, bearings will probably need to be replaced after that.


Mine ran into the red once for awhile after a hose busted and before I noticed the red light and the pegged in the red needle. It's been running fine ever since with no noticeable detriment.

Dan Shapiro
'82 928 5 speed "S package" Chiffon/Brown
Borla exhaust, Custom radiator

Had a similar problem not too long ago with the GTS. Both cooling fans decided to give up the ghost on a 100+ day in NorCal. Temp needle went sky high and oil pressure briefly went to zero before the car could be shut off. Just to make sure there was no damage, I had an oil analysis run along with new cooling fans, oil change, etc. Everything came back normal. The Mobil 1 even came back within specs. Car still runs great (took it to Thunder Hill and ran it all day on a 100 degree day with no problem, well, except for my driving...).

You're probably ok, but may want to consider an oil analysis just to be sure. It should tell you if there was any engine damage. You also may want to make sure your oil and antifreeze aren't contaminated due to a leaking head gasket.

I'd change the oil just to be safe, timing belt, rollers, etc along with the new water pump as well. I'd heard that electric cooling fan failure on these cars is relatively rare, but my new ones sure are a lot quieter than the old ones and now the temp doesn't get over 1/2, even on the track on a hot day.

Best of luck!!!
Paul M.

Experience 1:
I lost a water pump in my 83S a few years back and overheated similar to your experience (it was a very foggy evening and I did not notice any steam release; only aware of a problem when the red warning light activated).

I replaced the waterpump and all seemed well.... except for months I could smell the slight hint of antifreeze steam after shut down.

After many months I noticed some sepage and crusty build up around one of the head bolts; I clearly had a crack in the head. It turns out (I believe anyway) that when the motor overheats, the alumunium head expands at a faster rate than the steel head bolts/studs. The head then may crack at the washer/head bolt from the expansion pressure. There was no internal leakage and every thing ran fine, but this was unacceptable for me.

I ended up pulling the heads, replacing the cracked one, and doing the full monty valve job.

Experience 2:
My SO was driving my 944 turbo on a very hot summer day (about 100 degrees). The 944 tubo has a plastic ---yes plastic---elbow that comes out of the waterpump and feeds water to the turbo. This plastic elbow split---dumped all the water out while she was driving (some how she did not notice) and only knew something was wrong when the red light came on.

Given my earlier experince with the 928, I pulled the 944 motor and went over it (It is approching 100 K and likely needed a clutch soon so I figured, what the hey, you never really know your car until you can address each piston on a fist-name basis....)

The 944 head was not cracked by the over heat experience, but it was slightly warped and needed to be "decked" when being overhauled. But all will be well after the valve job. I'm glad I pulled the motor.

Owing to beach season, the 944 turbo awaits re-assembly as I write.

Conclusion: Water cooled Porsches do not like to be over-heated. This is not intended to scare you, just inform you of what I know. I hope your experiences are more forgiving.


Not what I was looking to hear. I was hoping someone would pick me up, put me in their lap, and read me a story about the impervious nature of a 928 engine in overheating situations, occasionally patting my head and saying "there, there.." . But since you mention it, I did have the head gaskets checked thoroughly, and no problems were found. Hopefully, a crack would have been noticed during this time. I'll cross my fingers.


928 Tips Home     Greg's Home