PHIL928

Fred,

I believe this effect was caused by an accumulation of small "overheats". This car had intermittent fans. Either only one, or a very weak pair, or not at all. Turned out to be a ground that was disconnected, making contact intermittently as it freely rubbed against it's correct mounting bolt.

However before Terry was able to fix the intermittent fans, he did change the cap to a 100KPa. This caused a full blown overheat the next day at the RTA because the pressure was not maintained in the system. So the 150KPa cap artificially forced it not to overheat and spill its guts in the past.
Then on further inspection of the cooling system Terry noticed the radiator had a bow in it. But it is quite hard to spot while the radiator is in the car, because the transmission cooler blocks one's view to some extent.

So neither the 150KPa cap, or the radiator gave way. Ironically it was the correct 100KPa cap that caused, or rather, allowed an overheat.

I noticed that the heater valve and the related small hose is new, now I'm not sure if they were replaced because they failed, or for some other reason. I know that the owner has been trying to get the AC colder, so this might have been done in order to try and solve that issue.

FredR

Phil,

It sounds as though something has been going on that should not have. The fans make a difference while idling but not at speed. If you cannot get the heat out the temperature goes up and so to does the pressure until something gives. First thing you know when the water pump fails is the temp needle rises suddenly and you quickly get an alarm. Ask me how I know?

All part of 928 ownership I am afraid. This is why I recommend going through the 30 point hit list and buy some security for 5 plus years otherwise you end up "stopping and starting".

Hope you get ti fixed quickly- sounds as though you need a radiator like Mark's?

Regards

Fred

FredR

By the way please pass on my commiserations to the owner. Doubtless you will get him well sorted out.

Regards

Fred

depami

Often the cause of this is a bad head gasket leaking compression into the cooling.

WallyP

50/50 mix @ 15 psig boils at about 265 deg F....

The passenger side tank on the GT blew out the other day, and yep, it was pretty spectacular. Lots of steam, and the engine quit instantly (very wet distributors!). Luckily, I was at the end of my driveway, so I eventually nursed it the fifty feet or so needed to get over the little rise so I could coast to its parking slot. Jeannie shipped me a new tank and gasket, and that job is now on the priority list.

FredR

Wally,

just goes to show - the 928 Gods do not spare immortals from grief- but they make it a little easlier on them by going pop on the door step!

Now when my S4 drive shaft snapped back in 1999 it went 60km from anywhere. At least when I managed to arc my battery lid shut that happened close to home as did the 3 punctures I have suffered and when I wrote off my late S4 -grrrh!

Regards

Fred

GregBBRD

If I've learned anything, over the years of working exclusively on Porsches, it's that the engineers, at the factory, generally have pretty good reasons for using the pieces that they do.....and you want to think carefully before you jump in and make changes.

There are certainly exceptions....sometimes the German engineers couldn't find the forest because of the trees....but generally, they are right on.

However, since the engineers had both Behr caps (1.0 bar and 1.5 bar) at their disposal (and they used the 1.5 bar cap on the 944 series) they probably had a damn good reason to use the 1.0 bar cap on the 928.

Besides that, the 928 series has an extremely efficient cooling system and rarely overheats with all the stock pieces. If a 928 boils over....there is something wrong.

IcemanG17

this is exactly what I expected.....the corrosion is horrible....this type of damage also effects the head studs, which are iron and go through the cooling jackets.....I have seen them SO bad they snap from rust...which 1st shows its self as a coolant leak outboard on the head gasket....but can end up corroding the whole engine.....to the point where it effectively becomes a "battery" and starts eating aluminum, typically in the head..... Often this is found in engines pulled from parts cars that have sat for a VERY long time...

The $300 used engine in the Estate suffered from this.....to the point that it ate through part of the heads...I guess it figured out it needed 2 cooling channels between cylinder 2-3???