Oil and Coolant Problem

Hi all,

I purchased a 928 S4 1989 US spec which had been in a car museum for about six years. At the time of purchase the Museum technicians changed the oil and did some basic checks to ensure it was road worthy. The car was imported into the UK. The Importers have started and moved the car to a testing bay, without any problems, however when they went for a drive to prepare for an emissions test, the car temperature started to rise and the temp warning light flickered on and then off. The tester immediately stopped the car and this was brought back on a truck. When they checked the radiator, the cap was full of gunk and also checking the oil dip stick this was the same. Given the long lay-off without bringing the car up to temperature, can anyone diagnose what the possible cause maybe. I am hoping it is not a failed cylinder head.

The pictures show the Oil Filler with Cap, Oil Dipstick, Top of the Expansion Bottle for the Rad, and the Expansion Bottle Cap.

 

Congratulations on ownership of an '89.  They - in my opinion are one of the best model years for the 928. 

The bad news is - the car most likely has failed head gaskets.   Hopefully the head surfaces themselves are not eroded.  The engine should not be run until the cause of oil leaking into the coolant (and vice versa) has been identified and corrected.    Go to Rennlist.com and search the 928 Forum for 'head gasket failure'.   A lot of information there.

Good luck and keep in touch both here and on Rennlist regarding the diagnosis and plan for correction.

Gary

Thanks, will do more research on Rennlist. I have to do the cam belt/waterpump/rollers, so probably best for engine out. Just out of interest, when the importers took the car for a test drive, before it started to overheat, it was noted that the engine lacked power and they thought it was in limp mode.

Failure to use the correct coolant (anti-freeze), or to change it every 2 years is a common cause of the failure.  And, of course the OE gasket would now be ~25 years old.   Even if they aren't the problem, they should be changed if you are planning on driving the car for a few years.   

Yes, engine out for all you plan to do is an excellent idea!!

Gary

The "limp mode" of the 928 is limited. The two major causes are

1. exhaust temperature sensor imbalance which may be caused by one of the two independent spark system failing, thus the engine is running only on four cylinders. A safety system in MY 1989 and newer 928s shuts off the fuel injection to the associated cylinders of that failed ignition system to reduce the potential of car fire due to raw fuel induced into the hot catalytic converter.

2. the mass airflow sensor is out of range causing the LH Fuel Injection module to go into a fault mode.

So, in addition to the potential head gasket problem, there may be other problems to resolve.

Hi All,

By way of an update. Managed to get the car into a 928 specialist. They suspect the heat exchanger that is built into the radiator has failed. Given the long layoff for the car, this is probably the cause.Oil under pressure when the car is running will be pumped into the cooling system and then the coolant under pressure will be forced back into the oil system when the car is turned off.He advised that Head gasket failure does not normally cause oil/water mixing as per other vehicles.

At the moment, they are working on replacing the oil, changing the radiator and adding new coolant. I may be lucky, you never know.

Gerry
Porsche 928 S4 1989