MilesOrbell

Just bought my first 928, an S4 1989 auto, Euro.

The coolant has oil in it due to an internal oil cooler leak into the radiator.

Any tips on best way to flush it out completely ?

Can I run a strong detergent mix or will that damage waterpump seals etc ?

MikeN

Congrats on the purchase.

1st thing to do is remove the two block plugs on each side of the engine......small screw in plugs that will drain coolant out of the engine block. With these plugs removed flush some clean water thru the block, then replace the plugs.

Had the same problem on a previous '89. Ran a couple of tablespoons of dish washing detergent (NOT DISH SOAP......dish detergent used in dish washing machines) and plain water thru the system, then drained (including block again), flushed with clean water again and again. Really cleaned the reservoir and then filled with coolant and water mixture. System came out very clean without a drop of oil. Use at your own risk, but it worked very well for me and came from a trusted 928 mechanic of all places.

Garth S

Double check the integrity of both rad coolers if you are in a 'repair' rather than 'replace' mode for the rad - and assure that it was not the trans cooler that was leaking; If the latter was possible, a complete trans drain is in order ASAP, as will be done on the engine oil ( coolant remains pressurized after engine shutdown, so can migrate in reverse to operating conditions).
Consider a wrap of pipefitters teflon tape on the block drains on reinstall - after removing them, that tip will be more apparent .... good luck with the new shark!

DoubleNutz

Did my collant flush before I left to Venezuela. I used Dex-Cool and RedLine Water Wetter- Strange but my 928 is running hotter than before when I was running the green stuff and mostly water!

Garth S

Strange ..... hotter by the mickey mouse gauge? .. or by an actual squeeze of the hoses, face near the block reality check? Nothing can beat an infrared gun to be sure, but my tool kit is lacking ...
I would be confused too, for there is no good reason to suspect a loss of heat exchange efficiency with a coolant flush - unless the flush stirred some crap out of hiding and casued a restriction in the rad core flow. There are the usual checks for fan operation and the variable flap contraption ( if present on your car); however, the heat exchange efficiency of any coolant mix should not be noticibly different: pure water is the best, but is little degraded by the essential antifreeze mix.

DoubleNutz

I am at that point Garth where I am about to drain all the coolant and put in just water (which incidentally my car seemed to run cooler on when my mixture of the green stuff was less that 10% and 90% water).

Garth S

Not a bad idea for a trial: save the dexcool mix, for I suspect that is not a problem. Pure water is excellent .... except for the issue of corrosion! Living in a freeze zone, I never paid too much attention as to how low you can safely go in % antifreeze. Must be a mix chart on the jug .. stay cool ...

Flott Leben

Not much beats water as far as heat transfer capabilities. Antifreeze reduces that capability but it does add rust inhibitors and will prevent freezing, to a point.

DoubleNutz

OK I dumped 2.5 gallons of of my 50/50 Dex-Cool mix (with water wetter) and replaced it with just plain old water... wow ...what a difference in the temp. The temp gauge needle is directly down the center of the guage in the stead of being directly over the 3/4 mark before it runs in the red.

SharkSkin

A gallon of coolant is all you need if you don't live in an area where freezing is a risk. That's about what you have in there now. In my case, that mix works just fine.

dr bob

The coolant includes some essentials like lubricant for the water pump seal, and some pH buffers that help in the long run. Coolant raises the boiling point some, with some help from the pressure cap. The 'Water Wetter' has some pump lube in it, probably plenty if you run two bottles in the large-capacity 928 system.

If you live where there's any chance at all of the engine getting down to freezing, you will need to run some coolant.

If you are straining the heat dissipation capability of the car with coolant, you need to clean the radiator and try again. Just a thought.

DoubleNutz

Bob I actually took an entire day and flushed and cleaned my entire cooling system 4x before replacing my former green coolant with the orange dex-cool stuff. I think I may have had too much coolant. I mixed it 50/50 with water before adding it too my cooling system and one bottle of RedLine Water Wetter.
Today removing the 2.5 gallons of coolant mix and just adding plain ol' water made a huge difference.

The Porsche maintenance manual reccomends a 50/50 mix of water to coolant for the temp environment I live in (PacNW it rarely ever gets down to ice freezing conditions in Portland). Correct me if I am wrong but I suspect that even one gallon of coolant to the capacity of the 928's cooling system would require winter temperatures to fall far below 32degrees for an extended period of time before it would freeze the coolant in the block.

the flyin' scotsman

DNutz.............most coolant containers have the mix ratios printed on them and the ratio is temp dependant. Where we're at with temps below -30C in deeep winter we require 50/50 (antifreeze/water).

When I was racing we had to replace all coolant with straight water ( you think oil is slick on a race track, you should see what antifreeze does) and some of the guys would use water wetter which increased the engine running temps...........perhaps this was your issue.

IcemanG17

Nutz
3/4's to red on the temp gauge for a 50-50 dexcool + water wetter seems quite hot...also since it isn't as hot where you live? How old is the radiator? Does it show any corrosion on the inside? Or maybe you have a "optimisticly hot" gauge?
Brian

Bill51sdr

'89's and later with the digital dash have a different temp gauge and 'normal' for them is just a notch below the 3/4 mark...