worf928

I've played with both 928 and 968 head gaskets. Other than the obvious differences they appear to be of exactly the same construction. At least for new ones out of the V-R 'bag.'

Is it reasonable to assume that the materials used by V-R haven't changed since the 80s? I don't know.

I'll take a magnet to the old ones and some new ones in the morrow.

worf928

So some sort of 'localized' 'defect' with the gasket?

928 GT R

Another possibility...

Whenever I hear museum docents discuss long term preservation of historical documents or artwork. I hear the term "acid free paper" being tossed about as essential to long term storage.

If there is paper in gaskets, could the paper in the gasket itself be the source of the acid that seems to "locally" eat the mating surfaces and simultaneously, not present itself throughout the entire cooling system?

Could the paper that gasket makers use have inconsistent acid levels? Do the gasket manufacturers set control levels for acidity in the paper they use?

Does it take sense to check the local PH pf the whetted surfaces of the gaskets upon removal with a focus on where corrosion is present?

I'm not in the business of repairing or rebuilding 928 engines and do not have access to multiple sets of heads as they are being removed. But if I did, I would start placing PH test strips directly onto the freshly opened and still wet mating surfaces of head gaskets to find out if there are more acidic conditions in areas of localized corrosion.

Keeping in mind that correlation is not necessarily causation, this testing would at a minimum create another data point in our quest to figure out how to protect our engines.

FredR

Jim,

It was random chance that you spotted this issue given you pulled the heads for other reasons. What is minor over three years can only be more serious over 10 plus years and clearly you do not know if corrosion was initiated from day one the coolant was filled or if it started the day before you pulled the heads..

From my perspective your reasoning that it is the coolant is a false logic given I can see no logical connection to tie it down to the G05 brew that could easily be the innocent victim here. Until such time as we can clearly understand what exactly was going on, it would be folly to eliminate any possibility 100%. Every engine has coolant, a head gasket and aluminium blocks- all potential variables. As I stated earlier if the coolant was duff the one would expect the corrosion to be on all wetted surfaces and this is just not the case or so it seems.

When we transplanted my S4 motor into the my current 928 during the strip down and inspection I found some corrosion on the water jacket about the size of a dime and nowhere else. The only logical explanation for that was some localised defect in the body of the casting material. Strange things happen!

FredR

That could be a possibility that might explain migration of coolant into the body of the gasket. Once it gets there the devils that cause localised acid formation in a stagnant layer kick in and off it goes.

If the coolant were the gremlin then everyone who uses G05 should expect to have issues but there is no evidence to support such that I am aware..

linderpat

Geeze; this thread is a tough one. I use the G-05, especially because it has historical good reputation and easy to locate locally. I don't know about the other types discussed above, and I know they are not easily sourced.

RET

This is a very interesting thread, particularly since it is nearly coolant change time. Unfortunately I can't contribute much to it except to note that some grades of stainless steel are magnetic, so testing the fire rings for magnetic properties is not conclusive proof of the material used.

Kiln_Red

I defer a lot on the conclusion of why this happened. But, as I understand, the coolant can't not be a catalyst for the defects at the heads. Maybe the way I understand it is incorrect, or oversimplified..

Somehow, and I don't see any possible way to tell, the engine cooling system had been introduced to some kind of corrosive elements. Probably not as a cause of the coolant type. The abnormality, in my opinion, occurs when actual corrosion related defects manifest. The coolant should act to inhibit corrosion. Well, in this case, it did not. I look at that like a definite product failure. Or, maybe, just not a product optimized for this application.

FredR

Austenitic steels (300 series are the most common grades) are not magnetic. Ferritic steels are magnetic (400series).

GregBBRD

Zerex has 11 different coolants for different applications, under their own brand. Why do you suppose they make so many different kinds?

Ignoring that G-05 doesn't list the "early" model water cooled 928 engines as an application, but G-48 does seems so....."Rennlist typical". (Don't bother me with facts, I just want to be able to rationalize what I used is correct.")

Mongo

G48 (blue coolant) is currently in use and also recommended by Mecedes. Not sure how much different it is than Porsche's G40. I've stocked up on several gallons of it since my whole garage is virtually all Mercedes, save for the 928. The crisis with G05 in this thread mirrors Dex-Cool nearly a two decades ago when I joined.

PS - ya'll may want to know it's easy to roll your car over from G05 to G48 as they are compatible with each other so obsessive-compulsive flushing isn't mandatory. It was for me when I was using 2-EHA Prestone

NoVector

belgiumbarry

reading all this hanky-panky , my supplier confirmed me that the (blue) G11 , which i use , is the same as G48.... i will sleep now better

bureau13

Do you happen to know if this applies to the Pentofrost HF as well? Is it the same as "G48?" I don't understand the differences between all of this tbh. Does the GXX signify anything other than a Zerex identifier?

Tony