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Cracked cylinder head?

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As a recent new owner of an '03 C4 cab I was a little disturbed to hear about engine failures particularly cracked heads and cylinder walls. My background is engineering so I was thinking about what would cause these failures. Some engines go over 100K miles and then have failures so they are probably not caused by manufacturing defects.

These failures brought to mind some advice I heard years ago about never running an engine WOT until it has reached operating temperature. There would be a huge temperature differential between the combustion chamber walls and the water jacket of a cold engine under WOT conditions. Could this stress cause the wall to crack like pouring hot water into a cold glass?

I have decided to be very careful about slowly running the engine up to operating temp before having some fun. Can't do any harm and it may prevent a failure.

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Wish it was that simple. Not just high RPM's on a cold engine. That's the worst part. Go get Porsche 996 the essential companion!! This guy looks into the engine failure problem. The best thing you can do is run it like you stole it. Let the engine come up to temp and keep the engine in the high rev 4000+. Don't baby the engine. E

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+1 - be very careful about slowly running the engine up to operating temp .

Porsche had to relocate/change the engine block manufacturing plant back in late 90's(could be the biggest reason)?.

Any cylinder head will crack if its overheated.

I know most of us are using G11-G12 with OAT anti-freeze.

But if the sysytem gets neglected, cavitation problem can occur which often causes overheating.

MB has been using G04 anti-freeze for their cars.

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okay, this thread has re introduced some issues i've been pondering for a bit now. My car runs on the hot side during summer conditions as it's a c4 daily driver in beltway traffic. I've cleared my rads, no really improvement. Fans are working fine...although I will be performing the fan hack that 1999 posting sometime ago and hopes that helps. But the Antifreeze comments here intrigue me. Can you be more specific and detail exactly what coolants we should be using in order to prevent cylinder damage? TIA

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  • 1 month later...

It is a personal thing,,,

Everyone should stick to what's recommended by the manufacture.

G11 & G12 with OAT are compatible with VW/Audi part #.

Since porsche has changed the color on their OEM antifreeze, Toolplant took a pic of both(VW/Porsche) lables to compare each other.

I tried to find it , but couldn't

IMO they are the same thing,,,,,Some belive G12 is the same as GM dexcool,,,

I've seen this Dex-cool(OAT) ruining thousands of engines + causing some major repair bills(class action suit).

Why? Probably just because of the fact that when the balance is upset ,OAT can come apart get neglected.

It is hard to tell U, what antifreeze U should be using.

Audi's been using the newest version of their AF G-12+(HOAT)yellowish,,, perhaps it's the reason they upgraded to HOAT.

I personally use Valvoline/ Zerex G-05 for my 986S.

Coolant, Chemistry, and Corrosion.


Edited by juniinc
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