Dharn55

Some of you may have been following the problem with my car a 2000 C4 Cab that had an intermix problem last September. I am one of many that have posted here with the issue. Well today I found the source of the problem and here it is

At cylinder #1, by the inner exhaust valve, right where Jake Raby told me to look, and right where Doug Donsbach had his. So I am a cylinder head away from being back on the road.

While some say you need to totally rebuild the engine due to the chance of bearing wear after the engine has run with coolant in the oil, I am going to chance it. I know 928 owners that have over heated an engine and froze it up, let it cool, changed to oil and driven for another 50K. And at ths time I don't want the expense and challenge of a total rebuild, too many specials tools and the installation of pistons 4-6 is a tremendous challenge.

In any case, with the exception of a bad oil cooler, which is seldom the source of an intemix problem, a cracked head may be the best case. Head are readily available, and not that hard to change out. Getting all the crap out of the cooling system is probably more of a challenge than changing out the cylinder head.

So I am about a s happy as I can be given that I had the intermix to begin with.

Doug Donsbach

That's so close in location to the crack I found in mine it's spooky!

Sorry it wasn't the cooler, but at least now you know what you're looking at.

Wanna try to get a group buy on rebuild parts?

Dharn55

Might work. I looked in my PET and it shows three numbers for what appears to be a cylinder head assembly (valves but not the cams, folloer etc. 996.104.003.02, 996.104.003.03 and 996.104.003.05. Doens not really differetiate what each is. When I looked at the pricing on Renntech.org, if you input 996.104.003.02 it shows superceded by 996.104.003.05 at a price of $1,998.78. If you input 996.104.003.03 it shows superceded by 996.104.003.05 at a price of $2,036.77. and if you input 996.104.03.05 it show a price of $2,695.92. Not sure what to think. I am going to call Sunset and Suncoast tomorrow and see what the real story is. If you can get an assembly for $1,998.78 list, then the Sunset/Suncoast price might be alot less, cloise to what some wreckers seem to be asking for a used head.

Also, a group by on the special tools, or just sharing the cost and passin gthem around might be worth while.

It really is spooky how close it is to your crack. But I bet Porsche would say it is just a coincidence, that has probably happened hundreds if not thousands of times.

Tbred911

great find! thx for posting... good luck with it...

OCNYPORSCHE

Thanks for posting. I hope it all works out. Makes sense what you are suggesting.

CosmosC4S

Wow, those look like identical cracks. It would be hard to believe that it's not a manufacturing fault.

Good Luck on the fix.

Doug Donsbach

Engineering is where I'd place the blame.

CosmosC4S

In my mind as a layman, I'm thinking something, directly or indirectly, happened in those exact spots during casting, to affect the integrity of that particular area. Most likely it was just one or a few batches of production.

Jake Raby

Glad to see I was able to help..

Give me a call tomorrow and let me get you some prices as I have some lines on these parts that others do not and I may even have a good used head.. I'd just need yours to measure the chamber volume from to ensure a match..

Congrats on the fnd!!

BTW- manufacturing isn't what creates this crack, it's thermal shock loads that find the weak link.. This crack only occurs in the engines installed into 996s from what I have seen thus far having diagnosed dozens of them.

CosmosC4S

No, manufacturing didn't create the crack, of course not. But manufacturing faults created the weak link for the crack to be possible. If there's more than a few similar incidents, then Porshe is to blame.

Jake Raby

Trust me, I agree with you 100%... I have seen fiorst hand more instances of this than probably anyone outside the Porsche reman factory..
This is one of the 17 MOFs (modes of failure) we have documented from the M96 platform.

Doug Donsbach

Well, Dharn's is a 2000 and mine is a 1999. Potentially, that represents a lot of space between batches.

Dharn55

My 2000 was manufactured in late 1999, so there may not be that much time between them.

Doug Donsbach

How do you know the manufacture date? Mine says 2/98 on the door tag but the VIN decoder at Renntech.org says it was built in 1999 and has chassis serial number 0368. Where is the engine serial number located?

As an aside, I just had a good laugh by reading the top of page 184 in Streather's book regarding the causes of cylinder head cracks: it all boils down to owner abuse!

Dharn55

I found some tags on the body that show 10/99. Also the car was delivered to the original owner (I bought it in 8/00 with 4,000 miles) 2/23/2000 so it had to be made in late 99.