Head Gasket woes

[Dvandy1]

Has anybody ever had to replace a head gasket twice on an 87 944 n/a? I just replaced this thing last week and haven't even gotten a plate for it yet and I was trying to bleed air out of the system and it started spewing white smoke. I've probably done 20 different head jobs on different cars, but this was my first Porsche and seemed to be the simplest but apparently not. I think the head shop shaved off five or six thousandths would that affect the compression enough to blow a stock gasket? Should I just try a wide fire? The one I put in was a victor reinz. Is there anything else that could cause the failure that I'm not thinking about? I guess it could have been a bad gasket, or I forgot how to torque a head.

[Arizona_928]

did you get all the milk shake out?

[Techno Duck]

What torque sequence did you follow?

[m73m95]

well +1 on it probably being the easiest one on the planet, so I can't imagine where you went wrong. Did you get the block clean? like spotless before you started putting everything back together?

My only other thought would be you either torqued it wrong OR, you wern't bleeding it correctly, and you got a hot spot on the #4 cylinder (Which is where they blow).....if you've been driving it for a week with a bubble in it, then it would be toast.

[Dvandy1]

yeah, I got all the milkshake out...in fact the oil still looks great I just have water in the number 3 cyl. I followed the sequence in my Porsche shop manual and cross referenced it at clarks garage. I have probably only had it running for about 15 min total and only about 5 min at a time. It was fine until my upper radiator hose rubbed on my alt pulley and put a hole in it and I immediately shut it down and ordered a new hose. I got the new hose on and tried to bleed the coolant and could never get it to bleed off. Then it started to smoke a little and I shut it down and pulled some plugs and found coolant in #3. I guess I'll try a wide fire gasket and make sure I clean the crap out of the block again before putting it back together.

[SolReaver]

Just for giggles, while you are in there, set a straightedge to both the block and the head to make sure you have a nice plane surface on both sides. Next, consider cleaning the mating surfaces to the "immaculate" level. The idea is to have two perfectly flat mirrors facing. These cars demand a level of clean that almost seems absurd. I actually lightly polish the mating surfaces. Clean out the bolt holes with a Q tip and solvent or Penatrating oil, again to a level of cleanliness that approaches absurd and neurotic.

When you pull off the old gasket, do it carefully and perform a "failure analysis" which, is fancy name for "what the hec went wrong". and get back to us.

[earlr85944]

As above, what torque sequence \ procedure did you follow?

[Dvandy1]

I followed the sequence in my Porsche factory shop manual and cross referenced it at clarks garage. I know I didn't clean it to an absurd level, but until I could feel no more old materiel left.

[earlr85944]

what were the poundages and intervals, the sequence is the same on all documentation

[m73m95]

I agree with the "clean it like crazy"

I got all the big stuff off with a razor blade (VERY CAREFULLY!!! You can do your own "custom" machine work on aluminum with a razor blade). Then polished it with a 3M buffer wheel on the mototool....then 0000 steel wool (again, carefull...like no pressure). The steel wool works good to get all the tiny tiny burrs off.

I use the same Reinz gasket, and haven't had problems.

Also.... its rare for the block to warp on these cars. The head will warp, but rarely the block. BUT, its still worth a check with a good framing square.

[TSNAPCRACKLEPOP]

when i looked in the book and the data on clarks, i used the torque angles, not ft lbs (since my 87na called for this)and 3 sequences of tightening to get it down. i also waited a couple of hours between sequences, and tapped the head and bolts with a balpein hammer between each tightrening.

i did not use new bolts, but maybe someone stretched yours?

[Dvandy1]

3 steps 20nm 50nm 90nm

[Techno Duck]

I have used 15ft-lbs, followed by a 90* turn, then another 90* turn. I waited about 30 minutes inbetween each step to account for some stretch. Did this on both my '87 n/a and my '88 951.

[John_AZ]

Originally Posted by Techno Duck

I have used 15ft-lbs, followed by a 90* turn, then another 90* turn. I waited about 30 minutes inbetween each step to account for some stretch. Did this on both my '87 n/a and my '88 951.

+1 and what TSNAPCRACKLEPOP said about the gentle tapping.

Do you still have the old gasket? Did it say "Turbo" in one corner. If it did, this may be the 2nd head job. The original head gasket did not say "Turbo".

The head was shaved 5 or 6 thousandths maybe you need the thicker head gasket #951-104-374.50 (per PET) $98 at PP. I do not know the max allowed to shave and still use the stock head gasket.

The WSM says to replace the head nuts, reuse the washers when you scuff one side so they do not move on torque sequence.

Sorry to hear about your misfortune. GL

John_AZ
1988 924S + 1987 924S

[Dvandy1]

as of this morning I ordered the wide fire gasket and will try that. I did notice afterward that there was a note in the factory guide saying that depending on your model you may need the other torque method, but it did not say which model. I guess I will try the other method with the comments in the other posts. Maybe the extra time to put it together will pay off in the long run. Thanks for all the help.

[2Tight]

+1 on the possible over machining of the head if it's been done twice. Do you recall if the witness marks are still visible? Was there any pitting from corrosion on either the head sealing surface or top of the block? It doesn't take much especially when a water jacket edge gets enlarged from corrosion.

[TSNAPCRACKLEPOP]

if i had to do the job twice, i would buy new bolts. check the threads in the block with a new bolt too.

[nynor]

unless you have raceware (or similar) headstuds, i'd recommend replacing them. you can tell if they are the stock studs by the thread pitch, which is 1.5MM, if i am not mistaken, vs. 1.25mm for the aftermarket performance studs. someone correct me if i am wrong about the thread pitch(es).

[Dvandy1]

never mind, the number 3 cyl has a crack in it about 1.5- 2 in long from the top down on the bottom side of the cyl. I guess its about time to sell it for what I got into it. Thanks for all the suggestions.

[nynor]

oh, that sucks.