guards red

Hi Steve, I wonder if I may ask a favour. On a very old thread you said the following to a guy asking about dealing with a potential cylinder head oil leak:

"David offers some good advice,.....cooling airflow tends to blow any small oil leaks everywhere making it tough to pinpoint the source.

Aside from valve covers and chain boxes, minor cylinder head leakage and case through-bolt O-rings are the most common sourse of oil seepage. I'd suggest that you get a can of carb cleaner and spray that off as well as possible to see where its coming from.

One can see most of the case through-bolts/nuts by removing the cooling fan and looking at the top of the engine case using a good light.

If the top of the engine is dry, I'd suggest retorquing the heads to start".

I have what I believe is a leak from the base of a cylinder and was contemplating tightening the head bolts a little. I'm aware that they are angle tightened and am aware of the procedure. I was going to go with another 2 degrees being the tolerance that Porsche advise. Is this a reasonable plan or would you suggest another method? I have read plently of threads about broken studs and the idea is scaring me silly so any advise you care to offer would be gratefully received.

Many thanks
GR

Steve Weiner-Rennsport Systems

It cannot hurt anything to try re-torquing the heads but I would NOT exceed factory specs. If you have a broken stud, you'll know in an instant since you'll feel no resistance with the torque wrench.

If the heads are all tight, I'd venture that its either a case through-bolt or cylinder base O-ring issue and thats not uncommon.

guards red

Thanks Steve,

as the Porsche specs from the manual relate to angle tightening, can I impose on you further and ask you how best to go about checking them? Should I just use a regular torque wrench and tighten them to a specified torque or just go for two degrees more?

Sorry if these are silly questions, I know that compared to a regular cylinder head the 993's heads have a very low torque so i want to make sure I don't overdo it.

Thanks Again
GR

matt777

One more question ... Should you break each bolt loose and then bring it up to full torque or just retorque? I would assume that this would be done one bolt at a time. Perhaps these thoughts are just a hangover from my water cooled V8 days.

geolab

I tried the easy way,
After I resealed the engine, and especially my oil return tube, it was leaking and I didnt know, I realized there was seapage under cylinder number 2 from underneath. I was not sure if the return tube leaked to the cyl 2 fins or it was the cylinder itself. When the Alternator was out, I inspected the top and it was dry. Few months later, there was still a mist on number 2. The fact that cleaning the oil in the fins was impossible for me, I was not sure if it was residual oil, or still seapage.
I was thinking of retightening, but the percentage chance that I would provoke a leak elsewhere haunted me.
I changed oil to 10W-60 castrol TWS a few months ago. and eversince the cylinder and undertray is dust dry.
maybe I was lucky, maybe it was the oil.

guards red

Thanks Matt, Geolab. I already run 10/50 in mine so this is not an option. I'm not planning on un-doing them first, just bumping them along a bit.... Scary stuff though so your thoughts are appreciated.

JM993

Hey Tal,

Here's my guess: It would appear as though the studs are designed to stretch based on the fact that they are initally installed with using an angle torque method. If I remember correctly, this requires the fastener to be torqued to a specific tightness using a standard torque wrench and then torqued using an angle torque wrench to stretch the fastener. However, since your fastener has been previously stretched, I think going the extra (past the standard torque wrench setting) would NOT be advisable.

Again this only my conjecture. I'm anxious to hear from someone smarter than me ( i.e. Steve) for a definitive response to your question.

Cheers

guards red

Hi Joe, how are ya? That's my understanding too but Porsche build in a plus or minus of two degrees in to the angle tightening method and I figured I'd take up this extra tolerance.. Not a lot I grant you but it may be enough to shut the tap so to speak. I read that a chap on the 964 forum had done just this though using a lb/ft setting which I wasn't too comfortable with. I've heard that they can loosen a little and perhaps that's what's happened to mine. Last roll of the dice really before I bite the bullet and have it rebuilt.

JM993

Doing well my friend. Hope you and your family are well. Will shoot you an email to catch up.

I see where you're going. According to my Tech Specifications Booklet, the head bolts are to be torqued as follows:

1st Stage - 20 NM (Wow, I would have guessed way more)
2nd Stage - 1 X 90 degrees plus or minus 2 degrees.

I share your concern. Seems as though comparing a few ft/lbs and degrees is like comparing apples and oranges. Also, since the bolt is already stretched, the variance provided by Porsche of 2 degrees seems like it should no longer be relevant.

Steve Weiner-Rennsport Systems

Loosen each one (at a time on a cold engine) and pull it up to 20nm + 90 degrees. Factory head studs/nuts don't usually loosen up like aftermarket ones do so unless you find a broken one, you should be OK.

Certainly a loose head nut can result in a leak at the cylinder base as well as the head surface, depending on how loose it is and for how long its been that way.

Assuming that all checked out OK, I would thoroughly clean the top and bottom of the engine with brake cleaner, re-install the fan, and run it for awhile before pulling the fan once again to see if you see any wetness around the through-bolts or at the cylinder bases.

Not much fun to do, but really the best way to resolve the problem.

guards red

Thanks Steve, Joe, the car is now partially dismantled and I am awaiting the purchase of another torque wrench as the two I have are now old. The torque angle guage I just bought turned out to be deffective too so I'll need another one of those also plus all the bolts removed during disassembly.

I'll post back with my results.

On a positive note I've just removed the spark plug under the PS pump expecting it to be ancient but found it to be new. I guess I should be more trusting!

Regards
GR

JM993

Good luck Tal. If you haven't bought the torque wrench yet, there's a guy on US ebay selling new Hazet torque wrenches. I picked up a 1/2 drive model for $167 US (retail price is over $500 US).

Cheers

Steve Weiner-Rennsport Systems

You are quite welcome,...

I think Hazet or Stahlwille will have what you need.