Broken Head Bolt on C4- & in denial...

[sms1305]

While adjusting the valves in my otherwise well running C4, I discovered a broken head bolt on No. 5 cylinder. After removing the (upper right) valve cover, the broken bolt was just lying there next to the spark plug. The broken piece measures about three inches long and does not have any threads on the portion I removed.

Q: Can the remaining portion be extracted from the block in place, without removing the engine?? (It seems to me that of all the locations, this affords the most access in the vicinity.) If so, any recommendations in the San Francisco area??

Q: Before I discovered the broken bolt, I also had a nagging tinny sound, almost like a heat shield rattle that varied with rpm. Does anyone know if not having the cylinder head anchored by all the required bolts could be the cause of this tinny, ping-like, rattle/chatter?? (I don't think that it is a heat shield.)

Facts:

1. The valves were all very close to good, with only 3 or 4 actually requiring adjustment, none of which were far off.

2. I have the following compression readings after adjusting the valves:

Front
(3) 170 psi (6) 185
(2) 170 (5) 165
(1) 170 (4) 170

I still don't yet have manuals, so . . . any advice or thoughts would be appreciated.


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Steve
'89 C4

[Leland Pate]

This is the first I have ever heard about a C4 snapping a head stud.
First thing is to stop driving the car.
The noise you were hearing was most likely the sound of your cylinder head smacking against your #5 cylinder.
I had a stud snap on my SC and I could definately hear a faint engine noise almost similar to an exhaust leak under hard accelleration.
Unfortunately, I have looked into this pretty throughly and have found no way to remove and replace the stud without dissassembling the top end.
If you are just going to replace the one snapped stud then you only need to disassemble the left bank.
But the cam tower, cylinder heads and cylinders must come off to properly heat and remove the stud with a stud remover (those suckers are really in there).

I would suggest you email Bruce Anderson and ask his advice... I've never heard of a post SC car snapping a stud.
Kinda scary actually.
If I can be of any more help please let me know.

Leland Pate
____911Sc Targa...(Master of the SC Universe)

[Leland Pate]

Oh and another thing.
Keep in mind that the Injection system and the exhaust system must come off as well so the job can get quite labor intensive.And keep in mind that the cylinder head and cylinder might require surface machining
due to the flopping head.
All of this for a stupid $24 head stud...
go figure.
BTW. does your C4 have the cylinder head gasket update? And I have been told that some '89-'94 cars had valve guide wear problems too... Just things to keep in mind since it looks like you'll be in there anyway.
Good luck!

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Leland Pate

___79 SC Targa

[This message has been edited by Leland Pate (edited 02-27-2001).]

[sms1305]

Having nearly no Porsche experience, but having reviewed the exploded engine views for the 911sc (I know that the engines are different, but I assume the general arrangement/design is similar), my sense is that I must, at least:

1. remove the entire bank of heads on the passenger side;
2. I assume this means an engine drop; (is it possible to do it in place?)
3. remove the cam and upper valve train;
4. pray that the stud can be removed while the block is in place;
5. inspect cylinder and piston cap (hopefully not catastrophic);
6. renew studs & replace heads

By the way, and forgive my ignorance, but what is Bruce's e-mail address?

[Kurt B]

Actually, put Bruce Anderson Porsche Performance into Altavista and a page ought to come up that has his email address. I'm dying to read his advice--speculation as to how your late model snapped a headstud. I have an 84 and now I'm pooping my pants.
Do you live in the northeast us?

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Kurt B
1984 911 Carrera Cabriolet

[This message has been edited by Kurt B (edited 02-27-2001).]

[Early_S_Man]

bruce1485@aol.com

www.911handbook.com

Steve,

The engine will have to come out, and at least two of the cylinders will also have to come off, minimum, just to be able to get at the remnants of the broken stud. More damaged studs (the coating of the 'microencapsulated studs' can be scratched or chipped ... causing corrosion) are possible, so at some point in the near future, I recommend testing all 24 to see if they can hold the installation torque without breaking ... you might as well find out now, right? In reality, you ought to plan on a top-end freshen-up, meaning replacing all 12 valve guides, at the bare minimum! Assembly/disassembly could be done by yourself, send the heads off for machine work ... tools, manuals, parts, and outside machine work need not exceed $2000 on the outside.



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Warren Hall
1973 911S Targa

[sms1305]

Regarding Leland's questions, I suspect it is pretty much original from the factory. I bought the car a little less than two years ago when it had just about 26,000 miles. According to Carfax, it looks like the car wasn't sold new until some time in '93. I bought it in Hawaii, thus, the low miles makes sense. However, the maintenance records were somewhat "thin" at the time of purchase, but the car was great. Anyway, I doubt that it has anything in the way of upgrades.

Interestingly, the local mechanic told me that as long as I wasn't racing, I could continue to drive the car. He is going to consult with some of his colleages to see if there is any creative way to repair the bad stud in place, without dropping the engine. If this is possible, I think I will go for it and realize that I may be in for a complete overhaul sooner than might otherwise be normal. If not, it looks like it's coming out! He said it was very unusual to see a C4 bust a stud.

[sms1305]

This just in...

"You will have to remove the engine and tear the top end off to get at the stud. I would probably recommend replacing all of the head studs, with RaceWare head studs."

Bruce Anderson www.911handbook.com

[Bill Wagner]

A head stud busting on a 964 is odd, UNLESS of course someone has worked on the car before. As you know, some of the early 964s had a cylinder head leakage problem (it would be found on '89, '90, and roughly the 1st half of the '91 production year).

When a defect exists in a car, it takes time for a manufacturer to recognize the problem and then correct it. Prior to Porsche implementing the cylinder and piston swap, what was the fix for this type of leak....over torquing the studs? Your car was a low mileage car when you bought it. A local p-car shop owner told me that when the cylinder leakage problem occured it would likely occur between 15K and 30K miles (if I recall correctly). Since your car has low mileage, it's possible that it developed this problem, and even though it was the oldest C4 on the market, it could have easilly occured within the warranty period and it may have the updated cylinders, pistons, etc. installed on it.

This is total speculation, but I can think of three possible scenarios where the head stud busting might occur:

1. Possibly your car had this problem to some degree and a mechanic attempted to "fix" it by over torquing one of the studs. This might have occurred if the work was done in the cars early years prior to a real fix being implemented (i.e. cylinder/piston replacement). Was this a Porsche procedure, or were shops left to their own judgement to try and fix the problem? I don't know.

2. Your car has the updated cylinders, pistons, etc. already installed (via a factory authorized repair) and the mechanic doing the work over-torqued one of the bolts.

3. A defective stud...just plain bad luck!

If you look at page 74 of Bruce Anderson's PORSCHE 911 PERFORMANCE HANDBOOK, it shows pictures of both the old and new style cylinders. I haven't done this on my '91 C4 (I already know it has the updated cylinders) but I think that if you look at both pictures you can tell whether or not someone has installed the updated cylinders on your car. If you look at these pictures, it occurs to me that you could likely bend something like a paper clip into an L shape and run it along the edge of the junction where the cylinder meets the block and determine what you've got on your car.

Why is this important? If you have the upgrade job and it was done by an authorized shop, you may have some recourse (like getting the job done for free or at least at a reduced labor rate). Contact Porsche, give them your serial number, and they should be able to tell you whether or not it was done, and possibly even who did it. On the other hand, if the stud was over torqued because it started leaking at a time when the problem was just surfacing and an "official" repair didn't exist, I suppose a mechanic may have been left to his use his own judgement and over torque a bolt to fix the problem. If the upgrade wasn't done, this may be a good time to do it even though it's a ton of money. Even though the car is old, I assume it still has relatively low miles on it and Porsche may assist you (they don't seem to treat their customers like Ford, Chevy, Dodge, or Mitsubishi do!! Perhaps they value return customers!).

Sorry you're having such bad luck with your car.

Bill Wagner

[sms1305]

Bill: Thanks for your comments. I have learned that there are three of three recalls still "open" on my car, evidence the PO(s) didn't do much in the way of dealer maintenance. Unfortunately, it appears that none of the recalls relate to my present problems. I checked the index of ALLDATA for my car and it did not indicate a recall, but did list a tech bulletin regarding cylinder head resurfacing, cylinder head torque, and crankcase studs. I like your theory re: correcting leaking head by over-torque, but you can read Bruce Adams' thoughts below. Also, thanks for your support. It is very frustrating, but, it is axiomatic that even good machines break. Still, it hurts both the gut and the wallet.

Bruce Adams responded to one of my e-mail as follows:

"Yes, there was a problem with the cylinder head to cylinder sealing surface. I thought you had a broken head stud, which is not the same problem. The leakage problem would be up at the top of the cylinder between the head and cylinder. Back when the cars were current Porsche would help with the problem, but there was not a recall and that problem was ten years ago.
Their definition of the problem was that you had a problem if it was wet to the touch.
You should be able to check with your dealer and they should have a record of whether or not the problem has been fixed.

1) There was no recall, but they fixed the problem under warranty if it occurred.

2) Check with your dealer and they can check to see if the problem was fixed by Porsche.

3) Your problem sounded like something else to me... a broken head stud."

Bruce Anderson www.911handbook.com

[Early_S_Man]

Steve,

If you can find the service records for your car through PCNA it would help, but there is another failure mode not mentioned by Bill, but it is alluded to in Bruce's Porsche 911 Performance Handbook, and it would have been caused by surface damage to the 'microencapsulated coating' of the studs when any warranty or non-recall work was done for the cylinder head oil leakage problem! Assuming that reasonable care is taken when the remnant of the broken stud is removed, evidence on a microscopic level, and viewable by either optical or scanning electron microscope, will prove whether corrosion or over-torquing (not possible, in my opinion) is the cause. The broken part of the stud you found has, most likely, been damaged by rattling around in the cam housing, and may not be of any evidenciary value.

By all means, see to it that the broken end of the stud is wrapped in a couple of layers of racer's tape, so incidental damage by tools will not occur during the extraction. The crankcase material (aluminum around the base of the stud threads) must be heated to 375 degrees F, so that the thread-locking compound (Loctite 'orange') is melted or softened before the stud can be extracted from the crankcase half!

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Warren Hall
1973 911S Targa

[Bill Wagner]

Early S Man (Warren):

Why wouldn't it be possible to over torque a head stud? Maybe you missed my point, or maybe I'm missing yours. I'm not new to cars, but I am new to Porsches. The idea of putting an air cooled cylinder on a block without a gasket seems very bizarre to me at this point.

To understand my point, consider the following hypothetical scenario:

Mr. Porcshe Owner goes out and buys a 964 C4 in 1989. After he drives it about a year, he notices a leak forming...perhaps a fairly bad one. He takes it back to the dealership and tells them to fix it. Since the car is fairly new, Porsche is still in the process of understanding (from customer reports) that this isn't something to be blown off, but they're still uncertain of the extent of the problem...after all some cars have it and some don't. At this point, no official "fix" exists. What's a mechanic to do? My guess, and it is a guess, is to attempt to seal the leak by torquing the cylinder bolts on the offending unit down more...maybe as little as 5 or 20 ft-lbs. This isn't accidental, it's deliberate. Heating the bolt up and tightening it to a higher torque level (deliberately) is a lot easier than pulling off the cylinder and re-machining it at Porsche's expense (and would they even approve of such a procedure at that time?). To me, this might have been a logical solution (but not nessecarilly a good one) considering the fact that there may have been no guidance provided by Porsche at this time. Such a condition could also exist if an independent mechanic, possibly not a Porsche specialist, worked on the car. Needless to say, as time progressed, I think it would be likely that the stud would eventually fail (although it may have taken years and/or miles to do so) because it wasn't intended to be subjected to the additional strain.

sms1305:

I would certainly try to call PCNA and get whatever records they have (if any). If you still live near where the original owners were, you might even be able to get some service history from local Porsche dealerships or mechanics...all they need is your serial number, but be advised that some of these places will purge their records after 4 or 5 years, and your car IS twelve years old. You might also call some of the local independents as well. I hate to say it, but this will likely lead nowhere, but it's worth a shot.

By the way, if you don't have a copy of Bruce Anderson's book and you want to test the cylinders to see if they're updated I can scan the pics he has in his book and e-mail them to you. I would think there would be some tell-tail signs of an update on the top of the cylinders, but his book (to the best of my knowledge) doesn't show them. The only pics I've noticed are of the bottom of the cylinder where it meets the block. Maybe your mechanics can tell by looking at them if they were updated. By the way, THANKS FOR THE E-BAY TIP!

Most of what I'm suggesting is a relatively speculative attempt to explain why a stud broke. I've NEVER heard of this in a 964 before, but on the other hand, I don't make my living tearing these things apart either .

Good Luck,

Bill Wagner

[This message has been edited by Bill Wagner (edited 02-28-2001).]

[sms1305]

My poooooor baby . . .
http://home.earthlink.net/~sstancliff/index.html

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Steve
'89 C4

[Early_S_Man]

Bill,

My belief that the head studs weren't overtorqued is based on the assumption that within a couple of years of manufacture, the OEM microencapsulated steel studs would not be capable of yielding before the threads in the aluminum crankcase pulled out. Although I do not know the actual grade steel used in those studs, most of the other studs in the engine are DIN grade 8.8, marked with a '+' stamped on the end. The 'normal' torque for an M10 grade 8.8 fastener is 32 lb-ft, or 50 N-m of torque, and I don't believe those studs would yield at anything less than 50-60 lb-ft of torque, and I do believe the threads would pull out of the aluminum block before that stress level was ever reached. But, maybe I'm wrong!

Also, I don't see how a technician at a dealership could, in good conscience, use even 32 lb-ft of torque on studs with a rated torque of 23-24 lb-ft in an aluminum block!

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Warren Hall
1973 911S Targa

[Bill Wagner]

Warren:

Thanks for clarifying that for me.

Good Luck,

Bill Wagner

[930fan]

The 930 3.3 heads do not have gaskets either yet they do not leak or at least mine doesn't. Why is that? Surely the combustion pressures are much higher in a 930 than a 964?

[Bill Wagner]

930fan:

I'm not sure anyone really knows for sure. It might have been a quality control problem of some type.

Before buying my C4, I looked at tons of early 964s (those that didn't have the fixes installed at the factory) and the problem seemed rare..I can't verify whether or not these were factory updated, I'm sure some were, but my GUESS would be that a lot weren't. Never the less, Porsche acted VERY QUICKLY (really probably about a year) in implementing the fix, so they must have known something was wrong.

One of the guys at one of the better known national Porsche tuners claims that this is heat related, and when they put the pan on the underside of the 964s (which has the primary purpose of reducing noise to some type of Euro spec) in some cases the heat could build up so quickly some of the studs would start stretching and warping, hence the leak. I don't know how accurate his assesment is, but it does make some sense. Looking at some of the pictures in Bruce Anderson's book it seems to make it clear that a fair number of 911s never used gaskets.

Good luck,

Bill Wagner

[sms1305]

The repair plan emerges.

I bought Bruce Anderson's book and read it almost cover to cover while flying coast to coast. I feel much better equiped now.

I think the only rational thing to do is to have a complete top end overhaul on both sides, including an inspection of all six cylinders and heads, replacing all 24 the studs with Raceware, and install Timecert into the crankcase. Due to the low mileage (38K), I believe (& hope) that I should not have/discover any serious bottom end problems or problems with the cams/rockers.

I also assume that I have the original configuration cylinders & heads (which do not have gaskets/seals). I intend to start a letter writing campaign to Porsche asking them to correct my engine. Does anyone have any sense whether there is any hope in this regard?

All that said, my question to the world is whether it is reasonable to reuse the original, no-gasket type heads & cylinders if, after inspection, they are determined to be "good?" At this point, I'm not certain, but I suspect that I have the dreaded cylinder leak referred to in Bruce's book.

Your thoughts are welcome, so don't sugar coat it!

[Bill Verburg]

No need to time cert the Al cases(3-3.8 Liter), unless you damage the case when removing the old studs, time certs are great for reinforcing the much softer, weaker mg cases. Be sure to update rod bolts while you are in there. Also think about replacing the dual mass flywheel/clutch with a more conventional RS unit. As Warren stated do all of the normal r/r while the engine is apart, ie seals, valve guides, plugs etc.

[Doug Zielke]

If you have not done so already, Steve, take a look at Paul Wier's Porsche engine rebuilding website. www.paulwier.com
There is a wealth of info there for all years of Porsche engines. Interesting price guides as well. They are based in Seattle. Maybe some one on the board has actually dealt with them.


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Doug
'81 SC Coupe
Canada West Region PCA