Chain noise
 

Ok, to add to all that has happened in the last several weeks I have another question to ask of you all.

I haven't been driving my car since the head stud problem arose but I did start it up and let it run for a while this weekend.
I noticed this after the weekend of the hill climb and it definately did not do this before. I'm hearing a distinct noise coming from my right bank. It doesn't do it until the engine is warm. The car had the tensioners updated about a year ago. We didn't replace the old chains or ramps because my mechanic said they looked good.
I called him today and he said I might have stretched a chain on the hill climb.
Is this possible?
And if so, is there something I can check?
I have contimplated removing the tensioner housing and having a look see but I kind of need to know what to look for...any ideas?
Like I said it is quite obvious after the engine is warm and sounds like a rattle...I even used the old screw driver on the housing trick and the right bank is definately making more noise than the left.
My mechanic said the head stud needs to be addressed but isn't fatal yet. He even said I might be able to drive the car until I can save up the money to have the stud fixed. But now this noise has me worried and I don't want to drive the car with a questionable tensioner/chain/?
And advice would be appreciated.

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Leland Pate

___79 SC Targa

I was thinking, about your stud. For a short term fix. You may be able to get the old stud out and put a new one back in as a short term fix until you go ahead and address the problem. That is if the stud is broken and not pulled. Down near the case you may be able to get some vice grips on the stud and remove it. This would certainly be better than driving it with the stud the way it is.

Leland, my 76 911 started with this rattled after a trip. But it would only rattle at low RPM. The problem was that the hidralic piston that holds the chain tensioned, lost oil and the chain got loose, and was hitting the housing. That is why it would rattle only in low RPM. Dont start your engine again, and have the piston refilled. My mechanic fixed it in a couple of hours, very easy.

Well great.
Your car failed with the tensioner update?
I was led to believe that those tensioners didn't fail like the mechanical ones did.
How exactly can the tensioner loose oil?
Is it something that I can fix?
Well now you've upset me...crap..I'll have to take a look at it.
If thats the case I'll be pretty pissed cause like I said they are only about a year old.



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Leland Pate

___79 SC Targa

I think mine is not updated, but there was no need to change any parts. My mechanic did the work, I dont know how he fixed it. He told me he just filled the piston again.

Dammit, I lost a long post so now I'm starting over. I'll be brief unless you ask for more details. The tensioner that lost oil was the OLD kind (they contain a measure amount of oil). Your should never be a problem.

I am sad your BRAT noise was a broken head stud, but I will continue to advise you, and others NOT to assume the worst. More often problems are simple.

I almos did not replace my ramps. They looked good and difficult to replace. I'm glad I replaced them though, as one was very beat up and two others were damaged. Could be one of yours is broken.

Stretched chains make the sprockets mis-shaped. A stretched chain tries to ride up in the teeth of its sprockets, instead of down in the valleys. So the valleys get worn on one side. This makes them (the valleys) kind of teardrop shaped.

Finally, the possible replacement of one broken head stud by reaching between the cylinder fins is very intriguing. I like this idea, as a temporary measure anyway, if it can be done. I would even drill holes into the stud if I thought it could help unscrew the thing. Perhaps I'm crazy (well, I know Im crazy) but this might fix the problem (at least temporarily) in a couple hours for the cost of one stud.

Perhaps there would still be compression leaking under the cylinder head. I'll be interested in others' thoughts on this one. It sure sounds like a method that would be preferred by mechanics if your car were theirs.

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'83 SC

I just looked at my engine in the cellar, I'm afraid if it was the bottom stud it would be very hard to impossible as the cooling tin surounds the stud. If it was the top this may work, again only as a preference to running the car with the broken stud. Warren?

Well, a lot of things have been going on, so I can't remember if it is cyl. 6 or 4 ... 6 seems to sound right, but ...

If it is the last, most forward bottom stud on #6, it might be feasible to replace it alone, but you would still need to pull the engine, take off the CIS system, the engine tin, and probably the oil cooler. And then you will need a couple of heat lamps, maybe a torch to warm up the loctite stud sealant.

You will need to replace it with a Dilivar stud, of course, since that's what all of the bottom ones are.

I guess the worst part of doing this repair is the concern that the head won't seal right even with a new stud because of the potential flame cutting ... like on p. 114 of Brtuce's book, 2nd edition!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 06-12-2000).]

Hydraulic tensioners do fail, not often, but it happens. Same with ramps, idler wheels, etc.

Driving a car with a broken head stud could cause you to have to replace a cylinder and head.

These studs are installed with Locktite and don't come out easily. Heat should be applied to melt the Locktite or one risks bringing out the case threads with the stud.

Sounds like your idea to rebuild the motor is a good one and yes, I like your idea to do it yourself.

JPIII

Talked to my mechanic again after dinner and he pretty much assured me that in his experience he has only seen one hydraulic tensioner fail and that was straight out of the box. He also doubts that I have broken a chain rail... he's guessing that I stretched the chain a bit. I couldn't get him to tell me if there was anything to look for to determine if that is the case or not. Any ideas?
Secondly, I have pretty much decided to do a complete rebuild on my motor. It just seems wisest given the facts. Chances are there is some damage to the #6 head so all of them are going to have to be sent out, I may end up replacing the #6 cylinder as well. And shoot may as well do it right the first time and go all the way right?
Looks like I'm going to have to sell my bike to pay for the rebuild.
Anyone want a cherry GSX-R 750?
Thanks for all the imput.

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Leland Pate

___79 SC Targa

[This message has been edited by Leland Pate (edited 06-12-2000).]

[This message has been edited by Leland Pate (edited 06-12-2000).]

Keep the bike! Look at it as needing to get done w/o the bike being sold, you will find a way.

The hydraulic tensioners do indeed fail at times. I've had two cases ( 79SC and 84Carrera) where it happened. On the Carrera, I would experience a random partial collapse after a fully warmed engine would cool for about twenty to thirty minutes. On restart, the left chain would rattle, gradually improving at idle as the tensioner seemingly filled and retained pressure.
On the 79, the engine was rebuilt and my wrench tested both tensioners by compressing them and found that one bled itself around the stem and the other bled at the port on top of the housing. He replaced both as a precaution.
So, the 'bulletproof' solution is not entirely without a kink in the armor.
Another symptom maskingitself as tensioner
failure
is a stretched chain which allows the left side chain wheel arm to contact the chain housing. The contact occurs just above the left side of the arm where the tensioner piston makes contact. Imagine a tensioner with excess travel pushing the arm up and making case contact.

Fred, is there any way I can check the chain by removing the muffler, shroud and chain housing

On my car (and yours I suspect) you need to put a jack under the rear of the engine because the rear motor mount has to come off along iwht the sheet metal and maybe the muffler. Then the covers can come off for inspection.

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'83 SC

A small point, guys ...chains Do NOT STRETCH! Wear of the pins, rollers, and holes in the links causes extra slack, and what appears to be 'stretch' is just an accumulation of wear, and it doesn't happen quickly at all!

Lee, you can probably pull off that chain cover without having to remove the cross-piece and rear mount. Just take off the sheet metal nearest the cover, until you can get to all of the 10 mm nuts holding it on, and have enough clearance to get the cover off past the studs!.

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Warren Hall
1973 911S Targa

This may be possible as Warren says, but I tried to get the rear sheet metal skirt off my engine once without success. The sheet metal is both under, and over, the rear motor mount.

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'83 SC



[This message has been edited by Superman (edited 06-13-2000).]

Guys,
On the demon chain rattle, in my 87 Carrera, I get a rattle just as it starts, hot or cold. it is enough noise that I feel that I should get after it.
Did try Mobil 1 15/40 last change and it is a little better but not good enough.
A few years ago, I took out the tensioners and they were fine but have some regrets at not having looked at what was happening with the chain housing covers off. Guess I wimped at the mess it would have made on the garage floor!!
Any thoughts would be welcome.
Ned Monaghan

On a related note,
Ned, I got your rebuild notes in the mail yesterday...Thank you!
I hope you got my E mail, some times our land link shuts down and dosen't bother to tell anyone. Again, thanks...I told all of my co-workers and they can't seem to understand why a total stranger would go out of his way to help someone like you have.
If you're ever in Idaho, give me a call... I definately owe you a drink or two.


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Leland Pate

___79 SC Targa

You're right Leland, the people on this board are just GREAT. The stranger thing is exactly right, and for the record, Mackgoo is a very patient man (thanks!). I kind of get the feeling we're all in this together despite geography. Just a bunch of mostly 'amateur' spanners who want to learn as much as they can and fix things themselves, and who happen to like Porsches. Excellent.

Leland. A check of the left chain for wear (not stretch...Thanks Warren) is to remove the tensioner ...don't let the chain slip..keep the wheel tensioned..and then clamp over the arm end and the top of the chain housing drawing the chain as tight as possible as if it was being over tensioned. If the end of the arm contacts the upper, inner edge of the housing, you'll see that it's obviously worn (or stretched, if you prefer).