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Missing bolt - exhaust manifold to turbo
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1898
Location: MI

PostPosted: Tue Oct 15, 2019 3:45 am    Post subject: Reply with quote

CÚdric wrote:
There is a certain sequence how everything should be torqued together aswell, if you dont have it I can send it.


Is their an official sequence?

Cool, but remember Chuck we had this little conversation here http://924board.org/viewtopic.php?p=398274&highlight=#398274 about installing it all loose and snugging it up as a package so it all pulls itself into its natural place where it wants to fit, not springing any parts of the system when tightened..

That could help for next time..

Carrera RSR wrote:
I take old hardware to my local nut and bolt store and walk out with new equivilents.


That's what I do too but the local store doesn't have fancy studs like that..


Chuck, how much torque do you think you put on all of these connections when you put it together?
Did you tighten em up real goodn'tight or were you afraid of over torquing them?

And yes that is the bigger US S1 931 turbocharger, good for 1 bar..

chuck21401 wrote:
Thinking back on it, I might have tightened the nuts on the turbo a bit much...I may want to back those off a 1/4 turn.
Other connections were snug but not too tight. Ideally should have a small torque wrench to be sure.


At final torquing you want it all very tight, very tight.. I'm not much for getting fancy with torque specs on most fasteners like these but basically tighten until you feel the torque rising exponentially in relation to how much more turn you are getting.. Especially those 4 big studs out of the back of the turbine manifold, you don't need to worry about snapping or stripping them unless you are using a pipe or something.. Tighten the hell out of them..
The smaller nuts on the WG, if you are on them with an open end wrench you are going to round off the nut with the open end before you will snap or strip them, unless you are using snap-on FD+ or wrightgrip open ends with teeth, the hex of the nut will fail well before the thread will with a usual open end wrench so go ahead and put some balls on them, about all you can get with an open end (which is all you can possibly get on most of them)..

If you tightened it and it didn't strip then it's not too tight..
I admit that you can tighten fancy engineered stretch bolts too tight without stripping them, bolts with long shanks like head studs, but not so much short studs that don't span a lot of distance of open shank in the middle..

chuck21401 wrote:

This one is hard to see, but missing the 3rd bolt that connects the exhaust manifold to the turbo (I've already replaced the two bolts on the other side).


Like these 3 bolts.. No way should you ever fully torque the top 2 without their even being one in the bottom.. That is how you break stuff, cast iron parts especially, they do not bend..

When installing these don't tighten any of them untill you have them all in, and then tighten them all 3 until they hit and a little snug like 1 ft/lb, then put 10-20 ft/lb on all 3, THEN you can fully torque all 3.. Bring them all in gradually together so that baby sits flat..

You will need to loosen your top 2, install the bottom one to snug, snug the tops, 10-20 on the bottom, 10-20 on the tops, full torque on the bottom, full torque on the tops..

BUT, you have your turbo to block mount loose now too, so that needs to be part of this process.. You need to loosen all 4 of those mount to block bolts and I would even say the 2 cap nuts that hold that mount to the bearing housing.. All rigid cast iron connections..
So we are talking 9 nuts/bolts that all need to all be brought in together..
All loose, all snug, all 1/4 to 1/2 full torque, then all full torque, so it all mates nice and flat..

If you don't do it this way then you risk putting a lot of preloaded stress into it in whatever which way..

IMO this is especially very important on rigid connections, even moreso on cast parts.. You should bring the entire system together as a whole in this manner..


I get that some of you guys like your fancy hardware but to me the technique of tightening systems like this is the most important..

And sorry, but lockwashers? Nah..
Couple red hot heat cycles and their isn't going to be any spring left in them to do any good imo..
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chuck21401  



Joined: 20 Feb 2005
Posts: 232
Location: Annapolis, MD

PostPosted: Tue Oct 15, 2019 6:09 am    Post subject: Reply with quote

Fasteddie313 wrote:
Cool, but remember Chuck we had this little conversation here http://924board.org/viewtopic.php?p=398274&highlight=#398274 about installing it all loose and snugging it up as a package so it all pulls itself into its natural place where it wants to fit, not springing any parts of the system when tightened..


Yes...and I thought that was what I was doing. At the time I didn't check anything else beyond connecting the exhaust to the turbo. And at that point I should have replaced the studs to the turbo and used lock nuts. And I should have checked things further upstream. For all I know, the turbo bracket and/or turbo to exhaust manifold could have already been working their way loose.

Carrera RSR wrote:
I take old hardware to my local nut and bolt store and walk out with new equivilents.


Yeah, we have Pep Boys, Autozone and Advanced Auto parts for the easy stuff. Everything else is mail order...even the local Porsche dealer.

Fasteddie313 wrote:

Chuck, how much torque do you think you put on all of these connections when you put it together? Did you tighten em up real goodn'tight or were you afraid of over torquing them?


Don't know. I tightened them down but didn't want to snap them. Like I said, one of the studs came out when I pulled the turbo, so who knows, the rest of the studs might not have been as tight as they should have been. But I am surprised to see one of studs missing...to get it in there I had to move the exhaust back. So how did that one escape?

Fasteddie313 wrote:
And yes that is the bigger US S1 931 turbocharger, good for 1 bar..


Not sure if she'll hold together at 1 bar.

Fasteddie313 wrote:

Like these 3 bolts.. No way should you ever fully torque the top 2 without their even being one in the bottom..


Good point. I saw a bolt missing and replaced it...didn't think about the other two. And when I replaced the 2nd bolt...didn't think about the third.

And when I tightened the exhaust to the turbo...well I didn't check to see everything else with the turbo was tight...since I didn't mess with that...I assumed it was fine. Turns out everything is one big rigid connection subject to intense heat and vibration.

Fasteddie313 wrote:

So we are talking 9 nuts/bolts that all need to all be brought in together..
All loose, all snug, all 1/4 to 1/2 full torque, then all full torque, so it all mates nice and flat..


And of course that's after removing the exhaust, installing new studs on turbo, reinstalling the exhaust, then lining everything up again.

Quote:
And sorry, but lockwashers? Nah..
Couple red hot heat cycles and their isn't going to be any spring left in them to do any good imo..


The last surviving lock washer was completely flat...so at least one data point to support that theory.
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poor-sche  



Joined: 06 Jan 2017
Posts: 69
Location: Los Angeles, CA

PostPosted: Tue Oct 15, 2019 7:51 am    Post subject: Reply with quote

What about using something like these...

https://www.stage8.com/turbo-locking-bolt-kits/

Never used them myself, but seem like they should work for the application.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1898
Location: MI

PostPosted: Tue Oct 15, 2019 8:41 am    Post subject: Reply with quote

chuck21401 wrote:

And of course that's after removing the exhaust, installing new studs on turbo, reinstalling the exhaust, then lining everything up again.


I'd do all the turbo cast iron bits with the down pipe completely off if I could or atleast completely loose to the downpipe so it is free to find its home to the block which I think is the most important..
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chuck21401  



Joined: 20 Feb 2005
Posts: 232
Location: Annapolis, MD

PostPosted: Tue Oct 15, 2019 10:09 am    Post subject: Reply with quote

Spent a bit more time under the car.

The turbo mount bracket was missing 2/4 bolts...the top and bottom bolts at the rear of the bracket. You can't see them in this pic...but they are above and below the turbo. The bottom one will be easy enough to replace...the one on top...not so much. Will be easier to access once the exhaust is out of the way. Who put the oil lines and oil filter there? Tight quarters.

In this picture it appears to me that the exhaust manifold had cracked and was welded back together at some point.


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Last edited by chuck21401 on Tue Oct 15, 2019 10:43 am; edited 1 time in total
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chuck21401  



Joined: 20 Feb 2005
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Location: Annapolis, MD

PostPosted: Tue Oct 15, 2019 10:25 am    Post subject: Reply with quote

poor-sche wrote:
What about using something like these...

https://www.stage8.com/turbo-locking-bolt-kits/

Never used them myself, but seem like they should work for the application.


Very interesting.
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Fasteddie313  



Joined: 29 Sep 2013
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PostPosted: Tue Oct 15, 2019 10:27 am    Post subject: Reply with quote

Yep, they all crack there and that looks like a good weld to me so that's a good thing.. Mine was cracked and I welded it too..
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CÚdric  



Joined: 27 Aug 2004
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PostPosted: Tue Oct 15, 2019 4:56 pm    Post subject: Reply with quote

Check your PM, i sent you the big package of all the files you need.

For me ive never had any need for special locking bolts etc, new hardware suitable for the job is good enough and havent given mee any issues.

Carrera, what i was trying to say was if there is a semi blown out gasket in there, it will be very very hard to get a good joint.

Slightly off topic...

In theory the fire ring is most likely better, since you have very little settling of the joint. A fiber gasket might shrink a tiny bit over time and relaxing the clamping force. If everything is torqued up and you have the correct length/quality bolts it should hold on anyway(many people dont though, and the results can vary) Many years ago when i worked with these things i did some clamping force measurements on different types of gaskets after long engine tests (by measuring the screw length with an ultra sound device). Its was a big difference between them, hence most use multi layer steel gaskets today.
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1953
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PostPosted: Tue Oct 15, 2019 6:50 pm    Post subject: Reply with quote

CÚdric wrote:
For me ive never had any need for special locking bolts etc, new hardware suitable for the job is good enough and havent given mee any issues.


I agree regarding Stage8. Just use quality fixings every time you rebuild. I do like to use aerotight nuts. Plus check tightness as part of your 6/12 month service regime.
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chuck21401  



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PostPosted: Tue Oct 15, 2019 10:40 pm    Post subject: Reply with quote

CÚdric wrote:
Check your PM, i sent you the big package of all the files you need.


Thanks!
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Tue Oct 15, 2019 11:06 pm    Post subject: Reply with quote

I used the Stage 8 kit Dan Beckett supplied, when I rebuilt my 931 motor. Worked great, no loosening, and is still in place on the exhaust manifold.

However, when I went in to swap out my turbo (for a rebuilt/upgraded one), there was quite a bit of corrosion - I was not able to reuse those fasteners, and went back to stock copper locking nuts on studs.

I don't know if the kit Dan specced was the same grade as the stuff Stage8 lists now, so I don't know if those will suffer from the same corrosion issues.
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chuck21401  



Joined: 20 Feb 2005
Posts: 232
Location: Annapolis, MD

PostPosted: Thu Oct 17, 2019 11:26 am    Post subject: Reply with quote

Fasteddie313 wrote:

Is their an official sequence?


Apparently so. The technical bulletins are very interesting.



Look like I need to buy a baby torque wrench and get smaller hands.

One of the notes mentioned that the turbos on the 81 models were "thermally improved by internal modifications."

The collar bolts and spacers were used in the 81/82 models and on repairs to the 80 models.
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Carrera RSR  



Joined: 08 Jan 2010
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PostPosted: Thu Oct 17, 2019 8:15 pm    Post subject: Reply with quote

If you think logically about the tightening sequence, you don't need to be an engineer to work out why the sequence is in that order. Start from the most unmoveable joint upstream (exhaust manifold to head) and work your way down stream......manifold to turbo, turbo mount to block, turbine compressor clocking, turbo to exhaust etc. etc. Include the J pipe, waste gate and exhaust onto that sequence and Bob is your boosting Uncle!
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chuck21401  



Joined: 20 Feb 2005
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PostPosted: Mon Nov 04, 2019 4:41 am    Post subject: Reply with quote

CÚdric wrote:
One things i noticed is that you have the old type gasket on the outlet, which you shouldnt have, if you have an s2 with the later turbine housing.


When I pulled the exhaust I found that I have both a ring (it's skinny) and the gasket between the turbo and the exhaust.

The tech bulletin (1983) features this graphic



Does that only apply to the newer turbos?

I'm a bit confused because the parts diagram shows a ring and a gasket.



Right now I'm about to install the new studs. Then will tighten everything back together...in order.



It wasn't easy, but I was able to install the missing bolt at the top of the turbo mount bracket (93112312403). I used a 13mm flex socket, extension and flex head ratchet. Getting the bolt started by hand took patience. The other top bolt is there...not sure how to get to that one. Maybe by removing the pressure pipe? I'll have to take a closer look.
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Carrera RSR  



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PostPosted: Mon Nov 04, 2019 5:05 am    Post subject: Reply with quote

I have always used new steel gaskets with a smear of very high temp exhaust sealant when reinstalling the turbo. So far I have not seen a failure. Never seen the expansion ring for the exhaust side. I have a fire ring for the manifold to turbine, but never installed it even though I have the later manifold and turbine housing.
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