Purpose of the 11311308309 diaphragm?

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Bhart
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Purpose of the 11311308309 diaphragm?

Post by Bhart »

I am working, cleaning up my 1987 S38 engine bay and under a whole lotta grunge, attached to the front of the cylinder head, I've found a caked up round steel device that RealOEM shows as a 11311308309 diaphragm. What is the purpose of this device. Can/should it be serviced?

What about the chain tensioner plunger access port from the same location on the head - what can or should be done from a maintenance point of view?
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Re: Purpose of the 11311308309 diaphragm?

Post by brickwhite »

To be removed and replaced with a S50 tensioner....

The S50 timing chain tensioner and crush washer Needs a 32mm socket torqued to 50ft/lb

http://bigcoupe.com/phpBB2/viewtopic.ph ... 3&start=75

Image

PNs - 11311405081 and 07119963418
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Bhart
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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

brickwhite wrote: Thu Jun 06, 2019 5:24 pm To be removed and replaced with a S50 tensioner....

The S50 timing chain tensioner and crush washer Needs a 32mm socket torqued to 50ft/lb

http://bigcoupe.com/phpBB2/viewtopic.ph ... 3&start=75

Image

PNs - 11311405081 and 07119963418
And this S50 timing chain tensioner will just bolt in to my S38 without any other changes or adjustments?
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Re: Purpose of the 11311308309 diaphragm?

Post by brickwhite »

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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

brickwhite - Thanks for the links. Google does now tend to deliver differently to different users, usually filling the first page or two exclusively with sales advertisements.

Great articles that have made the process much more clear to me now. The M5board installation directions are most intriguing, more complex than I'd expected and a bit daunting. I am working by myself here, in a land of SBCs and Hemis so finding someone familiar with the process to consult with could be challenging. The re-installation looks like the daunting part of the process. As I see from your link, you have made this conversion - what are the caveats I should be aware of?
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Re: Purpose of the 11311308309 diaphragm?

Post by brickwhite »

I live in Southern Missouri, you are preaching to the Choir on working solo...if its not a Ford 150 or a dodge cummins... they look at you funny and spit their chaw. No European Consults here.. But I found some locals on a euro car face book group.

As for the installation just make sure the slot lines up with guide arm. You should be able to feel it when installing. Make sure you hand thread it the first 5mm or so. Then torque to spec with the crush washer..

Google is easy... just clear history and cookies in your browser and don't use auto logins....
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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

I have now started changing over to the new tensioner. I have removed the original S38 unit and have offered up the new S50 part. I have only tightened the unit hand-tight and have a few questions;

In the process of preparation, the new tensioner piston popped open and the spring went flying. Cleaned it all thoroughly (3x) and struggled with the spring locating clip. I eventually found that a tiny 1/8" wide tie wrap worked ideally at holding the wire in place while I slid the piston & spring back together. There's no other parts involved internally?

I filled the outer 'cup' of the tensioner with engine oil, held the piston notch in place on the chain tensioner and tightened the cup by hand until snug. I next pushed down on the timing chains to see if all was snug and it depressed about 3/4" , I'll assume because ther is no oil in the tensioner gallery - correct? The chain seems very slack right now - would it be advisable to pull the sparkplugs and spin it on the started to get some oil into the tensioner? Any other suggestions?
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Slack chain.jpg
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Re: Purpose of the 11311308309 diaphragm?

Post by hornhospital »

Spinning up an engine before actually firing it up is always a good idea.
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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

hornhospital wrote: Tue Sep 03, 2019 1:59 am Spinning up an engine before actually firing it up is always a good idea.
Yes, I agree but is this amount of slack OK for an initial run on the starter motor?
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Re: Purpose of the 11311308309 diaphragm?

Post by Brucey »

if you are able to depress the top run of the chain like that with the tensioner 'installed' it either

a) ain't tensioning or

b) you have been turning the engine backwards. (V bad idea...)


FWIW the diaphragm unit is a secondary damper.

The main problem with the original tensioner in M88 and S38 engines is that (unlike the M30 tensioner) the thing quickly drains of oil when the engine is stopped. Since it (again unlike the M30 tensioner) relies partly upon direct oil pressure to apply pressure to the piston, (which generates more force than the spring does when the engine is running), this means the chain is not adequately tensioned when the engine is started from cold , and this carries on until there is something close to normal oil pressure/flow inside the cylinder head; this can take about ten seconds or so even in a good engine. If the chain is a bit worn then during this time it can flap about like crazy and if the engine is turned backwards with a worn chain all hell can break loose,

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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

Brucey wrote: Wed Sep 04, 2019 10:14 am if you are able to depress the top run of the chain like that with the tensioner 'installed' it either

a) ain't tensioning or

b) you have been turning the engine backwards. (V bad idea...)


cheers
I have turned the engine both forwards and backwards while I was measuring valve clearances... hmmm. This was with the original S38 tensioner still in place.

Brucey - Any suggestions on how I should proceed safely?

Brian
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Re: Purpose of the 11311308309 diaphragm?

Post by Brucey »

don't turn the engine backwards, even when checking the valve clearances. There is no need anyway.

As I said before if the top run of the chain is as slack as that there is almost certainly a problem of some kind with the tensioning. If in doubt have someone else take a look at it; there's only so much can be done using pictures.

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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

Brucey wrote: Wed Sep 04, 2019 6:29 pm
As I said before if the top run of the chain is as slack as that there is almost certainly a problem of some kind with the tensioning.

cheers
Unfortunately, I don't have any local resource people with knowledge on the BMW internals - we've only just recently got a Dealer after the last one closed.... in the early 1980's.

I did move then engine counterclockwise while checking valve clearances. The engine has not been started since the new tensioner was installed (filled the outer 'cup' of the tensioner with engine oil, held the piston notch in place on the chain tensioner and tightened the cup by hand until snug and then tightened onto the sealing ring). I have pulled the engine over clockwise, by hand, to TDC and all is still fine. I can still create slack between the two cam gears by pushing down on the chain. I have re-installed the upper chain guide and was planning to turn the engine over on the starter motor until oil pressure was achieved. Is this a good idea or should I proceed otherwise.

I was thinking this would be similar to a startup after complete renewal....?

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Re: Purpose of the 11311308309 diaphragm?

Post by Brucey »

in your photo it doesn't look as if you are having to push hard to get that amount of slack; if so this indicates the chain isn't tensioned properly.

Suggestion; is it possible that the chain/slipper is worn and the new tensioner simply isn't tensioning the chain because it doesn't have enough stroke? What happens if you refit the original tensioner? IIRC this tensioner has a longer stroke.

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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

Both tensioners seem to have similar working lengths under hydraulic pressure but the spring on the original has an effect even without oil pressure, constantly providing force. The new unit has only about 1/2" spring extension but without oil pressure it sits fully home. I can see that the original unit will have tension when installed from spring pressure alone. The end of the old tensioner that rides on the chain is showing significant wear.
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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

I have just re-installed the original tensioner and the pressure required to deflect the chain between the sprockets is considerably higher. I can still push it down the same amount but the slack is eliminated quickly when I trurn the engine over (clockwise) by hand.

Maybe the safe bet might be to just change the #13 (11311307782) tensioner for now so I can still use the car.
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Re: Purpose of the 11311308309 diaphragm?

Post by Brucey »

IIRC with the later tensioner and a new chain/guides, the spring pressure is active on the chain for the last half inch or so as the tensioner is installed. That yours isn't doing this strongly suggests that the chain and/or the tensioner blade is/are worn and really need renewal.


FWIW one method of preventing a lot of flapping around on start-up -and in addition ought to prevent any issues if the engine is turned backwards- (which works with either tensioner type BTW) is to manufacture and install a spacer in the tensioner body. The spacer needs to be sized so that

1) with the new style tensioner the spring is always acting on the chain.

2) with the old style tensioner the piston cannot be pushed back more than a few mm before it hits the spacer.

in your case I'd use 2) temporarily whilst planning for a new chain etc.

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Re: Purpose of the 11311308309 diaphragm?

Post by Bhart »

Brucey wrote: Thu Sep 05, 2019 10:34 am
FWIW one method of preventing a lot of flapping around on start-up -and in addition ought to prevent any issues if the engine is turned backwards- (which works with either tensioner type BTW) is to manufacture and install a spacer in the tensioner body. The spacer needs to be sized so that the old style tensioner the piston cannot be pushed back more than a few mm before it hits the spacer.

in your case I'd use 2) temporarily whilst planning for a new chain etc.

cheers
I'll have a closer look at both again and see what I can come up with. Will have to try and determine a working depth for the tensioner, protruding from the body.

I did make careful note, during startups in the cool springtime mornings (50F), but never heard any discernible chain noise or anything worrisome.
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