JHowell37

I agree with you partially as I ran mine for several months without oil in the tensioner. But we have one interesting phenomena out here on the east coast that doesn't occur in California. It seems that around here, it actually gets cold for part of the year. It wasn't until I got a warning out of the blue on a cold morning, that I checked the oil level in the tensioner and it appeared empty. Filled it up, drove it, and the light didn't come on.

Jim bailey - 928 International

Ah good call it could be a noisy CHAIN tensioner !! And Yes authorized Porsche Dealers often use our rebuilt parts Shops and dealers are a big part of our business.

Vilhuer

Mark, to which address you want me to send pieces from inside tensioner which had been run dry? They do not look very pretty.

Big Dave

Any update?

928DK

Finally got the pictures from Porsche-Aarhus today.




I think that they are talking about the bracket the tensioner is bolted to (where the bolt marked 26 goes thru) I'll talk with them again tomorrow.

Prices are in the second picture, divide thru 5 to get the price in US$ approximately.

Bernhard
___________________
1987 Slantnose 928 S4 Auto - GTS butt
Tungsten Silver/Grey
Led Dash,X-Over,Cats,Cf-Spoiler,KD-Override,SMT6,AEM-UEGO.
1989 Toyota Carina II Red/Grey

Leon Speed

Would be interesting to know what parts they want to replace for US$ 2500 - maybe the whole system? How much are they charging per hour for US$ 1500 to do the job? Only thing you can't influence is the 25% VAT...

mark kibort

Hey, i only know what i have seen.
Im not saying im right here. Im only saying it looks like there is very little damping, if any by the washers. Its like a solid post. dont know the spring rate, but maybe you do since you are usually right all the time.

as far as the oil goes, its heat transfer, as its primary function, for which time usually can fix this. (ie wait until engine is at full temp before beating on it)

now, the thing im most concerned with is the corrosion factor. when my engine comes out, we will see what has happed for 20,000 miles and no oil, and LOTs of racing!

MK

mark kibort

send it to my compuserve!

can you post them here??

Hey, its not like i havent seen a destroyed tensioner before. Scots engine orginally came with a totally mismatched tensioner set up, that was angling the piston in the housing due to misaligment of mismatched parts. AND, no oil just made it worse.

do you think your failure was due to just running it dry? Is it an older version or a new, S4 type?

mk

mark kibort

bolt 26 goes to the block! the entire tensioner is held to the block with 3 of those bolts. (maybe 4, i forget)

$2600 for a new block isnt that bad.
Mk

Bill Ball

Mark: Porsche make more notice of the dampening function of the oil in the MY83+ design tensioner than they do of its heat transfer function.

From the MY83 service bulletin:

"Toothed Drive Belt Tensioning Mechanism with Hydraulic Damping

The different amounts of drive torque during a revolution of the camshafts produce oscillation in the toothed drive belt, which could cause belt flatter (sic) and in exceptional cases, when belt tightness is not sufficient, even a jumping out of the belt.

The new toothed belt tensioner has been designed to hydraulically dampen this oscillation in the toothed drive belt.
....
The entire tensioning roller housing (2) is filled with engine oil. When toothed belt oscillation causes reaction on tensioning roller (10) and consequently tensioning roller carrier (9), e. g. oscillation in direction of the diaphragm spring set, the push rod (8) and Piston (6) will move in direction of the spring set. The piston now presses against the oil polster and attempts to compress it and the diaphragm springs.

The bimetal diaphragm springs rest on valve carrier (3) and the oil attempts to flow through the bottom valve (4). However, the oil flow also carries the valve along and the chamber is closed completely. Leak oil can still only escape between piston (6) and guide (7). Three relief bores (1) deliver the leak oil outside along the guide behind the valve carrier (3) again. In opposite direction, when the push rod moves away from the tensioning roller housing, the bottom valve opens and allows undamped oil to flow through the valve carrier."

mark kibort

sounds like there is enough "flatter" to be damped by the oil, but it also sounds like mainly its for keeping the belt from jumping teeth if it did become loose, caused by the "flattering"

maybe ill put some oil in mine and see if it all leaks out. I think mine was leaking out the front seal, so maybe there is still some in there, so, i really dont know if its bone dry.

thanks for the post. Now im worried! could also be one of the reasons why it jumped some teeth in that world challenge qualifying session at laguna a few years back.

Mk

Bill Ball

Bernhard:

I can't figure out what they are replacing from those photos.

In the PET screen shot, part 2, the tensioner roler arm or carrier, is referred to by Porsche as a "console", but that doesn't cost all that much.

That "bracket" bolt 26 goes through IS the tensioner housing itself. Part 13 is the entire tensioner assembly, including the housing and all the internal parts. 928 International will sell you a brand new one for $1095. Perhaps that's the $1381USD part.
http://www.mailordercentral.com/928i...105%20036%2000

The order screen shot doesn't tell me much. If they are listing specific parts, those are not 928 part numbers they are using.

mark kibort

I guess i should tell scot to put some tensioner oil in too. His i know is bone dry.

so, what is this "console " deal?? as far as I know, the entire tensioner is a solid piece and it all bolts to the block.


mk

Bill Ball

Well, I'm not sure it is that critical. The earlier tensioner had no such system. A lot of people run dry as so many tensioners lose oil soon after filling. I ran dry for months (discovered in retrospect) and the result was a stretched belt and a low-tension warning at 25,000 miles on the belt. The first time I got the warning I snugged the tension and ran an open road race the next day and drove for another month before I got the next warning. The second warning made me decide the belt was going bad. I changed the belt immediately and discovered the tensioner dry again. I was more careful to make sure it held oil after that. If your low tension warning system is working, you should get some notice long before it gets to the tooth-skipping stage.

the flyin' scotsman

Its not solid as in sealed............I would suggest that if your running the OEM tensioner that we consider what modern method can be used to completely seal the back of the tensioner rather than just the OEM gasket............isn't that where it mostly leaks?

...........or junk the thing and get Ken's replacement; no tension, leaks or anything else to worry to about (ok maybe other stuff but not related to this)