daveholland

Hi. New member here. I’m in the middle of doing the cam belt and need to replace the bearings in this lower cam belt tensioner. Been on to Porsche in Tonbridge, but the part number 928.105.561.1R does not compute. I read elsewhere that the bearing were 6201 type, but when I googled that, the size was a bit smaller than the existing. Can anyone Please help?

Zirconocene

Have you taken a look at PET for your car? I've not yet worked on the front of engine bits on my 928, so please excuse me if I'm totally off base with this, but I think the part you're looking for is 928 105 067. There look to be a couple of different revisions based on engine (maybe transmission?) type but hopefully this will be enough for your local dealer to make some headway in helping you.

As a reference, PET is hard to beat and provided for free. If you get a copy, I am looking at illustration 103-10, Part #19 in the drawing. It's not clear to me if the roller bearings are available separately; they don't seem to be called out that way in the document. Hopefully someone more experienced will jump in and set you completely straight.

Cheers

daveholland

Thanks for the reply. I’ve looked at PET and also spoke to Official Porsche Main Dealer parts department. Both refer to the part you’ve referred to, which is the single roller tensioner. I have the double roller tensioner which was used in later models, shown in the photo I’ve posted

Zirconocene

Got it, and it's a head scratcher. I looked through all the PET versions for all MYs and didn't see the dual roller type, so I thought that maybe it was just a misdrawn part.

That said, if you haven't seen this yet, perhaps this will help: https://jenniskens.livedsl.nl/Techni...9/MyTip990.htm

Good luck

FredR

Dave,

Greetings and welcome to the list!

I suspect you have the right concept but "the wrong way round" insofar as I know. The earlier versions of the S4 had the double roller and this was modified to the single roller that was used in my 90S4 motor and [AFAIK] in the GTS motors.

Irrespective of the models used, the bearings are commonly available and replaceable as I understand. Best thing you can do is contact Roger at 928srus.com. Their number is on their website. Roger is a most helpful chap and a fellow Brit and doubtless he will help you out either with the part you need or the part number you need to get them from a bearing outlet.

FYI as I am aware that roller [ the single one as fitted to my motor] does not take any load under normal operation and its raison d'etre is to prevent the belt from jumping off the engine sprocket in the event of backfire when the belt is then de-tensioned as it as the engine initially tries to spin backwards. Some years ago some owners had the false perception that such was not needed but that was just not the case.

Also possible someone will know the part number you need and post it for you.

daveholland

Thanks forbyour replies. I’m clear now on what I need to do. I was measuring the shell itself rather than the actual bearing, which is why the dimensions were not tallying with the quoted #6201 bearing size, shell obviously being larger than the bearing. Doh! Regarding Roger, I have bought stuff from him before and no doubt will again. These bearing are freely available in the UK fro SKF. I will try them first. Thanks again and glad I joined

Jerry Feather

I think you have found the correct solution to replacing he bearings in the two rollers. However, the title to your thread is not correct in that this item with two rollers (or even the similar one with only one roller) is not a tensioner; and in fact when installed, in a static situation, the rollers are not even touching the belt. I think the item may be referred to as an idler, and even then that is only kind of sort of. I think the item comes into play only when the engine is running at whatever speed causes the belt to flex between the sprokets that it runs on, and I think this item is there probably to keep the flex to a minimum or at least to keep the flex from causing the belt to jump the main crank sproket that is driving it. I think it might be sort of a part time idler.

One interesting thing that I cannot quite understand is that with the S4 belts of mine that I have changed I have found that one of the mounting holes in the item has been elongated up and down, and usually the hole on the left. The elongation appears to me to be from wear and probably from the belt vibration and flex. However, you will notice with yours that one of the holes is much larger than the other one even though the two studs that the item fits on are the same diameter. I don't know why, but I suspect that that simply has to do with whatever the flexibility might be in the location of the two studs in the block.

What I did with mine is measure the distance between the two stud centers and then carefully machine out the elongated holes and then press in a bronze bushing and ream it to the exact size for the stud. Now mine fit to what I think is "correctly." YMMV.

Jim Devine

Even new ones are slightly elongated- my best guess is they are that way to allow for some block expansion as it heats up.

Jerry Feather

Thanks, but of course we are both guessing.

Bedfordman

Hi Dave
are you sure you need new brg.? they might look bad but don't do much normally and might run free with a bit of a clean up.
BUT: I have one here, in Bedfordshire, UK. supplied by 928 Motorsports USA, new, and in sealed bag. Markings: SKF, Explorer, Argentina, 6201-2RSH/C3G..., last numbers hard to read as in plastic package...

happy to ship to you. -- or, if you have the number on your bearing you can order and get one nxt day from one of the online Brg suppliers here in UK. probably less than £10 for good quality item. Peter

daveholland

Hi
bearings were “notchy” so did need replacing. Thanks for the offer, but I’ve already ordered the new bearings which should arrive tomorrow. If they are not correct fitment, I will come back to you if I may
cheers

Mrmerlin

I fitted the plastic belt guide to my 82 and the both holes are elongated ( plastic guide was before the bearing upgrade).

ROG100

Lower Idler Assembly 83 to 87 - 90 to 95 - Single Roller 928 105 067 00
Lower Idler Assembly 87 to 90 - Double Roller 928 105 067 01

Ed Scherer

See also an old thread on the topic.

Mongo

Aren't these useless technically? I never changed mine but haven't had issues *knock on wood*