Wile working on the TB job (maybe should be TB war) I noted that the axle of a small roller just near the crankshaft is loose.

Any idea way this roller is there? Since it does not touch the belt.

Is it normal to have it's axle with a small lateral free play?

Thank you

 

a little free play is fine, actually they mount fairly loosely come to think of it. I think it actually probably moves 2-4 mm actually. Its only held on by a c-clip

Its just a guide roller, i guess it just keeps the belt in the right spot, but yes it rarely touches the belt. For a time there were 2 of these rollers on that iron bracket. The second one was added, and they a few years later removed I think. I dont think the GTS uses the dual roller version.

 

Looks like the c-clip is missing...or did you remove it?

The bearing is replaceable - 6201RS. I purchased one locally as it's a common size.

The bearing assembly is called the lower idler assembly and is there in case the TB is loose and keeps it in place and on the crankshaft gear.

Hope this helps,
Adam

 

Do not know if it is actually used. For a TB in good shape it should not touch this roller (anybody ever seen a worn one?) for a TB in bad shape then probably this roller will not protect you from serious issues

Marton

 

I agree - a properly tensioned TB will not touch the lower roller. On the past two TB's I did, the roller appeared to be untouched and slightly rusty. Both bearings were notchy, probably from sitting there, baked by engine heat and not turning for quite some time. I replaced them anyway.
Adam

 

The free play is on the axle. The roller is tight. I removed the C-clip to try to take it out. It is stuck like everything else. I just didn't force it out since it could increase the axle free play.

The condition of the roller is fine. With dirt on it. So it never touched the belt.

 

When I last changed my TB, the ball races were changed as they were "growlers" and unfit for reinstallation. It was also noted that the mounting bracket was slack on its two mounting pins and the holes appeared to be slightly worn oval. I renewed the bearing and reinstalled with slackness.

The reason for the guide rollers (I believe) is to keep the belt on the drive sprocket if the belt starts to "flutter", so that it does not jump a tooth or two.

Originally the 928, MY 1977 was supplied with a guide piece without rollers and MY 1983 the guide was fitted with a single roller.

In 1987 the guide was fitted with 2 rollers. I could not find any further reference to whether the 928 GTS had any changes to the guide design.

I reviewed my copy of PET and it shows that the original 1977 928 had the guide piece with no rollers. In 1983 guide piece was redesigned with a single roller, however, all other MYs are shown with a single roller. This is incorrect as my 1990 S4 is fitted with two rollers on the guide piece.

The various years Service Information Technik (SIT) shows at the introduction of the S4 the guide was fitted with 2 rollers. I checked the SIT for 1992 to 1994 for the GTS and there is on mention of modification to the guide, so I assume that the guide piece has been retained with 2 rollers, is this correct?

My next question is whether the guide piece was designed to be slack on the guide mounting pins. In engineering terms I believe that it should not have too much clearance and it should not move laterally on the mounting pins due to excessive wear or slackness.

It is my intention to machine up brass inserts at the next TB change to make the guide piece fit in correct alignment on the mounting pins so as to present the roller onto the TB as a flat surface, not a canted surface. By installing the inserts it will bring the guide piece into the correct axial alignment without too much clearance on the mounting pins.

Any thoughts?

Tails 1990 928S4 Auto

 

The lower idler assembly is held on by two very small c-clips. You will find them and the mounting pins they are attached to underneath the crankshaft gear. There is usually a little movement fore/aft of this assembly on the two pins.

The first lower assembly I encountered was frozen on the engine block by a build up of corrosion/crud that accumulated on the two pins. Not surprised as the car was missing its belly pan for who knows how long. Before I re-installed the lower idler assembly, I coated the pins with anti-seize for future ease of removal.

Adam

 

Tails,

I have a brand new lower idler assembly on the shelf. The hole nearest to the roller is very close to round; the second hole is oval in shape. This is a brand new Porsche part right out of the box.

I hope this helps,
Adam

 

A brand new expensive part. I know, I "loaned" a new one to a lister a long time ago....

 

Miguel:

That one looks 10X better than most I see. If it spins freely, leave it alone.

 

As Bill said its nice and leave it.

You originally asked about it being loose. They dont bolt on, its held on only by 2 small c-clips and thing rides on two small pins or dowels or whatever you want to call them. Because of this it just kinds sits there on those pins, so when its correctly installed, it will feel loose. It has a purpose, but i would say its one of the less critical parts in the cam drive system. That being said it should stay there and it wont get any tighter.

It does look like the bearing itself has lost its clip to the arm or bracket. I would look for that and replace that though.

 

Thank you all

I will leave the roller as it is.

My concern was the axle being loose. If it brakes could damage the entire system.

Now the next step is to remove the water pump gasket. It is stuck. Monday will buy some gasket remove product.

 

The factory puts on this gasket dry (no sealant) and dealers usually service this gasket without using cement. So, gasket remover may not help all that much. Use a single edge razor blade or a gasket scraper tool that will not gouge the surface. It will usually come off in big sections. Still, use gasket remover - it will soften the gasket pieces that don't easily scrape loose.

 

I had the same concern about the clearance where that little idler console slides over the block pins. Holes are slightly large, pins looked a little too bright, indicating that it's all been moving a bit. The dr's solution was to use some really thick grease on the pins, so at least it doesn't vibrate on there. There doesn't appear to be contact with the belt in static state, but it was clear that one roller was contacting at some point since it was a little worn, while the other looked new. The 'new' one had a frozen bearing inside, go figure. I guess they need to change positions once in a while to redistribute the grease inside.

The bearing is a common 6201 size. You can get those in double-shielded with a ZZ suffix, or plain seals with SS suffix. I pressed them into the rollers with a socket and the bench vise in seconds, and the bearings are pretty inexpensive. No need to risk using the old tired bearings.

Those clips were referred to by JB as "Jesus clips" in a casual conversation. The old ones get a little stuck in the grooves at the ends of the pins, and end up 'un-sprung' by the time they are out. One of the benefits of getting a "timing belt care package" from Jim was getting spares of those clips, along with all the other handy little pieces and parts. Otherwise I'd have replaced them with real circlip retainers. NOT with any of the e-clip style in that service, if anyone was thinking that about going that way... IIRC there should be little wave-washers in between the retainer and the little cast console.

HTH!