928Myles

'90 S4.
In the middle of top end refresh and want to replace the 'hockey puck' seals in the cams.

Have managed to do the two front. Drove a punch through the old seal (near the edge so you don't have the cam close to the seal) and then used a screw to push / pull the seal out. Managed to do both without removing the cambelt back cover plate (and all that entails).

Now looking at the rears.

I have read that it is preferable to remove the cam caps and reseal with loctite 574 or equivalent.

Problem is I don't have the correct tool to fit the bolts.

Can someone please tell me the correct socket type and size to fit into the 12 point bolt heads.

Also do I undo all 6 bolts or just the front 4.

Thanks,
Myles

Leon Speed

It's called XZN (in German also "Vielzahn", which means "multitooth"), size is M8.

All six bolts need to be undone. The lower rear bolts on the drivers side are difficult to remove, because the brake booster is in the way. There's no room to fit a wrench on the socket. Vice grips on the socket will work, and otherwise drilling a hole through the socket to use a screw driver as leverage.

You might want to undo the front caps as well in order to replace the oil galley plugs with pins used on later models.

Hilton

The XZN bits I have are a set with short and long bits. They're all 10mm hex diameter, so I can use a regular 10mm ratchet spanner on a short bit to get the tricky bolts, and then a 10mm crowsfoot to torque them.

My set looks something like this, although its not the same brand. My local automotive parts/tools place had the set.


There are only 5 plugs to replace - 3 on the 1-4 side and 2 on the 5-8 side, and they're under the rear caps. The front caps shouldn't need to be loosened unless you're having trouble seating the new cam caps.

sendarius

My former-mechanic father called them "triple-square", and that's what I used in a (successful) search to find a local supplier in Oz.

Lizard928

If they aren't leaking don't bother!!!!!

Loctite 574 is not cheap, most places don't stock it.

Additionally the triple square heads strip out super easy. If you do undo them make sure you have around 40-50 lbs of force pushing the socket into the bolt and make sure that your forces are in the right direction.
If you get them out re-torque to 15ft-lbs. and consider replacing with a regular Allen head bolt.

Leon Speed

Correct!

Myles, how about redoing the oil check valves. The o-rings certainly are hard and brittle by now. The passenger rear cam cap removed allows for easier access. I'll shut up now.

928Myles

Thanks for the responses.

Leon,
is the o-ring in the check valve 999 701 654 40? (So I know where to look)

Colin,
It is a bit hard to tell if these are leaking at the moment (lots of other crud about). They are such a PITA to get to I thought I would just do them as I have the cam covers off anyway. IIRC they are a common leak problem and there is something about plastic plugs that are blocking off oil passages falling out & affecting oil flow to the heads. Please educate me correctly.

Myles

Vilhuer

Very likely exact same pieces are available locally in different box. Have bought three or four of those over the years since some pieces are lost or broken. This is one of those tool sets which is a must for serious DIY work on any 928.

Leon Speed

Yes, that's the one. There is a procedure in the WSM on how to change these out. Common advice here on Rennlist is to check if the seats are tight if not they need to be fixed into place. There are some threads on this topic with more information.

namasgt

contact Rob Edwards he used some German brand that is the best. All the other brands you find in local part stores wear out and damage the bolt. Once the bolt gets damage you have to drill it out and you don't want to go trough that...

Podguy

I got mine from Snap On. Never had a problem with anything stripping. I got one for the fly wheel as well. Snap On is expensive but the quality cannot be beat. This is a place not to compromise on quality.

Rob Edwards

The one Greg suggested to me is a Hazet, #990-8. Go to this page and search it with 990-8. About $30 plus shipping, painfully expensive but less painful than stripping one out.

http://www.samstagsales.com/hazet.htm

MainePorsche

The rubber plugs have been superceded with PN 928.105.262.00 (or 08) the cylinder head plugs. Much better design than the rubber plugs. These aluminum pins fit precisely under the bridge and plug the the oil feed holes that fed the aft part of the earlier, longer camshafts. If these holes are not plugged you will get tappet/hydraulic lifter chattering. The valve covers have to come off for you have to remove the bridge to to place them. As Hilton said, there are 3 plugs on the Right and 2 on the Left.

Edit: I found this thread with pics that should be helpful for cylinder plug work.
https://rennlist.com/forums/928-foru...der+head+plugs

blown 87

Make sure the socket and the tool is absolutely clean or they may strip out.

928Myles

Progress report:
have all bolts out - 2 stripped. One I tapped out by turning with a chisel, the other I had to drill the head off then the rest came out by hand. I have ordered a set of M8 by 40mm 1.25 pitch SHCS's to replace them.

The caps were loose once all bolts were removed and I could not detect any sign of sealer between the mating faces.

I have been supplied with Loctite 518 as the 'equivalent' anaerobic sealer for assembly.

Cam covers, intake and other bits returned from the coaters yesterday. Will wash them out today.

Next job is to replace the chain tensioner pads and the check valve o-rings and make sure the seats are tight.

Thanks again for all the advise.

Myles