Ok22

I have a new-to-me 2003 A8L that ran and drove okay, but had DTCs for misfires on 1-4 and a crankshaft/camshaft position error. It turned out that the timing belt was off by a tooth on the 1-4 side. Looking further, the water pump had some incorrect bolts (wrong metal with wrong thread) and there were markings on the cam gears indicating that they had probably slipped the belt off at a random point and tried to fit it back the same. So, while I am 'in there' I'm replacing the timing belt, thermostat, water pump, camshaft tensioners, and chains.


Right now I have two questions:
1) Installing the tensioner on the driver's side my intake cam mark is not quite lined up and I noticed that the new tensioner is sitting higher than the old one. It looks like if it was a little lower the cams would align correctly. Has anyone else had this happen?


I probably over-compressed it with the tool 3366 and pushed it up. I'm thinking of (gently) pushing it down with a plastic trim tool to see if it sets it lower.


2) One of the thermostat bolts broke off when I removed the thermostat. Does anyone knows of a trick that will make the bolt come out other than patience, penetrating oil, heat, and vice-grips. I'm willing to try anything. Maybe a few drops of blood and a chant?

silverd2

First, I'm gonna assume you bought the correct cam adjuster for that side of the motor ... the two are "plumbed" opposite each other.

The compression tool cannot over-compress the piston (just a large internal spring) ... the tool will break first.

A perfectly working adjuster is supposed to lock back into full retard position when the engine is shut off...Piston up on the drivers side is the retarded position.

You can't hurt the mechanical (spring tension..hydraulics not involved) tensioning function of the adjuster ... a new one will settle into place once oil pressure is introduced (or even a couple of hand turned revs of the motor), which moves the entire piston (internal spring included) up and down to retard and advance the intake cam.

I would not worry, so long as the timing marks are close (less than half a chain link).

Cheers

jfrahm

With a hammer and punch you can often drive the bolt stub out, punching at an angle. I have had good luck with a punch I modded by grinding a groove into the tip, giving it two sharp lips. You only use one lip at a time. That shape has worked well for me. You'd be surprised how effective this can be.

Ok22

Thanks for the replies. The timing mark is good on the exhaust and less than 1/2 a link on the intake, so I should be good. For now I'm keeping the crank pinned and not installing the belt until I get that thermostat bolt out. Hopefully when I can give it a few turns, it will all settle in.

I'll try the hammer and punch. That is actually pretty similar to how I got the fan clutch off - chisel and an air hammer to bump it clockwise. I'll use a dremel on an old punch and give that a try tomorrow.

MikkiJayne

Can you weld a nut on to the bolt stub? Often the heat from welding will help free it off.

dgcantrelljr@verizon.net

Don't worry about the height of the chain pad on the tensioner, it will vary since they have not been run yet. They will clack up and down as you turn the engine over by hand with no oil pressure. Check, check, and triple check the timing marks on the cams, making sure that the cam lock bar goes on perfectly when the crank is locked with the pin. The timing belt pulleys on the cams are not keyed, they sit on tapered surfaces on the cams and will need to be loosened to allow them to spin on the cam shafts to allow for minute movement while setting the tension on the timing belt. Then they are torqued down to prevent them from moving. Wildest damned thing I'd ever seen (non-keyed cam pulley) but it works like a charm for getting that timing perfectly set. Be sure to follow the tensioning process to the letter. But I'm sure you probably already know everything I just said...

I replaced both tensioners on my 4.2 this summer after one decided to throw a chain pad. No valve damage since it never got that far out of time. Probably the most frustrating part of the job was the damned Torx bolts that hold the cam caps. I had to use brute force and vise grips to get the damned things loose. Couple that with the fact that they're Torque To Yield and have to be replaced anyway..... I had to helicoil a couple of the bolt holes in the head because the a couple of ones I torqued down decided to pull the threads out on the degree part of the process. I said f**k it and just torqued them all on 20nm (or was it 15?). Anyway, why they couldn't just use regular hex head bolts on this stuff is beyond me.

Ok22

I'm going to try to wrap it all up tomorrow. Thermostat first. I gave it a week of penetrating oil and a heat gun. The vice grips will still not move it. After reading all the suggestions, I have a punch modified and I am going to try welding tab/bump on the side of the bolt to seat the punch in while I hammer it.

Those cam cap bolts are probably the worst part of the job. Especially the outer ones at the back. I managed to drive a T35 bit into one that had stripped out, then on another one it wrecked the tip of my bit. I bought a new set of bits (it takes T-30) and managed to get the rest out. having a fresh tip on the tool really made a difference -and time for the penetrating oil to dissolve the varnish.

Ok22

Progress! I got the thermostat bolt out. I'm not much of a welder, but I made a good lump of slag on the bolt, tapped it with the punch a few times, then got it to turn with the vice grips.
I got the timing belt on and turned the crank. Everything looks pretty good, but the driver's side (L) bank intake cam is still not perfect. Link count is 15 mark to mark though, so I'm going to close it up and see how it runs.
Things went smoothly till I tried to put the plug back in where the crank lock was. Just a matter of positioning it right. It was getting cold in the garage and the plug was just not going back in, so I called it a day. No rush. A fresh start tomorrow or on the weekend....

spitanddirt

IIRC the link count between cam marks is 15 links on one side and 16 on the other. I do not have my manual in front of me, but I do remember that this is the case. I would not just "close it up and see how it runs" without being 100% sure that you have everything timed correctly. It's a solid engine, but I don't play around with timing because of how much work it takes to remove and re-install the timing belt and camshafts. I'll try to remember to check tonight and I'll post some pictures from the service manual.

Ok22

Thanks. Here's a link to where I got my info:
Bentley Publishers - Technical Discussions : A8 timing chain adjusters ...
It states that the earlier Bentley manuals were wrong (16 links both sides) and the corrected info is 15 left 16 right.

Here's an old post on the forum that shows it pretty well:
https://www.audiworld.com/forums/a6-...chain-2801380/

I have a Bentley for the A6 (C5) that covers the 40V engine, but the info is not detailed. Most of my procedure came from reading online.