Why exhaust camshafts wear out?

[Charly]

Here's another example, ASJ-engine 09/2000, 135 Tkm, both exhaust cams lost abt. 1cm of "hardened" steel !
(on cylinder 1 and 6)

[okkim]

Holy cow! What kind of oils were used, and was it on long life?

[Charly]

Oil change twice a year (spring and autumn) from new
to 90 Tkm 0W40 was used, thereafter 5W30, according to Audi Service directive, both fully synthetic,
regular Audi-Service from 2000 - 2008, same owner all the way.

What puzzles me is that just cylinders 1 and 6 (close to gearbox) are affected, on all others the cams are fine.

An oil problem should've resulted in bad bearings rather than cam wearing.

[2ny]

That Just happend to me does someone have a workshop manual, or know where to buy new cams for a resonable price?
and does someone know how to release the front bumper? need som serius help.

Regards Tony ( in Sweden)

[Sql_RS4]

I assume symptoms are like some regular "ticking" or "clicking" noises coming from the engine? I can hear something like that and it gets more frequent (ticks faster) with revs getting higher when revving a car at stop.

Anyone knows which parts need to be changed when you open it up and see what we have here?

Part numbers would be great so I can predict costs

[2ny]

You probably need, new cams and valve lifters.

[R5YUG]

Mine has done under 70k and I've just had to replace the cams, lifters, tensioner and chain on bank 1 - I suspect some of my problem may have been down to tensioner failure or incorrect timing when the belt was last changed by Audi though....

I wasn't expecting the bill though, only spotted it by luck fixing a leaking cam seal after a cam-belt service @ MRC. There had been that much movement in the chain that the top of the cam cover is scored!!!
Cam wear was worse on Exhaust bank, but pitting was visible on both but the major concern was the chipping on the cam cogs - seriously worrying. I urge everyone to check these each service, for the sake of removing the cam covers it's worthwhile doing. Esp if you start to hear some rattles coming from the lifters / followers!

[Contigo]

Scares the living hell out of me this. Any idea how to actually prevent it as it sounds like people who have had their oil and MAF's changed when necessary have still had issues?

[rhunter203]

I know exactly where you're coming from!! Lucus said you had the same problem as me, but you only had the wear on 1 side. unfortunately I had to replace both sides!!!

[wozza]

Looking at it and I think I'm right in saying that the cam shafts are identical on each bank for the exhaust I believe - just reversed I think.

Wouldn't this point to either

1/ Oil starvation at then end of the oil track where the pressure would have dropped off furthest from supply?
2/ A manufacturing fault on the Cams?

Basically does the argument for oil issues or type account for the fact that only lobes on cylinders 1 and 6 are getting nailed only.

I can see it maybe if an oil gallery is getting blocked at one end?

Maybe bolts for the caps have been replaced or swapped in those areas as they're meant to be wasted type (on one side of the cap) looking at page 17 of the S4 SSP 198. So the oil cam run up the bolt stem.

Also in the closeup pics the lower (exhaust) cam lobes are bone dry whereas the inlet have a nice track of oil on them...

The majority of the gasket leaks are at the same ends aren't they?

Just some ideas....

[rtd]

Scares the living hell out of me this. Any idea how to actually prevent it as it sounds like people who have had their oil and MAF's changed when necessary have still had issues?

i think contigo we might as well accpet that we will all been prone to this some time or other!

[rickoshea]

Another thought - frequent oil changes have been mentioned, but what about either poor oil quality, or using an incorrect oil grade ?

Rick.

[mikeyquattro]

Whats the cost of repair? I'm going to start an emergency fund!

[rtd]

Whats the cost of repair? I'm going to start an emergency fund!

i was thinking the same thing mike - may start saving towards this - its gonna happen!

[GregorFuk]

I think saying ‘It’s going to happen’ is a little pessimistic. I’m sure there are plenty of B5’s out there that have not suffered from this.

This is only my two cents but….

I used to own a 20V Turbo Fiat Coupe and those engines had trouble with bottom end failure on the 5th cylinder, this was because it was the last journal on the oil gallery. I believe the Subaru flat four had a similar issue. My hunch would be that the cam lobes for cylinders 1 and 6 are at the end of their respective oil galleries. They are also closest to the turbos so are exposed to the most heat. Any oil pressure related issues could thus result in cam wear.

It may be worth putting up a survey to gather some hard info.

Things to ask would be

Age of Car
Engine Code
Miles on engine
Servicing regime
Tuning/mods (if any)
Car ever tracked?
Other issues (MAF, EGT, Lambda sensor failure)


Any thoughs?