Why exhaust camshafts wear out?

[okkim]

I have seen many RS4 cams and heads, and I have noticed that the exhaust cams are worn out very often.

Does anyone have an idea what causes this? Too long oil changes? Bad cam material (although I think it is the same part number with S4...)? Too low oil pressure in the heads? Bad valve lifters?

I'm building a new heads, and I want to avoid it happening again...

[dummi]

the sodium filled exhaust valves transfer heat up through the tappets, and into the cams

[okkim]

S4 has the same valves, why that doesn't happen in it then? I really don't think that the heat could transfer so long through all those parts up to the cams.

[philipwalker]

The exhaust cams are the same part number accross the range of 5V V6 engines 2.4 2.8 2.7 T RS4 etc.

It does happen on S4 engines as well. Suspect case hardening on the cams pitting on the followers causing accelerated wear.

A pic of my old S4 AGB shown this a few times. Happened back in 2003 in a 1998 S4 covered 74k on Mobil one oil.

[dummi]

i wasn't asking you i was telling you, that is the mechanism for reducing heat at the combustion end by transfering heat through conduction out of the engine

[TopBear]

I have seen many RS4 cams and heads, and I have noticed that the exhaust cams are worn out very often.

Does anyone have an idea what causes this? Too long oil changes? Bad cam material (although I think it is the same part number with S4...)? Too low oil pressure in the heads? Bad valve lifters?

I'm building a new heads, and I want to avoid it happening again...

I had too have *all* my camshafts replaced by MRC to cure the misfiring on my RS4. Doug advised that he had seen this quite a bit on S4's\RS4's and attributed it to the longlife servicing regime, in that the oil doesnt provide adequate lubrication over the period.

[TopBear]

Pic

[okkim]

I know that the cams are the same in other V6 engines as well, but I haven't seen bad cams in S4''s (excepct on one motor).

Doug advised that he had seen this quite a bit on S4's\RS4's and attributed it to the longlife servicing regime, in that the oil doesnt provide adequate lubrication over the period.

So using good oils (what oils?) and change it often could prevent it happening?

[dummi]

make sure you are not using audi long life service oil get some 0w40 or 0w50 motul, it will help with general cam wear

[Doug_S2]

audi serviced cars run longlife and never get knackered mafs replaced or diagnosed in time - so the car runs too hot with oil not changed regular enough.

[neckarsulm]

The whole idea of a performance car like this running a long life servicing regime like a 1.8 just seems ridiculous, after all it had the highest output per litre of any production car! Don't tuned Evos need servicing every 3k?
thankfully mine was on fixed intervals but my friend's was on longlife with close to 20k between visits (it's on 100k + now).
An S3 I had which had been on longlife looked worryingly sludged up when you looked inside the oil filler cap...

[Virdee Autos]

I do a service on mine every 6k or 6 months whichever comes sooner using Synta Gold 5W40

But I do totally agree with everyone on the Longlife service oils used, and timescale! Totally ridiculous!

[philipwalker]

The long life oil service is for cars that cover higher daily mileage long motorway use etc. Many dealers will put a car onto longlife even when it only covers a few miles a day. The oil will have a hard time with this type of use. Problems may only start long after the car has fallen out of the dealer network.

Most of the problems with long life are due to mixing the long life oil with the incorrect top up oil. This caused sludge and blocks the oil pickup pipes in the sump. The 1.8 T engines are the worst affected.

The Long life service came about with the pressure from the contract hire/fleet companys to reduce the servicing costs.

Not sure the cam wear is a symptom of this, the example I posted was running on Mobil One changed every 10,000 miles, I think it was just the camshaft was not hardened correctly.

[tartan_rob]

I do approx 1800 a month and change the oil every 3 or 4k miles irrespective. I did this on the B5 S4 and the M3 before that, both with high miles. I have not had main engine mechanical issues - it may be coincidence but I'm sticking to what I know best...!

I did hear a report a while back where some oil company ran 2 BMW 320 at 120mph round an oval track for 40 days solid (apart from fuelling and std services), one had oil done as per dealer servicing (long life) and the other was done every 36 hours. After the run, both engines were stripped and analysed. The 36 hour oil change car had no measureable damage to engine components, the other engine had noticeable wear, nothing desperate but it was noticeable.

[Doug_S2]

With any oil and an original maf the oil does not last - I still get cars in with original mafs.