Ben Broder

Does anyone know if the engine in the S4 is an interference design, i.e., if the timing belt breaks do the pistons smack the valves causing major engine damage?

BillV

I don't have the answer but why take the chance. I've always changed mine on any car 5K before it's due. P.M. is still the safest way.

Jim De Arras

Still a good question. We changed the one on our Mazda MPV on schedule. New one lasted less than 100 miles (Defective belt was assumed). It can happen any time.

The Mazda is non-interfering, fortunately.

S4andy

My BMW 325iX had a warranty lasting 50K miles and a recommended timing belt replacement at 60K. Belt broke at 55K throwing valves into pistons leading to purchase of new engine, out of warrantee.

Sandy
'00 S4 Shuddering at the bad memories

Bob

The 2.7 is an Interference engine so change that belt.

TJW

broke, the camshafts would continue to spin down with the engine, preventing an actual collision.
Is the 2.7 like this, or will the valves collide with the pistons?

BillV

I agree! My wife's Toyota was scheduled to go in at 58K but broke 2 days early...non-interfering luckily. Took my '90 300ZX in at 55K to make sure...otherwise major damage.

BillV

Audi says change at 70K...scary thought!! -

Tristan

the timing belt is the very device which allows the cams and cranshaft to spin together. If the timing belt/chain breaks, then they spin independently of each other. Hence the original question, will the valves hit the pistons when both are at open/top dead center, respectively? Sounds like the biturbo is "interference" type.

TJW

breaks, camshafts stop, pistons collide, you're screwed" type, and another type where something keeps the camshafts spinning in sync with the pistons, even after the timing belt breaks.
I don't pretend to understand it, but the Mazda 2.2 litre turbo engine is of the second variety.
The Audi 2.7 could be the same.