Knock when pulling away (CDTi)

[Toby Waters]

Originally Posted by Reebmit

Glad you found your problem, still searching mine, I checked that bracket and mine is okay, also checked the crank pulley and that is fine. I can't see any pipes fouling etc so may have to enlist the services of the other half to start and stop the engine while I look around, Oh she will enjoy that!!

Thanks. Best of luck with finding it!

[bl52krz]

Originally Posted by Toby Waters

Checked the front suspension lower arm rear bushes yesterday and there is no excessive play. I placed a rag between the exhaust and the crossbrace, see below:

Checked the front suspension lower arm rear bushes yesterday and there is no excessive play. I placed a rag between the exhaust and the crossbrace, see below:



This silenced the knock, so the problem is definately the exhaust fouling the crossbrace. Either the engine is moving too much or the exhaust is hanging too low. The exhaust appears to have a join halfway down and I cannot see any MGR markings on the backbox. It does sit very close to this cross brace (approx 5mm).

had this problem on a 220sd. bought new exhaust. still the same. got under car and looked along the length of the exhaust, from back to front. noticed that the front down pipe from manifold was slightly bent off the straight line. this "threw" the exhaust off line . by the time the exhaust reached the back of the "prop hump"which it ran down, it was , when starting up,banging against the car underneath.

[Toby Waters]

Originally Posted by bl52krz

had this problem on a 220sd. bought new exhaust. still the same. got under car and looked along the length of the exhaust, from back to front. noticed that the front down pipe from manifold was slightly bent off the straight line. this "threw" the exhaust off line . by the time the exhaust reached the back of the "prop hump"which it ran down, it was , when starting up,banging against the car underneath.

Will have to investigate this. All the exhaust mounts look OK and there is very little movement in the backbox (so I think its unlikely to be hanging too low from the back). Must be something further forward or a dodgy replacement exhaust.

[redbaron]

So that's what it is?

I've had the same problem since the 15,000 mile marker (5000 miles ago),
but only when the engine is cold. It seemed to be coming from the rear on my ZT-T.

Thanks.

redbaron

[WeeMan]

Check the hangers, I'm sure we have 2 on the back. Also check the exhaust clamps are nice and tight.

[1gp]

Originally Posted by Toby Waters

Thanks for your reply.

The mount was brand new and unfortunately made no difference.

I don't think it is a top strut mount (although mine does knock slightly when parking). The top strut knock is much quieter and sounds like it is coming from the front of the car. This knock however is definately coming from underneath the cabin (although I know it is difficult to pinpoint these things).

I would expect that if it were excessive engine movement, causing the exhaust to hit something underneath, it would be due to the lower rear engine mount. Is this the only mount that prevents movement in that axis?

the strut top knocking etc is this a common sound when they fail on lock, when parking, its as if you can hear the spring moving ?

[itfc4e]

I had the same knocking sound until I had a new exhaust fitted and, hey presto, knocking sound gone. So I would suggest that the previous posts about the exhaust are correct.

[bl52krz]

Originally Posted by chris75

Have you looked at the front suspension lower arm rear bushes ? THese are located beneath your feet , more or less , and can produce similar symptoms . Usually if they are gone you can physically roll the wheel back and forward with your hands .

this would be my guess.
these can be obtained from Rimmer Brothers.

[rjs]

Hi great posts. I have same problem v short dull knocking only when foot to floor. Sound coming from just below dash in middle. Will try all above and report back.

[thundercat]

Try and tighten/loosen your front wheel nuts, if the wheel moves backwards/forwards while you are doing this, the wishbone bush is your problem