Tapping noise after de-cats fitted

[shapeshifter]

Since having my de-cats fitted, when I start the car from cold it makes a tapping noise until its warm, it sounds like a chain noise from the front of the engine however, I have also been told that it could be the pipes knocking on the chassis - can anyone cast some light on this situation?

[NTEL]

Could be a couple of reasons:

1. Slight exhaust leak from manifold / decat clamps caused by misalignment.
2. slight exhaust leak from decat outlet clamps.

Both of the above will improve as exhaust temperature rises

3. Near side engine mount has gone (not literally) and decat pipes are resting on plate.
4. Its late and I'm talking a load of bks.

Mike, how long ago was it decatted?

Edited by NTEL on Sunday 21st September 02:28

[shapeshifter]

NTEL said:

Could be a couple of reasons:

1. Slight exhaust leak from manifold / decat clamps caused by misalignment.
2. slight exhaust leak from decat outlet clamps.

Both of the above will improve as exhaust temperature rises

3. Near side engine mount has gone (not literally) and decat pipes are resting on plate.
4. Its late and I'm talking a load of bks.

Mike, how long ago was it decatted?

Edited by NTEL on Sunday 21st September 02:28

They were fitted a year ago, by the way, I've had the engine mounts replaced recently, so probably one of the other scenarios above, are the de-cat pipes easy to get off? I might try and re-align them.

[s6boy]

shapeshifter said:

NTEL said:

Could be a couple of reasons:

1. Slight exhaust leak from manifold / decat clamps caused by misalignment.
2. slight exhaust leak from decat outlet clamps.

Both of the above will improve as exhaust temperature rises

3. Near side engine mount has gone (not literally) and decat pipes are resting on plate.
4. Its late and I'm talking a load of bks.

Mike, how long ago was it decatted?

Edited by NTEL on Sunday 21st September 02:28

They were fitted a year ago, by the way, I've had the engine mounts replaced recently, so probably one of the other scenarios above, are the de-cat pipes easy to get off? I might try and re-align them.

My first guess would've been the mounts as well, just dropping the exhaust onto the bracing plate, then when up to temp all settles down. I'm now on the second lot of mounts in 3 and a bit years, so probably still worth checking especially if engine bay has been exposed to high temperature with little airflow like idling for extended periods after a long run etc.



ETA> Sorry just re-read the op and you say 'tapping' which is not how mine sounded when the mounts went, more like a heat shield rattle then.

Edited by s6boy on Sunday 21st September 12:54

[Snaaakeey]

Thread revival!

I’m having this exact issue.

Any ideas. Did the op find his issue.

I’m thinking exhaust manifold/ cat leak.