1800: Thump thump thump on releasing clutch from start

[142 Guy]

Originally Posted by sleek lemur

Exhaust is 4 branch manifold, which is pretty close to wishbone, but not touching. No, the noise is just rear of between the seats and the flexibility in that central mount does feel too much for me.

Been there, done that, got the tee shirt - maybe.

"4 branch manifold" and "Close to wishbone" raised a flag for me. I have a 142 E, so not the same car; but, maybe a similar issue. I have the IPD / Patriot 4-1 header on my 142 and was getting infrequent bangs on start up / take off / anything where the engine was supplying sufficient torque to cause it to rock on its mounts. After some investigation, I discovered a mark on one of the exhaust runners where it was contacting the end of the bolt that forms the lower A arm pivot where it protruded beyond the nut. Trimming the bolt flush to the end of the nut reduced the occurrence of problem. I completely eliminated the problem by replacing the new aftermarket engine mounts that I had on the car with some new OEM Volvo engine mounts which were decidedly stiffer than the squishy aftermarket mounts. I did experiment with some B30 engine mounts which completely eliminated engine movement; but, transmitted so much engine vibration to the car body as to render the rearview mirrors useless. Reminded me of a 1970 BSA Victor 441 which I had a brief drive on.

On the 140, there is a bracket that attaches to the transmission and the OEM exhaust is supposed to hang from this bracket. If the 1800E has a similar bracket they typically develop fractures so the bracket may look like it is intact; but, close inspection will reveal a crack which is allowing movement and banging of the exhaust system. Also, if so equipped aftermarket headers do not always match up with the supporting bracket so installers may delete the bracket which again allows for excess movement in the exhaust system.

[sleek lemur]

Thanks 142. The noise is defo prop shaft, between and slightly to the rear of the seats.strange thing is it's only on letting the clutch out firmly, but not aggressively.

If it get the car rolling at 10 mph in first and then absolutely floor it, no noise.