Technical Banging noise when gas pedal released.

[wickdogg]

Hello everyone!! I am new to the forum and need some assistance. I am fairly knowledgeable with cars, but my 1969 500L is having an issue. I have had a bump/bang that has been loud and annoying. When you release the gas pedal there is a loud bang in the rear of the car. At first I examined the motor mounts and found that they were worn/broken. I replaced the bushinging and the mount along with a new spring. The spring was a good deal taller than my other one. I did a small test drive and realized the new spring caused the bang to be even louder. I put the shorter sping back in and he bang was still there just not as bad. I am not sure if it is the exhaust hitting the underside of the car, engine/transmission jumping, or something entirely different. The transmission mounts are new as well and everything seems to be tight. I am baffeled as to why this is happening. If anyone out there has any ideas please let me know. :bang: Thanks everyone!

 

[oopsadaisy]

Hello and welcome.

Did this start happening suddenly or did it start as a minor noise and get gradually worse?

 

[wickdogg]

This sound has been going on since I have had the car. I thought replacing the mounts would fix the noise, but the new motor mounts didn't fix it. It is pretty loud and all looks fine underneath. The taller spring definately caused the noise to get worse. I put the shorter one back in. Can the spring be too short? I know the engine moves a lot in these cars. Any ideas?

 

[Abarth 695]

Hi, what about the transmission mount? If that was poorly worn out then would it cause the engine to "swing" more and the air fan housing or exhaust to hit the car? Have you got standard carburettor, I know some upgrades sometimes hit the top section of the engine bay.

 

[Bambino]

The exhaust on my car banged on the body when starting and occasionally on deceleration. I fixed the problem by fitting a spacer between the rear engine mount and the engine, thus lowering the rear of the engine by about 1.5cm.
Don't know whether this helps, but it cured my bumping.
Chris