Hi,
My daughter's '88 740 b230f has a rumble in the transmission housing area on kicking over and then vibrates, if in gear, while at idle. Placed in neutral the vibration stops.

This started to happen after new FCP Groton hydraulic engine mounts were installed. I'm not sure the mounts are the cause as it did not start straight after replacement.

I have since done the following -replaced trans mount and harmonic balancer which were desperately needing replacement,
-replaced leaking cat converter and missing engine pipe bracket.

Any suggestions appreciated. Thankyou in advance.

John H from Downunder

Go underneath the car and see how much clearance there is between the oil pan and the crossmember. There should be at least a half an inch. If they are touching, or even very close, you will need to replace the pedestals and brackets for the motor mounts. These are the four cast aluminum parts that connect the motor mounts to the crossmember and the engine block. I have an 88, that had a similar vibration. I tried everything to cure it, and only discovered the pan was on the crossmember while in the process of converting it from automatic to stick shift. I used the pedestals and brackets from a 90, 5 speed car, which raise the engine about 1/2" compared to the ones that came on my 88. Of course, as I was installing a stick, I changed over to solid motor mounts. The original liquid filled mounts did not appear to have anything wrong with them, so I suspect Volvo changed the design of the pedestals and brackets due to problems with the engine sitting too low.

I think I remember reading here that some hydraulic engine mounts don't seem to be as "hydraulic" as others. Perhaps the FCP ones don't dampen engine vidration quite as good as the real thing. The engine should shake slightly when idleing or you should be able the push on it and get it to move side to side slightly. If it just sits there and doesn't move when idleing or there's a big difference between the top and bottom fan to shroud gap then your mounts are still bad.

where did you get the engine pipe bracket?
I'm chasing much the same, although mine is when ever the engine is under load.
I've done everything that you've done, except the bracket.
Strangely, now that it's getting warmer, the vibration seems to be less - not sure why that would happen.

In my car the whole floor pan is drumming....

Hi,
Having 4 other Volvos I keep a good supply of parts.My bracket came from a parted car. It didn't solve the problem.

Have you installed new engine mounts? I'm wondering if they may be my problem.