Friday 14 January 2011

BMW E34 Rear Subframe Bush Removal Tool

I am planning on replacing the bushes that connect the rear subframe to the chassis. As I explained previously, these appear to be very worn out and getting worse.

The bushes pressed into the housing in the subframe. It is not a metal to metal fit as the bush has an external rubber coating over a steel cylindrical body. So even though it is a tight fit and requires a tool to remove and install them, hopefully removal shouldn't be too difficult as one can always heat to soften or even melt away the external rubber coating (with great care of course).

BMW of course have a special tool to remove and install the bushes. No doubt, you cannot by their exact one and workshop equivalents seem to be more of a kit to cover lots of different bushes (and therefore expensive) rather than just this specific one. So, of course, I therefore decided to make my own.

The bush is pressed into the housing from below. There are two slots missing from the outside shoulder of the bush so that you can put the tool against the bottom of the housing to pull against. Therefore you need some sort of forked tool that can straddle the bush, locate in the slots and pull the bush out into the fork.

Kit of Parts
I opted to make things simple and get some straight bits of bar machined to make 3 part of the fork. Slotted holes connect the two uprights so that the distance between them can be adjust to ensure a good snug fit. There is then a plate that sits on top of the bush, which is what pulls the bush out. The plate is designed with two flats to avoid the location pips inside the housing and also to catch the outside cylinder of the bush in case the centre piece tears away completely.

Top Plate

I am planning that the tool will also be useful for inserting the new bush too. I believe I can take the fork apart, use the cross member of the fork to bridge the top of the bush housing, and the top plate will become the bottom plate to press the bearing in. This is using the nuts, washers and threaded bar. When I actually do the job I will know for sure the best way to use this tool. Also if it is successful I will probably produce some drawings for the parts for other to make their own.

Some More Images

Tool on Bush
Components with Bush

1 comment:

  1. Looks like a great tool, can this tool also install a new bushing ?
    Do you have a drawing for the parts ?