rear subframe bushes

[deQuincey]

i will start pasting the text that appeared in the last CSL UK newsletter, thanks to John Renaudon


Rear Sub Frame Bushes.

I had a member contact me about changing the two bushes between the rear suspension sub-frame and the body shell.
In theory it should not be too difficult but you need plenty of good fortune. Get the rear of the car on axle stands, remove the rear wheels and put a trolley jack under the side of the sub frame you are going to tackle first. Undo the two bolts holding the bush steadying arm to the body shell and then undo the central nut holding the steadying arm to the bush. Remove the steady arm and then loosely replace the nut (to protect the thread of the bolt as you have to use a small club hammer [copper headed if you have one] to then to drive the bolt through the centre of the bush up into the car under the rear seat. If you are lucky the bolt will NOT be rusted into the bush.
Head of bolt which is fitted from inside the car under the rear seat
Special long bolt
Sub frame bolts (+ two the other side)
Central Nut
Now you can undo the four bolts holding the bush to the sub frame. Again if you are lucky these bolts will not be rusted into the sub frame. With these 4 bolts removed the bush should fall into the palm of your hand with the sub frame supported by the jack.
I was able to do this on my 2002Tii some years ago but I had fitted the bush to the sub frame and body shell with anti-seize grease on all the bolts when I had assembled it. Reassembly is the reverse and you have to drive the centre bolt back down into its splined housing with the club hammer before fitting the new bush and then refitting the four bolts etc.
The trolley jack just ensures the sub frame does not sag down too far when the end is not fixed to the car.
If the centre bolts are rusted then it can take quite a bit of force to get them up into the car. Once out it would be worth getting new ones because the thread will be damaged. If the
four bolts holding the bush onto the sub frame are rusted then you can cut off the bolt heads with an angle grinder and hope to prize off the old bush before driving out the remains of the bolts - but you will see they go through the full width of the sub frame which is quite a long tube to be rusted into and you need all four to be free.
If you have any doubts then it is probably better to get your local garage to do the work as they can drop the sub-frame at both ends on a hoist and get better access to the four nuts and bolts holding the bush to the sub frame (and possibly use a bit of heat) and/or the centre bolts.
Try one of the bush to sub frame nuts/bolts first as this will give you an idea about the state of the set before you start on the big central bolt. If it is really rusted in, replace it and head for your local garage –it does not need an E9 specialist.

 

[deQuincey]

now my own experience, not for the fainted heart, i may say it is a PITA if you try this while the subframe is still in the car, doable, but,...

schematic:

 

[Sven]

If you can drop the subframe by 5-6 cm that will help get access to the top two bolts which are otherwise nearly impossible to get a wrench on, or remove.

 

[deQuincey]

If you can drop the subframe by 5-6 cm that will help get access to the top two bolts which are otherwise nearly impossible to get a wrench on, or remove.

well i did it, aiming to a lot of difficulties and using my vast supply of tools, but finally i did it,

on the other hand your answer is a Little criptic to me, you say "if you can,...", but, can you ? i mean, have you tried it ? or are you speaking the theory ?

so if you loose the big nut can you drop the whole subframe that dimensión ? clearly 6 cm will grant Access to all those bolts

regards

 

[Sven]

Yes, I have done it. I dropped the subframe just a couple of weeks ago. I used a lift so the car could be raised evenly. You will also need to remove the bolt holding the differential to the body so the frame and diff. stay level and don't bind to the long vertical bolts that hold the bushings to the body. Remove the four small bolts and slip the bushing off the long bolt.

I already had the exhaust off. I suspect that it would limit how far you could drop the frame. Also, remove the bolts holding the driveshaft center bearing and temporarily support the center from the bolt holes with a wire.

I assume if you are going to all this trouble you are also replacing the trailing arm bushings?

 

[deQuincey]

Yes, I have done it. I dropped the subframe just a couple of weeks ago. I used a lift so the car could be raised evenly. You will also need to remove the bolt holding the differential to the body so the frame and diff. stay level and don't bind to the long vertical bolts that hold the bushings to the body. Remove the four small bolts and slip the bushing off the long bolt.

I already had the exhaust off. I suspect that it would limit how far you could drop the frame. Also, remove the bolts holding the driveshaft center bearing and temporarily support the center from the bolt holes with a wire.

I assume if you are going to all this trouble you are also replacing the trailing arm bushings?

wow, that is a major job, no i wont do all that it is too much work for my purpose, i said it was doable
thank you for the details

 

[Stevehose]

+1 if you're contemplating replacing these bushings then do them all. I dropped the subframe and did those, the trailing arm bushings, diff mount (repainted the diff also), rebuilt the half shafts, cleaned, rust proofed and painted the sub frame, new parking brake shoes, rear wheel bearings, calipers, etc. etc. Should last my lifetime I hope, I don't want to have to do the bearings again!

I assume if you are going to all this trouble you are also replacing the trailing arm bushings?

 

[deQuincey]

+1 if you're contemplating replacing these bushings then do them all. I dropped the subframe and did those, the trailing arm bushings, diff mount (repainted the diff also), rebuilt the half shafts, cleaned, rust proofed and painted the sub frame, new parking brake shoes, rear wheel bearings, calipers, etc. etc. Should last my lifetime I hope, I don't want to have to do the bearings again!

time is not due yet !
do not mention rear bearings,...:shock:

 

[deQuincey]

the sequence is:

support the car body with "S" and put a Jack "j" that must exert pressure to the subframe

undo nut "n" a bit and leave it there until undoing the two M8 bolts that fix the plate "p", then remove nut "n", the plate and put the nut "n" in place again

remove the rear seat, and put it out from the car, this will give you acces to the head of bolt "b", spraying some penetrant oil the day before wont hurt you ;-)

remove the Jack "j" from the subframe and use it to forcé the big bolt "b" up by means of exerting pressure on the nut "n" (this is a better method than hitting the bolt with a mallet, the top of the bolt use to be very tight in its housing), now remove the nut "n" and forcé the bolt completely out up (this time a mallet will do)

now remove the four M8x55 bolts (1,1´,2,5), leaving the subframe loose will grant a Little but enough Access to the head of those bolts, once the bolts are out, the bushing will fall down in the palm of your hand, yes

in order to remove bolt number 2, you must remove nut 3, and move a bit out bolt number 4 to provide way

clean well the surface and place the new bushing, if posible with the four bolts (1,1´,2,5) in place otherwise it will be very difficult to introduce them, secure them with the four nuts immediately and start tightening them while assuring the surfaces are in close and even contact, do them diagonally

it will be not an easy thing use the best tools, curved or similar to block the bolt heads while tightening the nuts, those are selfblocking nuts, so blocking the bolt heads is a must

if posible use new bolts and nuts

bolts 1,1´,2,5 are 10.9 quality
bolt "b" is a very special one, buy it from BMW
the nut "n" is critical, M14x1,5 is a high quality because it must stand 150 N.m torque, buy it from BMW

when new bushing is fixed use the Jack again to lift the subframe up while helping the bushing to accomodate its top side "6" into the body frame, the Jack vertically and a mallet horizontally, will help doing this

when the bushing is in contact with the body you can introduce the new bolt "b" in its place, accomodate the vertical marks of the bolt into their housing, and use a mallet to let them slip into place a bit, previously a dab of copper grease would help to this operation

then, place the plate "p" securing it with the nut "n", do the two M8 hexagonal bolts that support the front part of the plate, and finally do the nut "n", initially you will be pressing the bolt "b" until its final seat in the body, but when it stops give the prescribed torque as 150 N.m to nut "n"

do not forget to do nut "3",

and that is all

 

[deQuincey]

feedback on the results

handling has improved, the rear of the car now Works together with the front part of the car

a nice renewal,

 

[Nicad]

This is soon on my list . I am going to have to read this closely and hope my comprehension skills are not too degraded. Sounds like I will need a cell phone close at hand to call 911 if it goes bad