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Had the same problem on a '74 BMW 3.0 CS a few years back. Nut on top of the rear shock/strut was not tight enough. You might check that, as it's very easy to correct!
Gary
If you are casting the net wide then i would also include checking the gearbox mounts and also rear tailgate latch/adjustment and tailgate bumper pads
Interestingly, while building the exhaust I noticed that the gearbox mounts had no bolts in them! they now do, with exhaust hangers attached.
Tailgate I checked, all seems solid and secure.
Just retested - its really related to the brake in some way. If the car is rolling forward and I dab the brakes it makes a single 'clunk', same as when out on the road, driving over bumps.
So its either the brake system, which I have fully checked, or the transmission in some way.... and my current thinking is that its the CV joint or the gearbox mounts. I have the car on axel stands now so try to recreate the clunk by rotating the wheel by hand and pressing the brakes.
Had the same problem on a '74 BMW 3.0 CS a few years back. Nut on top of the rear shock/strut was not tight enough. You might check that, as it's very easy to correct!
Gary
Not bolted, but also not moving. I will bolt it down though just to rule it out - thanks
FYI: If you do not have the battery bolted down you are tempting fate- if the battery comes into contact with the lid you have an instantaneous 1500 amp welding machine that does a rather nice job of welding the battery positive post to the lid and wrecking the battery in the process and then a lid that will not open - ask me how I know!
I always insert a sheet of rubber between the post and the lid irrespective of the fact I have it well secured.
FYI: If you do not have the battery bolted down you are tempting fate- if the battery comes into contact with the lid you have an instantaneous 1500 amp welding machine that does a rather nice job of welding the battery positive post to the lid and wrecking the battery in the process and then a lid that will not open - ask me how I know!
I always insert a sheet of rubber between the post and the lid irrespective of the fact I have it well secured.
Its a great thought - but no battery compartment lid Something I still need to buy.
Its a great thought - but no battery compartment lid Something I still need to buy.
Now that was hilarious!
The biggest problem I had was how to get the lid unwelded from the battery post- I tried to sort of pry it off but there was no leverage angle - in the end I drilled a series of small holes around the periphery of the induced weld - eventually I got the thing to break free. Took the battery back to the supplier - told him there was something wrong with the [newish at the time] battery- they gave me another one! I did not tell any lies to be clear- just did not tell them all that I knew.
I looked at replacing the lid but figured it was a job and a half - used some two pack epoxy filler and a bit of wire mesh as a filler- touched it up with some Guards Red paint and called it quits. Good luck with that task.
I am a huge fan of your posted video's
I am struggling with a hard start cold & warm for over a year now and replaced almost everything...so I know it can be a pain in the *** finding the issue you have.
Did you check the following :
- rubber mounts of the gearbox ?
- rubbers of the stabilizer bar at rear end ?
In your video it seems as if a metal bar is hitting your trunk from below.
Hi Todd, In your video it seems as if a metal bar is hitting your trunk from below.
Gerrit
From what Garrit says here, and my own suspicions, I would look at the installation of the two kind of dog bones that connect the top of the rear hub carriers to the aluminum X-member in the rear. They are often taken out and them put back in upside down. They have a very significant curve in them to in fact clear the under body/frame of the car. When put in upside down they then will hit the frame over bumps. Here are a couple of pictures of what I am talking about.
Last edited by Jerry Feather; 06-13-2023 at 11:13 AM.
I am a huge fan of your posted video's
I am struggling with a hard start cold & warm for over a year now and replaced almost everything...so I know it can be a pain in the *** finding the issue you have.
Did you check the following :
- rubber mounts of the gearbox ?
- rubbers of the stabilizer bar at rear end ?
In your video it seems as if a metal bar is hitting your trunk from below.
kr
Gerrit
Hi Gerrit,
Thanks for watching the videos
Totally agree - it sounds like a metal bar tap tap tapping down there somewhere. I will check everything 'rubber'
From what Garrit says here, and my own suspicions, I would look at the installation of the two kind of dog bones that connect the top of the rear hub carriers to the aluminum X-member in the rear. They are often taken out and them put back in upside down. They have a very significant curve in them to in fact clear the under body/frame of the car. When put in upside down they then will hit the frame over bumps. Here are a couple of pictures of what I am talking about.
Thanks Jerry - I'll pop out now to check.... I haven't had the rear suspension apart yet but many things seem wrong on this car....
Thanks Jerry - I'll pop out now to check.... I haven't had the rear suspension apart yet but many things seem wrong on this car....
Todd
They look ok to me. I need to take a wheel off to get a proper look, but seem solidly attached and no gaps.
UPDATE: I found one of the spring clips was missing off of the rear calliper, which explained the clunk when I press the brake pedal. I was hoping that would solve the main clunking but it hasn't.
Ive gently lifted the gearbox and the mounts seem good and tight. Any lifting of the gearbox also raises the car (to some degree) and there is no separation.
They look ok to me. I need to take a wheel off to get a proper look, but seem solidly attached and no gaps.
UPDATE: I found one of the spring clips was missing off of the rear calliper, which explained the clunk when I press the brake pedal. I was hoping that would solve the main clunking but it hasn't.
Ive gently lifted the gearbox and the mounts seem good and tight. Any lifting of the gearbox also raises the car (to some degree) and there is no separation.
I'll keep searching...
Perhaps an interesting idea : why not put a small camera under the body at the rear to see what is actually happening ? You can try to put the camera at several angles each time you do a test run.
By the way I have a like wise clunk at the front, only when I turn and with a small bump in the road at the same time.
Further investigation lead to play on my steering rack. No leaks though.
Perhaps an interesting idea : why not put a small camera under the body at the rear to see what is actually happening ? You can try to put the camera at several angles each time you do a test run.
By the way I have a like wise clunk at the front, only when I turn and with a small bump in the road at the same time.
Further investigation lead to play on my steering rack. No leaks though.
I did think about that - but Im not sure I can attach it securely enough to see whats happening. My best hope is to repeat it in my garage (bumping it up&down or wobbling components). Nice idea tho!
06-12-2023, 10:51 AM
Something I still need to buy.
