33 replies to this topic

[Spitz]

That would be to the right of the engine.

Good it possibly be the engine mount on that side has failed?
The bottom rear subframe mount is prone to fail also ( if rubber ), and or the floor cracking if solid mounts were fitted ( happened to me...causing a "knock" )

[tiger99]

Have you checked that the bracket for the engine steady is still welded to the bulkhead crossmember? They have been known to come adrift, so only the top of the bolt is being held by the master cylinder mounting plate. You may need to remove that end of the steady to check it properly. A quick line of weld fixes it.

Also check that the master cylinder bolts are tight, so the plate does not move.

[james94]

Sounds like subframe mountings to me :). I had the exact same issue, best bet is to change your lower and upper mounts :) james

[Equinox_Monty]

This may help someone!
I have found the cause of my knocking sound.
Mine was when accelerating hard and letting off the accelerator quickly.
Silly as it sounds, it was just the exhaust downpipe (where it is 2 pipes not the main manifold) clunking against a bracket on the engine.
It has actually dented the exhaust where it has been pushing against the bracket.
I just bent the downpipe away from the bracket with a crowbar and thats sorted it.
I plan to edit this post in the next few days to upload a photo of where it was catching so others can rule this out.

[tiger99]

I don't know why that should cause the knocking, because the exhaust must actually be connected to a bracket which bolts to the gearbox/diff casing (otherwise it will break at or near the manifold joint), and if that bracket is in place it should not be moving against parts of the engine elsewhere. A fabricated tubular manifold may not have a joint in the usual place, but should also still have a mounting at the bottom. If that is the bracket which it was knocking against, the bracket needs to be properly fixed to the exhaust.

No doubt your picture will make it clearer. It may be correct, but it just sounds a bit odd.

[Spitz]

Curious also to see a pic

I've run an LCB for the last six years without it being supported at the diff.
Never had a crack or any other issue with it. I do of course have a good strap at the rear and in the middle to allow for movement.

[tiger99]

That is interesting. Maybe your LCB is sufficiently flexible that the lower bracket is not needed. Normally there are rather large bending loads fed into the exhaust due to the engine rocking on its mounts, especially when the steady bar bushes begin to wear. The lower steady, introduced around 1973, helped, but even so, standard exhausts would still fracture at the manifold joint if the lower bracket was not fitted.

The Somerford Mini web site shows various uprated manifolds, and they all have the lower bracket.

http://www.somerford...age=page&id=180

[Spitz]

Budget LCB

I think the important thing is the "give" in the rubber hangers

[Equinox_Monty]

Morning all.
The exhaust system is an "inherited" one from a previous owner. It looks cobbled together with masses of jointing paste everywhere.
As far as I could see, there is no support for the exhaust at the manifold end. There is a rubber hanger about half way along the full system and the rubber "donut" attached to the rear subframe.
I am assuming that the torque movement of the engine will probably bend it back with time and the knock will return.
Hopefully, I can get a new exhaust system by then!
As I say, I will upload a photo.

[Equinox_Monty]

There should indeed be a bracket at the downpipe stage but there is not one fitted. This allows the pipe to slap against the bracket.
Photo below.
New LCB acquired at Minifest today so I can seal it all properly.


I could just attach a clamp where its supposed to be but the system is blowing so badly that I want to sort it all out.
Thanks to all who pointed me in the right direction. I am not mechanically minded (with a mini ) and am just learning my nuts from by bolts (so to speak).

[tiger99]

Well, the very good news is that you have found the source of the knock. Random noises can be very hard to pin down, but this one left some very visible evidence.

[construction.mini]

I dont know if this problem was fixed but if not...... Mine was doing the same thing, the stearing rack was messed up or lose or something but it deffinately was the stearing rack on mine anyways I think to check you can jack up the car and pull on the wheels and if they move its that, im not sure dean from deans mini fixed it for me when he did my breaks. hope that helps :)

[jakejakejake1]

Been busy lately so haven't got to the bottom of my knocking, but the car is going in for its MOT tomorrow, so they will let me know if they find anything wrong.
Hopefully the MOT won't cost me too much!!

Jake

[Equinox_Monty]

Good luck Jake!
As a newbie, I ended up buying a carb LCB rather than an SPi / MPi one (with the lambda sensor recess).
I only noticed after angle grinding the downpipes off the old LCB as it had been welded together.
I plan to cut out a hole and weld a nut in place which matches the lambda sensor thread and mount it in that.
We live and learn eh!

[tiger99]

As steering rack knocks have been mentioned, I will describe how you can usually identify them. Set the steering approximately central. With wheels off ground, grab one inner ball joint (feel it through the rack gaiter) and try to move it up and down, back and forwards (not in and out of course, it should move that way). Repeat for the other end.

Normally most of the free movement will be at the passenger side (true on left hand drive too, I mean the non-driver side in each case), and it is caused by a simple, inexpensive nylon bush which supports that end of the rack, and can be relatively easily changed. See the Haynes manual for the details.