Previously known as theboybradley.
Posted 04 February 2014 - 10:43 PM
OK little update...
Took the lower engine steady off tonight and let's just say it was only connected at one end 
So went for a drive. It still clonked. So that's not the problem (and the steady is staying off for the foreseeable as it's almost certainly been detached for years anyway).
I can seriously hear and feel the clonk from right underneath where I'm sitting. So although the exhaust feels tight I'm going to check it again.
Camshaft & Stage Two Head
Posted 05 February 2014 - 12:55 PM
It could be the engine moving and pushing the exhaust against the tunnel as it does.
Previously known as theboybradley.
Posted 05 February 2014 - 02:53 PM
Good point. Maybe it reverberates underneath me as it does so. Better get under again and have a gander..
Rocket Man
Posted 05 February 2014 - 03:07 PM
Differential about to go? Check for play in and out on the pot joints.
Previously known as theboybradley.
Posted 05 February 2014 - 04:04 PM
Differential about to go? Check for play in and out on the pot joints.
I'll check it out. Is the test to wiggle it around or is there a more scientific way? Suspension not my strong point.
Weird I thought this would be part of the MOT?
Crazy About Mini's
Posted 05 February 2014 - 06:02 PM
What is wrong with your lower engine steady? Has it broken its bracket in the front subframe cross-member, perhaps? That is easily repaired by welding, and I always fit a second bracket, on the other side of the bush, so the bolt is in double shear, not loaded in bending. The brackets never, ever break again once that is done. Later subframes had a thicker single bracket, which reduced the incidences of fracture, but was not the correct answer to the problem.
Ot has it broken the bracket on the gearbox? That was also thickened, possibly around 1980 (I have had Minis with the thin and thick versions), and the newer one "should" be ok, but it is thick metal, and easily weldable by MMA, not needing anything as delicate as MIG. It is easily changed anyway, but had to be thickened yet again in 1990 for the 1275 engine, and I suspect that it may still fracture occasionally.
.You do really need the lower steady, as without it, not only will the exhaust knock, but also the gearchange rods will be distressed, the main engine mounts will have a short life, and excess engine movement may cause chafing and damage to the starter cable and other things.
If you have a pre-1976 Mini, with rearward-facing steadies, I would suggest updating it to the forward-facing type, as it does work much better, but not if someone has added a second top steady at the radiator end, as the lower steady then does not react the torque properly. Throwing more and more steadies at the engine is what some people seem to do, encouraged by certain aftermarket suppliers whose engineering expertise is highly suspect and who want to make a fast buck, but in most cases a road car is fine with the 1978-on lower steady.
See here for the various parts:
http://www.somerford...age=page&id=121
Previously known as theboybradley.
Posted 05 February 2014 - 07:23 PM
What is wrong with your lower engine steady? Has it broken its bracket in the front subframe cross-member, perhaps? That is easily repaired by welding, and I always fit a second bracket, on the other side of the bush, so the bolt is in double shear, not loaded in bending. The brackets never, ever break again once that is done. Later subframes had a thicker single bracket, which reduced the incidences of fracture, but was not the correct answer to the problem.
Ot has it broken the bracket on the gearbox? That was also thickened, possibly around 1980 (I have had Minis with the thin and thick versions), and the newer one "should" be ok, but it is thick metal, and easily weldable by MMA, not needing anything as delicate as MIG. It is easily changed anyway, but had to be thickened yet again in 1990 for the 1275 engine, and I suspect that it may still fracture occasionally.
.You do really need the lower steady, as without it, not only will the exhaust knock, but also the gearchange rods will be distressed, the main engine mounts will have a short life, and excess engine movement may cause chafing and damage to the starter cable and other things.
If you have a pre-1976 Mini, with rearward-facing steadies, I would suggest updating it to the forward-facing type, as it does work much better, but not if someone has added a second top steady at the radiator end, as the lower steady then does not react the torque properly. Throwing more and more steadies at the engine is what some people seem to do, encouraged by certain aftermarket suppliers whose engineering expertise is highly suspect and who want to make a fast buck, but in most cases a road car is fine with the 1978-on lower steady.
See here for the various parts:
Thanks. Yes I do plan to get it replaced, just can't at the moment. It broke at the point of mounting on the front subframe.
Tonight I inspected the pot joint to see if they could explain the knocking noise. OK, it's less of a knock and more a loud thwack. I'm no expert but I couldn't find anything wrong with the pot joints except the o/s one was covered in oil, most likely from my leaky gearbox 'red seal' which has been like it for ages. That whole side of the engine is pretty oily.
The exhaust is rock-solid and I swear it can't be banging on anything. Only other thing is the gear selector rod I noticed felt quite loose and the rubber seal at the box end did too, how loose are these meant to be?
Rocket Man
Posted 05 February 2014 - 07:25 PM
Differential about to go? Check for play in and out on the pot joints.
I'll check it out. Is the test to wiggle it around or is there a more scientific way? Suspension not my strong point.
Weird I thought this would be part of the MOT?
Just before my differential broke (besides the clunking) the new left pot joint would move away from the differential about 1/4 of inch. It was possible to push it back in by hand but after a short drive it would be out again. I can't remember how much slop back and forth it had before it broke but this was the replacement gearbox from Guess-works:
Previously known as theboybradley.
Posted 06 February 2014 - 10:43 AM
Differential about to go? Check for play in and out on the pot joints.
I'll check it out. Is the test to wiggle it around or is there a more scientific way? Suspension not my strong point.
Weird I thought this would be part of the MOT?
Just before my differential broke (besides the clunking) the new left pot joint would move away from the differential about 1/4 of inch. It was possible to push it back in by hand but after a short drive it would be out again. I can't remember how much slop back and forth it had before it broke but this was the replacement gearbox from Guess-works:
OK I'll double check this.
Can I just also ask about other possible culprits....... on a rod change transmission, is the lower of the 2 rods allowed to be slightly loose, as in you can wiggle it around a little bit? This is the one with the rubber seal and pin at the end. Just trying to rule this one out.
Also someone mentioned the steering rack earlier. What's a good way to test whether this is loose? Steering to be honest feels ok, not brilliant but then it's an old car!
I'm still going to replace the upper engine steady bushes. Would the engine moving slightly with sudden jolts/bumps make the whole setup including exhaust move? I.e. why I can feel the clonk under the floor?
Another thing that might help is that the clonk/thwack noise seriously sounded and felt like the car was backfiring when it did it. It wasn't, but it was that sort of noise. Any help? 
Crazy About Mini's
Posted 06 February 2014 - 12:49 PM
Your engine steady has failed at the same point as one of mine did, which is not surprising. I really do think you need to get it repaired asap, or you will continue to have problems. I did mine with a plain old fashioned arc welder, before the days of affordable MIGs, and did not need to remove the engine or subframe to do it, although I think I had to remove the starter motor and clear a few other bits out of the way.
As to the pot joints, they rarely make clicking noises, unlike the outer CVs, however the advice given above about the possibility of diff failure is correct (we hope it is not that!), and there is often some noticeable end float of the pot in the diff prior to failure. If the drive shaft will move up and down, or back and forwards (in relation to the car, i.e. radially with respect to the shaft) within the pot, it is worn internally and should be replaced. The balls and their grooves may also be worn, but to feel that you generally need to undo the hub and outer end of the shaft, and move the shaft in and out while applying some torque, to feel for roughness, however if you can turn the shaft slightly with respect to the pot, either the balls and their grooves in the pot and inner member are worn, or the shaft splines are worn. None of this is horrendously expensive, but tedious, and the oil needs to be drained before extracting the pot from the diff.
The gearchange rod does need to float on the roll pin at the coupling, item 24 in the link below, and will knock if the engine is rocking about. But, it should not move up and down in the gearbox casing, otherwise a serious oil leak is inevitable, and again it will knock. To fix that, for a very long time, you need the update kit comprising bush, gaiter, O ring and new oil seal, item 31, which costs only £5.14, and will pay for itself in avoidance of oil loss very quickly.
http://www.somerford...age=page&id=152
Previously known as theboybradley.
Posted 06 February 2014 - 01:41 PM
Your engine steady has failed at the same point as one of mine did, which is not surprising. I really do think you need to get it repaired asap, or you will continue to have problems. I did mine with a plain old fashioned arc welder, before the days of affordable MIGs, and did not need to remove the engine or subframe to do it, although I think I had to remove the starter motor and clear a few other bits out of the way.
As to the pot joints, they rarely make clicking noises, unlike the outer CVs, however the advice given above about the possibility of diff failure is correct (we hope it is not that!), and there is often some noticeable end float of the pot in the diff prior to failure. If the drive shaft will move up and down, or back and forwards (in relation to the car, i.e. radially with respect to the shaft) within the pot, it is worn internally and should be replaced. The balls and their grooves may also be worn, but to feel that you generally need to undo the hub and outer end of the shaft, and move the shaft in and out while applying some torque, to feel for roughness, however if you can turn the shaft slightly with respect to the pot, either the balls and their grooves in the pot and inner member are worn, or the shaft splines are worn. None of this is horrendously expensive, but tedious, and the oil needs to be drained before extracting the pot from the diff.
The gearchange rod does need to float on the roll pin at the coupling, item 24 in the link below, and will knock if the engine is rocking about. But, it should not move up and down in the gearbox casing, otherwise a serious oil leak is inevitable, and again it will knock. To fix that, for a very long time, you need the update kit comprising bush, gaiter, O ring and new oil seal, item 31, which costs only £5.14, and will pay for itself in avoidance of oil loss very quickly.
Thanks for your help. I'm not sure it's anything to do with the driveshaft as there isn't any significant movement from what I can detect.
Re. the gearchange rod it's the rod itself which moves when I grab it, not the coupling at the gearbox casing. I assume a bit of movement in one of the rods itself is normal i.e. it shouldn't be solid?
Crazy About Mini's
Posted 06 February 2014 - 01:49 PM
Yes, the rod will move, it is only held at both ends by similar couplings, with some intentional float on the roll pins. It is tighter at the gear lever end than at the gearbox, because less angular movement, and so less wear, occurs there.
In theory you can improve the operation of the gearchange by getting rid of the couplings and using half inch bore U/Js (easily obtainable, but possibly pricey), tightly pinned to the shafts, but I don't know if anyone has ever bothered to do that.
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