clunk!

Hi. I have a clunk from my back end (BGT 1973, UK spec, daily all weather, all terrain drive). I have investigated as much as I can think to:

The diff is fine, its not that sort of clunk, not a 'take up' clunk

The wheel bearings are recent and fine

The spring pads and bushes are poly, less than a year old, good.

The u-bolts are not loose

The boot is empty!

The propshaft is good (new less than 2 years ago also, kept greased).

The spring shackles are not loose, and in good nick

There does not appear to be a corrosion issue on the car in this area

Brakes are good, nothing loose there (new cylinders and shoes this year).

Here is the weird bit - the car did this in the spring, then after a day of pulling to bits and putting together, continued to. Then stopped all summer. Its started again now the wet weather has arrived. But, it seems to be bad for the first mile of the day, most noticable on the drivers rear side, esp. when weight is shifted to that rear side during cornering. Then, after a few miles, it vanishes again!

I am at a loss, and since its not falling to bits, not so concerned. But I have a theory, and want someone here to tell me how daft this before I say it someone who will tell me how daft it is! So, here goes:

The leaf springs are rusty. Could it be then that the early morning clunks are sort of 'stiction' caused by car sitting on wet driveway overnight - a small flash of rust causing the leafs not to slide, but more jolt past each other - after a few miles, this 'imaginary rust lip' would be got rid of by the spring having to work? In which case, lubrication?

I don't mind these clunks, part of an old car, but when they appear and I cant explain them or do anything about it, drives me a bit mad.

Thanks for any suggestions, they will be much appreciated.

Mick

Hello Mick, do you have wire wheels or steel rims? Could it be the wheels causing you the aggravation?

Jim B.

Loose battery?

aargh - should have said, sorry - alloy wheels, all nuts correct and tight. The battery - I was convinced it was this for a while, so good suggestion. I ended up in addition to the std hold down making a set of straps out of cable ties just to be sure - clunk! So, not battery..........

Are the two bolts which mount the shock absorber tight?

Shock link? Loose bumper mount?

sorry, checked them too (should have said in earlier post - rear dampers are Koni telescopics, no leaks, bolted up nice and tight). Top prizes for speed of suggestions though! I am feeling that my theory about leaf springs is not appearing too likely, so glad I aired it on the privacy of the internet!!!!

well, off for the communte home, in the dark and the rain, 20 miles or so, will see how my clunk is...............but at least I will keep schtum with my mechanic mate in the pub tonight about leaf springs - that could have cost me a pint!

Loose fuel pump? I chased a clunk for a year and it turned out the fuel pump was loose in it's bracket. Only found out it was loose after it died and I had to replace it.

Exhaust hangers etc., are they tight and where they should be. Perhaps your exhaust is wallowing around. (just a pint?) not likely .... :) LOL!

Have spent time underneath this morning - everything, including fuel pump and exhaust, is solid. All rear suspension/drive bits nice and tight, no play or movement in anything to be felt. No corrossion to worry about either. I am beat - so, just in case......have injected oil between the leafs of the rear spring on the drivers side - they drank a fair bit! I know I know, what a daft idea, but have ran out of anything else to cure the clunk. I will report back to say if this cured it (fat chance, but hey, it wasn't raining for 30 mins this morning, and wanted to get busy with something).

I had a similar problem on the rear of my 67 roadster. It drove me crazy. A clunk from the drivers side, it almost sounded if it was something in the trunk or the high side of the shock. I have the tube conversion and new springs. I eventually traced it to a loose exhaust and a missing hanger. One that was welded-up and attached properly, the clunk went away. Try putting someone your weight in the drivers seat and then go try to move the exhaust and see if its bumping anything. In my case the exhaust pipe was hitting the shock mount bolt. You may not be able to duplicate it, because usually it manifests itself on the road, when the suspension in working. I hope it's something simple like this. Good luck! Mitch.

Its a first - a leftfield idea of mine that seems to have merit! I oiled up the offside rear spring with 20-50 engine oil yesterday - have now done just under 150 miles without a clunk! The springs were very rusty, so a good wire brushing and a dose of oil seems to have cured it - I wish I could say that it was wholly my idea, but an old fella I know did say to me a few years back that I should be oiling the rear springs, and this stuck with me. Oh well, heres to the next weird noise!

Thanks for all of your suggestions, these were all things which needed a check to, and helped me work through this in a logical manner.