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MG MGB Technical - Front end clunk

I've looked through the archives for awhile now to try and find something similar, but to no avail. I have noticed a clunk from the right front area when reversing from my parking spot at work. It occurs when I have turned the steering wheel to almost full lock. It really does not happen at any other time, except the very rare occasion upon braking. This clunk has been there for years, but seems to be worsening.

Several years ago, I dismantled the front suspension and replaced the inner A-arm bushings with V8 bushings, plus did the upper and lower trunion bushings. The lower trunion bushings were in particularly bad condition. Tie rod ends and gaiters were replaced also by my mechanic. At the time I was hoping the clunk would be gone after this job, but it wasn't. I recently replaced the springs, and all bushings seemed to be in good condition. I have checked the tightness of the crossmember bolts and the condition of the pads between the frame and the crossmember, and they appear OK.

It would seem to me this leaves the kingpins as the only remaining culprit. When I raise the front of the car and grasp the top and bottom of the tire, I can feel a small amount of movement. Removing the wheel, I can see a small amount of movement at the bottom kingpin bushing.

I don't seem to have any of the symptoms of bad kingpins otherwise such as hard steering, wobble, wander or increased camber etc. That said, could this clunk be coming from the kingpins? Is any play in a kingpin acceptable?
Erick Vesterback

I had one similar and it turned out to be a worn bushing on the steering rack.
Sandy
ss sanders

Probably is the kingpin, up and down (end float) As well as bush wear. End float can be adjusted out, but pin and bush wear calls for replacement for which you will need to get your hands on a special reamer. The end play should be 0.002", adjusted with washers and shims. Some of the movement you detected while gripping the tyre 12 & 6 will be the wheel bearing end float. As for what amount of play, as detected by your other examination, is acceptable? A judgement call!!
Allan Reeling

Do you have spoked wheels? Could it be the splines on the wheel or hub that are worn? Secondly, could it be the disc brake pads moving in the caliper as it only happens when you reverse? Just some random thoughts.
Mike Howlett

LHD? If so right front is the 'free' end of the rack and that runs in a bush, so could be that as has been suggested.

Because of the wheel bearing end-float really you need two people - one to rock and the other to ... roll under the car and see what is moving. Or use a tyre lever or similar to lever things.
Paul Hunt

Had a similar clunk on my Cousins car for years - only when starting to reverse.
Eventually tracked down to slight wear/ovalisation in the outer wishbone - It must have been a tolerance issue with the pan or spacer as of course it shouldn't wear being clamped.

R.
richard boobier

Also what about wear in the rack to tie rod joints. (not the tie rod ends, I am referring to the inboard end of the tie rod)
This is worth checking as I had this problem years ago.
I believe this can be adjusted out by removing the gaiter and tightening it up.
Ian Buckley

Clonk under braking/change of direction is a classis symptom of wear in the thrusts either end of the bottom kingpin trunnion, allowing the eye of the kingpin to float backwards and forwards a few thou.
Paul Walbran

I will check into the steering rack end bush that is mentioned. The A-arm holes are not ovalized. The top and bottom trunions are as new.

This clunk is not really associated with braking. If I reverse and only turn the steering wheel partially, there is no clunk. If I reverse and turn the wheel almost to full lock, the clunk is quite loud. In fact its embarrassing when there are people around - I bet they are wondering if the front wheel is going to fall off!
If it clunks, then I may (not always) get a faint clunk the next time I brake.

I have bolt on wheels torqued to proper amount, not wire wheels. I used to have wire wheels, and thought maybe the clunk was associated with them, but there is no difference with the new bolt-ons.

I can see a small amount of movement of the bottom kingpin relative to the bottom swivel axle bushing, so there is definitely some wear there. Whether it is excessive, I am not sure. I guess its difficult to quantify. I don't mind replacing them if it will solve the problem or if this small level of wear puts me at risk of a catastrophic failure, and I will swap in a complete assembly rather than go the route of the reamer.

Thanks, guys, for your input.
Erick Vesterback

Just as a follow-up, I replaced the kingpins over the weekend with a remanufactured swivel-axle assembly. The clunk is now completely gone. Overall the ride feels tighter and it turns out, there were other rattles etc over minor bumps that I had attributed to other things, that have disappeared. So overall, I have noticed a huge improvement with the new kingpins. Even though the wear in the originals seemed minor to me, it was obviously enough to have made a difference in ride quality and was the cause of the clunk I was hearing. Thanks to all who responded.
Erick Vesterback

Erick: My 79 has a clunk only when the right had wheel goes over a bump. I suspect I have the same issue as yours. The car has 122k The front end was rebushed about 14k miles ago. Did you check the shocks for fluid leakage?

Cheers

Gary
79 mgb
gary hansen

I'd suggest, if you're not already doing so, greasing the front suspension every three months or 3,000 miles, whichever is sooner, and just before any official test
Nigel Atkins

Gary, my shocks show no sign of leakage. They operate smoothly throughout their whole range of motion. When you say re-bushed, did that include the kingpins? I put new bushings (including V8 bushings at the inner A-arms) everywhere else 15,000 miles ago but just did the kingpins. I probably should have done the kingpins first, since it made the greater difference. My mechanic at the time felt the kingpins were "pretty good", but I have had the same symptoms all this time.

Nigel, my plan is to grease them every oil change, or every 6 months, which works out to every 1500 miles or so for me.
Erick Vesterback

Erick,
I started at 6 monthly greasing but soon found it was adventurous to change to 3 monthly and just before out annual statutory official vehicle check (MOT)

3,000 miles a year must be just about around the minimum mileage to keep the car running well subject to the mileage being fairly evenly spread over the whole year (if possible where you live) and not one block of 2,000 miles in a two week tour leaving just 1,000 over 50 weeks

I once saw a B roadster out in the sun broken down so I went over to see if I could offer any help and the owner declined as he had someone coming out to him, when I asked him if he used it much he told me yes, 1,500 miles a year!
Nigel Atkins

Nigel,
For the past 6 years, I have used the car only in summer, and it has sat under my enclosed deck for winter (this car would be impossible to drive in these northern Ontario winters) and the most I could put on it was about 1000-1500 miles per year. Thankfully, soon I and the car will be on Vancouver Island, where I can resume my year-round driving with this car, and can rack up about 3000 miles per year. I agree, the car needs exercise to stay healhy:)
Erick Vesterback

good news Erick, aim for 6,000 miles a year

I've no idea what grease you use and what it goes down to in temperature but I'd at least grease at putting car into hibernation and again at coming out - believe me I loathe doing the messy greasing every time but wouldn't feel comfortable with the car if I didn't every 3 months and just before an MoT
Nigel Atkins

This thread was discussed between 28/07/2014 and 22/08/2014

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