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MG MGB Technical - Sources of front end clunks - when braking

I have some notions as to the causes of front end clunks when braking, but I don't profess to know them all. I have given all the usual suspects a good viewing and testing and none of them seems to be the obvious, jump out at you, cause.

Therefore, since there are many people with a wide variety of experiences on this BBS, I would like to ask what things you might check or you have found to be unusual sources of this problem. Think of it as an way of enlightening not just myself but giving anyone else who views this thread some hope of finding the cause. It can't hurt any of us. Many thanks in advance.
Bob Muenchausen

Bob,

Do you have wire spoke wheels?
Wheel/hub splines can clunk.

Mick
M F Anderson

Bob - What about the A arm bushings on the swivel mounted tot he cross member? That is a notorious source of clunks when braking, next to the worn splines, which was the cause of my clunk. Good luck - Dave
David DuBois

Bob. What you ask for is a tall order. Mayhap we should discuss something more simple such as, "If the US right wing feels we need guns to protect ourselves against imposed goverment, and, after invading Iraq to "free their people from the imposed dictatorship of Saddam Hussain", we find that all of the people are heavily armed, was it an "imposed dicatatorship"? I am sure the NRA will fund a scholarship for the best answer by a high school student.

I am not sure where to begin to answer your question as it can vary significantly. I will try to cover what I know, but there will be things I do not know or over look.

As Mick mentions, wheels are the beginnings. With wire wheels, you can either have bad wheel hubs or axle hubs which will sound as a clunk on breaking. So will a loose spinner or a hub that has been deformed by over tightening of the spinner. With bolt on wheels, a loose lug nut(s) can cause such a sound, often with a growling noise as you are driving. If, instead of using MG specific, 4" between centers for the lub nut holes, you used the more common 100 mm wheels that some have tried, the lug nuts do not tighten properly, the 100 mm hole tries to wear to 102.4mm, the lug nuts no longer hold because the hole is shifting and there is a clunk on braking. Broken spokes on a wire wheel can also cause a clunk with either the center lock or bolt on wires.

The brake pads can move in the calipers and cause a clunk. This can be caused by slightly too small a pad or a broken or worn spring. They will clunk as the brakes are applied.

The calipers can clunk if they are not firmly bolted to the back plates.

The rotors can clunk if they are not firmly bolted to the hubs.

The hubs can clunk if there is a little too much end shake.

The back plate can clunk if it is not firmly bolted to the kingpin.

The kingpin can clunk if it is not firmly bolted in. It can also clunk if the upper trunion bushings have worn and are no longer positioning it properly. Or, if the lower bushings are worn and not positioning it properly.

The upper kingpin trunion is bolted to the hydraulic damper. If the arms are loose, the bolt holding the two together becomes loose or if the dampers are not firmly bolted to the cross member, there may be clunk.

The lower kinpin section is bolted to the A arms and the bushings between them may go bad, allowing a clunk. The A arms may have an anti-roll bar bolted into them. If this is loose, it can clunk. The lower A arms are formed by the bolting together of two U shaped metal strips and the spring pan. If the bolts holding the spring pan to the arms are loose, there can be a clunk. The inner end of the A arms attach to the front cross member. Most of us use V-8 bushings which last longer than the factory bushing. If either bushing goes bad, you can get a clunk from this area.

All of this is attached to the front cross member which is attached to the frame with four bolts (two on either side) with some rubber packing strips. If any of this is loose, there will be front end clunk. The front cross member will loosen up over time and should be re-tightened anytime the engine is out. That covers most of the front suspension.

Then, we have engine mounts, tranny mounts, etc. If these are bad, or loose, it can allow the engine and transmission to shift forwards on braking, making a clunking sound. You can also get a clunk from loose equipment such as the alternator/generator and air pump. The radiator, if not held in sufficiently, can cause a clunk. I have seen them only held in with one upper bolt on each side. Allows movement of the lower radiator, causing a clunk. Same thing for the radiator surround. These, usually, will also cause a clunk on acceleration, as will bad wheels.

I have probably missed some things, but this will serve as a starting point for others to expand on.

Hey, how bout them Iraquis. Les
Les Bengtson

About the Iraqis: Didn't you think the overthrow just a bit easy?? ;-) I am reminded of Uncle Remus and tarbabys, but we digress.

I have bolt on wheels. I had checked the brake calipers and rotors, all appeared tight. No apparent looseness of the wheel bearings, or the kingpins or suspension bushings. And, as far as I can tell, nothing is loose that shouldn't be(except maybe the marbles in my head). One thing I haven't checked thoroughly, tho, is the mounting of the front cross member. It has not had new rubber bushings since new, and after 35 yrs, I suspect they may be due. But there seems to be no noticable drift of the alignment, so that may not really be an issue.

I plan on digging deeper soon, but I wanted to get a feel for what others have discovered or look for as that can be helpful for looking into things we unwittingly miss because they are just too obvious or "acts of God" that happen to .0001% of all owners, but they DO happen. I figured it couldn't hurt me to read what others had found to be true for them, and the same info would of value to anyone else on the BBS someday faced with the same problem. I hope we hear from some others too, Les, it is what richens this BBS and its archives for everyone.
Bob Muenchausen

Hi

I had a clunk when breaking hard on my GT. Having a quick look around found the lower wishbone bushes perished (only the poor standard not the uprated v8 ones fitted).
On strip ready to fit the v8 ones also found both king pin lower mounting bolt bearings badly worn. On fitting all new plus new sway bar bushes clunk has gone away. The moral of the story is IMHO its not easy to check for worn bits while they are fitted to the car. Decide on a course of action and be prepared to find additional work!

Gary
G Roberts

I went thru all the typical 'MG' clunking sources, all of which are described above. I solved my problem by replacing the bolts that connect the lower wishbone arms to the spring pan. There are three per side if you have a sway bar. My car is a '63, so I guess these bolts had seen enough, because they were not loose and the holes were still tight.
Todd Alkire

Les has listed many options to look into. My own clunk came from the damper pad area of the stering rack. I believe it was cured when I added oil and removed one of the shims. I suppose the wear on the damper mechanism created some lash in the rack and it clunked at the onset of hard braking. I did feel the clunk in the wheel so that was the path I followed.
John

For what it's worth,

I had a "clunking" that came up from the front end through the steering wheel when braking.

The fix was replacing the rear shoes, (the right side had gotten some gear oil from a bad seal in the hub.)

Not claiming this is a cure, but if everything else checks out ok, take a look at rear brakes.

glg

Two more to add - the holes in the outer end of the wishbone arms wear oval if the bottom link seizes, definite clunk here - also the spring can move in the spring pan, more of a boing than a clunk!( grease the bottom of the spring is the answer here).
Chris Betson

All good ideas, gents. Thanks a bunch!
Bob Muenchausen

The source of mine turned out to be a loose front crossmember bolt.

RE Iraqis: The US bribed them to stand down...
http://www.globalsecurity.org/org/news/2003/030524-iraq-bribes01.htm
Matthew Grosser

Anti-roll bar broken iside the rubber bushes, it happened to me and gave a thud on full lock, did I really corner that hard?
John.
John Prewer

The very very very first place I would look is the front pads. Check to see if the retainer clips are there. Providing its a front disc car.

While your at it might as waell add some disc brake quiet to the pads to stop any sqweeking.

Just my 2 bits.

later
Joel H
Joel H

Dito what Joel said. After going through what you are doing, I inspected the front pads and one of the retainer clips was not securly in its place. I could move the pad with a small screwdriver. I put in a new clip and the clunk went away
Cris

I have a front end clunk that is immediate even with light brake application. From the sound and timing I had always assumed that it was the front pads and/or calipers moving slightly. There is no noticeable looseness when checking by hand and I have tended not to worry about it.

BarryQ
73B
B.J. Quartermaine

<<I went thru all the typical 'MG' clunking sources, all of which are described above. I solved my problem by replacing the bolts that connect the lower wishbone arms to the spring pan. There are three per side if you have a sway bar. My car is a '63, so I guess these bolts had seen enough, because they were not loose and the holes were still tight.>>

Interesting, Todd.

My Dad's MGB is a '63, as well. When his car made the "front end clunks when braking" noise, a respected club member said that sometimes that is just the coil spring moving in the spring pan. The "clunk" that I heard made me believe that was a very plausible eplanation.
Carl

I suffered with this for awhile as well - real bad clunking sounds - ... and I used to really feel the road !

It finally went away when I replaced the front suspension (kingpin and coils).

Much better now.

Sudhir
sudhir menon

This thread was discussed between 09/06/2003 and 14/06/2003

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