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MG MGB Technical - Clutch pedal 'clunk'
|I have an intermittant "click" sort of "clunk" banging against my foot when depressing the clutch pedal in my 73 Roadster. It feels like there is something that shifts as the pedal goes down. I can hear it but mainly I feel it sort of slap against my foot. It can happen anywhere in the pedal stroke. It doesn't matter if I'm pressing the pedal fast and hard or slow and soft.|
I don't know the makeup of the pedal linkage system, but I would guess this is caused by a pivot hole in the pedal arm that has worn to oversized. Sometimes it stays in place and sometimes it shifts and a pivot post wacks up against the edge of the oversized hole.
Does this seem like a good analysis / guess of what is going on here? Can anyone tell me what to look at to repair this over the winter?
|Suggest you remove the inspection cover (plate) to the pedal pivot points for your clutch and brake master cylinders. Have someone work the pedal for you as you take a look-see. Might be bushing, pivot bolt, loose retaining nut or clevis pin. The system is simple in design and your problem should be easily found. If your 'B has a self-locking prop for the hood ('71 on), take it loose (at hood mount) and prop the hood near vertical with something appropriate - gives you much more visibility and working room.|
|BH, I think you may have hit it on the head with your diagnosis. It's what I would have said to check anyhhow. To check this go under the hood at the master cylinder/pedal box setup. Remove the cover so you can examine the pedals. At the top of the pedal there is a hole that a clevis pins goes into and thru the clutch push rod end. It will be held in place with a cotter pin. Remove the cotter pin and withdrawl the clevis pin. Examine closely the hole at the top of the pedal and the hole in the end of the pushrod, one or both may be elongated. Once this happens the clevis pin gets all worn too. It's a easy job to inspect it. You may have to find a new pedal I think you can remove it without removing the entire box assembly. Examine everything closely. I once had a midget where part of the top of the clutch pedal broke off, it sstill moved the pushrod and did not clunk, just didn't move the rod enough to engage the clutch.|
Hope this is of some help.
|You should be able to weld and file the pedal hole bit by bit to get it back to circular, only add weld to the worn side or you'll lose the reference. Replace the cotter pin and master push-rod. I did this on my roadster a few years ago, but more for reasons of a low biting point i.e. short clutch travel than clicking.|
|Paul Hunt 2|
|BH. I agree with what has been written. I would also add that the clutch master cylinder pushrod wears excessively. This is seen as an elongated hole in the pushrod rather than a circular hole. That, when combined with a worn clevis pin, or by itself, can cause problems. The pushrod is available, as a seperate part, from Moss Motors. I have found that all of the ones on my cars have worn excessively over the years and have replaced them with new pushrods and clevis pins. One more thing to check during your inspection.|
|Thank you all for taking the time to give me some guidance. It's been busy the past week and I completely overlooked checking back for additional responses.|
I will pull the box cover that is under the hood and check it out per your suggestions.
Best wishes for a good holiday!
|I doubt it is clevis pins or pushrod wear - more likely to be a corroded slave cylinder piston which is jamming in the bore or a thrust bearing that is stiff in the fork.|
|Chris at Octarine Services|
This thread was discussed between 11/12/2006 and 18/12/2006
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