Noise from Under Car

[december2020]

I am not sure you answer questions from abroad but thought I would try asking as you are extremely knowledgeable on MG's.
I have '78 MGB roadster with 72K on the odometer. Good condition. One owner before myself.

I have had the car five years.

The problem:

When the car engine is cold I can pull away no problem all good. But when it gets to operating temperature you get a click or light clunk from somewhere midships or forward left side I believe. It only does it when pulling away during/after releasing the clutch. No other symptoms. It literally is a momentary click and it does not do it again until I stop at lights or something then pull away again and 'click'.

I think the suspension joints are OK and lubed. I wondered if it was pads in the brakes but I inspected and checked them for movement. Also wondered if it was something in the clutch but it does not do it all the time and the clutch works fine. Ally wheels not spoked.

It is elusive in that I cannot locate exactly where the noise is coming from whilst driving. Otherwise the car drives great. The click has been with the car since I have had it.

I wondered with your vast knowledge if you have any possible suggestions what that click may be. Any info would be most appreciated.

Peter O'Connor

[JohnTwist]

If it is heat that makes a difference, then it's probably not the suspension.   My guess would be the exhaust as that is on the left side of the vehicle.  But what about the exhaust is causing the click / clunk?  There is a strap between the exhaust and the joint of the engine/gearbox which is sometimes missing and often loose.  If you can get underneath (just jack up the left hand side) you can grab the cold exhaust and push it back and forth -- that might give you a hint as to the source of the noise.  When you are starting off, the engine tips to the right (opposite direction of crank rotation) which might cause a clamp or strap to shift.  Let me know what you find!

Hope this little bit helps.  Roger Parker from the MGOC will probably weigh in on this since he's just up the road from you.

John Twist
SAFETY FAST!

[Art]

Hi Peter,

You might also want to look at the differential.  There are some spacer/thrust bearings between the gears that can wear or crack and fall out.  The characteristic 'click' occurs when the the driveline goes slack as you decelerate and stop.  A soon as you hit the gas, the gears move outboard to take-up the space and hit the housing creating that sound.

Early cars the washers were a fibrous material, which more often failed and fell out of place.  Newer thrust washers were brass, as are the current replacements (Moss part# 267-140) and still cheap at $4.39US each.

Replacement requires the differential case be opened and the axle shafts removed.   There is a way to install them without removing the gears and carrier, but at this age I might suggest checking all the gears, shims and bearings.  Also, with the axel shafts removed, I'd also advise to replace the outboard bearings, seals and the rear brakes, since they will have to be taken apart.  The axel itself need not be removed.

Hope that helps you.

Safety Fast!

Art