Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 M3W brake failure

For the second time I now have a customer with me who complained that his brakes failed with the pedal going almost to the floor. The back up circuit worked OK. the rear brake drum got so hot that the dust cap on the bleed nipple melted! On dismantling the rear brake which was very tight to get apart - over adjustment perhaps? - we found all to be well. everything working as normal, absolutely no fluid leaks anywhere - linings good - all parts free and working OK. I re set the automatic adjuster ratchet, put it all back together and all now works like new. Pedal back at the top, handbrake adjustment good, tested and found to brake as you would expect.

I think the very fine teeth on the adjuster allowed it to go one notch too far and therefore prevented proper release of the shoes - hence the overheating but why did the pedal go to the floor with no leaks apparent? and why has it magically recovered?

So the questions are:-
has anyone else had this happen?
Anyone got a theory as to what has happened?

As I say, this is the second car with identical symptoms, the first with me driving a customers car and the second reported by another customer. I find it all very worrying.

Phil

What year cars?

Phil, one likely possibility for the soft pedal is the brake fluid boiling. Any air or water in the lines turns to gas and becomes compressible, hence no brakes. Common problem with race cars and boiling brake fluid. Cools down, and brakes again. If the rear got that hot, certainly enough to affect the brake fluid!

I'd definitely flush the fluid and replace with quality synthetic.

Thanks trucking-on. Only problem is that, on car 1, the soft pedal continued for another 20 or so miles at reduced speed. Fluid already flushed out - first thing I did as it looked a bit dark in colour.

These are 2013 and 2014 cars Stephen.

Thanks Phil.

Phil, this could be brake fade.

If a lot of braking occurs ie. going down hill and reducing speed using the brakes constantly, or the shoes are over adjusted and binding the drums get so hot they expand away from the shoes, this results in the pedal having an excess of travel and the brakes not being that efficient.

This was a regular occurance on fire engines of yesteryear and was quite scary if you were not aware of the situation. Many a time a new driver would send the engine up with a defect on the brakes but this was a natural occurance when you had been driving hard on the way to a call.

If the drum was so hot that it had melted the dust cover this could be the problem.

Hope this helps in some small way.....


Rob...

The brake system is the same in all the M3Ws except for the reservoir changing from two in the early cars to one from 2013 on, so this problem being related to year should not apply. I go with Blue+4s theory of brake fade had the same symptoms when racing in my 4/4.

Surely brake fade would not cause the pedal to go to the floor?

How are the two circuits organised in the m3w?

On my ecomobile there are two disks at the front. One of them is part of the cbs and the other is the second circuit.
I needed it one time going down Oberslazberg because of boiling fluid.
Not a fun feeling but the second circuit worked fine - 🤯

I requested my dealer perform a brake flush/ fluid change at 3.5-4 years. He suggested it wasn’t necessary as I only had 5+k miles on the M3W. I insisted. Anyone else have similar experiences?