Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 2017 GDI +4 - Brake Pedal Creep on Hill

On my Dads new Morgan I have notice the if you are holding the car on the brake on a hill / slope that the pedal starts to creep forward, up to the point you apply the handbrake for safety. Otherwise the car brakes fine with no issues.

I notice legerwoods noticed this on their service in 2020 but no action was taken. It had a fluid change last year about 600 miles ago.

Is this normal or is it a case of sticking rear / brake master cylinder?

On that now what the replacement wheel / master cylinders are from non Morgan sources?

Many thanks Will

The part number on a replacement rear wheel cylinder recently supplied by BHM for my 2014 4/4 is: CW15953.

B & G or a Pair fro,m Classicpartstrader I have used these a few years ago for my Plus 8 9 yrs ago and still good.

If it's not leaking loosing fluid surely it can only be the master cylinder leaking internally

^^^ +1, but could also be the servo leaking internally. Are you getting white smoke out of the exhaust?

Edit, if it is the servo the fluid level normally goes down.

Many thanks for the part details, tracked down the master and wheel cylinders if needed. The servo is super simple so expect it is unlikely for that to go wrong..

There is no evidence of leaking fluid. The car brakes fine in normal driving, it’s just when you hold the brake pedal down when you’re on a hill that it creeps downward rather than being rock solid. Will try my 96 +4 tomorrow morning on the school run to see what it like in comparison as it turns out it is the same braking system.

Could it be a sticking rear wheel cylinder gradually moving with the positive pressure, next time it happens drive a mile or two and then check the temp of the rear wheels. If it is sticking then then it probably hasn't completely released and the wheel will be hot.

Next time you start the car, prior to starting, press the brake pedal hard and hold it there. Then start the car, you should feel the pedal drop as you gain servo assistance. Is this anything like you are feeling when holding on a hill? If so check the rear wheels for free rotation then using the foot brake with engine running..... safely jacked up and OUT OF GEAR of course! apply and check with peddle depressed to ascertain if you have breaking both sides and that they release and rotate unhindered when you release the brake peddle. If this all works fine then I would look to the master cylinder as the culprit. One last question does the brake peddle keep creeping towards the floor if you continue to hold pressure on it or does it reach a natural stop? I'm suspecting that it does! The brake master cylinder because of the way it works has a limited travel within its potential full range. This eventually causes cylinder wear within the usage range and when the wear gets to a certain level you start to get the fluid passing past the piston seal, this could either be due to wear in the barrel or more likely the piston seal.. If when you get this creep it stops at a certain point or slows radically then expect wear to possibly both areas whereas if it keep going then the seal is faulty. It might be possible to get a repair kit but frankly, just replace the cylinder complete.

Hi Sewin,
So when you start the car the pedal drops with the Servo assistance upon starting. So I expect that rules out the Servo?

If you hold the brake pedal down on a slope it will creep forward until it hits the floor!

Will jack the car up later and check the rear wheels but the drums are not any hotter than my 96 +4 and are equal both sides about 20 degrees after a drive.

Many thanks
Will

The fact that there are no apparent leaks and that fluid has been recently changed, my first port of call would be simply to bleed the system again, in case of trapped air.