Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing PLUS 8 Brakes locking on

Hi All,

I'm new to the forum. I have a 1994 Plus 8, and recently the Front Brakes have been locking on - especially when the weather is hot. has anyone else come across this issue? So far I've changed (not me really - the mechanic) the master cylinder and the hoses, we are just about to replace the front calliper pots.

Thoughts welcome.

Ian

Callipers is where I would have started. Think that will solve the issue but check also that any rub points on the edges of the pads are very lightly lubed with Ceretec or copper slip grease.

Starting on the calipers would have been my route in.

Yeah for me too the calipers would be the first port of call, though the hot weather would seem to risk being a red herring, given the temps that brakes can get up to in everyday operation...?

If indeed hot weather is found to be a determining factor, it would be interesting to find out why.

Good luck with the repair process.

My car had the same on a run a couple of weeks ago.
The pistons were not moving feely in the driver side calliper.
I have HiSpec callipers from Mulfab. I got a service kit , stripped it down, found the pistons were good but the internal seals not good.
The calliper seized, the pedal went soft, car was pulling to the right and very hot!
The fluid boiled, the pads were bad. I cleaned the disc, new fluid. The disc appeared true and unwarped, just dirty.
I have done a couple of test drives to bed in the new pads and so far brakes are ok. A couple more test runs to bed in fully and see if all is still ok.
When I pulled over due to the brake problem the brakes were really hot with a smell of burning and a small amount of smoke from the wheel. The AA came and cleaned things up and he followed me to check all was ok. It was and a careful drive home went ok.

Agree with the others here , the temperature is a red herring . Brakes are designed to run VERY hot and ambient temperatures will only affect this to a very limited effect.

Is this just the fronts locking , or are the rears joining in as well? If the latter then I would look at other potential causes , but if it is just the fronts then a sticky pad would would appear to be the most likely culprit BUT it would be most unusual to have 2 (or 4 ?) such problems simultaneously, so I am trying to think a little broader. Have the pistons in the calipers become "sticky" and not retracting? Again it is very unlikely that there would be all 4 pistons affected, but just check them all.

Unless the car has been modified with a brake bias adjustment, the front/rear balance is set by the master cylinder, so nothing can easily be changed in that respect.

I am not sure if 1994 is the old style brakes (drums manually adjustable) or the new (rear shoes auto adjusted? If the former try manually adjusting the rears up until they show more "bite" , this may help give a bit more power to the rear brakes and thus decrease effort on the fronts.

This one is really puzzling me.

Which callipers do you have? The originals are likely to be Austin Princess ones!
Mine are 4pot HiSpec Billet4 and one piston on the outside definitely sticky with the other on same side sluggish.
I can’t remember the Princess configuration.

I bought these
https://www.ebay.co.uk/itm/FOR-AUST...46890.l49286&mkrid=710-127635-2958-0
Terry Foxen G.E.E also has them in stock

Haven't fitted them yet, as using the brakes more aggressively seems to have freed up the piston that was sticking!!

Hi guys,

Greatly appreciate the replies. I'm going to replace the pots in the callipers. Well I'm not - the garage will! I don't know what type they are but they have 4 pots. Your comments about the temperature are sensible - maybe the issue is exacerbated and comes on more quickly on hot days.

The repair is next week when the spares come through. Thanks again.

Ian

While you are in the area, you would be wise to check the brake pads and the power brake assist function.

1. During the tour I had of AP brakes, they wanted me to try their newer calipers we discovered that the pads given to the MMC and our community, don't fit. They leave a lip which cpould have an unknown effect. Simply chamfer it off. https://www.gomog.com/allmorgan/brakehistory.html#WATCHPOINT:

2. The power brake assist harnesses the engine-created vacuum to assist in braking. I was reluctant to try it at first, but the good Mr. M. Baldwin convinced me over a pint. He was right, it is fine brake "assist" rather than power brakes (that IMHO, robs the foot [and the driver attached to it] of any brake "feel". Over time, something can malfunction with the system, For example, the underside of the vacuum hose to the engine, can become flaccid while the visible side looks great. In effect, the flaccid side acts as a valve and refuses to release the vacuum, locking the brakes on.Or the inner bellows can act the same. Should be easy to test..when your brakes lock, detach the vacuum hose at the engine.

I never wrote up the tour as I too think the Mulberry Hispecs are a better buy. But these Caparo thingies were given to me and they work fine

L.