Brakes jamming on.

[M.J.S]

Hi guys, not been on for a while as the car has not been used.

After a few months unused in the garage, charged her up and took her for her MOT last week. All seemed okay on a test drive and a 20 mile round trip to the tester. He noticed NSF brake binding ever so slightly but she passed without too much hassle and drove home fine.

Off the road a few more days as I stripped and cleaned the carbs and fitted a new oil feed. Rebuilt and took for a half mile test drive.

Then the problems started.

As I got nearly home I noticed her struggling and it was obvious the front brakes had started binding. I limped her into the garage and took a look. The fronts had locked almost solid.

The pistons did not want to go back until I released the bleed nipples. Pads removed I carried out the usual in and out with the pistons and wd40, cleaned a made sure everything was free, pistons sliding freely, etc, put it back together, out for a drive and all ok.

The day after I jumped in her, reversed her out of the garage and didn't make it out of the drive before the brakes jammed on.

Crawled her back in, front wheels up, both siezed solid. Took osf off and couldn't slide pistons back. Released pressure with nipple and both sides appeared to free off.

Is it possible for the master cylinder (or servo) to stick or not release the hydraulic pressure? Could it be caliper related?

Could it be something else? Any known common probs?

I didn't want to take the calipers off because I've a horrible feeling the brake pipes are siezed and will twist and snap if I try.

Frightened to use her now even on a short test in case the fronts jam on and I'm stuck. Left her in the garage with the front wheels off.

She's a Oct 1972 130/5 by the way, with a genuine 32k on her. Master cylinder methinks original.

[robertverhey]

tried disconnecting the vacuum feed to the servo?

[john.p.clegg]

MJS
Which type of servo do you have,there are strings on here re sticking air valves that need a little help,either extra spring or removing an o ring (I've heard)

John

Incommunicado for the next week (Italy)

[gerrym]

MJS, as previous replies have alluded to, the servo is a primary suspect in this. The best way to eliminate this as the cause is to provide a hydraulic jumper between the inlet and outlet pipe connections.

A couple of points:-

1/ You mention the use of WD40 - not sure what you mean but hope it was not anywhere near the calipers. Danger of destroying the rubber boots and seals, or contaiminating the pads.

2/ Brakes need to be serviced. This means stripping hydraulics apart and replacing any worn or corroded parts and replacing seals. Of course this also assumes the brake fluid has been replaced on some sort of schedule. The implication of this is that old age and/or infrequent servicing may just have caught up with your brakes in a number of areas. Get them right, you may not have a 2nd chance.

3/ Actually keeping on top of classic brakes is not that hard. Companies like Classiccar provide rebuilt components at very reasonable prices. You mention a fear of destroying the hydraulic pipe. Replace that too, its not difficult and using a good flaring tool and CuNi makes it even easier. The connection between the flexibles and the calipers should be just a short sacrificial length of flared pipe (about 8" long)

Best regards

[alexblack13]

Hi Guys,
Gerry just beat me to it on the wd40 issue..... Bad news! The calipers now need to be stripped and rebuilt properly as the stuff will ruin the seals etc.

I spent ages on a woodworking machine with lots of air solenoids & shuttle valves etc. leak after leak after leak. I had worked my way down a manifold bank of about 6 valves when I started smelling the stuff. Interrogating the owner I discovered that he had filled the filter / lubricator unit on the pneumatics system with ...... wd40!!!!!! Expensive mistake that was!

Keep it well away from your brakes.It is a very good product and has loads of uses,but car brakes are def' not one of them..

Take care now and strip / rebuild those calipers. Lubricate only with proper brake grease / lube or clean brake fluid.

Alex B....

[M.J.S]

Thanks guys. I used wd40 as a generic term, but its actually a rubber safe high pressure lube designed for lubricating pistons, pulleys etc around rubber belts or seals.

The servo I don't think is the original type, and is quite new. Looks like an MGB type. Will try bypassing it and see what happens.

[gerrym]

"Rubber Safe"

Methinks this is a realtive term and may not apply to the compounds used for the brake seals.

In any case, if the pistons need external lubrication this almost by definition an indication that something is not right.

Regards

[gwiz22]

MJS,

I had a similar problem when I first acquired must Plus2. What servo do you have? If it is a Lockheed then it could be the small plunger under shell like cover on the side of the unit. Classicar Automotive sell a little spring, about ?3.00 which when fitted under the plunger, assists the plunger to move back and release the pressure. I have a drawing of where the spring should go somewhere, I will try and find it and post it for you. To chack if it truly is the servo and not the master cylinder, disconnect the servo, howeber, make sure you plug the pipe so the inlet is not taking in unwanted air.

Regards
GRaham

[leifanten]

Graham,
great if you post it on the site, as I experience the same with my +2

Thanks