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Front brake locking up

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Front brake locking up
#1
  This topic is about my 1974 MG MGB
Donwold Avatar
Donwold Donald W
Grande Prairie, Alberta, Canada   CAN
1974 MG MGB
So I was hoping that one of the MG gurus could help me out with this one, The other night my wife and I were out cruising around in the B, it was running beautifully, but after our last stop and on the way home it started acting a little sluggishly. I immediately suspected the brakes and I first thought parking brake but it wasn't engaged. I pulled over a few blocks later and realized that the front drivers side wheel was pretty much locked up. After calling the daughter to come and rescue us, I went home and picked up some tools and headed back to see what the problem was. During the trip back it of course started to pour rain and every stop light was red. I finally got back, put the top up, pulled off the wheel and found the brake pads still snug on the rotor. I managed to get the caliper off and tried to pry the pistons back, I managed to get it home and immediately started looking for answers here on MGExp. I couldn't find anything that I thought would only affect one wheel. I can move the brake pistons back in with a clamp but every time I hit the brake pedal the pads just don't seem to want to release. The only thing that I could see wrong when I had everything apart was that the pistons weren't aligned like they are supposed to be with the lower section towards the hub. Could this be an issue? The brakes were redone completely in the last couple of years sometime before I bought it last summer, new master cylinder, calipers, hoses, the whole shooting match. I'm starting to think the old girl is testing me to see if I'm worthy. Any suggestions?

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Billm Avatar
Billm Bill Masquelier
Santee, Ca, USA   USA
Sounds like the "new" hose on that wheel was defective- it is an inexpensive thing to change and verify and very possibly the problem
BillM

Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
One wheel only can mean either a faulty brake hose or a piston assembly gone bad. I had the former once (took my garage weeks to find out!) never the latter. That's why I am biased towards the faulty hose possibility... grinning smiley

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Mark C Silver Member Mark Cross
Marysville, Ohio, USA   USA
Open the bleeder and try to retract the pistons again. If they move with the bleeder open then the hose is your problem, if not, then there is crud or rust binding the piston. Or one of your pads is in a bind?

Mark..

MGUK Paul Wiley
Watton, Norfolk, UK   GBR
I have a 'thing' about disk brakes. The original calipers would have had a reasonable amount of red grease round the pistons under the outer weather seal. On modern calipers it is fairly easy to inject additional grease in later life. My '77 car has had the calipers replaced - probably with reconditioned ones just before I bought it. The pistons are very stiff to press in and are probably poorly lubricated.

I have had several cars stuck with disk brakes which refused to release. It is easy to fix at the roadside with a spray of WD40. BUT this is an emergency cure, not a proper maintenance job.

Unlike modern calipers the weather seal seems to be a felt seal in a shallow steel ring pressed into the bore of the caliper. This make injecting new grease rather tricky. Either the seal has to be removed first, probably damaging it or the piston removed first. However, the red grease helps protect the seals from sticking and the cylinder and piston from corroding. I use a small syringe to do the injecting. If the weather seal is removed, the gap can be cleaned of old grease using WD40 and the tip of a cotton bud or similar. This grease will probably be brown from a build-up of small rust particles and is best removed before re-greasing.

Red brake grease is a special grease to use on the seals and adjacent parts in hydraulic brake cylinders. It is not easily available at the corner car parts store but can be purchased via the dear old internet in 1lb/400gm tins. What did we do before the internet?

chris Avatar
chris Platinum Member Chris Roop
Pendleton, OR, USA   USA
Or a misadjusted brake light switch. If you haven't futzed with it lately though, that isn't it.


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tomkatb Avatar
tomkatb Larry Baygents
Dayton, Ohio, USA   USA
1963 MG MGB
Easy roadside test. One side is the sign it is not the switch or master.

Drive till it gets stuck. no smoke. Jack the nearest pan. Wheel Should be locked or close. Blip, open quickly the bleed nipple. Close. Does the wheel turn?

If it does it was the hose. If not the piston is sticking. Might be just new seals. Easy to fit a pair of new calipers. Maybe cleaning and greasing. How much time do you want to spend working on it.?

Having the pistons twisted from correct orientation is often a squealing issue.



L.W.(Larry)Baygents
63B
77 Spit

chris Avatar
chris Platinum Member Chris Roop
Pendleton, OR, USA   USA
I beg to differ since I had one side lock up and dealing with the switch took care of it.
Edit: And yes, I know it isn't logical, but I had already replaced hoses, pads, calipers, and the m/c.



Edited 1 time(s). Last edit at 2017-05-17 05:49 PM by chris.


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Donwold Avatar
Donwold Donald W
Grande Prairie, Alberta, Canada   CAN
1974 MG MGB
So I finally had time to pull the caliper apart and I found a bunch of crud in behind the pistons. The brake fluid also looked like well used motor oil. I cleaned everything up, flushed the lines, and everything seems to be working again. I ordered the caliper rebuild kit from Moss and I will probably install it asap but for right now the sun is finally shining and I think some road testing is in order. (I think short trips will be prudent). Thanks for all of the advice!

Don

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chris Avatar
chris Platinum Member Chris Roop
Pendleton, OR, USA   USA
Cool! Neil Cassady, one of Ken Kesey's bus drivers, didn't like to use brakes. Always staying in motion. At one point, the bus didn't have brakes. you could be like that. grinning smiley


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Donwold Avatar
Donwold Donald W
Grande Prairie, Alberta, Canada   CAN
1974 MG MGB
Minus the LSD of course!

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