MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Serious Brake issue

I believe my brake system has been contaminated with DOT 3. Both rear cylinders have failed. Am I going to have to replace all softgoods in the whole system - including flex lines?
If yes is there a complete kit I should look for, and can someone with reasonable mechanical skills do this properly?

Thanks!
Brian McKie

Brian, Are the rear brake cylinders leaking fluid? Why do you say they may have been contaminated with DOT 3 fluid? To answer your questions, anyone with reasonable mechanical skills can work on MGB brakes. If you want to replace all soft items and flex hoses I don't know of any place that sells a complete kit. but some places do offer front and rear brake kits. If you do not know the previous maintenance history of your brakes and the rear cylinders are leaking I would replace them and the rear shoes if they are contaminated with fluid, adjust the rear brakes, flush the brake system with DOT 4 fluid if that is what you plan to use and bleed the brakes. If the brakes are ok after that I wouldn't worry about DOT 3 contamination. There is lots of information in the archives about DOT 3 brake fluid not being compatible
with British car braking systems. My only comment about that issue is that I have Ford Motorcraft DOT
3 with 550 degree dry boiling temp in my 68 GT and my brakes work well. It has been in the car about six
months and no problems so far. End of my DOT 3 discussion. Get back to the list with a little more information and you will get some good suggestions on what you should do. Good luck, Clifton
Clifton Gordon

Brian-
I presume that you're saying that some DPO put American DOT3 brake fluid in the system and that the seals, which are made of natural rubber, are being dissolved by the American-made DOT3 fluid and are now failing. Get a Mighty Vac and pump that suff out of the system right away before it does any more damage, then flush the system with denatured alcohol (available at any pharmacy). Afterwards, refill the system with either Castrol LMA DOT4 brake fluid or Valvolene SynPower brake fluid, and bleed the system. Don't forget to do the hydraulic system for the clutch, too. Good Luck!
Steve S.

Brian. Brit-Tek market a "major brake" overhaul kit which contains rear wheel cylinders, new flex lines, new front rotors/discs, new front pads and new rear shoes. In addition, a master cylinder rebuild kit and two front caliper rebuild kits would be in order. As Steve notes, a system flush would be in order to remove any contaminate from the lines. The advise to consider rebuilding the clutch hydraulics is also a good idea. That system would also need to be fully flushed when doing so. A clutch master cylinder rebuild kit, a slave cylinder rebuild kit and a new clutch flex line would be required.

But, before you do this, might I suggest that you examine the nature of the failure? The rear brakes are non-self adjusting. The owner/driver needs to adjust the rear brakes periodically. If this is not done, depending on the amount of wear on the rear shoes, it can allow the pistons inside the rear wheel cylinders to protrude excessively and leak when the brakes are applied. This is rare, but I have seen it happen once, many years ago. I would expect that, if the root cause of your problem is contaminated brake fluid, you should also be seeing signs of caliper seal failure and MC cylinder failure as well as failure in the clutch hydraulic system. All of the work can be undertaken by an owner who is careful and has a good workshop manual. Les
Les Bengtson

This thread was discussed on 13/10/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.