TRseks Posted November 28, 2013 Report Share Posted November 28, 2013 (edited) I seem to have a brake problem with my 70 US TR6, I have not driven the car much and the brake pedal was soft and brakes did not seem to work as they they should. Anyway I have bought discs/drums/pads and hoped that this would improve the brakes together with a proper bleeding. Yesterday I replaced one of the rear drums, cleaned everything and lubricated the adjuster, the rear cylinder looked rather new and shiny so I didn't do anything with this. I assembled everything and adjusted so that the drum locked up and backed up so that the wheel was turning freely, the bleeding went fine as long as I actually filled up the front reservoir (missed this at first and I could not figure out why no fluid came out..!.) When I finished the pedal felt much firmer than before, a result I thought as I actually only had done one wheel... It seemed to need a lot of pressure to be able to lock the wheel, but as the wheel locked it would not turn freely again. I backed off the adjuster one click and the wheel turned freely again. But when I apply the brakes same thing happens again, when I apply hard pressure on the pedal it seem to suddenly give a little, I can hear a low "thud" and a hardly noticeably shock can be felt in the pedal and also when I hold my hand at the back wheel resulting that the wheel can not turn freely, this is the left rear wheel, I have not checked if the right wheel also lock up. I will do the rest of the discs/drum but this does not seem to be correct. Could it be a problem with the master cylinder? Or maybe the piston in the rear cylinder is not moving freely enough? The car was standing for at least 5 years before I got it but I can see that a few brake lines is replaced and the fluid that came out looked ok, just a little darker then fresh fluid. Magnus Edited November 28, 2013 by TRseks Quote Link to post Share on other sites
Richardtr3a Posted November 28, 2013 Report Share Posted November 28, 2013 It sound as if the master cylinder is not releasing the pressure. Be careful with buying a new cheap one. It might be better to have your relined and new rubbers all round. Quote Link to post Share on other sites
Peter Cobbold Posted November 28, 2013 Report Share Posted November 28, 2013 (edited) Check that the wheel cylinders will slide in the slot in the backplate. I use a mix of waxoyl, molygrease and coppaslip to keep them free enough to be slid to and fro by hand Peter Edited November 28, 2013 by Peter Cobbold Quote Link to post Share on other sites
TRseks Posted November 28, 2013 Author Report Share Posted November 28, 2013 Thanks guys, I did not even check if the cylinder was sliding in the backplate, will take everything apart again to check, hopefully it might not be the master cylinder... Quote Link to post Share on other sites
Denis Posted November 28, 2013 Report Share Posted November 28, 2013 (edited) My 6 only ever failed the MOT once...due to sticking rear brakes...With the Drums off everything looked brand new...but behind the Wheel Cylinder rubbers the steel Pistons had rusted! Edited November 28, 2013 by Denis Quote Link to post Share on other sites
TRseks Posted November 28, 2013 Author Report Share Posted November 28, 2013 Hmm, if the piston is rusted I guess it will be difficult to get out, would it be possible to take off the brake shoes and press the piston out using the brake pedal? I can see that these cylinders are under £15 new so if it`s that it will not "brake" the bank Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 29, 2013 Report Share Posted November 29, 2013 Hmm, if the piston is rusted I guess it will be difficult to get out, would it be possible to take off the brake shoes and press the piston out using the brake pedal? I can see that these cylinders are under £15 new so if it`s that it will not "brake" the bank Not if you heat it with a blow lamp it wont! Be aware that the seals and fluid are likely to go up in flames though. You will have the thoroughly inspect the bore of the cylinder once in bits for damage/corrosion marks. Reject if any, unless you have a repair scheme that involves a cylinder hone. The removal of the old cylinders will usually mean the need for a cylinder fitting kit (3 spring plates and a rubber per side plus a bit of swearing) The other issue can be the refusal of the brake pipe to undo without shearing off - enjoy. Clamp the rubber brake hose off to stop the fuid all dribbling out once you have released the pipe from the cylinder. Make sure you remove the clamp after the job is complete though. Another trick is the addition of a plastic bag fitted over the mcyl fluid hole and then held in place by the filler cap to form an airtight seal (creates a vacuum to stop major fluid leakage) You will have to remove said bag when you refill and bleed so no worry of forgetting it is there. Cheers Peter W Quote Link to post Share on other sites
TRseks Posted November 29, 2013 Author Report Share Posted November 29, 2013 (edited) A little update on yesterdays late night session in the garage. It was as expected a stuck piston in the rear cylinder, it came out using the brake pedal, lots of dirt inside the cylinder but after a good clean and polish the bore was actually very good as was the rubber seal, after assembly and bleed everything worked as it should, I half expected a leak but guess I was lucky; no leak. But after putting a lot of pressure on the brake pedal I noticed a leaking master cylinder.... seems like old cars can easily have more than one fault! I have ordered a master cylinder repair kit, struggling to open the hollow hex bolt over the tipping valve in so had to order a 1/2 inch allen bit, tried to get it out using a bolt that I welded a nut to but the bolt broke, tried 4 times but no luck so this nut seems to be a very tight fit. Edited November 29, 2013 by TRseks Quote Link to post Share on other sites
Alan Gill Posted November 29, 2013 Report Share Posted November 29, 2013 I dismantled my master cylinder recently, and to remove the tipping valve allen screw I used a "diff filler cap" tool. This tool is needed if you have a differential filler cap that has a sunken "allen key" type filler cap. This tool can have a 4, 6 or 8 sided allen key. Yes, this tipper valve IS very hard to remove. Inspecting the inside of the master cylinder revelled corrosion down the cylinder. I ordered a new OE cylinder, from TRGB. Note. No commercial relation with TRGB, just a happy customer. Alan G Quote Link to post Share on other sites
Denis Posted November 29, 2013 Report Share Posted November 29, 2013 (edited) Hmm, if the piston is rusted I guess it will be difficult to get out, would it be possible to take off the brake shoes and press the piston out using the brake pedal? I can see that these cylinders are under £15 new so if it`s that it will not "brake" the bank Yes Cheap as Chips! I just replaced them, watch out for those annoying retaining clips on the backplates! And the **** that came out of the rear brake lines was part of the problem too! Edited November 29, 2013 by Denis Quote Link to post Share on other sites
harrytr5 Posted November 30, 2013 Report Share Posted November 30, 2013 Also check where the hand brake lever pivot has not worn a groove in the back plate.Mine had and I welded this up and linished it flat. No more clonks from the wheel cylinders. Regards Harry Quote Link to post Share on other sites
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