Peter Douglas Winn Posted November 7, 2020 Report Share Posted November 7, 2020 I think I have an airleak in the braking system. Any ideas how to find it without doing a strip down? Handbrake nicely tight. No loss of fluid. No water in the fluid. No leaks/fluid at any joints/connections. No fluid around the pistons. Dual circuit system. Bled the system severtal times and after a relatively short time the brakes are soft again. Put a load on the brake pedal for a couple of days to exclude the air. What more can I do without going through a complete strip down? Quote Link to post Share on other sites
stuart Posted November 7, 2020 Report Share Posted November 7, 2020 Master cylinder problem then. Stuart. Quote Link to post Share on other sites
Steves_TR6 Posted November 7, 2020 Report Share Posted November 7, 2020 i had a very tricky to diagnose issue on a previous tr6, eventually traced to a cracked flare on one of the brake pipes coming out of the master cyl this sucked in air but did not leak fluid, took weeks to find ! additionally some tr6 master cylinders have faulty reservoir to cylinder seals, causing leaks or again sucking in air. so my suggestion is air is being sucked in somewhere HTH steve Quote Link to post Share on other sites
Peter Douglas Winn Posted November 7, 2020 Author Report Share Posted November 7, 2020 That is exactly what I am worried about, sucking air. Theorectically is everything new about 4000 miles. How do I find that air leak? Quote Link to post Share on other sites
Peter Douglas Winn Posted November 8, 2020 Author Report Share Posted November 8, 2020 (edited) Something else last week I tightened up the handbrake and after the brakes were so good I could lock them. A week later after standing in the garage, I took the car for a drive and the pedal went down a long way and pumping did help. I do not see any connection as I only touched the adjuster. When the brakes lock or nearly is there extreem pressure in the system? Edited November 8, 2020 by Peter Douglas Winn something extra Quote Link to post Share on other sites
Steves_TR6 Posted November 8, 2020 Report Share Posted November 8, 2020 it does sound like air is getting in to the system Peter when i had air being sucked in through the flare, or if you have a dodgy reservoir seal, then i'd expect you to be able to see bubbles in the mc reservoir when the brakes are operated ( by an assistant!) one other possibility is the rear wheel cylinders retracting under spring pressure from the shoes, hence the handbrake temp fixed the issue this can be made worse if your rear brake cylinders are not 'floating' nicely, due to dirt or old 'grooved' backplates. good luck tracking this down ! Quote Link to post Share on other sites
Peter Douglas Winn Posted November 8, 2020 Author Report Share Posted November 8, 2020 OK the easy one is the brake cylinders. I don't quite understand what is happening. Are you saying air is getting in, through the rear cylinders or are you saying the movement of the cylinder, is making it feel like air in the system. As I do everything alone, I have no help. No family or friends in the near (all dead) and on top a disabled wife. I will have to rig up a mirror system or a film camera to look into the reservoir. How the hell did you find that cracked flair? I could have found it using the replacement technique. Out of that I don't know. If it was leaking that would be easy. Quote Link to post Share on other sites
Steves_TR6 Posted November 9, 2020 Report Share Posted November 9, 2020 hi Peter i was meaning that the rear wheel cylinders might be retracting a little under return spring pressure, thus your first push on the brake pedal moves them out again but does no braking. some people fit 'residual pressure valves' to alleviate this but i've never tried those. with my leaky flare i had tiny air bubbles being drawn into the MC when the pedal was released, i replaced the brake lines to cure it. I think you need a systematic approach to track the problem down Peter. I'd consider isolating the problem by blanking off one of the MC outlets to determine which half of the system the problem is in. Perhaps block off the rear circuit and test CAREFULLY! the braking system with only the fronts working? Steve Quote Link to post Share on other sites
Peter Douglas Winn Posted November 9, 2020 Author Report Share Posted November 9, 2020 Now that is making sense. If I block off one MC orifice does anybody know what is the the thread for the unions? I do know mine is not metric. Somewhere in the back of my mind is 1/4" UNF. I thought the car was basically UNF with the exception B.S.P was only for the fuel ystem. 1 or 2 threads are odities. Quote Link to post Share on other sites
stuart Posted November 9, 2020 Report Share Posted November 9, 2020 3/8" and 7/16" Stuart. Quote Link to post Share on other sites
Peter Douglas Winn Posted November 10, 2020 Author Report Share Posted November 10, 2020 Thanks I can find a screw and use it as a plug. Quote Link to post Share on other sites
JohnC Posted November 10, 2020 Report Share Posted November 10, 2020 On 11/8/2020 at 7:32 PM, Peter Douglas Winn said: A week later after standing in the garage, I took the car for a drive and the pedal went down a long way and pumping did help. Just a thought, but is it possible you're suffering front pad knock-back caused by worn or loose front wheel bearings or flex in the stub axle? If that were the cause, pumping the pedal would eliminate the problem until the next time you put plenty of load on the wheel bearings/ stub axles. I used to get a lot of pedal travel the first time I applied the brakes after reversing out of my driveway on full lock. A stub axle strengthening kit from Revington solved the problem. Of course, if the pedal gets soft just sitting in the garage, that isn't the problem! JC Quote Link to post Share on other sites
Peter Douglas Winn Posted November 10, 2020 Author Report Share Posted November 10, 2020 I think the bearings and stub axles are OK. The front end was done about 5,000 miles ago. Also new Mintex brake linings from TR Enterprises and new Pistons from Rimmers. The back end piping renewal must be finished but it was always OK. Quote Link to post Share on other sites
Steves_TR6 Posted November 10, 2020 Report Share Posted November 10, 2020 JohnC raises a valid point. Peter, does you brake pedal 'go soft' with the car standing or only when you move/reverse it ? i replaced the original stub axles with some beefy ones from Classic Driving Developments, but the 'anti knockback' kits work too. steve Quote Link to post Share on other sites
astontr6 Posted November 10, 2020 Report Share Posted November 10, 2020 On 11/7/2020 at 8:34 PM, Peter Douglas Winn said: That is exactly what I am worried about, sucking air. Theorectically is everything new about 4000 miles. How do I find that air leak? In the past there have been bad batches of TR6 Brake Master cylinders?? Have you got one of these? Bruce. Quote Link to post Share on other sites
Peter Douglas Winn Posted November 11, 2020 Author Report Share Posted November 11, 2020 Steve I don't know I must try it. I have heard about the MC problems but I don't know exactly what was wrong. So I don't know if I have got a bad . It was replaced about 4 years ago. Quote Link to post Share on other sites
stuart Posted November 11, 2020 Report Share Posted November 11, 2020 55 minutes ago, Peter Douglas Winn said: Steve I don't know I must try it. I have heard about the MC problems but I don't know exactly what was wrong. So I don't know if I have got a bad . It was replaced about 4 years ago. That time frame puts it into the area of the problem ones Im afraid. Though most didnt last as long as this. Stuart. Quote Link to post Share on other sites
ntc Posted November 11, 2020 Report Share Posted November 11, 2020 3 hours ago, Peter Douglas Winn said: Steve I don't know I must try it. I have heard about the MC problems but I don't know exactly what was wrong. So I don't know if I have got a bad . It was replaced about 4 years ago. It will be at the end of the line as Stuart posted, I strongly recommend you change it as they can fail without warning. Quote Link to post Share on other sites
Peter Douglas Winn Posted November 12, 2020 Author Report Share Posted November 12, 2020 If it is the MC would a repair kit be OK or is it a metal/plastic problem? For various reasons I have not used the car that much. The MC could have been laying in stock for a long time. The reason I am concerned is, I found a tiny drop of fluid under the MC and also under a union. As it was so small I could not taste it to tell whether it was brake fluid or condense water. The garage is dry and underground so why condense water? Quote Link to post Share on other sites
stuart Posted November 12, 2020 Report Share Posted November 12, 2020 1 hour ago, Peter Douglas Winn said: If it is the MC would a repair kit be OK or is it a metal/plastic problem? For various reasons I have not used the car that much. The MC could have been laying in stock for a long time. The reason I am concerned is, I found a tiny drop of fluid under the MC and also under a union. As it was so small I could not taste it to tell whether it was brake fluid or condense water. The garage is dry and underground so why condense water? Im afraid you do need to replace it, the problem wasnt only confined to internal parts. Stuart. Quote Link to post Share on other sites
Peter Douglas Winn Posted November 12, 2020 Author Report Share Posted November 12, 2020 ok ist any supplier on the black list for this part? Quote Link to post Share on other sites
stuart Posted November 12, 2020 Report Share Posted November 12, 2020 2 hours ago, Peter Douglas Winn said: ok ist any supplier on the black list for this part? I buy mine from TR Shop. Stuart. Quote Link to post Share on other sites
Peter Douglas Winn Posted November 12, 2020 Author Report Share Posted November 12, 2020 thanks Quote Link to post Share on other sites
Steves_TR6 Posted November 12, 2020 Report Share Posted November 12, 2020 (edited) Hi Peter as others have said there were a lot of duff MCs being sold a few years ago. for the modest cost i'd buy a new one, and i too recommend the TR Shop. for bleeding the brakes, esp with a new MC i recommend the Gunsons Eezibleed pressure bleeder, but make sure you only have 10 psi in the tyre. i have a special modified tr6 reservoir cap that you are welcome to borrow if you wish to take this route. in fact i could post the whole kit to you if it helps as it's not heavy so wouldn't cost a lot. steve Edited November 12, 2020 by Steves_TR6 Quote Link to post Share on other sites
Andy Moltu Posted November 12, 2020 Report Share Posted November 12, 2020 The problem with that batch of master cylinders was with the casting/machining resulting in the seals failing to do just that or failing prematurely because of the machining. As for bleeding the old fasioned 2 man bleed is hard to beat. Pump up, hold the pedal down, release the nipple until the pedal hits the deck, tighten nipple, top up and repeat until the pedal is rock hard. Quote Link to post Share on other sites
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