SeanF Posted December 27, 2018 Report Share Posted December 27, 2018 I have recently put my 74 TR6 back on the road after a complete ground up restoration and have covered about 120 miles so far. I am having trouble bleeding the brakes properly and am looking for any tips on how to solve this issue. No matter how much I bleed the front circuit, I can't seem to get all the air out. I can get what seems like most air out and get a decent pedal using my vizibleed kit but this will progressively fail with use and the pedal gets softer and softer until it will only stop at very low speeds. Had fun coming down Biggin Hill yesterday! I have gone around and made sure all the unions are tight and don't seem to have any leaks. All new Automec Pipe kit and new SS flexible pipes around (goodridge on front and moss own on rear), rebuilt calipers with new cylinders and seal kit, new bleed nipples and rear drums, new rear cylinders, new seal kit in MC. Using Dot 4. Any tips as to where I'm going wrong? Did not bench bleed the MC. Could this be the problem? Hope everyone had a good Christmas and best wishes for the new year. Sean Quote Link to post Share on other sites
harrytr5 Posted December 27, 2018 Report Share Posted December 27, 2018 Sean you know there is two separate circuits. Small tank at the front for rear wheel and large tank for the front on the master cylinder (but you knew that anyway, just trying to help) There were a few dodgy master cylinders out there a while aback, perhaps this could be one of them. Quote Link to post Share on other sites
Steves_TR6 Posted December 27, 2018 Report Share Posted December 27, 2018 On my last car i had a simolar problem, eventually traced to air being sucked in at a cracked flare on the mc so maybe check your connections are tight ? could also be a dodgy mc as mentioned by Harry, these suck air in or leak between the plastic reservoir and steel cylinder. you might also check the mc isnt leaking into the servo good luck! Quote Link to post Share on other sites
RogerH Posted December 27, 2018 Report Share Posted December 27, 2018 Hi Sean, are you mistaking a softer peddle for longer and longer peddle travel. There has been an issue with new calipers. The piston seals seem to be quite stiff and draw the pistons back too far into the caliper bore. Stuart has a trick that works. Get a piece of calibrated wood. Press the brake peddle down and jam the wood in place - leave for 24 hours. Either the brakes will work after that or the wood will be shorter. Roger Quote Link to post Share on other sites
harrytr5 Posted December 27, 2018 Report Share Posted December 27, 2018 Roger, I just remembered! I had to do that on a TR4A and it worked really well. Something to do with the memory of the seals and not my brain this time. Regards Harry Quote Link to post Share on other sites
SeanF Posted December 27, 2018 Author Report Share Posted December 27, 2018 1 hour ago, RogerH said: Get a piece of calibrated wood. Press the brake peddle down and jam the wood in place - leave for 24 hours. Thank you Harry, Steve and Roger for your replies so far. Yes Harry, I do know there are two circuits but I guess I forgot that they have the same piston mechanism so I guess air in one can still travel to the other so I the problem could be in the rear circuit. Roger what do you mean by calibrated wood? Do they sell that at Howdens? Cheers, Sean Quote Link to post Share on other sites
RogerH Posted December 27, 2018 Report Share Posted December 27, 2018 Hi Sean, It must be exactly the right length +/- 3 or 4 inches or there abouts. Roger Quote Link to post Share on other sites
iani Posted December 27, 2018 Report Share Posted December 27, 2018 I had the same issue with new callipers and a TRW master cyl this year, all garbage, replaced with recon callipers and m/cyl (thanks Conrad) and all was well. The tipper valve in the m/cyl wasn’t working properly and the seals on the callipers were oversized. Quote Link to post Share on other sites
John McCormack Posted December 28, 2018 Report Share Posted December 28, 2018 I had a similar problem after I rebuilt my m/c and installed a new Rimmer booster. It turned out I had made a mistake in assembling the m/c. The kit was a generic one for different similar cylinders and I had installed a seal not intended for my cylinder. Once I reassembled it correctly all was solved. And embarrassingly, I made a similar error on my restoration project TR2 last week. I new immediately what the problem was on this occasion. At least in both cases it was only an hour or so to remove the cylinder and fix it. Quote Link to post Share on other sites
Rogcastle Posted December 28, 2018 Report Share Posted December 28, 2018 Hi Sean Does your pedal gradual go to the floor, if so it's a problem is likely to be with the MC as there are two circuits one to the front and the other to the rear. If you have a leak on either, your pedal should only go halfway to the floor. If the car has been standing for a long time the bore of the MC could be pitted. In that case you need a new one or if you have a original one it could be worth having it refurbished. Roger Quote Link to post Share on other sites
stuart Posted December 29, 2018 Report Share Posted December 29, 2018 OK Before you go doing anything else just try the old tricks first. Pump the pedal until its the hardest it will go and then jam it down with a bit of wood between the pedal and the seat (Trial and error with your bit of wood until you can find one the right length or move the seat backwards or forwards!) Leave at least overnight but 24hrs preferable then see what you have. What you can also do in the intervening time is check over the whole system for leaks/swelling of flexis/or anything untoward like calipers or cylinders leaking whilst under constant pressure. Stuart. Quote Link to post Share on other sites
stallie Posted December 29, 2018 Report Share Posted December 29, 2018 The calibrated broomstick handle worked for me. It is now labelled as such and lives behind the tool chest. Quote Link to post Share on other sites
SeanF Posted December 30, 2018 Author Report Share Posted December 30, 2018 Thank you all for your replies. First call will be the stick trick when I get back later in the week. Sean Quote Link to post Share on other sites
Richard71 Posted September 1, 2019 Report Share Posted September 1, 2019 Thread revival...….. I've tried all of the above, piece of wood for 24hrs etc and still cant expel all the air, the front seems to be the issue. While on a trip a couple of months ago my front brakes overheated, lots of smoke, major brake fade, you know the story. I travelled the 500+ miles home with no problems at all but soon after as a precaution I changed the pads. Only since changing the pads have I been having trouble with all the above symptoms. I'm beginning to wish I had left the original pads in place. So, I ask, does this sound like a M/C problem? Quote Link to post Share on other sites
RobH Posted September 1, 2019 Report Share Posted September 1, 2019 If all you have done is changed the pads Richard, it may be something to do with that. I wonder if the heat may have done something to the seals in the callipers or carbonised deposits in the bore so that when you pushed the pistons back to fit the new pads the seals got damaged ? Quote Link to post Share on other sites
Richard71 Posted September 1, 2019 Report Share Posted September 1, 2019 2 hours ago, RobH said: If all you have done is changed the pads Richard, it may be something to do with that. I wonder if the heat may have done something to the seals in the callipers or carbonised deposits in the bore so that when you pushed the pistons back to fit the new pads the seals got damaged ? Possibly. But, I found a old post about a sticking tipping valve, the poster suggested giving the M/C a thump with a hammer, I thought that's worth a go and done exactly that, pedal felt better, took the car for a 15min drive and the brakes were hugely improved, but will require further bleeding to get the existing air out. Does that sound a likely problem? In the meantime, I've parcelled my original M/C & servo to be sent off for overhaul, I believe the way forward is to have the M/C bored and a stainless steel sleeve fitted, not sure though if that relates to the problem I've just had? Richard. Quote Link to post Share on other sites
Waldi Posted September 1, 2019 Report Share Posted September 1, 2019 The SS sleeve (or not) probably has nothing to do with your issue. But it will reduce the potential for future problems related to corrosion of the bore, which is a common issue on our cars, and not only on the MC. I had mine sleeved too during overhaul. If you doubt the condition of the callipers I would remove them and remove the pistons for new seals and dust caps. Make sure to oder the correct dust caps. It is an easy job, and not too expensive. I installed new SS pistons, the old ones were...corroded, part of the hard chrome (?) surfacing had come off. Regards, Waldi Quote Link to post Share on other sites
Richard71 Posted September 1, 2019 Report Share Posted September 1, 2019 15 minutes ago, Waldi said: The SS sleeve (or not) probably has nothing to do with your issue. But it will reduce the potential for future problems related to corrosion of the bore, which is a common issue on our cars, and not only on the MC. I had mine sleeved too during overhaul. If you doubt the condition of the callipers I would remove them and remove the pistons for new seals and dust caps. Make sure to oder the correct dust caps. It is an easy job, and not too expensive. I installed new SS pistons, the old ones were...corroded, part of the hard chrome (?) surfacing had come off. Regards, Waldi Thanks Waldi, All my brake components have in the last 2-4 years been replaced and/or overhauled. This only happened after pushing the callipers back, I think that upset something in the M/C. If I have time tomorrow evening I'll bleed the brakes again and test drive. Quote Link to post Share on other sites
Waldi Posted September 1, 2019 Report Share Posted September 1, 2019 Go for it Richard:) If the calipers have been overhauled I would not open them too. Cheers, Waldi Quote Link to post Share on other sites
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