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TR6 Brakes Failure

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BritFan Edward Kaizer
Godfrey, Ilinois, USA   USA
!975 TR6. Rebuilt the brake master cylinder back in June and have had no problems. Parked the car middle of October after a 70+ mile club drive, brakes worked fine. I started the car this afternoon to drive it one more time and put it up for the winter. Got 1/2 mile down the road and applied the brakes to stop for a light and the pedal went to the floor. Desperately started pumping to get a pedal to no avail. Managed to pull into someone's front yard and stop with the emergency brake (only going 25mph at max). When I got home I continued to pump the brake pedal to see if I could get even the slightest feel of resistance....nothing. Checked the master cylinder fluid level and both reservoirs are full with only a couple of very tiny air bubbles popping up briefly in the rear brake reservoir while pumping (and those stopped). I see no obvious leaks around the master cylinder or vacuum boost and no fluid in the driveway.

Before I tear into the master cylinder and other parts of the brake system, I thought I'd pose a question. Has anyone experienced this sudden complete brake failure after sitting? Any suggestions before I tear the system apart?

Thanks for any help,
Ed

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TRoutMac Avatar
TRoutMac Pete Chadwell
Bend, Oregon, USA   USA
I had something similar happen many years ago (over 25 years ago) after (if I remember right) simply bleeding the brakes. And it was a NEW master cylinder from TRF. Fortunately I wasn't on the road when it happened. And I never did actually figure out WHAT happened. But I rebuilt the master and it's been fine since… for twenty-five plus years.

BritFan Edward Kaizer
Godfrey, Ilinois, USA   USA
I'll be towing the car to my storage facility tomorrow. Then I can get underneath and look closer.

I've given more thought to what happened. Seems to me that if I'm getting no fluid loss (reservoir level is still full) there might be an internal leak inside the master cylinder (fluid blowing by the seals as pressure applied). You curing a similar problem with a rebuild seem to confirm that, Pete. But what would cause this to happen in such a short time? Hoped someone would have responded with a “Had it happen to me and here was the cause and fix....”

Oh well, guess I'll try to find the cause and post what I can to the rest of the Triumph clan. Thanks for your response Pete.

Ed

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rjc157 Avatar
rjc157 ralph c
pearl river, new york, USA   USA
No fluid loss tells me it has to be the MC did you rebuild it or was it a rebuilt unit maybe the piston got stuck if there is no pressure at the pedal I can't see how your going to bleed the system I think you have no choice but to take the MC out

BritFan Edward Kaizer
Godfrey, Ilinois, USA   USA
Someone else rebuilt the master cylinder Ralph. Worked fine for 4 months and has set for over a month at least once during that time. I would think if the piston got stuck I'd experience a solid pedal instead of no pedal. But I think you're right, going to have to rebuild again. This time I'll do it myself and check the seals for tears.

Ed

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, Georgia, USA   USA
This has to be a significant issue with the master cylinder. Your car has a split brake system. For the pedal to go completely to the floor and no loss of fluid, means that both sides of the split system are failing, which is very unusual. I would suspect that whoever rebuilt your MC made a mistake(s) or there is trash in the system. Have you ascertained that there isn't a problem with the brake pedal linkage? Perhaps the pedal is moving down, but nothing else is moving. If the linkage is OK, I would definitely replace the MC and bleed the entire system completely making sure that all fluid in the system is flushed out. This might be a good time to switch to DOT 5 silicone fluid if not already done. If you have DOT 3 or 4 and switch to DOT 5, make sure you flush out the system completely since DOT 3 and 4 are not compatible with DOT 5. The brakes are the most important part of a car.



Current: 1973 TR6 W/Overdrive

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1963 TR3B W/Overdrive
1962 TR3A
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Edited 1 time(s). Last edit at 2017-11-30 09:27 AM by glcaines.

titanic Berry P
Albany, Oregon, USA   USA
There is a small seal on a plunger in the master cylinder that prevents the fluid from flowing back into the reservoir when the brakes are applied. If the this sealing is leaking, it might account for the complete loss of pedal. Also, a broken return spring in the master cyl. could be the culprit.
Berry

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YankeeTR5 Dan M
Seattle, washington, USA   USA
I wonder if the seals were put in backwards when the MC was rebuilt? This might offer enough resistance at first only to fail down the road. I may be all wet on that and if they were put in backwards they'd fail right out of the box. Still, I'm curious. Definitely in the MC though and fluid getting by seals.

barry s Avatar
barry s Silver Member Barry Stoll
Alexandria, VA, USA   USA
1972 MG MGB GT
1974 MG MGB
1976 Triumph TR6
1980 MG MGB
To begin, I'd suggest that the brake pedal going to the floor should dictate down shifting (if possible) moving to the right and readying the hand brake. Pumping the brake is fool hardy and a waste of time.

As the brakes worked for a period of time before failing certainly suggests a component failure in the MC. However, before undertaking any R&R, I'd see what's happening at each wheel when braking. With an assistant, have the helper depress the brake as you open each bleeder to observe what if anything is expelled.

An internal leak in the MC can result in fluid leakage into the cabin, so don't just look under the car.

I recently replaced the brake MC in my 6 with a new TRW unit, to correct a leak of the outermost seal onto my foot. The new unit began to do the same within 3 weeks. The vendor replaced with another and all was well.

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modandrocker Steve N
Greensboro, NC, USA   USA
I too have had my fair share of MC problems until I had Apple Hydraulics to resleeve the unit with brass. That's been several years ago without a drop of fluid loss and am as confident as a Checker Taxi. PS, I have no financial interest or obligation to the aforementioned company.

BritFan Edward Kaizer
Godfrey, Ilinois, USA   USA
Here's an update on the brakes. Finally got the TR6 towed to my storage facility. The holiday season got busy so I wasn't able to work on anything for a couple of days. Just for S&G's I decided to try and bleed the brakes first. I NOW HAVE BRAKES!! But I still think I have a problem, there has to be a leak internally. Since there is no drive scheduled until our club Polar Bear Run in February, I'm going to let the car set and see if I can duplicate the problem. In the mean time I'll order a kit and rebuild a spare master cylinder I have. I had planned to change over to DOT 5 fluid this winter so now I'll have a clean master cylinder. Buckeye Triumph has a nice piece on a procedure for change over.

Thanks for the input I received from everyone. This forum is really helpful and you guys are great.

Ed

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