Intermittent brake seizing

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Llessur
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Intermittent brake seizing

#1 Post by Llessur » Tue Apr 04, 2017 6:53 am

Have had an intermittent issue with the 2500 since I have had it where occasionally the brakes stick on after/during a run. It's the Australian model with the tandem brakes.

The last time it happened they were stuck on pretty hard - it took a fair bit of power to get the car back round the corner to the driveway (luckily had only travelled 50 metres or so from home).

Judging by the heat and metallic tinkling noises coming from various corners of the car when I got back it seems to be an issue that affects front and back simultaneously so I am therefore presuming that it must be either a master cylinder or servo/booster issue (although will bear in mind things like seized caliper pistons, wheel cylinders, collapsed hoses etc).

Are there any known problems that make one or the other more likely? The car hasn't been on the road in 10+ years and is gradually being recommissioned.

Am tempted to just chuck a new or rebuilt master cylinder on it together with new hoses and pads (as I'm a bit wary of aged braking components, especially with a car that's been out of service for a while) but don't want to miss anything obvious.

Cheers all.
Adelaide, South Australia (ex-Brighton, UK)
1977 2500S - White

My 2500 blog: https://triumph2500blog.wordpress.com/

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David Withers
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Re: Intermittent brake seizing

#2 Post by David Withers » Tue Apr 04, 2017 7:46 am

As a first step, you could feel each wheel after a run. If one is hotter than the other three it would suggest a calliper piston tending to seize. If each side is at a matching temperature, the problem is likely to be further back in the system.

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Llessur
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Re: Intermittent brake seizing

#3 Post by Llessur » Tue Apr 04, 2017 8:18 am

Pretty sure it's all for wheels equally based on the heat and clinking (is that a word?) coming from them after the last occurrence - that's why I suspect a master or servo/booster problem as opposed to something wheel-specific. Just wondered if there were any known issues with either or any trouble shooting I could undertake to rule out either? Otherwise I'll start with the master and move onto the servo if it's no better​...
Adelaide, South Australia (ex-Brighton, UK)
1977 2500S - White

My 2500 blog: https://triumph2500blog.wordpress.com/

johnnydog
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Re: Intermittent brake seizing

#4 Post by johnnydog » Tue Apr 04, 2017 2:33 pm

As the car has been standing for for 10 years, then my first thought is the master cylinder, especially as you say all wheels are affected. Old brake fluid left in a system for a good few years, especially if it has absorbed some moisture, will cause corrosion in the bores of the master cylinder (and wheel cylinders) causing them to seize solid.
I would slacken the brake pipe union where it enters the master cylinder under the bonnet, and with an assistant watching to mop up any brake fluid seepage, see if there is any movement on the push rod when the brake pedal is operated gently, with the return of the pedal being the main concern. The return spring on the pedal box should be sufficient to return the pedal to its initial position.
Press the pedal again, and if the pedal has no pressure at all behind it then it indicates the cup in the master cylinder has been forced further down the bore in the master cylinder on the initial press and got stuck. If the pedal is very heavy, or there is no movement, then the master cylinder is again the likely culprit.
You could check all wheels in turn as David says to establish whether the pistons in the callipers and wheel cylinders are operating ok.
Even if you have one or both wheel cylinders stuck solid, there should still be movement on the master cylinder push rod.
Before you stand on the foot brake, I would consider removing the rear drums and visibly check the wheel cylinders for movement first because the drums will be harder the remove if the wheel cylinder stick in the on position!
I doubt that an issue with the servo would cause these symptoms.
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1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
1970 Mk2 2000 in Valencia Blue
1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
1976 Mk2 2500S in Carmine Red

tony
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Re: Intermittent brake seizing

#5 Post by tony » Tue Apr 04, 2017 7:37 pm

When I got my S going after sitting for 6 years I replaced hoses and wheel cylinders. I was lucky with the calipers and master cyl. Brakes were excellent after that.
Probably for the cost of a master cylinder, in your case, probably worth replacing it. :P
Tony.
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1999 BMW Z3.
2006 BMW 325ti.
Hopefully not needing too many bits.




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Re: Intermittent brake seizing

#6 Post by Llessur » Thu Apr 06, 2017 7:30 am

Thanks all, think I'll probably end up replacing the master cylinder. Want to do a bit of a brake overhaul anyhow.

Does anyone have any recommendations for new pads and shoes? I'd rather go asbestos-free over NOS as don't really want to be near any asbestos dust next time I undertake brake work. I'm not a natural risk taker.

I know some asbestos-free pads have had a mixed reception based on other threads. I'm not by any means a spirited driver so it would just be fairly gentle road use.
Adelaide, South Australia (ex-Brighton, UK)
1977 2500S - White

My 2500 blog: https://triumph2500blog.wordpress.com/

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