Technical brake seize

[littlemouse]

Hi all, i have a bit of a problem with the brakes, i took my car out for a run yesterday, after about 15 miles the brakes locked on and the brake pedal went hard with no travel , left the car for about a couple of hours and the brakes were back to normal again, any ideas on fault before i start stripping things off to trace problem

 

[dragonwagon]

How old are the brake flexible hoses - could there be a restriction in one or more due to failing walls ?

 

[Bambino]

If all of the wheels seem to be locking, I'd put my money on a dud master cylinder. If the car seems to be pulling to one side, see which wheel hub feels the hottest after a drive and that will usually be the suspect corner.

As these cars don't have boosters, split systems, proportioning valves and disc calipers the system is much simpler to diagnose and fix.

In the first instance, I'd just change the brake fluid and see if that makes any difference. Brake fluid absorbs water over time, which when heated expands and can lock up the brakes, or conversely, when it vapourises to steam, the pedal then goes very soft because steam is a compressible gas. Checking the flexible hoses and movement of the brake shoes while you are bleeding the system with the wheels and drums off, is also always a good move. This is simple routine maintenance and will give you a lot of information on the overall health of the system.

If the problem persists, remove, strip and rebuild the master cylinder. Kits are available.

If you've done all of this and you still have a problem, buy another car ...

My humble opinion,
Chris

 

[jjacob]

Agree with what Chris said above in diagnosing the problem. You need to find out if all wheels locked up or just one. If just one, then most likely a seizing wheel cylinder. If that is the case, you should replace all four wheel cylinders, as where one is seizing the others are not too far behind in doing the same. I would not rebuild them. New wheel cylinders are cheap.

However, my guess is that the problem is with the master cylinder. If it locked, then you should replace it rather than rebuild it. A locked master cylinder has issues that are most likely not resolved with renewing the seals.

In fact, on my car I replaced all of the wheel cylinders with new ones, and rebuilt the master cylinder (was like new on the inside). Brakes are too important. The parts are all cheap.
John

 

[littlemouse]

thanks for the advice guys, i always seem to end up working on the rest of the family's cars, this particular one was just imported from Italy for my mother by my farther who already owns a RHD 500, i have owned my 500 for the past 15 years and all its ever required is 2 wheel cylinders.

I think i will replace all the wheel cylinders and either replace or rebuild the master as well, however, just a seized cylinder wouldnt give a hard pedal with no travel at all me thinks or am i wrong.

cheers
claudio

 

[Bambino]

I think i will replace all the wheel cylinders and either replace or rebuild the master as well, however, just a seized cylinder wouldnt give a hard pedal with no travel at all me thinks or am i wrong.

Claudio,

Because the pistons are in close proximity to the discs in a disc brake system, when a caliper seizes it rapidly heats the hydraulic fluid with dramatic results.

As the wheel cylinders are somewhat thermally removed and present a much smaller surface area in a drum brake setup, a seized wheel cylinder usually only effects the braking on that corner which is why I think that your problem will be more central, ie: the master cylinder. As mentioned above, parts are relatively cheap and I'd go for at least a m/c rebuild or replacement.

Chris

 

[littlemouse]

Chris

The master cylinder is fairly cheap so not worth rebuilding existing, as are the cylinders for each corner, so it looks like new mc, new wheel cylinders and flexible hoses if look suspect and some nice fresh brake fluid, hopefully that will sort it

claudio

 

[Peter Pick-Up]

How old are the brake flexible hoses - could there be a restriction in one or more due to failing walls ?

Rubber brake hoses are to be replaced after 10 years, no matter how many mls/km's and no matter how they look.( that's why there's a production date (month/year) stamped on EVERY brake hose, original or aftermarket)

Brake fluid change every two years.

 

[littlemouse]

Rubber brake hoses are to be replaced after 10 years, no matter how many mls/km's and no matter how they look.( that's why there's a production date (month/year) stamped on EVERY brake hose, original or aftermarket)

Brake fluid change every two years.

Must admit didnt know about the brake hose life, i wonder if the production date would still be visible after 10 years plus, brake fluid change every 2 years is advisable but how many cars are running around with brake fluid that has long past its date i wonder, i used silicone fluid on a kit car i built many moons ago and never had any problems for 20 years plus with any of the braking system, these days there seems to be a lot of pros and cons for silicone and sometimes you dont know who to believe and whether its all the main stealers, brake fluid manufacturers in bed with each other trying to discredit the silicone fill and forget stuff and it doesnt damage paintwork if spilt

 

[Peter Pick-Up]

I use Teflon RVS braided hoses, they last forever.

http://www.helperformance.com/

 

[Bambino]

Chris

The master cylinder is fairly cheap so not worth rebuilding existing, as are the cylinders for each corner, so it looks like new mc, new wheel cylinders and flexible hoses if look suspect and some nice fresh brake fluid, hopefully that will sort it

claudio

Excellent plan

Chris