Strange brake problem.

[Bob Purton]

My Isetta [Thumper] has developed a strange problem when in storage
over the winter. I went to get the car out last friday and the rear brake was
locked on, the hand brake had been left off so I knew it wasnt this that was
stuck but the linings had opened out by themselves and locked up the wheel. Out
of desperation I released the bleed nipple and some brake fluid under pressure
shot across the garage! This freed the rear brake but the pedal was still right
up tight. I started driving the car home but half way home the brakes started to
come on again by themselves, I released the bleed nipple once again with the
same effect and finally got it home. I did notice last year that the brake pedal
once depressed was taking its time returning to its rest position. I guess
something somewhere in the braking system is not allowing the fluid to return
and pressure is building up inside. I thought I would fit a new master
cylinder and work my way out from there replacing things untill I solve it. Has anyone got any
ideas or have experienced this before? One thought that crossed my mind was a collapsed brake hose?

[Jim Janecek]

I vote collapsed brake hose as well.  Otherwise the front brakes would be doing the same thing.
This seems isolated to the rear. 

[Bob Purton]

It could well be Jim but I did fit a brand new hose on the rear last summer.[it could be a duff one]  I have followed all the copper pipes through and none are crushed or damaged at all. I did have a simular problem once on a mini powered Berkeley and it turned out to be the master cylinder sticking. All suggestions welcome.

[golo2]

Hi, from the depths of sunny Paignton (on hols with Lee T)  combined guess is wheel cylinder
If brake hose collapse no fluid could get to wheel cylinder so brakes unlikely to work
Guess no2  adjuster rod from pedal to master cylinder has expanded so not allowing fuid to return to master cylinder
Guess 3 rear whel cylinder and handbrake lever arm have seized to back brake not allowing brake to self centre after application

Meanwhile still not done schmitt steering or points as Scenic threw up ECU faults and rev limit to 3K   also locked its keys inside (not possible say Renault) so daughter has driven us south!
Let us know the actual solution========

[cuscus47]

Hello Bob:  I have a vehicle that I worked on yesterday and completed today.  No, you may not ask what one, for you may stop reading this.  During the year, the brakes work fine and stop on a dime, but when I park it for Winter, about November, and try to move it in March, the Rear Brakes are always seized.  Not the single front one. (oops, cat's out of the bag).  This has happened the past three Winters.  I have to release the tightening adjusting screw which open/closes, the rigid end of the shoes.  It always takes about three full turns.  I never need to readjust. They are not self-adjusting.  I just yesterday took all the parts apart, washed in cleaner, and reassembled, flushed out the lines, slaves and master, cleaned the reservoir, all with ethanol, blew it out with air and let dry overnight. and today replaced with Dot 5 fluid.  I have no idea if this is going to fix it, I won't know until this time next year.  Brakes work now as good as they ever did, but will they last next Winter?  You can read all about this process in this coming up issue of Conveyancer.  Later, Ian.

[Bob Purton]

Hi Ian. What a trooper! Still offering helpfull suggestions even whilst on your holidays! Sorry to hear about the trouble with the Renault.
I checked the rod and it had free play so cant be that, the rear cylinder was new last year and both this and handbrake lever are all greased and free moving. Will let you know if and when I find the fault. Cheers, Bob

[Bob Purton]

Hi Other Ian! Well well! It appears the three wheeler gremlin is creeping into our garages in the winter time and is tightening up our brake shoes! Isnt that weird! Its not the same issue as mine though as after adjusting the shoes I went on a run and the rear still just locked up again after a few miles. I will not be  reading the story in Conveyencer though, the wife doesnt allow pervy mags in the house but will be treating myself to a copy of Stu-pots new book, there is Reliant history in the family and any book signed by Elvis has to be a good investment! Thanks .  Bob

[Basket case]

Brake fluid is 'hydroscopic'!
It absorbs water, that's why they say never use brake fluid from a bottle that has been open for more than 3 months.
Could this be causing the 'nipple squirt?'. Damp garage over winter, poor seal on the master cylinder?

[Jim Janecek]

so you don't get this excessive pressure buildup on the front brake cylinders?

[Bob Purton]

No Jim, Just the rear one. Even after releasing the pressure via the bleed nipple the brake pedal is really bolt upright with barely any travel.

[Big Al]

On rear hose failure. In winter it was very cold so the fluid will have reduced volume. If the pipe has failed, then on expanding, if relatively rapid temperature rise, it would pressurise. You freed it off. On driving it is exhibiting the normal failed pipe locking of brakes.

[Bob Purton]

Yep. I guess it has to be somewhere on the rear cylinder feed otherwise the fronts would be locking as well unless the pressure is going to the point of least resistance as there are two cyinders per wheel on the front.  Thanks everyone for all the input. I will report back when the fault is found. At least this thread got us on a tech topic and away from ebay and the price of Peels! 

[Bob Purton]

Right, problem solved but the jury is still out on what it was! The new master cylinder arrived this afternoon. I fitted it and decided to take Prof Ian Hellings advice and wind in the rear shoes by three turns. I have just returned from a half hour drive using plenty of braking and the locking up has vanished!  Now was it the new master cylinder or the Hellings treatment?

[Chris Thomas]

Dear Bob

My untechnical guess is that the sub zero winter temperatures are the cause of the problem as Ice can do a lot of damage externally and internally to components. and most metal components will contract. I have a rectangular box section on one of my cars that is almost round where being partially full of water, it froze and the expansion forced the RHS to balloon.

Now that the weather has improved the ice will have gone or returned to water, and the components will have expanded. Ian's suggestion of slackening off the adjuster may be just returning things to where they were last year. Why the rear wheel, that is a mystery, unless the slave cylinder, had some dirt in the bore, but you did clean it out and it made no difference.

Maybe you should consult one of the major brake compont manufacturers for their suggestions.

Chris Thomas

[Big Al]

Tense nervous braking? Then don't waste a second. Take Hellings!

Could be hydroscopic frozen water damage nurdlizing the master cylinder. Not a failed pipe.