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Humber Heavy Utility Brake Failure


Ian L

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Last year I had the brakes fail on my Humber Box 3 times, the 3rd & final time was catastrophic (for the Audi Q5)

Symptom was that the brake pedal would depress about 4-5 cms & lock solid but no braking effect, when I released the pedal & pressed again the brakes worked ok, I investigated the fault thinking it must be a linkage or pedal jamming on the chassis ? but no fault found.

On the 3rd & final time the pedal stuck down but would not release, in the morning everything was ok again, brakes worked & pedal was free :confused:

Today I removed the master cylinder & on close inspection I found the rear seal distorted & unseated.

I have a new seal kit so attempted to push the new seal in (which is shaped like a flat topped airgun pellet) but it would not seat in the base groove & kept popping out & distorting the sealing flange :mad:

Anyway I'm going to phone the wellknown supplier tomorrow and advise him that the seals appear to have a fractionally oversize lip & see if he's had any other queries ?

Has anyone else had this problem or know of a remedy ?

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First question: What state are the flexible hoses in? Sounds like the inner lining of one or more may be flapping and acting as a valve, stopping the fluid. Second: What brake fluid are you using and how old is it? May not be suitable for the cylinders and seals. Third: Are the shoes adjusted as manual on snail cams.? If not can lead to all sorts of weirdness. I'd suggest sending all cylinders , wheel and master to be relined.

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First question: What state are the flexible hoses in? Sounds like the inner lining of one or more may be flapping and acting as a valve, stopping the fluid. Second: What brake fluid are you using and how old is it? May not be suitable for the cylinders and seals. Third: Are the shoes adjusted as manual on snail cams.? If not can lead to all sorts of weirdness. I'd suggest sending all cylinders , wheel and master to be relined.

 

Hi Tony its nothing to doing with hoses or brake adjustment, a master cylinder seal has popped out of it seat & folded over (see photos) the new seal kit does the same.

Why ? poor manufacture ? anybody had the same problem ? I will be phoning the supplier today.

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The only time I've ever heard of this happening was on the old Mini Metros. It happened to a girlfriend of mine, but that happened only once. The master cylinder was changed. The problem then was described as 'A problem with the springs moving to far'.

 

Maybe the master cylinder needs re-sleeving?

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Hi Tony its nothing to doing with hoses or brake adjustment, a master cylinder seal has popped out of it seat & folded over (see photos) the new seal kit does the same.

Why ? poor manufacture ? anybody had the same problem ? I will be phoning the supplier today.

 

Ian,

Not had that happen, but have to say that the rubber valve needs care fitting in to the 'top hat' to ensure the rib around it is seating correctly. It should not blow out like you photo shows. I used an aftermarket kit recently without a problem.

 

cheers Richard

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Ian,

Not had that happen, but have to say that the rubber valve needs care fitting in to the 'top hat' to ensure the rib around it is seating correctly. It should not blow out like you photo shows. I used an aftermarket kit recently without a problem.

 

cheers Richard

 

Hi Richard here's a couple of photos of the 2nd new seal & the brass valve, as you can see this one is also popping out so either a bad batch of seals or there's a fault with the brass section of the valve ?

 

I phoned the kit supplier today & he gets his kits from the same manufacture as everyone else ? he's going to try some new seals into some secondhand brass valves & a new brass valve from an unopened Lockheed kit & get back to me.

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Is there any contamination or pitting on the brass? It looks as if something has pushed against the side of the seal to turn it back. Was there any sort of mechanical action or did it just fit then collapse of it's own accord.

 

Just had a completly barmy thought. When you trail fit, is the seal subject to suction as you bring it out? That might pull the seal out of place.

Edited by Tony B
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This arrived today, its a new Lockheed brass cup & seal.

The verdict is that the new seals are fractionally harder material & have a larger rim & longer skirt, he was able to get a new repo seal to fit an original brass cup but only with some scraping to the brass cup & seal.

I'm much happier now with an original :-D

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