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Rear Wheel Locked Up While Driving

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#1 Norris73

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Posted 08 December 2018 - 09:08 PM

Hi Guys,

 

Super odd one this, hopefully having many minds on this may get me closer to the answer as to what went on the other night. On Tuesday I took my '79 Clubby Estate for an MOT at a classic specialist near work. They tweaked the rear brake adjusters and gave a quick check over then, MOT'd with no problems/advisories (Thanks to DomCr250 for the wheel hubs!, which cured the play in the front offside wheel). On collecting the car I noted the brake pedal felt fantastic! about 1/4" movement in pedal before brakes applied, and they felt the best they have ever felt (original twin leading shoe drum setup). However that evening when driving home after about 3 miles, I suddenly felt the car pull/ hold back, I pulled over after a few hundred yards. The rear nearside wheel was red hot! with smoke pouring from it. I jacked the rear and the wheel was locked up completely! The offside also had a fair bind on it when checked, I backed the adjusters right off and proceeded home with caution.

 

The following day I re-adjusted all adjusters and got the pedal back to the way I have had it for my 3 years of ownership - about 1 1/2" of pedal travel before brakes applied. Not having ever driven another drum braked car I figured this was normal, the car has always braked adequately. After speaking with the classic specialist he listed a number of parts that could have caused this issues - Master Cylinder, Rear Hoses, FAM7821 valve. The Master was changed in 2006 (converted to GMC227) by the previous owner/Have bill from Garage that carried out the work - £450! the rear hoses were fitted by myself in 2016. This afternoon I checked FAM7821 and I could feel slight dampness. After operating the pedal a number of times I could definitely detect brake fluid appearing from the end of the valve nearest the wing, the corrosion on the subframe turret suggests this may have been leaking for some time! The classic specialist told me that 'FAM7821 can release the brakes slowly when sticking and then the drum gets hot its expansion then grips the shoes'

 

So I will be replacing FAM7821 valve, but the question is, does this sound correct can this valve being faulty cause the rear wheels to lock completely up (after being adjusted correctly with slight shoe rub), Im sure this leak could be the cause of my long pedal travel, though!

 

Ideally I would like to replace the pipe and unions feeding from the valve to the front brake banjo union - Part HMK006 and HMV009 as mine look a little rough, however these appear to be obsolete/ No longer available, any ideas were I can get these?

 

I have attached a couple of pictures of the offending valve.

 

Thanks in advance,

 

Olie

 

 

 

 

 

 

 

Attached Files



#2 ukcooper

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Posted 08 December 2018 - 09:12 PM

sounds like air in the system ,and its pushing the pistions open, my 10p worth



#3 Wiggy

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Posted 08 December 2018 - 09:15 PM

Have you checked to see if the handbrake quadrants are free moving?

Just because maybe the garage tugged the handbrake on harder than you do, thus moving the quadrants to a point that they don't normally go and then seizing.

Just a random thought that popped into my head.

Edited by Wiggy, 08 December 2018 - 09:23 PM.


#4 imack

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Posted 08 December 2018 - 09:30 PM

You obviously shouldn't have any fluid leaks so that needs dealing with, but 1/4" of pedal travel is too little, sounds like the brakes may have been incorrectly adjusted.
Is the brake pedal returning fully? Not unusual for the pedal to seize on its pivot or even the clevis pin. This causes the brakes to drag and overheat and the expanding fluid cant return to the master cylinder as the port is blocked so the the expanding fluid pushes the wheel cylinder pistons out and locks the brakes.

#5 cal844

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Posted 08 December 2018 - 09:31 PM

Does sound like the handbrake may be over adjusted(or the quadrants moved to the point of seizure)

That valve does look a little damp, you may be to bypass it and fit the inertia valve to the rear circuit, see Retroman on here for parts at a good price

#6 Norris73

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Posted 08 December 2018 - 10:30 PM

Some good sugestions so far, thanks to everyone for their input.

 

I checked the handbrake quadrants and cable the other day, and all appeared to be free, and operate smoothly when an assitant operates the handbrake. With the way I have it adjusted it goes to 4 clicks, 5 if you really try! The other day after collection from garage it was 3 clicks max, and resistrance felt in handbrake even prior to 1 click.

 

The brake pedal appears to be returning correctly (well above the clutch pedal), and cant be pulled any higher than its resting postion.

 

Im starting to think the rear brakes were simply over adjusted, the shoes expanded because they were dragging, and bound the brakes up. I always find that 3x quater turns on the rear adjusters back from a locked wheel seems about right with only a very light rubbing of the shoes against the drum.

 

Thanks again for the suggestions,

 

Olie



#7 Wiggy

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Posted 08 December 2018 - 11:09 PM

Pretty poor show by the garage, if that's the case.

I'd be checking out the brake shoes. It can't have done them any good to get that hot. Don't know if they're riveted, but you really don't want the friction material coming away from the back plates.

#8 Spider

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Posted 09 December 2018 - 01:40 AM

As you've suspected and from your description here, I agree, that the Bulk Head Pressure Limiting Valve needs to be replaced. It may be the only issue. though, I don't like these valves one bit. IMO, they are junk. I think Retroman also has a similar view of them. There's much better and cheaper valves around that will do the job and without the fuss of these valves. One type of valve is that that was fitted to the early cars.

 

The other item to check that I'm also suspect of here is how the Master is plumbed, the lower port should go to the rear brakes with them and make sure it is return all the way to the stop in the Master itself, otherwise, as you drive, the brakes will come on by themselves and lock that way.



#9 Rorf

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Posted 09 December 2018 - 04:50 AM

As a side line when was the brake and clutch fluid last changed? Many car owners are not aware that these fluids should be changed at least every two years to prevent internal corrosion due to water being absorbed by the brake fluid.

 

I would agree that the rear brakes had been adjusted too tight. Might be time for a full brake inspection and yes replace FAM 7821. The oily engine compartment is certainly keeping the rust at bay :D



#10 Norris73

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Posted 09 December 2018 - 02:33 PM

Mokespider - I think you maybe spot on!

 

Just looking at old pictures of the engine bay, it looks as if the master cylinder to FAM7281 pipes are reversed!! I would really appreciate it if you could confirm my suspicions. I have the GMC227 pipe work conversion kit in stock so changing this shouldn’t be too much of a problem! Am I right in thinking that since 2006 when this master cylinder was fitted for the previous owner by a garage, that the rear and front braking efforts have been reversed! and its passed MOTs in 2006, 7, 8, 9, 10, 11, 15, 16, 17 and 18 with it like this!

 

Can it really be as simple as reversing the pipes from the master cylinder?

 

Thanks again,

 

Olie

 

 

 

 

 

 

Attached Files

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  • Attached File  2.jpg   44.14K   0 downloads


#11 Spider

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Posted 09 December 2018 - 05:18 PM

Yes, it does appear the Pipes are Reversed, or should I say, weren't Reversed.

 

With the Master you had previously, the Green or Black Tag, that is how they are plumbed, but with these, they need to be reversed. This is because this Master Cylinder, unlike the one previously fitted, has a stepped bore, with the bigger section at the bottom. I think these's a flyer from AP in the FAQ on this.

 

I don't think that is the issue with your wheels locking on as they did, but certainly unhelpful!



#12 Retroman

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Posted 09 December 2018 - 09:36 PM

As per Cal and Spider bin the FAMWTF valve they are a useless invention

 

We do a replacement kit

 

http://www.retromini...roducts_id=1289

 

If you need any fitting advice  just PM or email



#13 Spider

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Posted 10 December 2018 - 02:09 AM

We do a replacement kit

 

http://www.retromini...roducts_id=1289

 

 

 

Good work and ACE job.

 

This IS the way forward with those silly bulkhead valves.



#14 Mini Manannán

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Posted 12 December 2018 - 11:02 AM

As said, bin the FAM7821 .  I had problems with soft brakes.  Replaced or adjusted almost everything to no avail.  Put a brake proportioning valve in and it's like light and day compared.



#15 Norris73

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Posted 29 December 2018 - 04:40 PM

Me again, this nightmare continues. In the end I went with a FAM7821 (brand new from minispares) simply because my Clubman Estate is totally original and wanted to keep it that way. I have fitted the new valve and new master cylinder pipe work to the valve. I have been trying to bled the system for two days now, using Eezibleed kit, one way valve one man kit and the old fashioned way. Unfortuntley what ever I do I always end up with an ok pedal, but it sinks towards the floor when under emergency stop kind of pedal pressure. Im running out of ideas and have put nearly 2l of fluid through the system now, I cant see any obvious leaks, and have good flow to both brake circuits. When driving around my drive and applying the brakes the car lurches forward, suggesting the front circuit is working fine, but not much effort from rears.

 

Going through the cars paperwork the master cylinder appears to have been replaced in 2003 - not 2006 as previously thought. I have a brand new yellow tag cylinder in stock so my thoughts are to fit this tommorow and try from there, it feels as if the cylinder isnt working properly on the rear circuit - perhaps it was damaged while trying to bled the brakes?

 

My other mini never gives me much grief when I come to bled the brakes, but my Clubman on the other hand is always a total nightmare! Does anyone have any ideas?, could the master cylinder have been ont he way out?

 

Thanks,

 

Olie







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