411 brake problems

[peter dowdle]

I finally managed from sources in the UK and Australia to obtain a master cylinder repair kit for my series 2 411 Bristol. I employed a professional experience mechanic to fit the kit , ensuring it went back together correctly.
After much fiddling I had everything back in place. The pedal came good after some bleeding. Job completed after a short test drive.
Next day I drove the 35 Km to have the wheel alignment done. Upon opening the bonnet I found the front brake tank overflowing and the rear one nearly empty. ENOUGH
From the advice given on this forum I purchase a mid 70s Range Rover new cylinder.
Fitting was fairly easy. Parts required
1/ A plate with 2 studs fitted to back of firewall
2/ lengthened push rod ( extra 15mm )
3/ Two new brake lines to extend to boosters.
All fitted together easily

BRAKES ARE FINE

[Claude]

I have read through the postings on the 411 Master Cylinder, but I would appreciate some clarification and assistance.

Initial symptoms: 411-S1 has stiff rear brakes.

1. Problem One: The flex hose to the rear axle was completely blocked. Replaced it with H892 found at Sterling Brakes in Auckland (last one). Now fluid flows to rear, but brakes still stiff.
2. Problem Two (maybe) I removed the rear calipers (Girling 12/3HP). They seemed in relatively good shape (they were rebuilt in 2004, but not driven since), but needed a bit of surface cleaning on the top of the pistons due to sitting. Two trips to the brake shop and $200 later, I put them back on car, jacked up both rear wheels, removed wheels, started the engine, the wheels would no turn when in Drive at idle. Applying some power would turn, but clearly the pads were gripping.
3. With the engine still running and still in gear, I loosened bleed valve on the caliper, fluid came out, immediately the brakes released.

This points to something upstream keeping pressure on. Options include:

• Master Cylinder needs to be removed, inspected, probably rebuilt
• Hose on the Master Cylinder is partially blocked (works on braking, not on release)
• Servo needs attention of some sort
• There is a pressure relief valve that I don't know about (is there one?)

1. If it is the Master Cylinder, it is unclear how one removes it. One comment about an impossible to remove split pin. Is this something I may encounter? I would appreciate a step-by-step removal instructions that I can then summarise for others (the problem with forums is having to read through all of the dialogue to find the core information necessary to solve the problem).
   .
   A. If it is removed, what is it? How can I find out how to rebuild it. What is the manufacturer (Girling/Lockheed?), what generic part number, what other vehicles use the same master cylinder.
   B. Alternatively, what more readily available equivalent is available? I read about Land Rover, sounds like a more difficult procedure, and I read one comment about using a modern master cylinder. What would be the best alternative retrofit?
   .
2. With the hose, it looks easy - get another one. I'll do that when the shops open.
   .
3. With the servo, if I disconnect the vacuum and the servo is the problem, does it release the brakes, or do I need to make a bypass line and unbolt the in/out brake line nuts to eliminate the servo as a suspect?
   .
4. And finally, am I missing anything else?

My hunch is that the rubber hose at the Master Cylinder is partially blocked... it will work when foot pressure is applied, but closes down when back pressure wants to release the pads.

Finally, BODA asked if they could use my postings of the "shadetree mechanic" steps taken, so I have been documenting the findings for future owners in a way that eliminates the back-and-forth, but provides the helpful directions for those of us too far from a qualified repair shop. Clarity in answers will be appreciated by future Bristol custodians (Bristols can last forever, it's the current owners who come and go).

[Kevin H]

Originally Posted by Claude

My hunch is that the rubber hose at the Master Cylinder is partially blocked...

Must be different to the 411 S5 - there's no rubber hose connecting to the master cylinder on my car...

According to the 411 Owners Manual the master cylinder should be a Girling product.

It does sound very similar to the issue Peter Dowdle had.

EDIT/PS: Claude, please post a photo of the master cylinder

[Claude]

Originally Posted by Kevin H

EDIT/PS: Claude, please post a photo of the master cylinder

Photo of master cylinder and servosMC.jpg

[peter dowdle]

Thats the same as mine. As I said if you need any advice on removal and replacement Im only to happy to help .

[Kevin H]

Originally Posted by Claude

Photo of master cylinder and servosAttachment 1133

That's very different to mine (411 S5).

[peter dowdle]

Kevin your series 5 cylinder is the same as the range rover one i have fitted except the plastic tank is slightly different in that it has a fluid lever sensor fitted to the lid.

[Kevin H]

Peter do you have the part number for the Range Rover master cylinder that you used? I want to see if it is the same number as the MC Girling list for the Bristol 411.

I'm intrigued as to how/why Bristol used a different MC on the 411 S1&S2. I have the Girling Parts lists for the Bristol 410 and 411 and the photo of yours doesn't appear to be the same as the MC listed for either vehicle.

Nor can I find a MC in the Girling catalogue illustrations that looks like the one on your's and Claude's cars.

However, the part number on Bristol's parts list for the 410 is also slightly different to the part number listed by Girling for the 410!

The joys of low volume, hand built cars!

[PEU186F]

Claude

Too many issues one after the other can seem daunting but the best approach is to follow a logical elimination path.

Releasing the pressure after the servo allows the brakes to come off, so it's either the servo or the master cylinder that is holding them on, now that you've eliminated the brake line between the servo and the callipers.

So release any pressure between the master cylinder and the servo, simply by loosening a connection point.

If the brakes don't then come off it is the servo that's the problem, if they do then it's the master cylinder, or possibly the brake line between the master cylinder and the servo. To eliminate the latter try loosening a connection point at each end of that brake line

If it's the servo it's a case of rebuild or replace, I'd be pretty certain that there must be someone in NZ who rebuilds them, if of course you can find them.

If it's the master cylinder do just check that the brake pedal is free to return fully before you attack it.

My knowledge of V8 brakes stops at the 410 which uses twin Girling master cylinders, callipers and connectors but Lockheed servos (Lockheed 4258-405). I believe that the 411 is similar apart from the single master cylinder.

Roger

[peter dowdle]

As i mentioned in my earlier post I had similar problems > To clarify the problem can you post a photo of the master cylinder. Series one and two cars have varying master cylinders than 3 4 & 5. My series 2 had an unusual type off a commer 3 ton step thru van. Parts and replacements are very hard to source. It also has an unusual mounting system , for these reasons the range rover cylinder is the way to go. If you decide to go down that track I can guide you through the conversion. Yes the original cylinder if the same as mine is very hard to remove and replace.

A photo if you can please