The Triumph Dolomite Club - Discussion Forum

Hi All,

So, still slowly recommissioning my 1980 Sprint and next on the list was a look at the brakes, which, following a long layup were non-functional, pedal has no resistance at all. Fluid reservoir looked empty.

So my first step was to check for obvious leaks (didn't see anything obvious) and then bleed the system with a Gunson Eezibleed.

So as per instructions, pressurised the system and started with rear brake bleed valve, apart from a couple of nasty-looking drops of dirty fluid, nothing came out of the valve. So I suspected some kind of blockage somewhere, but in order to more precisely locate the issue I went to the front brakes and bled there - in this case the Eezibleed system pushed through fluid and things seemed to be as expected.

I didn't want to press the pedal too hard because of risk to master cylinder seals, but my impression was the pedal feel was still very bad.

So my questions is, do these symptoms yet pinpoint a likely culprit in the rear brake circuit or do I need to test or replace some other things first to better lock down where the issue is. I was considering that the cause could still even now be within the master cylinder, or the tandem brake valve, or the pipes, or even maybe the rear brake cylinder itself being blocked.

What would be the recommendation for next steps, Brake master cylinder kit because it is likely to have been damaged anyway if the pedal has been abused?

Cheers
Ian

Disconnect the front of the rear flexi and see if fluid issues from the forward pipe, if it does, your rear flexi has collapsed internally and needs replacing. That should then see the rears able to be bled.

If that doesn’t resolve matters, you’ll need to systematically check for crystallised fluid throughout the system

Thanks very much for the pointer, just a very stupid question, where in the circuit is the rear flexible pipe just so I am sure I am looking at the right thing?

Located inbetween the brake pressure regulator and the rearaxle.

When nothing comes out of the pressure regulator that part can be faulty also. Checking by taking the brakeline off and see if fluid comes out of the brakeline.

When nothing comes out the brakeline the pwda is stuck towards the rear.

Did you check the bleedscrews at the wheelcilinders? Sometimes these clogg also.

Jeroen.

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I agree with Alun in respect to the rear hose being the first thing to rule out but if it is not the problem you may have an air lock and I would crack open the rear brake line connection on the master cylinder and then operate the brake pedal to check that you can get hydraulic fluid leaking out at this point. You need to take care to catch the leaking fluid as it will damage your paint work if it gets on it. I expect you know this. If you can't get fluid out at this point you know you have a master cylinder problem. The relevant piston may have stuck and not be returning when the pedal is released as a result of lack of use. You could then try back feeding the rear brake line from the bleed nipple using a syringe to see if this would free it up. If you get hydraulic fluid out at the master cylinder pipe connection I would then move to the tandem brake connection as you call it and again crack open the rear brake line connection and check you can get hydraulic fluid to this point. If you get it here just move on down the line.

Thanks all, sounds logical.

I will start from font of the rear flexi and either:

a) move up if I see no fluid there, keep moving forward to each joint until I get to the master cylinder and then check that as per Richard's post, or

b) If I do see fluid at the rear flexi, then I will check that tube for collapse first, if OK, I will move backwards until I find the culprit, ending up at the rear bleed valve

Will report back, thanks again for all your input!

Ian

In response to soe8m's comment that "When nothing comes out of the brake line the pwda is stuck towards the rear." I have read and heard various owners state that the pwda shuts off that section of the brake line if there is a leak but when I have been looking at the parts of the my 1500 Dolomite tandem braking system this does not seem to be the case. I have noted that the master cylinder reservoir divides into two sections and I believe that the section with the leak will just dump it's hydraulic fluid and that the other brake line continues because there is still hydraulic fluid in the part of reservoir that serves it. I include the following photograph which shows the master cylinder reservoir and you can see where there are two sections within the reservoir.
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I have looked at the pwda I can't work out how it could shut off the hydraulic path. See photo of pwda

It doesn't shut off or isn't designed to shut off as a safety. The plunger moves towards the less pressurized (leaky) cicuit and makes the switch switch on the control light.

BUT, on several cars that I have owned which stood for many years the PWDA's were corroded inside. This is a common thing. The plunger moves towards the pressureless side and get stuck obstructing the flow.

It happens to the rears as that are the ones most people start bleeding. Rear bleeding screw turned open, press the brake pedal, piston moves towards the pressureless rear circuit and blocks. Due to the corrosion and muck inside it will never be able to travel to the middle again as the passage is obstructed.

It rarely happens at the "front" part as there is no chance for obstruction even if the plunger is pushed towards the front circuit. There is alway's a passage where pressure can be at the front pushing the plunger back to the middle.

Seeing a car with such a device the best is to start bleeding at the rears with the front bleeding screws open also.

Jeroen

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Many thank soe8m for the detailed explanation. I am glad you are on this forum and happy to pass on the knowledge you have gained over the years.

I'm with Jeroen on this. The Dolomite seems particuarly prone to collapse of the rear flexi hose, but dual circuit cars are always a nightmare to get bled correctly because of the pesky PDWA valve on the bulkhead. Lack of use and water in the fluid compounds this problem by rusting the PDWA piston in place making it all but impossible to get fluid through the rear circuit.

My own personal (if slightly extreme) solution to this, is to delete the PDWA entirely. It means making 3 new metal brake pipes (or having them made) for the front circuit and replacing the PDWA with a 3 way union for the front circuit and an inline joiner for the rear one. But trust me, you won't miss it! Except when bleeding the brakes is 10 times easier, you won't even know it's gone!

The purpose of the PDWA is to generate a warning light on the dash when one of the 2 brake circuits loses pressure, 9 times out of ten this is because of a leaky rear wheel cylinder. But it doesn't really tell you anything you don't already know as any such pressure loss will be immediately accompanied by a increase in pedal travel!

So I delete the PDWA and use the wiring to power a float level sensor in the master cylinder cap (one from a Saab 9-3 fits perfectly) This will warn you of fluid loss BEFORE the pedal loses pressure totally, so is a better system than the PDWA. In fact the PDWA was ONLY used (on British cars at least) for around 4 years in the late 70s, after which it was abandoned in favour of more reliable systems.

If you are interested in this solution, I can supply a PDWA delete kit, comprising 3 metal brake pipes (in Kunifer) and a 3 way union and inline joiner for £25 including postage.

Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
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Thanks Steve, PM sent.

If you keep the PWDA,bear in mind you bleed the front first not the rear-as per the Triumph workshop manual.Left front,right front then rear.

Hi All,

Just a quick update on this - the rear flexible hose does seem to have been the culprit, as I cut through the cable and no fluid came out....closer inspection once removed revealed internal rust and gunk. Also, as soon as removed the flexi hose joint, fluid immediately came out, so I think the load sensitive valve assembly seems OK.

So, I will need to replace the flexi hose, but also the rear brake lines also look dodgy so I think whilst I am doing the flexi it is probably worth doing those as well.

Steve/Carledo, though I don't think I need your PDWA delete kit on this occasion, are you able to supply these parts (rear flexi GBH124, rear pipe 30972 and rear pipe 30973), or am I better off ordering them online?

Ian