71 replies to this topic

[Ethel]

 

That's a bummer that it's now come to this, however, by the looks of that break in the reservoir, I'd say the plastic has gone brittle.

As for going Single Circuit vs Tandem, I'd suggest looking in to your local Registration Laws. I'd say off hand, if it came with a Tandem Master, you'll likely need to stick with it.

Our local registration laws are not that strict. For roadworthy, as long as it works... so there's no issue here.

Though, I will get a price for the Gmc167 dual master from my local supplier. I will probably end up getting a new one to replace what will come out. Since I already did the new lines for that setup. Besides, a new one will probably last many years without issues.

 

Not just local regs. Should the unthinkable happen, it's just the sort of thing insurers will jump on to avoid paying out. You can argue your case if there's a NLA superseded part you can quote, but there are no recommended preceeding parts. 

[miniGTS]

Here, it's unlikely that insurance will know what the vehicle came with. As long as it passes a roadworthy and engine modifications are declared, there won't be any issues.

[miniGTS]

Nice one !

When I rebuild the master, should I be using a small amount of silicone paste on the seals when I assemble?

Rubber Grease or Brake Assembly Grease or at the very least, Brake Fluid is what to use on assembly.

If you have an old 1 thou feeler strip, you could cut a thin strip off that and rub it on some 600 wet & dry or similar to smooth off the edges. Then when assembling the PDWA Shuttle / Piston, put the feeler strip down the bore to cover over the ports, insert the Piston, then remove the strip. This should avoid damage to the I Rings if there's an edge on the ports in to this bore.

Also, should I seat the spacer into the bottom of the chamber first, then drop the piston in?

I put it in together last time, which could have caused the issue with the damaged o ring because the spacer takes a firm push to get it in. Thinking about it now, it seems to make better sense to first put the spacer in place then carefully fit the piston... With red rubber grease that I now have

[Spider]

The only Cylinders I've re-kitted have been the early types that only have the O Rings and no Plastic Spacer, so sorry, I don't have any experience here to offer.

However, reading the instructions, I'd say, yes, drop the Spacer in first, fit the O Ring on the Piston only a few mm, don't push it up to the shoulder, then fit the Piston Assy in to the PDWA Valve and fit the top threaded cap (with a copper washer !). It should then find it's own position.

 

[miniGTS]

I've rebuilt the master with new seals and extra care but it still leaks through the PDWA switch.

I've settled on changing it to a single line and rather ordering a new one to avoid any further delays and issues with brakes.

Thank you for the help with this but either I'm doing something very wrong or there's some other issue going on inside the bores.

[Spider]

I have found a zillion times over the years that once a cylinder leaks in service, then it's the end of the road for it, save for sleaving as you had done with the main bore.

The rubber seal kits are a maintenance kit, not a repair kit.

[miniGTS]

My new single line master cylinder arrived today so I made some new brake lines as necessary for the change to single. Tested with methylated spirits, no leaks and pedal felt good. Then flushed and bled the system with dot 4 brake fluid and the pedal feels good.

Sooo hopefully that is done and dusted so I can move forward and get the engine in... Hopefully this weekend.

[Spider]

Nice work !

Bit of a road and shame the Tandem couldn't be sorted, but sounds like you're moving forward again now.

[Bobbins]

Is using methylated spirits a standard way to test a system for leaks?

[miniGTS]

I used it as suggested on this forum and other online sources when testing a new system. I did complete new lines, wheel cylinders and calipers so used the methylated spirits to test the system for leaks before flushing and bleeding with brake fluid.

Methylated spirits is safe for the seals in the system and won't damage paint if there's a leak.

[Bobbins]

That’s useful to know, I’d not heard about that before and my system will be 95% new when I come to fill it. Cheers.

[Spider]

That’s useful to know, I’d not heard about that before and my system will be 95% new when I come to fill it. Cheers.

 

 

I think it was me who first suggested this. It's in the factory manuals that Methylated Spirits can be used for cleaning brake parts as it's inert to the rubbers used. I have flushed new systems with Meths to not only clean the system, but also checking for leaks - Meths won't damage your paint and we all know the disastrous results Brake Fluid can do,

 

The only caveat I'll put on this, is that it's important to flush the system thoroughly with Brake Fluid following.