Brake Fluid Reservoir pipe diameter

[JJ Autosleeper]

Does anyone know the right diameter for the pipe from the brake reservoir to the master brake cylinder?

My van is 1970 PB.

The one I have fitted may be bit too small a diameter as I’m getting problems bleeding the brakes. Thanks.

 

[PaulJL]

Welcome to the pita job of bleeding the brakes. I think it's a 3/8 pipe.
I have recently replaced the reservoir with a modern alternative which meant I could fit a pressure bleeder.

 

[JJ Autosleeper]

Hmmmm, I think I have an 8mm or so pipe on there. I’ll double check. I remember having to heat it up in boiling water to get it onto the master cylinder anyway.

 

[Panky]

That should be plenty big enough, you would have trouble pushing enough fluid out to overcome the size of the 8mm inlet pipe. Try clamping the slave cylinder plunger so it can't move and try bleeding again.

 

[JJ Autosleeper]

There is no slave cylinder on the brakes as far as I know, just wheel cylinders and the master. Run via a three-way splitter on the chassis outrigger in the engine bay. I may try the clamping method for clutch bleeding though. I seem to remember that was hard also last time I did it.

We’ve got the brakes bled now but it was a struggle getting rid of the air in the system. We had to go round three times. My friend said it must be the feed pipe to the master being too narrow restricting flow to the master. I think he’s right. Will get it changed to a 3/8” or 10mm pipe. It does not seem to effect the braking just makes it hard to bleed.

The reason for the bleeding was needing to rebuild the front wheel cylinders as the o/s cylinder had seized after just two years. This had led to excess heat and the shoes were cracked that side also. So I rebuilt the cylinders using plenty of red rubber grease and fitted new shoes. See picture of the overheated shoes (rhs) versus regular two year old ones. Plus I fitted new flexible hoses from and back.

Road tested ok yesterday. Braking much better than before.

Ps. This was picked up on an MOT test brake check. I’d recommend everyone get this done periodically regardless of it not being mandatory anymore. £40 well spent IMO.

 

[Panky]

Ah sorry I thought you were bleeding the clutch for some reason I should lay more attention

 

[JJ Autosleeper]

Final result was the existing hose was a 3-4mm hose. The hose that was fitted was significantly stretched to fit over the spigot on the reservoir. See photos with the stretched section next to a cut section for he actual diameter.

I replaced it with an 8mm id EPDM hose from an eBay seller who rated it for Brake Fluid. I hope this will make bleeding the system easier.

Note: from my research best not to use fuel hose.