Air in brake system

[fallingoffalot]

In the middle of rebuilding my front disk calipers, done the one that was binding. Doing the other one Ive somehow managed to get air I to the system. I think I let the reservoir get too low. The pedal was firm after I'd put the first one back together, but now it goes straight to the floor.

Does this mean I have to bleed the master cylinder?

Or will just regular bleeding at the caliper fix it?

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[subheatadey]

First get a Gunson brake bleeding kit, cheap as chips. You need to bleed your brakes start with the one furthest away.

 

[fallingoffalot]

Ok thanks, ordering one now

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[fallingoffalot]

.....one more brake question if anyone is able to help.

My rebuilt brake still drags slightly, it's not too bad and it has always been like this, in fact it was a bit worse. So does it matter and what would I need to do to make it completely free?

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[67westy]

If you have a 68 and are now on discs have you checked the residual pressure valve has been removed or had the ball bearing taken out?

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[fallingoffalot]

I've no idea I'm afraid, it was installed by the PO, or even in South Africa, before he got it. How would I check?

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[67westy]

It's located on the master cylinder. Some info here https://www.thesamba.com/vw/forum/viewtopic.php?t=556325

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[fallingoffalot]

Thanks, I'll check, but it does say under the last photo in that article "Hope this helps 67 only disc brake conversions." (apparently mine's actually a 69 MY although built in Dec 68.)

 

[mike202]

There’s quite a bit of information on here as well if you do a search for ‘residual pressure valve’

It looks as though drum brakes need a residual pressure valve fitted on the master cylinder but disk brakes don’t, and you have to have it removed from the front brake circuit if you are just converting them. Otherwise the disk brakes drag.

There are M12 to M10 conversion connections sold by CSP (maybe others as well) or you just remove the valve fittings on the existing connector.(s)
Like in the pic from that link in the Samba.

There’s also mention by some about needing a brake pressure regulator like a late bay, if you covert the front brakes to disks.

I’m hoping to do a CSP conversion in the future but I’m starting to think it might be too big a task for me to take on! [emoji2955]


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[67westy]

I reckon you are more than capable Mike I'm planning to do plenty of pictures when I do mine so will hopefully give you a good idea of how difficult it is

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[67westy]

Thanks, I'll check, but it does say under the last photo in that article "Hope this helps 67 only disc brake conversions." (apparently mine's actually a 69 MY although built in Dec 68.)

As Mike said it's the same for any drum to disc conversion. I'm sure I've seen a thread on here about it, will see if I can find it.....

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[67westy]

Here you go http://forum.earlybay.com/viewtopic.php?t=63957

Sounds like csp also sell a converter as well. I think a quick look underneath will tell you if the valve is there and if it is you will probably have to take it out to check it

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[mike202]

I reckon you are more than capable Mike I'm planning to do plenty of pictures when I do mine so will hopefully give you a good idea of how difficult it is

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Thanks for the vote of confidence Adam! [emoji3]

There was an article in camper and bus in May/June 2020 edition in the ‘how to’ section but he changed the MC as well which means moving brake lines. He actually bought a servo type MC.

Looking forward to pics of your conversion.


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[fallingoffalot]

Thanks for the replies guys. Latest issue.... The boot won't fit! It's the same size as the others and the others all went on ok, but this one simply won't fit, it's too small for the mounting lip. Any suggestions? I can't omit the boot can I?

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[fallingoffalot]

Noooo, pressure tested the Gunson kit at 18psi, and it exploded my header tank!! Looks like I need a new one!

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[67westy]

That's a nightmare. Never easy with these old buses! You definitely need the boot, have you tried swapping then around to see where the problem lies

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[thejinx]

Can’t you do it the old fashioned way. Get someone to sit in the bus push the peddle down. Someone under the bus and crack of the furthest bleed nipple. Liquid squirt out peddle hits floor close nipple build pressure repeat. Until you have done them all. Ensuring you fill the reservoir as you go along.

Google it for a better description.

 

[fallingoffalot]

Yeah no idea what I'm going to do about the boot. They were all the same, and I've tried swapping them over, it's literally about 1mm in diameter too small, why would VW make the lip bigger on one side?

The calipers have different identifications on them, one is a "53" and the other is a "56" they look the same have same dimensions, but maybe they're slightly different.

I'll see if I can find the old boot and phone Bigg Red and see if they can match it.

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[Moseley]

Argh, you beat me to it... I’ve commented previously that I don’t like those one-man bleeder kits for exactly the reason you have shown - the reservoir and hose connection down to the MC are not designed to see pressure, and the only way to test if they will withstand it is to do as you’ve done. The issue being that for most people, the system will be full of brake fluid so if a hose or other part fails, you’re emptying all that lovely corrosive brake fluid into bits of the van that are incredibly difficult to access to remove all traces of it.

I know it’s too late now, but maybe stick to doing it the old fashioned way with a helper - you’ll generate a lot more pressure using someone’s leg than you will with a partially deflated spare wheel.

There are brakes on the market which are designed without dust seals. There is a school of thought that dust boots will do more harm than good if anything gets into them - I.e. moisture will cause the piston to corrode, dirt and debris has got no chance of being cleaned away. New dust seals will certainly prolong calliper life, but if you consider how many vehicles are on the road with split or damaged dust seals, it is likely that if you ran without them, you will be doing no worse damage than these would. It will certainly reduce the life of your piston seals though, as they will be immediately subjected to abrasive material. How soon that might lead to a failure is anyone’s guess...


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[mike202]

18 psi sounds like a lot to me ! Is that what the kit recommends?

I don’t think those plastic reservoirs are made to withstand much pressure, if any. They are just to contain the brake fluid surely.




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