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Disc Brake Upgrade

Well I am back at it, working on my 59 Bug once again. I have installed front and read disc brakes with the kit from AC Industries. The kit came with a new master cylinder. I hooked up my old 59 reservoir and green line to the new master cylinder. It was a little hard getting the green brake line over the master cylinder nipple, but I did it. Made me think that I should have used the blue feed line, which seems to have a bigger inside diameter.

Anyway all seemed fine until I started to bleed the brakes. I keep getting air in the lines. I also noticed that when I left the cap off the reservoir that the system seemed to work better and didn't get air bubbles in the line.

Or is it possible that the master cylinder is defective? Any help would be appreciated.

Reply to
ARL
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One thing the repair manuals fail to tell you is to leave the cap off the reservoir while you are bleeding. I found out from personal experience, as you did, that the bleeding process goes smoothly when you leave the cap off. This is because air has to displace the brake fluid level as it falls during bleeding. With the cap on, air can't get in and the brake fluid won't enter the master cylinder when you pump the pedal; at least not much fluid will enter. Just make sure after you finish with each wheel that you check the fluid level and add more if the level gets too low. If the reservoir empties, you have to start over with the first wheel.

If you look at the reservoir cap you will see a pinhole in both the outside and the inside of the cap. This allows air in as the level falls.

Randall

Reply to
Randall Post

I once ruined a brand new masterpump by failing to notice small caps on the plastic feed nipples. They where the same colour as the nipples..

Hooked up the hoses to the reservoir and pumped away, the dry pumping action ruined the m.c.

After this incident I bought a force feed unit, comes with a container for the fluid with a valve adapter/stem and different adapter lids for different reservoirs. Works like a charm, I hooked it up to a inflated bicycle innertube. Saves you of lowering the airpressure of one of the tires to the max recomended

15 psi.

J.

Reply to
P.J.Berg

Last time I did my brakes I made a force feed unit but instead of a tire I used one of those portable inflators you run off the cigarette lighter to pump up balls and air mattresses. A tire might have been easier.

Reply to
Michael Cecil

The small one you used could be ok, otherwise be very carefull with compressors and forcebleeding, very easy to pop one of the small hoses or the adaptor lid.

J.

Reply to
P.J.Berg

I used a long cord with a reed switch so I could turn it on/off from under the car while I lay there with the bleeder valve wrench in one hand and the output bottle in the other. I think the hose I used to attach to my adapter cap would pop off before the brake fluid reservoir hoses.

/waits for Shaggy to tell story about using an industrial compressor...

Reply to
Michael Cecil

Thanks everyone for all your suggestions. I may look into a force system. But what about the green (smaller ID) feed line versus the blue feed line? Does it matter at all. I would like to keep the original reservoir.

Reply to
ARL

What is the difference between the two ID's? If you are able to fit them on the nipples of both m.c. and reservoir you are good to go.

J.

Reply to
P.J.Berg

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