In my 66 F100 I completely rebuilt the braking system. Got rid of the flowerpot M/C. Put in front disc brakes with rear drums brakes. New single diaphragm 7" power booster, new dual port 1-1/4” bore M/C, new proportioning valve, all new lines to new wheel cylinders. I bench bleed the M/C and gravity bleed the lines. All lines have fluid to the wheel cylinders and there are no fluid leaks from any connections. Issue is as I attempt to finish bleeding out the lines, I get no pressure or buildup at the brake pedal and at the wheel cylinders it drips like an eyedropper. Rear brake shoes have been adjusted to the rear drums and drums spin about 1 and half rotations freely. I have not tried to do a pressure or vacuum bleed system yet. The booster hose is connected to the carb, but engine is not running at this point. Never went this far with a braking system before, so any suggestions or input to the issue?

 

couple of things
may have to bench bleed again. happen to me an that was my issue
also is the proportioning valve adjustable?
possible closed off to area you want it to be?

 

If understand correctly, the M/C is of the front disc rear drum type, if of the 4 wheel disc variety then perhaps excess pressure to rear brake cylinders?

IMO, until the leak is fixed at the rear brake cylinders I do not believe bleeding the system will have any effect. Suggest pull rear drums to determine the source; perhaps the brake cylinder cup is not seated, the brake cylinder arms are not aligned, or both. Once the leak has been solved I would go thru standard bleeding procedure, I do have a vacuum pressure system but over the past 45 years have never used it on the 65's; with a helper I start from the furthest rear and work forward checking MC fluid level thru out the process. If you do have the Vac. system then process probly less labor intensive? Anyhow, food for thought?

 

Dave, I don't think he has a leak at the rear cylinders - I think he is saying he is not getting a good flow when bleeding them and it is coming out at the pace of an eye dropper.

Chad

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My Trans Am uses a combination valve that requires a special tool to allow bleeding - or you can fashion your own tool. But, it looks like this. It holds open the metering valve plunger.

https://www.ebay.com/itm/KENT-MOORE-...wAAOSw~UdZ3kLG

Might not be an issue for you - but it might be good to keep in mind this *could* apply to other valves, too. This might be what Bert65 is getting at, too.

Chad

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Chad, I thank you for the clarification!!

 

Thanks all.

Bert65 - I will bench bleed the M/C again and see what happens. As far as I know, the proportioning valve isn't adjustable, however, after reading Chad's last post, I might have to dicker with the metering valve plunger - that did not cross my mind! I'll do this before messing with a bench bleed again.

Chad is correct Dave, I see where I might have gotten you confused. When I have the pedal pumped and held to the floor and open the bleeder valve, it drips out like an eyedropper, and no pressure buildup at the brake pedal.

Here's a picture of my set-up. Sorry pic is so big, don't know how to reduce it.

Al

 

it looks like a pv2 valve if so they sell a cheep tool for it on fleebay it keeps the pressure differential valve in place while you bleed your lines

 

This ad shows the bleeding tool for the PV2 that hello113 mentions and it gives a bit of a description of how to use it.

https://www.ebay.com/itm/Proportioni...NVdhBW&vxp=mtr

Chad

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You should get pressure build-up from a good m/c even if the system has air in it, although it won't hold.
A couple things that have worked for me:
-"Stab" the brake pedal hard and fast if you think you have a bubble of air in a line,
- If you think you might spill or leak fluid, mix a 10% solution of dish soap and spray it liberally on nearby surfaces, and keep them soapy. The brake fluid will rinse off later without paint damage.
Eric

 

I'll take a look around to see if the bleeding tool came with the kit (booster, M/C and combination valve). I don't believe it did. The only paper work was info on how to bench bleed the M/C and plastic shipping plugs for the M/C. If not laying around, I'll order one.

 

Al:
You may be just having the difficulty that's inherent in starting with a system that is completely void of fluid. I like to vacuum bleed initially until all four corners have some fluid. You won't get any fluid coming out of the bleeder with the pedal held to the floor...only while it travels. Everyone has their own system/way of bleeding but mine is this.
-open the bleeder and have your assistant press the brake pedal slowly.
-instruct your helper to say "down" when the pedal touches the floor and close the bleeder valve.
-you say "up" when the bleeder is closed, that's when your helper knows they can release the pedal.
-when the pedal is up...repeat...until no air bubbles come out at the bleeder. You won't have any significant pressure at the pedal until all four corners are bled. It's tedious, but it does work better than any other method I have tried. I run silicone fluid which is difficult to eliminate air from and difficult to avoid leaks.
As far as the metering valve...watch for leaks under the rubber cap at the front. The imported ones are notorious for leaking and ultimately I had to source an oem. Still have the contact if you need one....good luck!

 

Thanks Eric. Have never bleed the brakes that way before, I'll give that a try. I did bench bleed the M/C again last night and will gravity bleed again tonight. Can't do more till the Combination Valve Bleeder Tool arrives, had to order one.

Question to all: If I never had any pressure while pedal bleeding the brakes prior, would the pressure differential valve be off center?

 

Al:
Never had an issue with mine being anywhere but centered. By either gravity bleeding or vacuum...if you have fuid in all four corners before applying significant pressure, you should be ok. Again, others here may have valid techniques and opinions that vary...but also work.

 

All good points. It can be tedious for sure.

I like to pressure bleed brakes using my pressure pot. It holds up to a gallon of brake fluid and I have adapters for single and dual masters. No helper needed. Saves lots of aggravation.



Chad

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