Bleeding Brakes

fasttback · Oct 9, 2006

I have just switched out my brake lines to stainless and installed a set of original front discs and an original proportion valve over the old drum stuff.

I'm having a hard time bleeding the rear drums. I have a vacuum gage that I'm using to bleed the brakes. The fronts tested fine, but the rear drums have no fluid after applying the vacuum gage to both sides. I do notice a hissing sound coming from the proportion valve(?) when under 15-20 inches of vacuum. Is this thing holding up my bleeding efforts? The factory manual doesn't mention anything special besides setting the caliper pistons to their proper position.

GoinBroke · Oct 9, 2006

Believe it or not I had the same problem yesterday. I have redone my whole system and borrowed a vac pump to ease the brake bleeding. The front went ok but when I went to the back I pumped, pumped and pumped some moreand could only get a trickle of fluid. I resorted to the old fashioned way and they bleed and pumped up like normal.

1320stang · Oct 10, 2006

Are you still using the original fruitjar master cylinder? If so I'd suggest upgrading to a dual master cylinder, but make sure get a disk/drum one and not a drum/drum one. One for a '67 will work, that being said, I don't know if there were different fruitjars for the disc brake cars or not. My '65 coupe is a diskbrake car and I plan on upgrading to the dual master cylinder. Not sure what you do with the proportion valve then, use the same one or not.

I know this doesn't answer you question, but it's something to think about.

dennis112 · Oct 10, 2006

1320stang said:
Are you still using the original fruitjar master cylinder? If so I'd suggest upgrading to a dual master cylinder, but make sure get a disk/drum one and not a drum/drum one. One for a '67 will work, that being said, I don't know if there were different fruitjars for the disc brake cars or not. My '65 coupe is a diskbrake car and I plan on upgrading to the dual master cylinder. Not sure what you do with the proportion valve then, use the same one or not.

I know this doesn't answer you question, but it's something to think about.

There are different fruitjars for drum vs. disk brakes. For one thing the drum MC has only one outlet (unless it is an early 64 1/2), the disc has 2.

To convert a 65/66 with 4 wheel drums, use a 67' Mustang MC for drum brakes. To convert one with discs, use a MC from a 1975 Maverick with manual disc brakes. Plan to use your original pushrod.

As far as a distribution block, you can reuse your existing one as all it is is one big "T". For 4 wheel drums, buy a plug an cap off one of the outlets. Then separate the front tubing from the rear. The front gets T'ed together through the now "plugged" distribution block and the rear line goes directly to the MC.

For a disc car, use your existing distribution block "as is" for the front brakes. Route the line to the new MC's larger bowl. The rear brakes also get routed to the MC. You must continue to use the existing proportional valve, or buy an adjustable one if yours is questionable.

Cool67 · Oct 10, 2006

fasttback said:
I have just switched out my brake lines to stainless and installed a set of original front discs and an original proportion valve over the old drum stuff.

I'm having a hard time bleeding the rear drums. I have a vacuum gage that I'm using to bleed the brakes. The fronts tested fine, but the rear drums have no fluid after applying the vacuum gage to both sides. I do notice a hissing sound coming from the proportion valve(?) when under 15-20 inches of vacuum. Is this thing holding up my bleeding efforts? The factory manual doesn't mention anything special besides setting the caliper pistons to their proper position.

I would think a "hissing" sound would be an indication of a leak. I had bought a new straight double flared brake line that had the flare poorly done and it caused a leak in my brake lines. Careful examination showed that the end of the flare was at a diagnol and not flush with the mating surface.

fasttback · Oct 10, 2006

GoinBroke said:
Believe it or not I had the same problem yesterday. I have redone my whole system and borrowed a vac pump to ease the brake bleeding. The front went ok but when I went to the back I pumped, pumped and pumped some moreand could only get a trickle of fluid. I resorted to the old fashioned way and they bleed and pumped up like normal.

I tried this last night after bench bleeding the mc, but no luck. It was worth a try though.

fasttback · Oct 10, 2006

1320stang and dennis112,

I did switch out my old "small" jelly jar for the "bigger" jelly jar. It has also been rebuilt. In addition I have the disc brake distribution block and K/H disc brake proportion valve (freshly rebuilt also).

Right now the problem seems isolated with the mc. It bench bled ok, but I can not get fluid out of the mc while bolted on the vehicle with someone pumping the brakes (even with the brake line disconnected in front). Is there a difference in the pushrod length from drum to disc in a 1966? My mc piston from the drum to disc is the same in respect to the pushrod hole and overall length.

I will probably buy a Maverick mc, but I do want to know where the problem lies?

dennis112 · Oct 11, 2006

fasttback said:
1320stang and dennis112,

I did switch out my old "small" jelly jar for the "bigger" jelly jar. It has also been rebuilt. In addition I have the disc brake distribution block and K/H disc brake proportion valve (freshly rebuilt also).

Right now the problem seems isolated with the mc. It bench bled ok, but I can not get fluid out of the mc while bolted on the vehicle with someone pumping the brakes (even with the brake line disconnected in front). Is there a difference in the pushrod length from drum to disc in a 1966? My mc piston from the drum to disc is the same in respect to the pushrod hole and overall length.

I will probably buy a Maverick mc, but I do want to know where the problem lies?

I doubt if the rod length is causing your problem, although I can't really say I have compared the 2.

Right now I am wondering about the rebuilt K/H. Try loosening up the fitting on the master cyl side of it and bleeding it. Does it give a good strong shot? If so, then good. Then try on the other side of the K/H. You should still get a good amount of fluid when the pedal is pushed. If not, that is your problem. If you get a decent shot, it is time to look for balloning at the rubber hose at the rear.

If you do not get fluid at the MC side of the K/H, time for a new MC as that one didn't take the rebuild. If no fluid on the down stream side of the K/H, replace it with an aftermarket adjustable valve.

By the way, I never recommend rebuilding MC's and wheel cylinders. You never know how much wear and taper the bores may have without sleeving them. Better to purchase new for your safety and sanity.

fasttback · Oct 13, 2006

Just got home for the auto store with my new '75 Maverick mc. It seems not to be direct "bolt in" piece. The threads on both the front and rear bowls are of a different size from the Mustang. Is this the right one #2536440?

dennis112 · Oct 14, 2006

fasttback said:
Just got home for the auto store with my new '75 Maverick mc. It seems not to be direct "bolt in" piece. The threads on both the front and rear bowls are of a different size from the Mustang. Is this the right one #2536440?

The treads will be different on on the MC compared to the stock early brake tubing nuts--this is normal.

You will need a pair of adapters that any well stocked autoparts store should have. Look in their brass fitting section.

The front and the rear adapter may be different in some cases so do a visual before leaving the store.

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