After going thru all of the great advice from the replies to my original post I accomplished the following....All shoes were adjusted to lock the wheel and backed off slightly. Made a pressure bleeder and adapter for the MC. Bled all 5 points with a good stream from all of them. Never saw any air. First application saw the pedal go to the floor with little resistance. 4 pumps later pedal went hard just off the floor by a couple of inches. Applying really hard pressure to the pedal made it very slowly go down. At the moment I'm assuming a bypassing MC. Any thoughts?
- Thread starter wremele
- Start date
wore out
Well-known Member
It certainly sounds like the master cylinder may be leaking internally under heavy pedal pressure.
On the other hand, I don't think that is the likely cause of the other problem.
Can you post a photo or at least a part number of the Hydrovac? Are you SURE you aren't missing a second bleeder on the Hydrovac?
MANY have a bleeder in the vacuum valve area, near where the fluid comes in from the master cylinder and another at the far end, where fluid exits the booster to supply the brake cylinders.
Also, does the system loose any fluid as the pedal is heavily depressed a few times, which COULD indicate the Hydrovac is leaking INTERNALLY
used red MN
Well-known Member
- Location
- Coon Rapids, MN
First how is the fluid in the MC reacting after you
release it from the a pumped up hard pedal? Does it
..fountain.. in the reservoir as was mentioned as a
symptom to check in your first post? If so that is a sign
of air still in the system. When you are testing the
pedal by pumping it up is the engine running or not?
Should be able to check the master cylinder for leak-
by in the following manner. Purchase a flare line plug
of cut a short end ..not much more that an inch. of old
line the proper size to fit in the master cylinder fitting.
Pinch the line shut and braze it to seal it. The gravity
bleeding while you are attaching it should be good
enough to test it once installed. Obviously, with the
plug installed the pedal should not bleed down. If the
MC tests okay for no bleed-down I would suggest
pulling the vacuum supply hose off at the Hydro-vac
and check for fluid. If all else fails I would recommend
at least trying a couple good bleed cycles at each
wheel with a pumped up pedal and the engine running
to see if you can move the air out with the higher
pressure built up.
release it from the a pumped up hard pedal? Does it
..fountain.. in the reservoir as was mentioned as a
symptom to check in your first post? If so that is a sign
of air still in the system. When you are testing the
pedal by pumping it up is the engine running or not?
Should be able to check the master cylinder for leak-
by in the following manner. Purchase a flare line plug
of cut a short end ..not much more that an inch. of old
line the proper size to fit in the master cylinder fitting.
Pinch the line shut and braze it to seal it. The gravity
bleeding while you are attaching it should be good
enough to test it once installed. Obviously, with the
plug installed the pedal should not bleed down. If the
MC tests okay for no bleed-down I would suggest
pulling the vacuum supply hose off at the Hydro-vac
and check for fluid. If all else fails I would recommend
at least trying a couple good bleed cycles at each
wheel with a pumped up pedal and the engine running
to see if you can move the air out with the higher
pressure built up.
Are the wheel cylinders mounted level in the rear wheels or do they lay at an angle? If they are at an angle the bleeder will not let all
the air out ! We used to bleed them with the wheel and drum off -- We would stick a small feeler guage in the the slave cylinder . it was a
slow process but it worked. Keep us posted and good luck! Roy
the air out ! We used to bleed them with the wheel and drum off -- We would stick a small feeler guage in the the slave cylinder . it was a
slow process but it worked. Keep us posted and good luck! Roy
Steve@Advance
Well-known Member
Sounds like the one I fought with, dumped a gallon of fluid through over several days of frustration. Turned out to be a defective booster.
Replaced the booster, it bled out and was working in a matter of minutes!
Replaced the booster, it bled out and was working in a matter of minutes!
Welding man
Well-known Member
- Location
- West Virginia
Do not bleed the brakes with the engine running. Pump the petal up until the brakes get hard and bleed all the vacuum off the booster.
Hold steady pressure on the petal and start the engine. When the engine starts and the vacuum builds you will feel the petal drop
slightly under your foot, if it doesn't you have a vacuum problem or a booster problem. If it keeps dropping you have a leak in the
system or a bad master cylinder.
Hold steady pressure on the petal and start the engine. When the engine starts and the vacuum builds you will feel the petal drop
slightly under your foot, if it doesn't you have a vacuum problem or a booster problem. If it keeps dropping you have a leak in the
system or a bad master cylinder.
Wremele,I believe your problem is the use of hydraulic hoses on your brake system, is that the hoses are swelling up and not providing solid pressure.Replace them with steel brake lines and proper fittings.To many hoses on the brake system and not designed for brake use.
wore out
Well-known Member
WOW, I hadn't looked at the photo, the hydraulic hose appears to be new, so I don't think it is causing the current problem, but WHO the *^&& came up with the idea to use a hydraulic hose on a brake system???
That is an old single brake system and ANY component failure will lead to NO brakes. (Rubber possibly incompatible with brake fluid.)
Where would the liability for that land in case of a crash due to failed brakes?
caterpillar guy
Well-known Member
IF he does not use any hoses how does he steer without breaking the lines from the frame to the wheels by way of the spring flex and the front wheels turning. As fro the lines from the booster or the Mc the copper /nickel line is the way to g. It can be bought in pre cut lengths ready to bend and put on or in rolls and you cut to fit. though you will have to flare it and have the nuts on it first.
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