D series brake problem

[Fred Demmon]

Finally got some time to work on my Wagonmaster(1974-4x4 3/4 ton )

On the maiden voyage I discovered a very hard pull to the left. So I decided to replace both calipers and pads. I got the parts together and finally got some time to install them.

When i pulled the wheels the right rotor would not spin. I pulled the caliper and disconnected it from the brake hose. I thought it strange that the hose did not start leaking. I dumped the caliper over and some really nasty fluid came out(but not much) I wanted to push some of the bad fluid out before installing the new caliper. When I hit the pdel it was rock hard. This caught me off gaurd because I expected the pedel to go to the floor.

When I got out and looked there was still no fluid on the ground.
I went inside an pressed very hard on the pedal, and held the pressure for 30 seconds and got a small amout of fluid on ground(1-2 oz's)

I pulled the other calliper and again no fluid, pressed the peddel hard and held it for 30 seconds.This time the peddle travelled towards the floor, but only under hard pressure
I got a little more out of the right calliper(less than an oz) and more out of the left (about 3oz's)

With out peddle pressure no fluid cpmes out.
Any ideas why I have 2 open brake hoses and don't have fluid just draining the Master cyl dry?

[jeff campbell]

sounds like mcyl., problems,its not dry is it? had to ask.unhook the line going to the front brakes an see what the pedal does then.? maybe the plunger is stuck in the bore?jeff

[J.J.]

What kind of shape are your brake lines in? I have had to replace the metal hard lines because rust had formed on the inside. I would check the MC as suggested, and take the lines loose at the MC and try to push air thru them with a compressor. At least you will know, and the brake fluid will be fresh in the line. Orielly carries a rebuilt MC Cardone unit for your truck. There are two different ones, depending on if yours is considered a "heavy 200" or not. Are the rear ones engaging as well? Also, another thought is that if you need to replace the rubber lines, there is a cheap Chebby alternate that requires a slight modification. I don't remember the application, but Levi at Old Iron Off Road did his this way. He is in the vendor section on this board.

Hope this helps.


JJ in TN

[Fred Demmon]

Master cyl/Booster looks to be fairly new. It has a sticker for Silicone brake fluid ONLY right above the M/C on the Booster

Fluid levels were full, Have not pulled the rears to check. Was going to inspect them after the fronts were fixed

Just thought of something else.....Not sure it it matters.
Brakes are power asst, but I did not have truck running when pushing pedel.

It has the larger caliper, so my guess it is the HD 200

[pwschuh]

Wild guess: Is the fill cap off the resevoir? Capilary effects could be holding fluid in lines if the system is not open at both ends?

[Fred Demmon]

Lid was off and if I hit the pedel too hard fluid would squirt up out of the front portion of the master cyl a bit

[stu simpson]

Originally Posted by J.J.

What kind of shape are your brake lines in? I have had to replace the metal hard lines because rust had formed on the inside. I would check the MC as suggested, and take the lines loose at the MC and try to push air thru them with a compressor. At least you will know, and the brake fluid will be fresh in the line. Orielly carries a rebuilt MC Cardone unit for your truck. There are two different ones, depending on if yours is considered a "heavy 200" or not. Are the rear ones engaging as well? Also, another thought is that if you need to replace the rubber lines, there is a cheap Chebby alternate that requires a slight modification. I don't remember the application, but Levi at Old Iron Off Road did his this way. He is in the vendor section on this board.

Hope this helps.


JJ in TN

X2, the rubber portion of the lines could also have herniated and closed off. They might look fine from the outside but on the inside, yuk. I think the application JJ is talking about is the early C20 2wd brake lines. They are a little shorter but not by much. They also have a slightly shorter weird-*** right angle banjo hard line at the end that might make you want to modify your bracket for same.

[lev1a]

Several possibilities here. Master could be bad, blockage in the line IE rust or collapsed rubber hose, and or there could have been a leak in the front brake circuit and the prop valve shut down the leak and the prop valve has never re centered. Are you getting fluid to the other side? The way I always solve a problem like this is to start cracking lines open and see where and if you actually can get fluid to move. Just for a test take the line feeding the front brakes off of the master and both hoses off of the calipers and give them a good blast of compressed air and see if you get anything out the other end. Put some coke bottles over the hoses just to catch the crap coming through so you don't have a mess and to see what kind of trash is in the lines. If you don't get any air then you know there is a blockage somewhere.

[Fred Demmon]

Ok tonight I pulled the lines from the master cyl

I hit the pedel an had a solid stream from both ports of the M/C
I tried blowing air thru the lines and NOTHING out the end.
Then it occures to me the brake light on the dash has been on the entire time so I look at the proportioning valve and the the pin is sticking out the back about 1/4-3/8 of an inch

I tried to push the pin back in, but it did not move.
Do I need to crack the lines to recenter the pin

Nice call Levi

[Will Marsh]

Probably pushed the prop valve over center. Pop the bleeders open on the rear and see if it recenters and works. You might have to get some pressure in the front system to make it recenter itself, or pull the switch out and push it back to center by hand.

HTH,

Will Marsh