Brake issues M882

[44CCKW]

I,m working on a M882,Trying to get the brakes to work.I have replaced the rear shoes and wheel cylinders.Also the front calipers, pads and outer rubber hoses.Installed a brand new master cylinder.I,ve bleed the master cylinder and installed it and have bleed the entire brake system several times and still have no pedal pressure.The pedal goes all the way to the floor.Rear shoes are adjusted correctly.No leaks anywhere.I am lost at this point.Could this be a bad metering valve?

 

[N1265]

I had the same issue when I did mine a few years back, I cant remember if that brake rod going to the master cylinder is adjustable or not. If it is , check that. On mine I had to bench bleed the master when it was bolted to the truck. ( and then gravity bleed the entire system starting with the right rear wheel )

At any rate, I know I did not have to change out the meetering block .

 

[nattieleather]

Check your rubber hose between the frame and the axles. If they are collapsing or have a small hole allowing air in that could be frustrating your progress. That and what N1265 said about the push rod. Other than that it may be that you just have a lot of air in the system and need to bleed it again. Make sure your master is bench bled properly and go through the whole system.

 

[44CCKW]

I will go thru the system again,And replace the hoses you mentioned.The last time I had this happen,It was a pin hole in the metal line on the frame behind the fuel tank.But I do not see any leakage here.

 

[Bob H]

Twice I have bought replacement master cylinders that were bad, once for a M882 and then again on my W400 Amb.
Each time It took a while to realize where the problem was.

 

[44CCKW]

Bob,That was my original thought.I bought a rebuilt from NAPA and I thought it was bad,So I then bought a new production from Advanced and I,m getting the same results.I had this same issue on another truck a while back and after bleeding everything a thousand times I finally got a good pedal.

 

[44CCKW]

Well,It turn out to be a bad brake booster.

 

[M543A2]

My suggestion is to be sure the master is correctly bled. You need a couple of lines off a parts truck cut to about 12" so they can be screwed into the master and bent around upward and then downward to go into their respective fluid reservoirs of the master, ends down under the fluid level. Work the master until no bubbles come out of the lines. You need to eliminate this possible problem before condemning other parts. We have had this problem with a friend's unit. This bleeding cured the problem.
Regards Martin Sacks