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92 wd250 breaks/vacume pump help
Just bought a 92 wd250 5 speed today. The guy claimed the brakes were good but the vacume pump was weak. The pedal will bottom out and sound like a big trucks air brakes and then grab a little when your press it again they work. He replaced the master cylender and booster thinking they were the issue but they wornt. I have read about self adjusters and it sounds a bit like my issue but I’m not sure, does it sound like a vacume pump issue? Any help is appreciated. |
By "big trucks air brakes" - do you mean there's a whooshing sound? Does the pedal have a lot of resistance before it bottoms out? In my experience, a weak vacuum pump or a bad diaphragm in the booster would cause you more resistance to pedal travel than normal. With a torn diaphragm, you would likely be hearing vacuum noise most of the time. You could test the vacuum pump and booster with a vacuum gauge while the engine is running. On my '96, there is a small vacuum line that comes off a tee in the hose going to the booster. If you have a similar setup, disconnect that line and hook up your vac gauge there. If vacuum is lower than spec, pull the vacuum hose off at the booster and cap it with your thumb. If vacuum is still low, you either have a failing vac pump or a leak in the line between the pump and your finger.
Improperly adjusted brake shoes could cause the symptoms you're describing. How easy do the rear drums come off? Try measuring the distance across the shoes and compare to the inside diameter of the drums. Do the adjusters turn easily, or are they all crudded up? Try manually adjusting the brakes and see if it helps |
Yes I meant by big trucks a whooshing air sound. When you just tap the pedal it bottoms itself out and after it goes to the floor catches and jolts you foreword and it almost stops itself. I have the truck all torn down to restore it and am planning on getting all new lines for it. I was told buy a guy at the auto parts store that if the lines were never blead after the new booster it would do this. Is that true? P.S. I’m KBS chassis painting the whole frame from bumper to bumper I scraped all the old undercoating off and it’s like the day it came off the line. Going to keep it that way. |
Whether the lines need bleeding depends on whether you took them off the master cylinder while replacing the booster. If you pulled the lines off the master cylinder, then yes - they probably need bleeding. On the models like my '96, I believe some people just swing the master cylinder out of the way and leave it resting while they replace the booster (yes, they are "flexing" the lines somewhat when they do that).
Have you thoroughly bled the brakes, and/or have you checked rear brake adjustment? |
https://cimg1.ibsrv.net/gimg/www.die...035a2237b0.png https://cimg2.ibsrv.net/gimg/www.die...66f2f5199c.png No, I have not gotten around to much lately on the breaks because it is in 1000 pieces in my shop. I have a complete frame up resto on it new leaf springs all around tires breaks were surprisingly good, new southern cab and the works. Painted the frame with kbs coatings rust seal and cannot scratch it I will be doing the same on the entire cab and fenders so they cannot rust. |
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