Weird Brake Issue

[matthewh]

So lately I have been having a couple weird issues with the brakes on my '93 W350 dually. For awhile, the Parking and the ABS light would come on, usually at low rpms, and disappear at high rpm's, figured a ground issue, just been waiting for all the evil snow to go before fixing it.

Well I ventured to the U.P yesterday to retreve a new engine to swap into my M37. After 3 hrs of seat time, finally decided to exit and stretch. As I slowed to pul off into a gas station, I noticed the brake pedal was hard, almost to the point of standing on it to stop. Got out, checked everything under the hood, no loose hoses, fluid good, no leaks, etc. Climbed back in, and pedel was great, worked like it did when I got the truck, nice, responsive/touchy, good brake pedel feel. After another hour of driving, slowed down again for a turn, same thing, hard pedel. Let off, downshifted, tried pedel again, great pedel, almost kissed window.

Since then, the Parking and ABS light stay on constant, and the brake pedel feel is a gamble. Even short drives threw town, or light to light offer either hard pedel or great pedel.

The vac lines look good, but I know they can deteriorate inside, causing similar issues. Is the ABS valve to blame? Did notice this winter, when the ABS worked on slippery roads, it would hold the rear brakes locked for a sec before rolling again. I own 3 first gen's, and this one has by far the best brakes of all and I would like that face meets window feeling back again.

Thanks

[ellis93]

Sounds like the vacuum pump is taking a turn for the worst.

[matthewh]

Oh that's awesome Is there a way to test it, can I hook a Vac gauge to the line at the booster and get a reading? What am I looking for, vac wise?

Am I correct in assuming that these are either Dodge or Cummins only parts, my local Carquest wont have what I need? Are they rebuildable, or a throwaway unit?

Never done a vac pump before, so all advice is welcome. Any tips/tricks always welcome

Thanks

[PToombs]

Yeah, Tee a vacuum gauge in the line, I saw a post recently and can't remember what it should be. Above 20hg though, I remember that. It may also be the fitting at the booster plugged or sticking (it's a check valve), or a bad booster too.

[Dodgebob1980]

The vaccum pump is rebuildable. It has small paddles inside that wear out. sometimes you can just use emery cloth on them if they have rough edges. But I know you can get new ones. just couple o rings and a gasket to seal it all up. Pretty simple deal really.

[ellis93]

They are rebuidable,I'd probably say more than 15 or 20 inch lbs of vacuum is optimal,and I've no idea on where to by parts......I think genos garage had a Kit one time.

Edit
What they said

[matthewh]

Ok, well I'll start with the simple stuff and go from there. Get some readings, check/replace the lines and fittings, etc.

I did find a recent post, should be around 25 or so.

[matthewh]

So I tee'd in a gauge, and I'm only getting between 5 and 10 hg of vacuum, kinda just sits right around 7, and there is no longer any assist when braking.

Priced out a new vac pump threw Chrysler, there willing to bone you for $990, plus $54 for a different line . My local Carquest can get me one for $370 plus $40 core, and I found one on Rock Auto for $270. If I didn't need the truck now, I would try to rebuild it, but since I'm kinda dependant on the ride daily, guess I'll save the core and tinker with it when I get time.

Any body have luck with Cardone parts? There the mfg for both the Carquest one and the Rock Auto.

Thanks

[ellis93]

Cardone is all your gonna get these days.....such is life. Is it schit? Sometimes. But I use tons of it and in reality it seems to hold up well with an occasional part blowing its wad every now and again

[matthewh]

Cardone is all your gonna get these days.....such is life. Is it schit? Sometimes. But I use tons of it and in reality it seems to hold up well with an occasional part blowing its wad every now and again

Ok, sounds about right. Was on another forum where a guy had issues with 3 reman hydroboost units for mid 80's Chevy diesel, and they were Cardone.

It is what it is, I guess if it holds up another 20 yrs, can't complain

[ellis93]

Cardone is all your gonna get these days.....such is life. Is it schit? Sometimes. But I use tons of it and in reality it seems to hold up well with an occasional part blowing its wad every now and again

Ok, sounds about right. Was on another forum where a guy had issues with 3 reman hydroboost units for mid 80's Chevy diesel, and they were Cardone.

It is what it is, I guess if it holds up another 20 yrs, can't complain

Let me guess......wouldn't prime up? I've had lots of trouble with a couple of them,but I figured out how to get that corrected.

[matthewh]

I believe so, he said he had bolted it on, followed the FSM for bleeding the system, and it wasn't any better than before. Had to remove it and replace with another one. That one gave him fits as well, but finally ended up working out.

Come to think of it, probably used a lot of Cardone products, just don't realize it. Usually just walk into Carquest and get what I need. Most of its reman anyways. I know I've had MC issues with them leaking out the top and being crappy in general, but found out its the same as the Napa ones, just a different box.

[matthewh]

Finally got a chance to tackle this job today. Other than having to sacrifice a 1-1/16in socket (had to make a long socket to remove the oil pressure sender) all went well. Was able to leave the p/s system intact, that was nice not having to bleed that system.

Apparently, not only did I have a bad pump, but the main line was bad, or going bad as well. After instillation, I tee'd the gauge in at the pump, and started the engine, it pegged the gauge at 30hg, and collapsed the main vac hose to the booster guess I'll be replacing it as well.

Brakes are better, have to feather the pedel to keep from locking them up at full application. Should be real good once I get a new hose on it

[matthewh]

Been awhile since I last posted on this issue, but still been having occasional issues. Sometimes, I'd have a hard pedal, other times, its be ok, but after a couple uses, it would get hard again. The light on the dash would come and go, etc. Well, the other morning, the truck developed an annoying whistle, after a few miles, was an ear splitting one. Turns out, the booster was pulling a vacuum from the cab, and depending on how the pedal was sitting, created a leak and whistle. Threw on a remfg booster this morning, now brakes are really touchy, as in brake hard at 25 and lock all 6 wheels on dry pavement . Other than having everything new on the vac side of the brakes, it seems to be back to where it was when I bought it.

[PToombs]

The remanufactured boosters are junk, 90% of them. Guy on TDR was telling how they are remanned, they just reseal and paint them up, IIRC. If the old diaphragm doesn't have a hole, back in it goes!