Hydraulic problems Dodge W-200

[farmersamm]

Don't like asking for help in mechanicin' stuff. Usually don't need it.

Brakes on truck at about 20%. Takes about 1/8 mile to come to a full stop.

New brake linings all the way around. New wheel cylinder, and new caliper. New master cylinder, and booster. GD brakes still spongy. And, yes, they've been bled. Two methods used, gravity bleed, and pedal bleed. And the master cylinder was bled before hooking it into the system.

Pedal solid as a rock when engine off. Pedal goes halfway to the floor when engine on. Lousy braking. Damn thing won't even skid when on gravel. But all friction surfaces hot after repeated braking. So the brakes are grabbing, but not enough.

Has anyone experienced touble with the holdoff valve on these trucks? And what are the signs of failure? It's the only part of the system that I haven't been able to check because there's no data on how to check it.

Pulled boocoo loads last Sunday in this shape. Not really crazy about doin' it again. Could wind up killing somebody.

Seems like I got a 5000lb paperweight right now. Any ideas?

[STwelder]

Hold off valve? What make model of truck. What type braking system ( air assist, Vacuum canister, fluid assist )?
Sounds like, if vacuum type that you are loosing vacuum through the booster, but this speculation could go on forever. Make model and type of braking system please. After posting I seen what type ( I think ) system you have. Does it have the power stearing lines going to the master cylinder?
And bleeding the master cylinder before hooking into the system is not advisable. I would bleed it while bolted to the booster, then vacuum bleed the rest of the system.

[denrep]

Normal pedal is high and hard with engine stopped; drops away with booster pressure when engine is started. That era Dodge with power booster, never had a really solid pedal feel, although they had adequate stopping power.

Random thoughts:
Is a mismatch of booster push rod/ master cylinder/ pedal linkage, not allowing MC piston to return home against stop. Without full return, MC valving will not function.

Are calipers/cylinders installed so that bleeders are at the top? *
Seats or washers in place at all hose and bleeder connections?
Rear shoes adjusted out to drums?

For clues, watch fluid return to master cylinder with cap off.
After aggressive pump-up:
High volume of return, no bubbles = out of adjustment drum brakes.
Bubbles in returning fluid = air in system.

Clamping one flex-hose at a time will help isolate component which may be air-trapped or introducing air into system.

* I'll put my money on this item, but I'm not eating any more auto parts! :D

Good Luck

[David R]

For the rest of you, its vacuum operated booster. With hydraulic brakes. W200 = $wd 3/4 ton.

Do you have 20 inches vacuum Ideling?

Drive the truck in the gravel and see which axel (Wheel) is skidding, front or rear. Does it have ABS? If not you still have air or the shoes need to be adjusted. Its a simple system, What year is the truck?

Mechanic for 30 years.

David Root

[mrmikey]

Shot in the dark here, how are the flex lines, could they be collapsed internally not allowing pressure thru completely.....Mike

[duaneb55]

Shot in the dark here, how are the flex lines, could they be collapsed internally not allowing pressure thru completely.....Mike

Had that happen on an Astro van years ago but that just left me with no rear brakes.

I agree with denrep and David R on adjustment. If the rears are way out of adjustment, most of the pedal travel goes to filling the wheel cylinders and the shoes may never contact the drums or at least with much force. Once the 'rear' MC piston contacts the 'front' piston then the front brakes start to apply but at that point it's all front and little/no rear application.

edit: With proper rear adjustment, the rear piston should never contact the front as the fluid 'link' between the two forces against the front piston.

[farmersamm]

I'm pretty sure the rear shoes are adjusted right. I always do them by hand because the self adjusters have never worked right. I tighten them until there's severe drag on the wheel, whack the brake backing plate with a hammer to recenter them and tighten again if loose.

Denrep------ All bleed valves are on top. I'll check the flow coming back to the master cyl. today

David----- Only the left rear locks up on gravel, and only for about 2 feet with me standing on the pedal. Will check vaccum today

Duane------ I hear ya. As I said, I think the rears are OK, but I'll go ahead and ck. the adjustment again.

I sure appreciate this. I'm getting pretty frustrated, and pretty desperate.

BTW- There's a valve in the system downline from the master cyl. which diverts more pressure to the rears than the front discs at low speed stops. But the manual says that it's supposed to be inoperative on hard stops. I can't find anything in the manual which tells how to test the damn valve. You'd think there'd be something there, it's a Dodge factory manual.

[farmersamm]

STWelder--- I'll go ahead and go in today and get a vaccum bleeder. Maybe that'll help. I've always done it using the pedal with a hose and bottle hooked to the bleeder valve at the wheel. I have the hose set up so that it comes up from the valve, not down. It won't let air back in that way.

Again all, I sure appreciate the help. I'm goin' nuts:cry:

[duaneb55]

STWelder--- I'll go ahead and go in today and get a vaccum bleeder. Maybe that'll help. I've always done it using the pedal with a hose and bottle hooked to the bleeder valve at the wheel. I have the hose set up so that it comes up from the valve, not down. It won't let air back in that way.

Again all, I sure appreciate the help. I'm goin' nuts:cry:

Are you saying you run a hose up to the cab so you can pump/pump/pump without shutting the bleeder valve? If so, I'd say you've got air that just keeps moving back and forth in the lines rather than purging out. Maybe I've just misunderstood your set up description.

ST, Not always the case on 'pre-bleeding' the master cylinder from my experience. I don't recall the specific vehicle but I did one where the requirement/recommendation was to bench bleed the MC prior to installation or "extreme difficulty in properly bleeding the system" could result per the tag on the reman unit. ??

[Oldiron2]

I doubt this site has anything more than your manual does, but you might still check it for information about your valve. [This post borrowed from another site which I moderate.]

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"Tons and tons of repair manuals for almost every existing car".

http://www.bedlib.org/ebsco.html

Click on the AARC logo, enter "lib" as user and "access" as password.


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[tony j]

were the rotors and drums cut? Rough machine surface? Were cheap pads used on the fronts? when you bled the rears, was the fluid escaping the about the same on both sides, also for the fronts? (Did one side dribble and other piss....) What year? Does it pull when braking? things to consider... i have seen cheap pads on heavy trucks increase stopping distance alot, pedal hard, doesnt want to stop... usually happens right after the brake job.... later tony

[mrmikey]

Heres a link to some pages from Alldata, see if they help any http://www.snapdrive.net/files/502764/brakes.zip posting the year would give me a better chance of getting the year right on, I just took a stab at a '94 .
I've got Alldata up to '06 if it helps any.....Mike

[farmersamm]

Tried all of the suggestions, everything cks out and I've come to the conclusion that the hold off valve is probably bad. It is supposed to block pressure to the front wheels from 5-135 psi which allows the rears to grab first. Supposedly to prevent skidding on ice.(Finally found the section in the manual that covers it:rolleyes:)

I'll cobble together a pressure tester that can be tied into the line. That way I can see where the pressure actually is/isn't.

Probably a non available part anyway:laugh:

[David R]

Just a few more things. If ONE rear locks up, then there is a problem with the other. The fluid goes through the hose then to both rear wheels the same. YOU HAVE A PROBLEM THERE Fix it. Pull the wheels, look for grease, shoe problems, adjustment.....

The valve you are talking is the "metering and proportioning valve". They rarely go bad. I have replaced one in 30 years. There is a little brass button that will pop out if the pressure is uneven front to back. This is also where your "Brake" light on the dash is attached to.

In MY opinion, vacuum bleeders suck. :) . I work alone all day every day. I open the bleeder on one wheel furthest from the Master cylinder. Pump the pedal 10 or so times and LEAVE IT OPEN. Make sure the master is still full. Let the fluid gravity bleed Watch for air bubbles. Close it up after 5 minutes or so and move on to the next closest and do the same thing. Once all 4 have been bled, work the pedal with the engine running. If pedal feels good, stop. If not, put an extendable prop rod on the pedal with the engine running. Start with the furthest bleeder again and open it. Once fluid has stopped, close it. Do it a couple of times if it makes you feel better resetting the prop rod each time you open the bleeder. Electric seats are the balls for this. Move on to the next wheel....

If you don't have good brakes after a quart of fluid gone through the master, then some thing else is wrong.

Don't blame the valve you don't understand, its probably not the problem.

All this doesn't count if you have anti lock brakes. Sometimes you need the scanner to bleed the ABS unit. Some ABS units have bleeders on them.

On a few trucks that I have had problems, I bought plugs. Put one in the front of the master cylinder. Leave the line off. Drive the truck in gravel and feel the brakes. Switch the plug (you might need a different size) and try the other axle. This will show problems like brake hoses swelling (only seen it a couple of times) or show where to look for the problem.

YOU HAVE TO FIX THE ONLY ONE REAR LOCKING PROBLEM BEFORE ANYTHING ELSE.

I have seen frozen wheel cylinders and brake pads that would not move in the sliders from rust underneath the clips. If the little tin backing plates on the pads have rusted so they are "thick", they will eat up brake pedal travel fast. I don't even put them on.

I missed what year it is and if it has 4 wheel, 2 wheel or no ABS.

I just keep adding to this. On rear drum brakes they are "Self energizing dual servo action". All this means is the littler shoe (smaller friction) goes in the FRONT.

I don't care what anybody or any instructions say, the master will eventually bleed its self or the push rod is not adjusted properly. It needs a little free play.

David :)

[David R]

To test the proportioning valve, open one bleeder. Push on the pedal. Fluid will squirt out and you will feel a Click in the pedal. The brake light on the dash should come on at the same time as the click. Close the bleeder pump the pedal once or twice. Push on the pedal again kinda hard. It should "click" again and the light will go out.

Daym, I could go on and on......

David

[farmersamm]

The one wheel locking was so feeble, that it was wimpy. There's simply no doggone pressure getting to the damn cylinders.

This all started about 2 months ago when I had to replace a wheel bearing. They're a mess to replace on the full time fwd. Anyhow, I disconnected the right front line. After putting everything back together the problem showed up. Let it go, because up till now the truck's been parked. It worked perfectly until the repair.

I probably didn't need to replace the booster and master cyl. Oh well money down the drain. Linings, pads, and other stuff incidental to this go around is ok, it needed to be done anyhow.

The shop manual says that you should feel a "bump" (quote) as you press on the pedal, and it goes down past the first inch. This is the test for the hold off valve (as opposed to a proportioning valve, which this truck doesn't have, although some do). I don't feel any bump. I can wire a test light into the brake light circuit (most of it burned up in a small electrical fire about 10 yrs. ago) and do the test you mentioned. It only applys to the switch though.

I suppose the only thing left to do is to manually extend the piston on the valve, block it, and rebleed the fronts. This is also suggested in this section of the manual.

[mark8310]

If it happened AFTER a service, where you had to disconnect a line, right away, I think a bleeding problem. Occassionally you'll get a little nook or cranny, or a little bent line, where an air bubble just refuses to leave. No real solution I can offer, been there, done that, after a lot of bad words, and extreme measures (up to and including hanging the vehicle from a loader or forklift), generally got the problem fixed eventually.

[farmersamm]

Here's the section on bleeding the system with the valve that's in the truck. I hope it's legible.

[farmersamm]

If it happened AFTER a service, where you had to disconnect a line, right away, I think a bleeding problem. Occassionally you'll get a little nook or cranny, or a little bent line, where an air bubble just refuses to leave. No real solution I can offer, been there, done that, after a lot of bad words, and extreme measures (up to and including hanging the vehicle from a loader or forklift), generally got the problem fixed eventually.

I'm at the point of not hangin' the thing offa loader, I'M READY TO DRIVE THE LOADER OVER THE TOP OF IT!!!:angry::angry::cry::jester:

[mark8310]

Ahhhhhh,,,,, Farmersamm, you don't even know the half of it. Someday, gotta tell the story of an old '46 GMC truck, not much bigger than your dodge, spent most of it's life hauling tremendous loads of hay over the Sierras on the OLD Highway 80 (before they civilized it), with a little dinky gasoline six-banger, and vacuum over hydraulic brakes. Oh, yeah, and an aftermarket hydravac :D. Unfortunately, I couldn't deep-six it, not my choice, last real job I had, boss said "fix it" so I did. Spent a few more years, as a manure spreader, running up and down hills and canal roads,,,,, but when you wanted to stop, it STOPPED!!!!!!!:cool:

[denrep]

Someday, gotta tell the story of an old '46 GMC truck...

mark8310 - Then I'll tell about the hydraulic braked three-axle trucks; 15 cylinders to bleed!

Farmersamm,
When a brake system has had major work I don't bother with the bleeder screws at first. Take the bleeder right out and use your finger tip to act as a check valve over the bleeder port. This will move out an initial high volume of air/fluid. Then replace the bleeder for final bleeding.

To displace stubborn air pockets:
1) The pedal needs to be stroked aggressively until pumped up.
2) The pedal-pusher must hold pressure on the pedal and must not let off until asked.
3) Pedal must not be allowed to bottom out on any bleed cycle.
4) Pedal-pusher must warn bleeder-man when pedal is low, so that bleeder can be closed before pedal bottoms.
5) Once pedal-pusher confirms that pedal is pumped-up and being held, bleeder should be cracked open and closed in quick cycles to agitate fluid and encourage air separation.
6) Pedal must be released slowly, not simply dumped. This ensures that make-up fluid can be slowly drawn from the reservoir.

If it's trapped air, this should get it.

[farmersamm]

mark8310 - Then I'll tell about the hydraulic braked three-axle trucks; 15 cylinders to bleed!

Farmersamm,
When a brake system has had major work I don't bother with the bleeder screws at first. Take the bleeder right out and use your finger tip to act as a check valve over the bleeder port. This will move out an initial high volume of air/fluid. Then replace the bleeder for final bleeding.

To displace stubborn air pockets:
1) The pedal needs to be stroked aggressively until pumped up.
2) The pedal-pusher must hold pressure on the pedal and must not let off until asked.
3) Pedal must not be allowed to bottom out on any bleed cycle.
4) Pedal-pusher must warn bleeder-man when pedal is low, so that bleeder can be closed before pedal bottoms.
5) Once pedal-pusher confirms that pedal is pumped-up and being held, bleeder should be cracked open and closed in quick cycles to agitate fluid and encourage air separation.
6) Pedal must be released slowly, not simply dumped. This ensures that make-up fluid can be slowly drawn from the reservoir.

If it's trapped air, this should get it.

GDit, I've been *****footin' around on the pedal. Gently pushing it in. And I've been using a one man bleeder. So now maybe I'll get on the right track.

It's gonna cost me a 12 pack to get help, but WTH.

Thanks man!!!!

BUT THE FRONT END LOADER STILL REMAINS AN OPTION:D:D

[farmersamm]

What really drives me crazy is that I've done similar work on the Ford, and it didn't do this. Bled it, drove it.

[duaneb55]

GDit, I've been *****footin' around on the pedal. Gently pushing it in. And I've been using a one man bleeder. So now maybe I'll get on the right track.

It's gonna cost me a 12 pack to get help, but WTH.

Thanks man!!!!

BUT THE FRONT END LOADER STILL REMAINS AN OPTION:D:D

...and the man STILL has a sense of humor! Must be that fresh Okie air.:)

Can't get Clarence to help for a pat or two on the head?:D

[Sandy]

Farmersamm,
When a brake system has had major work I don't bother with the bleeder screws at first. Take the bleeder right out and use your finger tip to act as a check valve over the bleeder port. This will move out an initial high volume of air/fluid. Then replace the bleeder for final bleeding.

To displace stubborn air pockets:
1) The pedal needs to be stroked aggressively until pumped up.
2) The pedal-pusher must hold pressure on the pedal and must not let off until asked.
3) Pedal must not be allowed to bottom out on any bleed cycle.
4) Pedal-pusher must warn bleeder-man when pedal is low, so that bleeder can be closed before pedal bottoms.
5) Once pedal-pusher confirms that pedal is pumped-up and being held, bleeder should be cracked open and closed in quick cycles to agitate fluid and encourage air separation.
6) Pedal must be released slowly, not simply dumped. This ensures that make-up fluid can be slowly drawn from the reservoir.

7) Peal pusher must not wear size14 or larger.
8) Pedal pusher must understand "slow and easy". (bleeder hoses blown off and fluid shot across the shop is a bad thing)
9) Pedal pusher must not play with audio devices, dash controls, knobs, levers, buttons and/or any other inboard dodaas.
10) Pedal pusher should not be someone you live with or need to talk to for at least two weeks. (there will be words before the job is complete)

;)

[denrep]

...10) Pedal pusher should not be someone you live with or need to talk to for at least two weeks. (there will be words before the job is complete)

Don't let off!
Don't what?
LET OFF!
Oh... let off. Okay.
Did you just let off!?! :realmad:

:laugh:

[mark8310]

:laugh::laugh::laugh::laugh:

[farmersamm]

Quote by Denrep......" ....stroked aggerssively......"

We are still talkin' brakes here, aren't we????:jester::nono::blob4:

Aw hell, tomorrow's a new day. Thanks for the advice, eventually somethin's gonna work. Try the pump action tomorrow.

[Tractapac]

Don't let off!
Don't what?
LET OFF!
Oh... let off. Okay.
Did you just let off!?! :realmad:

:laugh:

Ahh, you've heard us bleeding brakes!

[David R]

You guys are funny. I remember my dad having my mom pump the pedal for him. After a bunch of frustration, he just looked at the brake lights to see what she was doing.

NOW WE KNOW what happened. I would suspect the brake hose on the wheel you did the bearing on, or at least say the front brakes have the air in them.

I do use the finger as a check valve trick if I have a helper which is rare.

Pushing the pedal agressivly will force air out of high spots in the line. Sometimes that is the way to do it.

With my method of pump the sh*t out of the pedal and a bleeder open, when you let go of the pedal, it sucks air back onto the wheel cyl or caliper, but it comes out easily.

You took a simple job and turned it into a blow job. :laugh:

I do that now and then.

David

[farmersamm]

WE HAVE LOCKUP!!!!!!!!!!!!!!!!!!!!:cool2:

Positive tire shredding lockup on all 4 wheels.

THANK YOU DENREP, DAVID, MARK8310, and ALL OF THE REST OF YOU.

The aggressive pedal pumping did the trick. I never would have thought of it on my own. I hope I can return the favor one day.

Moral of the story...... (DON'T LET AN IDIOT OWN A SET OF WRENCHES :D:D)

[duaneb55]

WE HAVE LOCKUP!!!!!!!!!!!!!!!!!!!!:cool2:

Positive tire shredding lockup on all 4 wheels.

THANK YOU DENREP, DAVID, MARK8310, and ALL OF THE REST OF YOU.

The aggressive pedal pumping did the trick. I never would have thought of it on my own. I hope I can return the favor one day.

Moral of the story...... (DON'T LET AN IDIOT OWN A SET OF WRENCHES :D:D)

:blob3::blob2::blob4::blob1::blob3::blob2::blob4:

I KNEW you'd get it!

[David R]

Glad to hear it, welcome to my world.....

David :)

[Tractapac]

I wonder if Farmersamm has any tread left or whether there are sets of flat spots all round his tires?

[duaneb55]

I wonder if Farmersamm has any tread left or whether there are sets of flat spots all round his tires?

Well we know he's got a niffty bead-breaker when it comes time to put new sneakers on that thing.:D