pigeonman

I've been a mechanic all my life but this one has me stumped . Brake pedal goes almost to floor "sometimes" . Master cylinder right ? I replaced it with a new one , same problem . So I returned it and got another new one , Pressure bled system . Same problem . Feels just like air in system . Anyway since the truck is old and its worked a hard life , I went ahead and completely rebuilt the brake system . New front rotors , rebuilt calipers /pads . Replaced the drums in rear / new linings / wheel cylinders / spring kits and self adjusters . All 3 brake hoses . Booster and hose to vacuum pump . I even bypassed the RWAL valve to test . Same problem . I cant believe it . The only thing NOT replaced is the proportioning valve . The part is no longer available from dealer and nobody carries one at the parts houses . Nothing in the wrecking yards around here either .

This truck is making me feel like an idiot .

Would a valve from a 3/4 or 1/2 ton Dodge work ? Any other valve from another manufacturer work ?

Any advice , I'm whipped on this one and not even sure the proportioning valve is the culprit at this point but its all thats left ... just a hunch .

Thanks for reading this and any advice

Bob

twichit

I used one off an 88 d-250 gasser on my 93 w-250 diesel it worked but I don't know as it would be something you want to do , aweek after I put mine on I flipped my truck and toteled it , and i'm not sure as to the valve might have been part of the issue, hopefully somebody else on herewill know more then me jm2c

countrygent

I have always had problems with not the best braking on my 93 350. My buddy who used to work in Dodge parts at the time said they had sold a number of the pro-valves. I replaced the master,booster, front stuff and rear stuff. Being old school and finding out as you did, not available on the pro-valve or ABS unit. NOTE: that is one thing you did not mention. When bleeding, you need to bleed the ABS unit before the rear shoes. ANYWAY, I gutted the ABS, took off the pro-valve and installed a manual proportioning valve from SPEEDWAY AUTOMOTIVE. Being a disc/drum system they say to install a 10psi residual valve in the line going to the rear and a 2psi for the front discs, also from Speedway. This is stuff rodders use on there vehicles. Got a good improvement and I can get under the hood and adjust how much braking I want up front. PURPLE THINGY-Man. Pro-valve, BLUE THINGY-2psi residual valve. 10psi valve mounted in the rear. THIS IS OF MY OWN DOING AND NOT TO BE GOSPEL. Take it or leave it. I would say if you went the bone yard route, places like Barely Used Auto parts, could tell you the interchange of the part. I would guess that a 250 and a 350 might be different because of the weight of the vehicle. Maybe not.

loch

You said "sometimes" does it work properly at times as well? And can you mash pedal with truck not running after a hour and still have vacuum?

pigeonman

Yes at times the pedal seems firm . But a lot of the time it feels like the master cylinder is bypassing and the pedal sinks away . Or a spongy feel like air trapped in a line . I've bled with a partner and with a pressure bleeder , got good stream of fluid at all wheels . Have followed the procedure to a T and bench bled master on bench and cracked fittings all the way down the system to bleed until I get to the bleeders . And yes I bled the RWAL first . I never get any air out either after the initial bleed out . I dont know if booster will hold vacuum for a complete hour , but has good vacuum and new check valve came with the booster . It seems to be working good .

In all my years wrenching I've never seen a bad proportioning valve to be honest and it seems like it would just effect bias to front and rear wheels NOT make pedal spongy ....... but theres not much left to try . Has anyone here had a bad one ..... what were the symptoms ?

I did check pushrod clearance at M/C to booster too . Even added some clearance to be sure piston is returning all the way . And I push in that pin on back of the proportioning valve too when I bleed .

Appreciate all comments , I figure with all you Dodge truck owners someone has been through this before and I'm at the right place .

Things like this make you hate being a mechanic

Thanks again !

Bob

countrygent

Hay Bob. I do hope you get a positive fix on this. As I mentioned everything I did as you, and got frustrated and did my thing with the manual pro-valve, I got an improvement, but still not what I would consider a good firm STOPPING pedal.Just don't seem like I could lock them up if I had to. My wifes 98 Durango will put you thru the windsheild on hard braking.I pull a loaded 16x6 1/2 ft trailer up to our place in the mountains of E.TN, and I have to rely on my trailer brakes to much to stop me. Keep hollerin HELP!!!

pigeonman

LOL , I hear ya countrygent . Of all the vehicles I own the bigger Dodge truck brakes are by far the worst . They suck , BUT , I LOVE that Cummins engine so I have to put up with the rest of the truck . I hear the new Dodges with 4 wheel discs are a different breed and far better . Still love the darn thing even with the drawbacks .

I'm off to the wrecking yard again to scrounge . I'll keep ya posted on the outcome of this headache .

Bob

KD93

Bob have you thought about doing a rear disc conversion? There's a write -up in the sticky about it. I don't know if this is going to help your problem or not, and would be a pain as you've just replaced everything. I'm not sure how it is on our vehicles, but when I was riding motorcycles I would very very rarely use the back brake. Sometimes for traction when starting, (kept the front wheel on the ground!) or trailing it a touch in a corner to flatten the back tire a bit, (more traction.) But when stopping, even emergency braking, I would only use the front. Why? Because 80% of all stopping power came from the front, and that was with a 51% / 49% weight ratio front and rear.
I don't know what percentage our proportioning valves are set to, with regards front and rear, but if anything I'd be looking to up the front percentage. That may make towing a bit weird if you don't have trailer brakes though!

loch

I don't see the proportional valve being intermittent, not saying it cant happen. How much play was between pushrod and MC? It should be between 1 and 5 mm. I still would look at vacuum, its capable of producing intermittent symptoms. Remember we have a vacuum pump, it can also give you fits, might pay to check the vacuum pressure.

I have said this in here before and its still true, if your truck has weak brakes theres a problem, the design on our trucks is very old, long before Cummins came out. Its a proven design and it works well, if you stomp on mine your napping on the dash. I can only suggest things from experience but never assume you have to tolerate weak brakes, its dangerous to you and others.

maybe368

X2 I would be leery of condemning the PV. I believe that it is probably reacting to a bad component or vacuum problem, or maladjustment of the push rod, ETC., ETC.. Mine are finally working properly after going through the entire system, only to find that a front disk piston was stuck in the tube. There is light at the end of the tunnel, and I'm pretty sure it's not a train......Mark

csx293

Been there. I have been doing brakes on cars for 20 years and never had a brake problem kick my butt until I did the brakes on my truck. I replaced everything just to have the same problem as you. I talked to an old timer that I used to work with and right off the bat he said that there is air in the lines - solution as follows: have a buddy hold the pin of the proportioning valve while you bleed. You'll be doin' the snoopy dance!

Bruce M

The tool to hold the pin on the proportioning valve out is C-4121, but it is used to pressure bleed the front brakes only. If you are pushing the brake peddle to bleed the tool is not needed. I had the same problem as you with air in the line. After bleeding the anti-lock, right rear, air come out of the left rear.
At that point my son who was pumping the brake peddle said the brakes were great.
Still we bled the right front and last the left front with no air.
Used almost a quart of brake fluid.
The only problem that I had was the brake light switch inside the combination valve (as you say proportioning valve) went to ground and would not recenter, causing my brake and anti-lock lights to stay on.
So I removed the wire going to it. The brake and anti-lock lights function normal now.
I must have crud in the combination valve that keeps the switch off to one side grounding it.
I checked on line and have not found a replacement valve.
Will have to check the junk yards until I find one so I can take mine apart and see what the problem is.

maybe368

I don't want to get ad removed or anything, so I hope this is ok Here is one out of a 97 on ebay, the description and item number. Right now it is only 10 dollars...Mark
Description: Brake splitter / proportioning valve removed from a 1997 Dodge Ram. Engine was Cummins Turbo Diesel.
Mounts by the master cylinder.
Good shape.
item number360268814599

ebteckx

okay, I had this same problem. my fix is NOT recommended but it may be something to try to eliminate a potential problem. same scenario, replaced master, calipers, wheel cylinders etc. bleed the truck so many times i was sleeping with the bleeder wrench lol. I bypassed the rwal, bleed the truck once and the pedal has been firm ever since. Like I said NOT RECOMMENDED for extended use but that may isolate your problem then you can hunt for a rwal. hope that helps

pigeonman

I tried bypassing the RWAL right after putting on a new M/C . I hooked lines together with an adaptor fitting as I read they can be a problem . Actually the pedal did feel firmer BUT it would still sink down sometimes which is the original problem . I could get the truck to lock the rear wheels up pretty easy without the valve . Thought I had it licked but the pedal going almost to the floor still remained .
I tried this too ..... I clamped off all the rubber brake hoses with special clamps . This would isolate the problem to the the master cylinder to see if it bypassed , or front or rear section of the truck . Pedal was rock hard , so I figured it was a sticking caliper or wheel cylinder and replaced all with new and reman parts from NAPA . And just as before a crappy spongy pedal .
This thing is a nightmare Anyway the guy is bringing it back this week and I'll take another crack at it .
I will post what I found when I get it sorted out .

Thanks all ,
Bob

PS : This is a friends truck , I charged him a pittance to do the work as a favor and I stepped in the do-do he said he'd been fighting this thing for a long time before I ever got ahold of it . Favors sometimes backfire LOL He's cool tho .
Myself I have a '94 2500 Ram Cummins . Fought some brake problems on that one too . Turned out to be just an air lock in the 4 wheel ABS unit itself and was pretty easy to sort it out . Put the bigger wheel cyls in back and it has excellent brakes now .