Brake problem?

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Rob

Rob

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This is in my 90 Dodge Ram not the A-body but brakes are brakes so was hoping someone would have some ideas. I lost my brake pedal pressure the other day out of the blue, pedal went to the floor but with a few pumps it comes back up. You have to do that each time. Had a look, the brake shoes were toast, replaced those, one side of the e-brake was seized, replaced it, bled everything, no difference, oh, wheel cylinders are fine and no line leaks. Put in a new master, bench bled it and all, it's even worse now, no pedal and it only comes back a bit. Any ideas??
 
OK if you pump your pedal then stand on it [push it really hard] does it still go to the floor.

Basically if standing on the pedal keeps it from bottoming out then it's the master cylinder.

If it still go's to the floor when standing on it, then it's something else like a hose or wheel cylinder.
 
Not sure. There is such a thing as a bad reman'd master cylinder. There is also a lot more bleeders and bleeding to do with antilock brake systems.
Correct bleeding proceedure from a manual will help.
 
Yep, could be your ABS controller. Don't remember off the top of my head the bleeding procedure, but it's not fun. Looks like it's time to pop for a manual. Sorry.
 
If you stay on the pedal it goes back to the floor. The lines were bled the conventional way and then again with a pressure bleeder. It's a 1990, I doubt it has ABS, I'm stumped :munky2:
 
Yep, 90s had ABS on the rear. The controller is mounted on the frame rail just about mid cab.
 
Did you bleed the master lines, you know pump hold crack line loose & tighten ect.....

You might find yourself bleeding a hell of a lot of fluid to get your pedal back.

Say did your check light come before this happened and if abs can you hear the compressor?
 
90's had ABS, that's odd, before this happened my rear brakes locked up a couple times during the week under light pedal pressure so hmmm I'll check into that as well.

The master was bled as well and the first time I lost the pedal one of the lights that show all four wheels came on briefly but I don't even know what that's about. I just bought the truck a couple weeks ago and haven't sorted out the ins and outs.

Starting to suspect a bunk master cylinder, got a rebuilt one so who knows, taking that back and getting a new one, see if that helps.

Thanks for the suggestions guys
 
Sounds EXACTLY what I went through years ago the first time I had problems on an ABS car. Never even considered it to be a controller problem because Id never dealt with them b4. Felt like a total fool for spending so much time on a simple brake job.
 
Well with the exception of the master cylinder everything I've replaced needed to be so I guess that's the good news. It never occured to be that a 90 would have ABS, I would have thought mid 90's or so. I'll definitely check it out.
 
I bought a 1990 Ram brand new, and still have it. REAR wheel ABS was standard equipment, as is stainless exhaust system.
My ABS does not work correctly anymore, but the brakes operate normally. I bled my system the old fashioned way, and got all the air out.
There is also a bleeder mounted directly on the ABS block, which is mounted inside the frame C channel, over the drivers side rear axle.
If you bleed it well, and still have a pedal that goes to the floor, the master cylinder is leaking down, and needs to be replaced.

Good Luck.

George
 
Thanks the additional info George, we'll be trying a few different things today and see what happens. Not even sure if a replacement control module is available in town. First thing to try will be bleeding this thing at the control valve, didn't even know it was there and then go from there. What a headache :angry7:
 
I've got a question for you guys that may have owned one of these ABS typ Rams, the module and valve are fairly expensive and I've never been a fan of that stuff anyway. My question is, can I just eliminate it altogether? Remove it and add some line and away I go? If not any guess which part is more likely to fail, the electronic module or the hydraulic valve, they're not available in town so I would have to order them and I don't want what I don't need.
 
Antilock brakes will work exactly like non ABS when the RABS valve fails. In other words , the warning light always on in the dash doesn't mean you can't stop.
You still need to get the air out of the rabs valve to get a full pedal.
 
Redfish is right.
I had problems with the proportioning valve which is located in the frame C channel in FRONT of the drivers foot area. There is a secondary valve built into it whose name escapes me right now. This valve was messed up on my truck, turning on the ANTILOCK warning light, but like Redfish said, the brakes will operate normally even with the light on. I was able to clean and repair this small valve. It lasted a while, then the light came on again.
Having said all that, there is also an exciter mounted on the differential which reads wheel speed. There could be build up metal shavings on it causing it not to send a signal. My truck has a Dana 60 rear, and it is mounted up top of the carrier.
If you look in the service manual, there is a rather long testing procedure you can follow to diagnose the RWAL system. I started to test mine, and after the electrical part of the test passed, I kinda gave up as I didn't want to spend money for something I really didn't like anyway. I would rather drive with conventional brakes. I know I can stop a vehicle better than some computor can, but that is my own opinion.

If there is no pedal, you either have air in the system somewhere, or a bad master cylinder.
Keep looking dude, and good luck!!!

George
 
1990 Dodge RAM, 4x4

Well I'm still going freakin nuts, here's the full run down of where I'm at and how I got there:

I'm driving along going down a hill, go to brake and I suddenly I have no pedal, the 4 wheel light thing on the dash flashes for a second. I pump the pedal and it comes back up and I brake fine. As long as I pump it a few times the pedal comes back.

I drop it off at my son's as he's a mechanic so I get him to do most of my work, he owes me :-D Anyway, he has a look under the hood because I mentioned I had some leaks as well so could he check it out, the power sterring pump is about empty so he figures there's a vacuum issue. Topped up the pump, no difference. Pulls the back brakes off, they're cracked and totally worn out, replaced them, front looked ok for now, bled the system, still no pedal. The RWAL system has been bi-passed at some time so it's not a factor. Replaced the master cylinder, bench bled it, no pedal. Got another master as the first one was a rebuilt and maybe it was crap, this one was new, bench bled it to death and bled the whole system again, no pedal, pressure bled the sytem, no pedal. :angry7: Oh, and there are no leaks anywhere, wheel cylinders work fine, calipers seem fine although he said one was a little wonky so he gets another.

At this point he takes it to the brake shop a few doors down from his shop. They conclude that the calipers aren't working quite right and the rotors are screwed up, they replace them and guess what, no freakin pedal :angryfir::angryfir::angryfir: There's 4 brake techs staring at this thing without a clue. If you clamp the line by the caliper you have full pedal, unclamp and it's gone :banghead:

What the hell could be wrong???? :cussing:


He
 
You clamp the rubber brake hose, and the pedal is there, then you unclamp it and the pedal goes away?
There is air in the calipers if the above statement is true.
Dumb question, but are you SURE the bleeders on the calipers are at the TOP of the caliper?
These trucks are designed so there will be NO front brake action until the REAR shoes contact the drums. Having said that, make sure the rear brake shoes are adjusted correctly. There should be slight drag on the drums if adjusted right. Also, check the bleeder screw that is in the frame C channel for the rear brakes, above the axle, drivers side. There could be air in there if you didn't bleed it here.
If everything checks out, my educated guess would be that you got the wrong master cylinder for the truck.
Is the original MC still around somewhere? Maybe you can rebuild it, or at least get a number from it to verify the replacement is correct.
Also, there are 2 brake CALIPERS that were available in 90. Bendix & Chrysler. I dunno if the brake caliper style would determine the master cylinder used, but you might want to check into it.

Hope this helps some.

George
 
May or may not apply here but I had a 1993 caravan that had the hydraulic unit replaced. Could not get the air out of the system and turned out to be the hydraulic unit holding air because the ABS did not open the valves to let the air out. I did not have the scan tool to cycle the ABS to bleed it either. Neat little trick is to drive the car in a safe place and slam the brakes real hard to try and activate the ABS. This will open the valves and push the air into the rest of the system where you can bleed it out. May have to bleed several times but it worked for me and I got full pressure back after doing this. ABS brakes need to be bled with a scan tool to get it the first time. If you don't have the scan tool, activate the ABS the old fashion way.:-D
 
1990 has rear anti lock only. He said if he clamps the front rubber hoses, he'll get a pedal. That tells me there is air in the front calipers that he can't get out, or the wrong MC for the calipers used, if there is a difference at all. In this case, the RWAL should have no effect on his problem.

George
 
My years as a service writer for many dealerships have shown me many weird things. My money is on the master cylinder also. Some master cylinders shouldn't be bench bled. Something 2 do with blowing gaskets slowly. Many car manufactures rec. installing the master cylinder and then bleeding it. Just a thought. Are the rear brakes adjusted properly? would not rule out bad proportioning valve.
 
Thanks for all the extra tips and ideas, I will run it by them in the morning and see if anything helps. One thing we can eliminate is the RWAL/ABS issue, it is not plumbed into the lines at all, must have crapped out at one time and somebody bi-passed it altogether.

I sure hope we can resolve this soon, it's making me crazy :munky2:
 
This Year My 94 Dakota Loss All Brakes. Changed Calipers And Bled All Lines. Still No Brakes. Talked To The Garage And They Told Me That Dodges Were None Too Take Forever To Bleed. So I Bled Them Each Side 15 Times. You Would Not Believe After The 7 Or 8 Time I Bled Them The Air Started To Come Out. My Brakes Are Fine Know. So Bleed And Bleed And Bleed. Took Two Cans Of Brake Fluid But That Was Cheap Enough. Good Luck.
 
George R said:
You clamp the rubber brake hose, and the pedal is there, then you unclamp it and the pedal goes away?
There is air in the calipers if the above statement is true.
Dumb question, but are you SURE the bleeders on the calipers are at the TOP of the caliper?
These trucks are designed so there will be NO front brake action until the REAR shoes contact the drums. Having said that, make sure the rear brake shoes are adjusted correctly. There should be slight drag on the drums if adjusted right. Also, check the bleeder screw that is in the frame C channel for the rear brakes, above the axle, drivers side. There could be air in there if you didn't bleed it here.
If everything checks out, my educated guess would be that you got the wrong master cylinder for the truck.
Is the original MC still around somewhere? Maybe you can rebuild it, or at least get a number from it to verify the replacement is correct.
Also, there are 2 brake CALIPERS that were available in 90. Bendix & Chrysler. I dunno if the brake caliper style would determine the master cylinder used, but you might want to check into it.

Hope this helps some.

George
Click to expand...


A couple more questions:

If the back brakes aren't adjusted properly you say the front won't come on, would that have an affect on your pedal or you just have crap for brakes?

The bleeder screw for the rear brakes in the frame, is that something that is independant of the RWAL valve? I ask since the valve has been bi-passed.

We've tried two different MC's so it would be odd if it's the wrong one unless you're onto something with the caliper having to be a matching set with the MC? We do have the original MC so we can look into that angle.

Thanks again guys!!
 
moparwedden said:
This Year My 94 Dakota Loss All Brakes. Changed Calipers And Bled All Lines. Still No Brakes. Talked To The Garage And They Told Me That Dodges Were None Too Take Forever To Bleed. So I Bled Them Each Side 15 Times. You Would Not Believe After The 7 Or 8 Time I Bled Them The Air Started To Come Out. My Brakes Are Fine Know. So Bleed And Bleed And Bleed. Took Two Cans Of Brake Fluid But That Was Cheap Enough. Good Luck.
Click to expand...

Just saw your post, it's been bled a hell of a lot but not as many times as you mentioned. I'll throw that angle at them too, thanks.
 
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