master cylinder took a dump

[paccool]

Took the travel trailer down to our sons place for thanksgiving. On the way down had to get onto the brakes hard a couple of time due to traffic and the light panel lite up. Brake light and Anti lock light came on. Looks like the master cyl died. It is leaking out the rear of the unit and the rear fluid level was down. The rear brake section sprayed up when the brakes were pumped.



I hope I can find one tomorrow at the NAPA dealer here in San Luis Obispo. I thought it was the booster at first but I think that is ok. The vacuum pump is pulling about 18" of vacuum so it's ok.

The pickup doesn't like coming down here-seems like something goes out everytiome we come down here.

 

[keimmmo]

If you have a leak, the master cylinder is dead. After replacing the cylinder, if the pedal falls away like you still have a defective master cylinder, you might want to check the anti-lock valve inside the frame rail just over the spare tire mount. If it fails, it too can cause the pedal to feel like a bad master cylinder... been down that road!



Another heads up if you don't already know it is that when you bleed the rear brakes (if needed) you have to bleed the anti-lock valve first then the right and left wheels. If you don't bleed the anti-lock valve first, you will never get the system to work properly!



Good luck. Hope this helps. When I had problems, I was on my own and had to figure out everything myself! I LOVE this site!!!



Steve

 

[Baron]

yeah that is where I am at now... ... new master cyl and still soft pedal! What does a new anti lock valve cost more or less?? Any way to fixem??? baron

 

[keimmmo]

If the anti-lock valve goes bad, when you hold pressure on the pedal, it will slowly fall away... just like when a master cylinder is leaking within itself. If the pedal is just soft and does not fall away, you probably just still have air in the system.



If it is just a soft pedal, the front brakes bleed like normal. On the rears, you MUST bleed the anti-lock valve first!!! When it has good fluid, you can go to the wheel cylinders. You can bleed with someone pumping the pedal or use a pressure bleeder. Really nothing strange here. Treat it like any normal brake system, just add bleeding the anti-lock valve.



If the pedal is falling away, you can verify that it is indeed the anti-lock valve by removing the lines from the brake cylinder and installing plugs. If the pedal falls away, it is the master cylinder. If it is firm, it is the anti-lock valve. If you wish, you can further verify this by plumbing in a piece is brake tubing in place of the anti-lock valve. Should make them feel fine if the valve is bad.



I was on the road when my anti-lock valve failed. I bypassed it to get home. The brakes work that way, but the rears are really touchy and easy to lock up!!! I DO NOT recommend keeping it this way!!! It was a better option than no brakes, but NOT SAFE!



I couldn't find any way to rebuild the anti-lock valve. The only place I could find a new one was from the dealer. Seems like it cost about $160-180. Rough! But, better than no brakes!!!



Don't forget to reset your anti-lock computer after replacing the anti-lock valve. I don't remember for sure how to do it, but it seems to me like you just unhook it and it forgets the previous problems. I could look it up in my manual if needed.



Steve

 

[Baron]

do you mean to pull off the lines going to the anti lock valve and plug them (it)... ..... muchas gracias amigo ... ... ... baron

 

[keimmmo]

That would probably work, but I pulled both brake lines off the master cylinder and put in plugs. That eliminated every possibility of problems anywhere else in the system. If the pedal falls away with plugs in the cylinder and no lines connected, the only possible cause would be the master cylinder! If the pedal is solid, you can eliminate the possibility of a bad master cylinder. My idea was to eliminate options until there was only one left!



I might also comment that I have never found this information in a shop manual... not even the factory Chrysler manual! This problem is not limited to our diesel trucks either. I have seen it on gas pickups and vans of similar year models since I had my problem.



Steve

 

[paccool]

Well, it looks like my problem was the master cylinder. Was able to get a new one (not rebuilt like the last one) From NAPA in San Luis Obispo on Friday. We bench bled it , took quite a bit of fooling with it to get all the air out. Put it on and vacuum bled all the lines. Bled enough to change all the fluid out in the lines and wheel cylinders. Didn't bleed the antilock unit. Took it out for a couple of panic stops to see how wverything worked, all seemed to be ok. The trailer brakes did not work and I went ahead and drove home without them. I know, that was not a smart thing to do !



Took it easy and watched the traffic in front of me , didn't have any problems. Now need to tear the trailer brakes apart and see what happened to them. They were not working real good the last few times we took the trailer out so I suspect I will need to replace most of the stuff on the trailer now.

 

[willyslover]

my old friends saying comes to mind... Taint one thing tis another

LOL..... sorry to see all your brake troubles BUT damnn glad you didn't have a wreck with pretty new looking rig and hurt yourself and your Misses

So how did you get through SF traffic without the brakes working on the trailer without hitting one of the road warriors

 

[paccool]

VERY CAREFULLY!



Sure glad no one pulled out in front of me though.



Hell Gary, I wouldn't have this problem if I wasn't such a tight wad, been wanting a new trailer but hate to spend the money. Also have not found a trailer arranged like we want.



One of these days!



Stan

 

[Baron]

what is the complete process of "bench bleeding" the master cylinder???? baron

 

[paccool]

One way is to install short lines from the outlet and dump the fluid back into the top of the unit. Clamp the unit in a vice, pump the cylinder by hand with a blunt device until the air is removed from the main bore of the unit. This is the way most of the units show that I have seen.



The instructions with the new one I got showed the above way as well as plugging the outlets and then pumping the cylider the same way. This didn't seem to work very good, the air couldn't get out easily. Not sure how they figure this will work good.



We had a hand vacuum unit and ended up using it to get all the air out. Then used that to bleed the system.



Stan