Brake power booster problems????

[RamAZ]

I have been having problems with my brake system again. At stop lights pedel slowly goes down then holds firm. Truck stops good but I guess it could stop better if the power booster was not leaking. I just change the rotors, pads, hoses, master cylinder and calipers about two months ago. Should have changed booster then, I'll know better next time.



Tested power booster this morning per manual and with motor off and when I depressed brake pedal I could hear a hissing sound for a second or two under the dash.



Looks like I need a power booster. I will change all the vacuum tubing when I change booster.



If I'm on the wrong track let me know.



Thanks in advance.



Jim

 

[RamAZ]

I installed a new booster late yesterday and bled the system. Only drove around the block, seems to stop better. Will know more this afternoon. Next project will be rear disc system from EGR, Dodge rear brakes SXXK... ... ... ... ... .....



Jim

 

[Case500D]

RanAZ,



After putting rear discs on my W-250 and then doing a complete brake job on my W-350 I have made a few observations and learned a few things. I think the W-350 with 3" rear shoes and 1" wheel cylinders stop much better than the discs do, especially with a load on. The 1" cylindres apply more force than the 1-1/8" cylinders, so the hydraulic force on them is greater. I put new drums, adjuster kit, hold down kit, shoes, and wheel cylinders on. I also replaced the e-brake cables. The brakes are staying adjusted and the truck stops very well. The rear duals lock up nicely and can put a lot of rubber down fast. I also did the front brakes. I can push the pedal down 1/2" and get very positive results. I guess I am saying that you might make sure the rears are functioning before investing in rear discs. I think keeping the drums will be cheaper. This is just my opinion and I am not trying to promote one product over another, just trying to help you save a bit of money.



Jeremy

 

[RamAZ]

Update on booster install.

Well the booster is in and the problem still exsists. Stops fine but pedal still slowly releases and goes down. I still need help,



I checked the hose at the vacuum pump and it was soft, so I took the clamp off and removed the hose and there was a small amount of oil in the hose, the oil did not drip out but was present. Maybe the hose is collapsing? I going to replace it this afternoon after the truck cools down and also the weather.



Has anybody else noticed if there is a small amount of oil in the line. I hope I don't need a new vacuum pump. Some oil in this line doesn't sound good.



Any help appreciated.



Jim

 

[62MaxWedge]

Jim,



I'm having similar problems. We are fighting air trapped in the system somewhere.



I recently installed a new NAPA booster two weeks ago and am still pulling air from the system, particularly in the rear. I have been using a "power bleeder" which seems to help, however, air is trapped in the system.



I have checked all connects, and are tight and sealed with no signs of leaks.



Eric

 

[RamAZ]

62Max Wedge. Thanks for the reply. I will bleed again in the next couple of days. Yesterday, late I drove some more and the pedal was low. When I went out to leave for work this AM the pedal was high again. The pedal was good and didn't move down at stop lights for the first couple of stops, then started to move down about the time I got to work. On the way home today the pedal moved down at every stop but stopped fine. It was 109 today.



Must be air trapped in the line somewhere. I also test the vacuum pump this morning and it was at 27 - 28 on the vacuum gauge, so the pump seem to be good.



The saga continues. Thanks again for the reply.



Jim

 

[62MaxWedge]

Should be master cylinder. Sorry.



Yes, heat does play into the equation. I've noticed the same condition. After I've really slammed them (brakes) they feel surperb, then after a few hits, back to weird pedal at times.



Let me know how you make out

 

[CDegner]

I had what sounds like the exact same symptoms. Pull up to a light and the truck would stop jsut fine. While I sat, the pedal would just slowly "bump" down. I say bump down because that is what it felt liek it was doing. I had tried out 2 other master cylinders before I got one that finally worked right.



Mine was solved with a new master cylinder and RWAL proportioning valve.



Hope this helps a little.



Carl

 

[southpaw]

brake pedal creep rear shoes dragging

Hi Jim and Erick, I too am having a hard time eliminateing pedal creep as well as rear shoes dragging. I bled the brakes as per one discription in the book but i just read another procedure calling for a hose and bottle containing fluid at the rwal valve. I'll try that next. I too believe there is trapped air in the system somewhere. I was down a couple of weeks ago and the brakes were dragging so i did the no no thing and took the truck to a local brake and tire shop they found the axel seals leaking and replaced them but didn't bother refilling the dif. with oil . I took the truck home and filled as per the book. When I bled the system the brake fluid in each cylinder was rather dark so I believe when the shop bled the brakes they probably used a pressure unit and didn't touch the rawl valve nor the wheel cylinders. Have either of you found the answer to your brake problems? This is happening with my 93 2500. auto 2 wheel drive.

 

[RamAZ]

Changed RWAL.

Well I got to the pedal creeping down problem Sat. mourning. I replaced the RWAL valve and bled the valve as per the manual.



I now have good brakes, stops good and the pedal finally stays up. When I installed the RWAL I put the tubing into the can of brake fluid first. It took for ever to get the air out but all is well, at least for now. I believe the problems with pedal creep was more the way the RWAL was bled than the master cylinder. Anyway, I have a new valve and seems to work for now.



Thanks for all the help.



Jim

 

[jdross440]

I had this same problem with my 92 W250. I have replaced the brake booster 4 times in 180,000 miles due to ruptured diaphams.



I found that the air in the system that causes the pedal to go down is in the Rear Wheel Anti-lock valve located in the LH frame rail above the rear tire. It has a bleeder valve on it and being the highest point at the rear, the air is trapped in it. After bleeding this unit, the firm pedal returned. Sometimes it took more than one try to get all the air out of it.

 

[RamAZ]

Well I changed the RWAL valve week before last and bled per the manual. Pedal has held for over a week now. Hope it stays that way. Nice to sit at a stop light and have a firm pedal.



The bleed of the RWAL is a real bugger, thought I would never get the air out, I then followed the sequence as listed in the manual.



Thanks to all who replied. This is a great site to ask questions and get some idea where to state to look for the problem.



Jim

 

[62MaxWedge]

Jim,



Between the two of us and this site, I think it is finally nipped in the bud! When I hit the pedal, it is like matting the throttle, although opposite reaction! This thing stops wonderfully!



Thanks to all for the help!Oo.

 

[southpaw]

Brakes

Well I'm glad someone has been sucessful cureing the brake gnomes. I worked on mine this weekend went thru 2 qts of brake fluid. as i was topping off i saw something float to the top someone sometime dropped a piece of bottle seal into the master front resevoir. I pumped all the fluid out and cleaned everything re blead the system, its much better the peddle is firm but still creaps down some with heavy foot pressure. Also the rt. rear drum is still dragging. I still believe there is trapped air in the system. Next i will check the booster and vacuum. I think the biggest obsticle for me and i know for some others is not having a decient place to work. My driveway isn't good and no fair raising you hood in the street. Oh i long for my shop in Mo. Thanks for the responses and suggestions,and am glad you have your brakes working. Tks K. E.

 

[southpaw]

Rear brakes

Oo. Well it looks like most of us having brake problems got them fixed at about the same time, and it was probably the same problem for us. Mine was the needle valve in the rwal also. it was replaced and noe the brakes are fine. The cost was steep but not as steep as the dealer would have been and I really like to stop. tks for all the replys. KE.