My 95 250 PSD has 340k on t and now i am having some serious brake issues. A while back I started to get a mushy brake pedal and figured it was the master cylinder so i replaced it. the brakes were "firm" for about three days then back to crap. I figured it must be the cylinder;so i replaced it again but this time being more careful bench bleeding the cylinder and truck brakes and had sme problem. my buddy said i didnt bleed the master so we just took it off and bled it and all the truck brakes AGAIN and the pedal still has some mush to it. anyone else have this problem? any ideas? thanks

 

rear brakes been adjusted lately? tighten then up good see if there is any improvment. also be your rear abs valve. it on the drivers side frame rail right under the drivers seat. I have built a bypass line before for testing this but it been so long ago that i don't remember the fitting sizes.

 

Tim, shame on you......... Bob, vacuum pump all the way.

 

Thier both right, siezed rear brake adjusters failing to adjust can give you mushy brakes.

I just did my rear brakes, damn harware snapped and chewed out my drum, it appeared the brakes adjusted with using the e-brake from what I saw, try depressing and releasing the emergency brake pedal about a dozen times and check for improvment.

I've also noticed siezed front caliper pins and customers write trucks up for mushy brake pedal.

 

Vacum pump will cause an extremely hard pedal not a mushy one. The rear brakes self adjust when braking going in reverse. Oh yeah I will soon not have rear drum brakes! ordered my parts to build my own rear disc brakes yesterday!!

 

TJ, rear disc conversion? Let us know how it goes!!! Parts Cost, How difficult, Is it worth it, etc. etc. and pictures, pictures and more pictures. By the way, I'll try and get the bumper pictures and some measurements for you today.

 

TSM makes a kit for it now, it's about $750 for everything. I'll be watching how Tim does it, and for how much. Here's a link to the TSM kit:

TSM rear disc kit

 

Tim, are you sure on that, I scribed the adjusting wheel on my truck and it was rotating with E-brake application.

Also just did rear brakes on a 98 f150, simular adjustment setup, it for sure turned the adjusting wheel over 3/4 of a turn.

 

It might turn with the E-brake also. But I do know for sure it adjust when you back up and hit the brakes. I never hit the e-brake on any vehicle in these parts as the cables have to be replaced when they stick. Never a good thing especially since the drums won't come off the cable need to be replaced and the customer isn't happy cause they can't have their car back.

 

I have not experienced this myself, but, a friend of mine went through this. Does your truck have cruse control? IF SO, then you might have a problem with the switch on the master cylinder. Trucks with cruse control have an electric switch located out at the end of the master cylinder. What my friend experienced was constant air in the lines. What was happening was that every time the pedal would come up, air was being sucked into the master cylinder through the cruse control switch. The funny thing is, brake fluid was not coming out of it! The leak was inside the switch, not around the threads where the switch goes in the master cylinder.
By the way, the purpose of this switch is to de-activate the cruse control when you touch the brakes. Hope this helps. John

 

yeah, I had to step out for a bit so I couldnt carry the conversation.

The fleet shop I work if the cable is siezed, you replace it, its all about safty and liability so that is no option.

As for my truck, I use the e-brake everytime a turn off the truck just so it wont sieze.

I'm not arguing, the rear brakes do adjust in reverse

With that out of the way and back on topic, from expearence a few weeks ago, I could not get the brake to adjust, I would start locking up the front brakes in reverse and still was getting nothing out of it. I pulled the wheel back off to make sure everything was fine and it was but what I was seeing is I was not getting any adjustment application. Thats after I installed the drum with the wheel marked and lug nuts installed. After hitting the e-brake it adjusted and got good rotation. I kinda screwed around with it for an hour and the only thing I gathered is that if the brakes are grossly out of adjustment that they have difficulty adjusting themselves up, where the self adjusting is only good to maintain an adjustment. I have not given it any real thaught since I did the brakes and got it on the road, now I'm just thinking it through in my head. When I come across another rear brake job I wanna try the e-brake theory, get it to adjust to where its happy and see if the reverseing will further the adjustment kinda like a "fine tune". I do know that after I worked the e-brake, the drum had some drag when I was pulling it off.

All in all, if you need to adjust the rear brakes, pull the plug on the backplate and use a flat screwdriver and turn that wheel. You dont have to go to the extent of pulling it apart and dont go to tight when adjusting the rear brakes

 

What you said does make sense, you hit the brakes, in the switch will be a little plunger, with an application the plunger will contact and seal, with brakes released it looses the seal and draws air.

Kinda like a leaking fuel suction line, no fuel leak but it draws in air.

 

I do have cruise control so that could be the issue. is there a way to find out besides pulling the electronic dammit and screwing a plug into the hole? bled the brakes pulled the master and then bled again so it feels like there is still lots of air in there. i am going to try the back-up brake adjustment and see if that helps if not i will have to go old school and adjust the rear. thansk for the help and i will hopefully be bringing good news soon...

 

I guess you coulod just put a plug in it, I really dont know if thier will be any other electrical issues by deleating that cruise switch though, for driveway testing I guess it would be fine. I dont want anything to happen if its tied in another circuit somehow. maybe someone will jump in.

 

just buy a new one normally they leak externally the same switch is used on the newer trucks and expeditions that are recalled for the fires but the recall doesnt apply to our trucks even though its the same part number sensor with the same problem, i've never had the sensor cause any brake problem, just inop cruise control and occasional melted wires, my first guess is in the rear brakes but if they aint warped and they are adjusted good and the drums dont have the rust ridge then its not in the rear, make sure there is no rust ridge for the shoes to catch, it will cause that every time. if your master cylinder never drops then you have an internal problem, no visible leaks on the frame? was the booster wet when you took the old cylinder off? if so it could have eaten the booster out but it shouldnt come and go as you stated, rabs valve could cause an intermittant pedal problem but thats normally associated with a light. make sure of the obvious, if the self adjusters are on the wrong side they will unadjust in a day or 2's driving, if the caliper pins are loose or bent it will cause it, loose wheel bearing are a stretch but i've seen it, if nothing comes up i am goin with the accumulator in the rabs valve is damaged, no way to test that one just a reeplacement.i cant think of anything else to check over i will have to sleep on this one, a good challenge, i need more of these