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Discussion Starter #1
Hello All, so my trucks front brakes were sticking and burning in the spring so I had my mechanic install new calipers and hoses. Drove it a few miles and it did it again, so under warranty the calipers got replaced again. It had only stuck on me once more before summer and all summer was fine . My truck is not a daily driver and maybe gets 1,000 miles a year hauling firewood and some building materials. So all through summer it was fine and this morning was 40 outside and the front passenger was cooking again on my way into work! So could this be bad fluid a bad master cylinder or a proportioning valve?Any ideas would be grate. The truck is a 1989 w 250 4x4 auto with the Cummins motor. Also the slave cylinder was replaced two years ago because it was not returning the brake pad to its regular position.
 

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It sounds like you may want to look and see if your master cylinder is properly working as well as check the quality of your brake lines. It could be that your lines are clogged from rust.

Did you replace the calipers or a mechanic?

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The rubber lines break down inside causing this issue. I would change all 3 2 front and 1 back bleed the system and you should be good, I am recommending all 3 because of the year
 

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Discussion Starter #4
So a mechanic did the work and the rubber hose/ line was replaced along with the calipers but not the copper lines. The master and the copper lines/valve are really all that was not done. is there a way to check if the master cylinder is failing ?
 

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Sounds to me like you have a problem in the master cylinder. That is where I would look next.
 

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You said the slave cylinder was changed out, are you talking about the clutch? I assumed you meant the master cylinder.

If you haven't changed the master that is most likely the problem. It is rare the steel lines have issues.

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Discussion Starter #7
The brake booster is what was replaced two years ago,I guess its time to learn how to swap a master cylinder. Should I leave the lines and replace the the master first and see how that goes?
thanks for the help. Who do you recommend for the parts,is Rock Auto Okay for that part or NAPA better?
 

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The steel lines are usually fine. If the lines weren't empty they shouldn't rust. If they were dry for a long time (no brake fluid) then they could rust and cause an issue.

Replacing the master is a cinch and shouldn't take long at all. 2 bolts mount it to the booster, 2 lines for brakes (1 front, 1 rear), and a small bracket for the lines.

-Drain all the old fluid, I use a large syringe or brake bleeder vacuum to get it out
-Remove two brake lines going to master (careful brake fluid eats paint up if left)
-Remove 2 nuts holding master to booster

Reverse order to put back on.

ALWAYS prime a new MC on the bench.

As for ordering, I got mine from Rock Auto but went with a brand I know and trust in brakes, Raybestos

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I had problems with calipers sticking due to phenolic pistons. 3 occurences this summer on used calipers. These were the 2wd calipers though. They seem to swell with age and/or with old brake fluid, and jam. Steel pistons don't swell, but rust and heat conduction are the other concerns there.

If the MC sticks somehow, it affects both sides, not just one. Stuff can also rust and get sticky in the iron proportioning valve on these trucks.

Rockauto and Napa will have considerable overlap on what they stock. Most stuff is reman'ed offshore or Mexico these days.
 

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Remember there should be a small clearance between the Booster rod and master cylinder and also between the brake pedal and booster. Bit of Plasticine on the end of the booster rod, fit up the master and then remove and see how far the Plasticine has crushed, will tell you the clearance.
Have also had Phenolic pistons that were tight in the callipers.
Cheers Steve
 

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That W series has a third flex line on the front axle. That line comes from the frame to the axle. If both front calipers are sticking that is the line to replace.
 
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