Rookie brake question

[AECS]

I have been beating my head on the wall with the front brakes. Sanity check please. Is it the front circuit on the master cylinder that is supposed to have the small line and go to the front brakes? it has the larger reservoir as well? Thanks.

Been messing with them for months to get them right. The fronts are dragging, not locked, but dragging way more then they should. I have replaced everything but the hard lines, and no change. I am thinking there may be debris in them and before I disconnect at the master cylinder and the distribution block on the cross member and drain/ blow air/ force break cleaner through want to make sure I am not chris crossed.

 

[cucvrus]

You have replaced the calipers and the caliper bushings? The brakes are still dragging? Are we working on an M1009 K5 Blazer or a K30 variant? The larger reservoir goes to the front brakes. If you are working on the truck the slides on the knuckles need to be cleaned and lubed so the calipers can return to neutral after being applied.

 

[AECS]

it is the 1009 (K5) I have replaced the booster, master cylinder, valve on cross member, flexible lines, calipers (and rebuilt the replacement calipers) They slide great, (installed without pads to test) if I crack the bleeder valve it oozes fluid, so I am thinking it is holding just enough pressure in the line to keep them from releasing completely.

To clarify, they are not locked, they release enough that I can rotate the wheel with about 20 pounds of torque. It drives but the hubs get warm from the constant friction.

 

[cucvrus]

Have you checked the wheel bearings and the spindle bearings on the outer drive axles?

 

[ehuppert]

So, you've replaced everything...... Try backing off on master cylinder mounting nuts to ensure master isn't slightly applied at rest!

Have seen mismatched or incorrect parts more than once!

 

[Barrman]

Where did you get the new proportioning valve on the front cross member? I ask because the last I looked, they were no longer available new. That part though should not affect your dragging brakes though.

Is the truck pulling to one side constantly? That would be a clue as to which side is the issue.

 

[nyoffroad]

So, you've replaced everything...... Try backing off on master cylinder mounting nuts to ensure master isn't slightly applied at rest!

Have seen mismatched or incorrect parts more than once!

Never heard of that BUT with all the "will fit" parts and china crap out there I could see a master cylinder being out of spec enough that it could cause it to not release all the way. Would be odd but well worth checking! I'll file that thought away for future use (who am I kidding I'll forget this in 5 min)

 

[AECS]

Have you checked the wheel bearings and the spindle bearings on the outer drive axles?

Yep, they have been replaced and repacked, spin freely with no brake caliper.

 

[AECS]

Where did you get the new proportioning valve on the front cross member? I ask because the last I looked, they were no longer available new. That part though should not affect your dragging brakes though.

Is the truck pulling to one side constantly? That would be a clue as to which side is the issue.

It is an aftermarket unit machined out of solid brass, was not cheap at all. I will have to find the url for the company that made it. However I only replaced it while trying to fix this issue, I figured it could have a blockage that was not allowing the breaks to fully retract. It does have a slight pull to the left under hard breaking.

I cant find the place, but the receipt was right stuff inc.

 

[ehuppert]

So....

Jack front end up. Apply and release brakes. Spin wheel ensuring drag present. Crack bleeder at caliper.... Spin again If drag goes away that means residual pressure is applying brakes! CLOSELY inspect hard lines. Have seen kinked/smashed lines cause problems, but not so common....

When you say oozing.... Fluid will gravity bleed with system at rest when bleeder open. With that many pieces replaced you should have bled any residual crud through...

Proportioning valve really shouldn't be part of the equation if brakes working properly...

 

[vanaisa]

I had once brand new front brake hose, damaged inside and leaving pressure to brake. (Made in Mexoco).
Not CUCV but still....

 

[Mullaney]

I had once brand new front brake hose, damaged inside and leaving pressure to brake. (Made in Mexoco).
Not CUCV but still....

.
Agreed - especially when discussing cheap imports. Stupid things will definitely happen. Looking for cheap to save a dollar isn't new.

We had a vendor where we purchased the rubber Deuce and 5-Ton lines (frame to axle) in bulk. This would have been around 1983 and I don't know where or who now, but their manufacturing facility had a QC problem.

I will never forget that "goose pimple" finish on those hoses.

I had just completed a 5-Ton rebuild from the frame up. Rebuilt axles were installed, then the plumbing started. Got those new hoses and everybody in the shop was all worked up for one reason or another...

Long story made much shorter: Sitting at a railroad crossing waiting with my foot on the brakes. Pretty quickly the brake peddle roared down to the floor. I was scrambling to get the truck in gear and the truck stopped. I got out and walked around back to see the Pintle Hook crammed into the grille on the front of a pickup truck.

Thankfully the rail grade crossing was up hill rather than drifting down hill into the train.

Lots more to the story, but thankfully nobody got hurt. Rough cost for the bumper was a hundred bucks and the guy was just as happy as me.

 

[AECS]

Got it straightened out. Disconnected all hard lines to the front. Sprayed brake cleaner through all, the lots of nasty came out, even though upon bleadin was all clean and purple Compressed are to dry, did it twice. Calipers release nice now.

But a wheel bearing job is coming, I ran it like that all winter and up till now, to work 40 miles each way 5 or 6 times a month, so I am sure the added heat took a toll on the grease.