1986 Winnebago Elandan right front brake locks up (turns out, they all were)

[zaa]

Hello folks,

We've had a lot of fun using our 86 Elandan motor home this year.

The right front brake locks up. I had replaced the rubber hose because I wasn't getting any fluid pressure from the master cylinder. That didn't solve it, so I replaced the master cylinder, and everything seemed fine, for a while. I am able to open the bleeder to release the pressure on the caliper, which indicates to me that the caliper is not the issue. I'm down to the proportioning valve. I intend to tackle it this weekend, but I'm not entirely sure where it's located.

Thanks,

[circleD]

If its like my P30 it will be on a frame cross member in the front between the 2 tires. Then look under a bell housing I believe and there you go. I have seen a few that's more on the drivers side but I believe that was done by PO. There's not much room at all to access it. Maybe 1/2" clearance. I suggest spraying the bolt that holds it and wait so you don't round it off. There's a good chance you'll get upset and rethink about fixing it  . Old Rock and Roller has messed with his in a post so try to use the search box and research. Good luck.

[M & J]

Oldrockandroller was our old screen name. Our P30 blew a steel line exactly when we pulled up at our house coming in from a camping trip. I hand formed a replacement line but getting to the prop valve will test you. It is on our 87 on the crossmember as D said, but you barely have enough room to get your fingers in to feel it. I loosened the valve from the cross member to move it up to get wrenches on it. But soak everything with penetrating oil. And the prop valve is no longer available if it is bad. Now that I remember, I loosened the flare nut while the valve was bolted in, but had to let it float free to get the new flare nut threaded then remounted it to tighten. Brush up on your bad words, you'll need them.

[Froggy1936]

It is very accessable with the engine out . Frank

[M & J]

Good tip Frank!     lol

[TerryH]

It is very accessable with the engine out . Frank

Excellent Frank.

[cncsparky]

My bet is the caliper for that side that is locking up.  Had the same thing on a PU years ago. 

[M & J]

Has all the symptoms of a collapsed flex line but he said he replaced it. I'd rather rebuild a dozen calipers than mess with that prop valve and lines.

[Rickf1985]

The prop valve is nothing more than a distribution block for the front brakes, it splits the one line into two, Right and Left. The odds of a problem with that section are slim to none. I lean towards a bad caliper of a defective new brake line.

[bluebird]

I agree. Doubt the prop valve is the problem. I had that problem with my Itasca, and it was the master cylinder. I'd loosen the front brake line from the master cylinder and see if the pressure is released before replacing any of the other parts. Seen bad reman master cylinders before. I'd rule out the caliper because it releases when the bleeder is opened. Could also jack up the left front and see if it's dragging too. Mine did but didn't lock up like the right did. Mine would slide the right tire in my rock driveway.

[DRMousseau]

I've been watchin this topic for a short bit,... tryin to recall a similar problem.
What baffles me is that you have only one pressured caliper!

I'm going to rule out the Proportioning Valve, unless it's also serves as a distribution block,... those having an individual brake line for each wheel. In most older systems, Proportioning Valves only have a single outlet the front, and a single outlet to the rear. Those lines lead to a "distribution block" on the rear axle, and on the frame or front crossmember that separates the line to the right and left. And I suspect that your problem is exclusive to the right front brake line system.

You noted you first changed the hose because there wasn't any fluid reaching the caliper. But I'm not totally clear on whether this problem was evident first. Hose change didn't solve problem, and a change of master gave some relief, but was short lived. Since your problem is exclusive to the Right Front only,.. I suspect an obstruction, on the wheel side of one of the brake line connections, between the distribution block and the wheel caliper. This obstruction is allowing fluid flow in one direction only, and then plugging the connection on release, preventing return of fluid and pressure in the right side brake lines.

This obstruction MAY have prevented fluid flow in the hose first, and repositioned itself during the change and subsequent fluid bleeding. Such obstructions often, are only noted under pressure,... when it forms a tight seal due to that pressure. This may have been experienced first, and then moved down-line when the hose was changed. This can be from rust which forms in the line, OR from something introduced into the system,.... like thread tape or sealants used on connections in a careless manner.

CAREFULLY, inspect your steel brake line to the right side wheel caliper from the distribution block. Pay very, VERY close attention to the areas held by retaining clips that secure the crossing brake line to the chassis to prevent movement. These may appear solid and fine, but the backside against the frame is often an area of failure due to rust between frame and lines (or within the retaining clip). Make SURE this is solid by removing the line from the clip!!! If it bends or breaks in doing this,... then be glad it didn't fail while driving!!!! Replace those lines if you have any doubts. Rust dislodged from these areas CAN plug the brakeline before complete failure.

When changing or replacing brake components,... flush the brake lines THOURGHLY with clean fluid. YES,.. change your brake fluid! Don't jus bleed the caliper of air, but flush ALL old fluid and moisture in the lines from the master to the wheel cylinders. Although difficult, I try to catch old fluid in a clean container to check for rust particles, moisture, etc. This is important to doing "a good brake job" and fluid is the cheapest component in repairs.

MANY folks don't realize they may not have functional rear brakes for any number of reasons. Most braking effort is on the front wheels, and the lack of rear brakes may not even be noticed or overlooked.

Ask me how exciting it is when front brakes suddenly fail (due to the above reasons), while driving a 6-ton RV in busy afternoon, stop-n-go traffic on multi-lane streets!!!!

[DaveVA78Chieftain]

I'm going to rule out the Proportioning Valve, unless it's also serves as a distribution block

For the the P30 front wheels (front disk; rear drum) the answer is yes it does.
Left side of this drawing is for the front wheels.  The top port is for the LF, the bottom port is for the RF.
The metering valve for the front holds off pressure to the front wheels until a predetermined pressure is reached to allow the rear shoes to overcome spring slack.  The proportioning valve section (rear wheel side) is used to limit the amount of pressure applied to the rear wheels to prevent rear wheel lockup during light load conditions.



PS: The Dodge motorhome chassis also is like this.

[DRMousseau]

YUP! It Sure does!!! And Dave described it operation exactly.

I recognized it right away! AND,.... I Now remember doing the right side brake line in two pieces!!! I have the joint jus behind the cross-member on the right side, and explains why I could remember exactly WHERE the front distribution block was. Knew it wasn't on the cross member,... and the prop valve was jus rear of the member on the left.

This means your problem (which I still believe is an obstruction), MAY be INSIDE the proportioning valve, or anywhere between it and the wheel caliper. Again, look carefully at those areas UNDER the retaining clips on the frame. Those clips are a "catch-all" for dirt and moisture. The lines can be clean and solid on each side of the clip. but that clip may be the only thing holding the pressure in a rusted thru line beneath it!!! This is why I stress the removal of those clips while inspecting brake lines.

I would likely replace the metal lines from the valve to the caliper, flushing the valve through BEFORE attaching the line to it. BE VERY CLEAN!! This also means making clean bends and ensuring the line is solid and secure it's full length. Watch the "pass thru" of the frame to the caliper line,... making a clean bend that doesn't touch the sides of the pass thru hole to prevent "vibration wear" in that area.

IF,... you cannot flush fluid thru the proportioning valve outlets, then I would personally replace it. I'd rather a new dependable valve, than a questionable repair.

[tiinytina]

Gone (1987 P30 chassis) has disks front and back... all lines, calipers, and pads along with master hydroboost cylinder replaced after my "oh-Sh**!!" moment in heavy traffic and 105F temps...... don't know if the 1986 chassis is the same but I don't recall a proportioner on ours.   

[Rickf1985]

Disc brakes all around would not have a proportioning valve since there is no need to hold off the one set of brakes until the drum brakes engage. They all engage together at the same time with discs.

[DaveVA78Chieftain]

Gone (1987 P30 chassis) has disks front and back.

For the P30 chassis it depends on which brake option you have:

JB7 - Vacuum power booster; Front disc (12.5" x 1.28"); Rear drum (13" x 2.5");  Mostly used on bread trucks, not motorhome chassis

JB8 - Hydroboost booster; Front disc (12.5" x 1.54"); Rear drum (13" x 3.5")

JF9 - Hydroboost booster; Front disc (14.25" x 1.54"); Rear disc (13".75 x 1.54")

Disc brakes all around would not have a proportioning valve since there is no need to hold off the one set of brakes until the drum brakes engage. They all engage together at the same time with discs.

However, I somehow want to say for disc/disc there is a sort of metering/warning valve that
  A.  Detects loss of pressure in either the front or rear circuit (brake light)
  B.  Provides metering such that rear pressure is less than front so that the rear does not lock up due to weight shift.

[Rickf1985]

I got ya on that one Dave! W% There is no metering, there is a safety switch which illuminate the light if a line blows or something similar. As far as brake differential................. you gave the answer in your description of the brake codes. Look at the size of the rear rotors compared with the front. That is your metering.

[zaa]

Hello again, folks,

Sorry for the lack of updates, real life reared its ugly head, I've been busy with other things.

I've not had a chance to even climb under the motorhome since I posted this, but I certainly appreciate all the knowledge you've shared here. This vehicle is a single rear axle, dual rear wheel, with disc brakes all around. When I do get time to tackle it, I'll be sure to take some pictures, and report back.

Thanks again,
Z

[ClydesdaleKevin]

I had a similar problem on our old 77 Itasca with a P30 chassis.  Caliper locked up on the passenger side.  Turned out it was a ring of rust that caused the piston to lock up once it got past that ring of rust, once the pads got thin enough.  A quick solution was replacing the pads after forcing the piston back in with a great big C clamp.  Later I replaced the caliper, and the problem was permanently solved.  It had front and rear disks.

Kev

[lngfish]

I was told after my right front caliper hung up and wheel got HOT on a trip that these calipers are SELF-CENTERING and hang in SLOTS ie GROOVES.

When doing maintenance, yearly this mechanic said. clean and anti seize the gooves.

But who does that.

[DaveVA78Chieftain]

Well, on my Dodge M400, I do because of just that reason.  I also check for excessive hub temps on a trip now as I have had that issue crop up a few times from the rig sitting for several months.  Hub can heat up in 5 to 10 miles due to this.

[DRMousseau]

I much prefer to do my OWN brake servicing for this very reason. "Time is money", less time spent by service techs, means more money earned. But more time spent by me, means more money saved!

"I", will spend extra time scraping and brushing parts clean AND carefully coating all slide contacts and pins with anti-seize to prevent corrosion and insure full easy movement. This includes the bleeder threads to insure that it will not corrode and seize up as typical. I will also inspect tab corners of brake pads and carefully file or grind to smooth and remove sharp corners that may cause hanging and carefully apply anti-seize to ensure free movement. I will take extra time to carefully remove and inspect caliper boots for unseen damage and to expose and clean the piston ensuring full and free movement, and replace any parts necessary. This extra time, small expense and added effort is MORE than worthwhile in long term quality performance and money saved. I also find future servicing to be MUCH cleaner and easier due to these efforts. AND, I can personally inspect and service other components, including brake lines and hoses, steering joints and components, shock, springs, hub bearings and more.

I also have a quick 10min. checklist routine for EVERY stop on extended trips that includes lugs, wheel, tire, hub, axle, and brakes. This was once a courtesy of full-service gas stations, and with the changing times, is now MY responsibility.

[zaa]

Not to resurrect an old thread, but I recently had this problem, so I thought I'd share my findings.


I've replaced the master cylinder, and all the lines headed from the distribution block to the right wheel, including the rubber hose. I have a caliper, if the problem persists, but things seem better now. One symptom I noticed was that I got much more fluid from the left caliper bleeder than the right. After replacing the metal line, I have equal flow. I have yet to get it on the road to test, but I have high hopes. Mainly what I wanted to share was the type and location of the distribution block. My RV is a 1986 Winnebago Elandan P30 chassis with disc brakes all around. The block was located slightly to the left side on the front cross member, underneath the harmonic balancer. It was relatively easy to get at, and a shot of PB Blaster helped crack the lines loose without much trouble. While I couldn't actually SEE it, I got my phone up in there and took a picture. Hope this helps someone else on their search.

[Oz]

Resurrecting an old topic IS a good thing to do.  It's much better than starting a new one.  This helps keep all relevant information in fewer places and makes it easier to find it all, which helps others better and faster!


Thank you for doing so

[zaa]

A follow up on this issue.


First off, when I say "locked", I mean that the brake slowly applies, after multiple stops, until the dragging is too much to reasonably continue driving. The brake pedal action gets progressively higher.



After finally having weather dry enough to test drive (not get stuck in the drive way), the brake locking issue persisted. Yesterday, I changed the right caliper + pads, then I removed and cleaned the distribution block, and wouldn't you know, it still happened.


I feel sort of silly about this, and I can't really recall why we were so focused on the right wheel, it seemed to be the one getting hot, but this time when it locked again, we cracked the bleeder on the left wheel, and both front wheels freed right up, so obviously the problem was either master cylinder or hydro boost. At this point, I'm presuming that all the brakes are actually being applied, though I've never thought to check the rears.


I read about some folks having problems with the hydro boost leaking when the engine was revved, so we tested that today. I took the master cylinder off, and watched the rod in the hydro boost for quite a while, at low and high rpm, low temp up to 160 degrees engine temp, but the rod did not creep forward at all. I had also read that the rod being too long could cause this problem, so today, I made a shim to put between the master cylinder and hydro boost, about 1/16" thick. Now, I'm not going to say the problem is totally gone, since I've been wrong so many times about this, but we drove around for an hour outside of town, on 55mph roads, with lots of stops. I drove normally part of the time, and used more aggressive braking other times. After all that, the pedal felt normal, it did not lock, it stops surprisingly well (I hope I didn't break my factory clock when it flew off the wall!), and the rotor temperatures were average 230 degrees front, 260 degrees rear when we ended the test drive.


If it does happen again, I have a 5/8" wrench handy so I can loosen the master cylinder from the hydro boost to see what the heck is really going on, since I can't seem to reproduce the problem while stationary.


What's strange is, before this all started, we were returning home from a 300+ mile drive on the (presumably) original master cylinder. I don't understand what would have changed *while driving* to suddenly start this behavior. Since it started, it's been easy to reproduce, you only had to drive for 10-15 miles before it would act up again, but only if you used the brakes. I had installed a new master cylinder when this problem started, and I did not change the rod.


I'm going to say I'm "cautiously optimistic" about it, but I have my eyes on a rebuilt hydro boost, if it continues. I can't imagine what would change as I drive that would make the hydro boost change its operation. The only other thing I could think of was, if the master cylinder was somehow sticking partially engaged, but for that to happen with the old, and new cylinder seems very unlikely.


Anyway, I'll keep posting my findings, and eventually, hopefully, the solution, providing my sanity holds out. This is not the only problem I'm chasing right now.


Thanks,
Z