Severe Swerve When Braking 1992 Safari Continental (Oshkosh Chassis)

[borg8of9]

I recently purchased a 1992 Safari Continental on an Oshkosh chassis with the Bendix Hyrdo-Max brake system (not air). The motor home lurches violently to the left under hard braking from freeway speeds. It swerves enough to the left to be dangerous.

A shop familiar with truck/RV braking systems overhauled the brake system and the problem still exists. A suspension shop has not found anything wrong in the suspension. The front tires have been swapped left to right and right to left and that has had no affect on the problem. All four rotors have been replaced and all four calipers replaced with rebuilt calipers. The brake lines and brake fluid have been replaced.

I really need some help regarding what else could be the issue, or who/where I can turn to for diagnosing the braking problem.

All suggestions are welcome.

Thanks!

[wolfe10]

bprg8of9,

Welcome to the FMCA Forum.

Boy, that is a tough one, as the parts you have replaced should have addressed the problem.

With a violent pull to the left, first suspect would be that the front right brake is not working or working very poorly. A crushed brake line over to the right front wheel could cause that, but would certainly have turned up when they tried to bleed the new line and caliper (and no fluid would come out).

That system has been used on thousands of RV's and it is a good one.

Are your calipers floating calipers or are they fixed with pistons on both sides? If floating calipers, lack of lube of the slide area (probably left front) could cause it to drag, but unlikely an issue with brand new calipers.

[toneyamurphy]

This is just a shot in the dark but do you have a proportion valve in the system? If so it may not be sending pressure to the right front during hard braking.

Just saying as this is just a shot in the dark as I do not know the system.

Toney Murphy

[OLDMARINE]

borg8of9
Welcome.

Only two things come to mind:

Bad proportioning valve or a bad brake hose that is coming apart internally ,other then a smashed brakeline
as Brett mentioned.

Good luck. Let us know the final fix.

[dickandlois]

bprg8of9,

Proportioning valve equalizes pressure front and rear. Bad flex(rubber) Line between the steel line portion of the system and the new calipers. A possibility!

The one question I have, is the coach equipped with ABS? Do you know if the shop ran a test and complete system bled of the system.

The proportioning valve supply fluid to 2 ports on the ABS pump, one for the rear brakes and one for the front brakes. Any air in the ABS system or defective valve could cause one caliper to apply less pressure.

ABS systems have 4 brake lines feeding each caliper independent of the others.

Rich.

[wolfe10]

My assumptions:

No ABS on 1992 coach.

OP stated that the brake lines (flexible lines) were just replaced. Unlikely that the same symptoms would apply before and after replacement, yet they be the cause of the problem. That is why I wondered about a crushed brake line to the right front (the metal line). BUT, a crushed line would not allow one to bleed that caliper.

[huffypuff]

Brett, I worked on a truck one time that had a flatten steel line from a tow hook. It slowed the fluid but didn't stop the flow. The brakes on that side could be bled and release the caliper but not enough flow for even braking. I had a 93 Oshkosh chassis on the Southwind DP with hydro brakes and it didn't have ABS.

[hermanmullins]

The first week in December 2014 one of our chapter members had almost the same problem as in the OP. Three Christmas Rallies on a row he has had problems with his coach. This year he had one brake that pulled his coach to the left and the brake got so hot it almost started to burn. His coach a Monaco Knight had a crushed brake hose on the front left. The pressure when applying the brake was enough to stop but there was not enough pressure released to release the caliper.

A very good shop worked over time and had to go into San Antonio to get a brake line made. Although he had to replace the caliper and pads, and also flush the system, due to the heat he can now Stop and Go without any problems.

Herman

[huffypuff]

Yes Herman, it would be thought that a brake hose or caliper was the blame but the OP replace them to fix this problem. It could have due to age a rust spot on the line that may or may not leak. I remember my 93 Southwind Oshkosh chassis had the master cylinder and electric motor underneath. It wasn't easy to even check the fluid level as you had to remove the cap and hold a mirror over the master cylinder to see it. Time to raise the coach high with the leveler, put jack stands under and inspect all lines front to rear.