Update to ABS Valve Replacement post

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Update to ABS Valve Replacement post

January 25, 2017, 10:48:25 pm

I originally started a thread asking for recommendations/help on replacing a leaking front ABS valve here:

ABS Valve replacement recommendation

About a year ago when the issue first arose I went to FOT and talked with an individual in service who said something like 'yeah we've had customers with your issue before and never found a solution' and didn't seem particularly interested in pursuing a solution.

However, after a rather circuitous route around NAC I ended up back at FOT talking with James Triana and accompanying him into the shop where, in fact, they were replacing the ABS valve with a standard relay valve on another coach. At this time they don't seem concerned about DOT as they put them in MH's before it was ever required.

I set up an appointment on the spot and yesterday had the ABS valve replaced with a standard relay valve, the front ABS sensors removed and the ABS controller disabled. I spent last night at camp Foretravel and the air pressure only dropped 5 psi overnight (instead of the previous 80+ psi). Since my previous coach didn't have ABS, or even disk brakes, and I was comfortable with that I'm an even happier camper now!

Hopefully, this will show up for others in a similar predicament.

Re: Update to ABS Valve Replacement post

Reply #1 – January 25, 2017, 10:54:55 pm

Could you post a picture of the valve?

Re: Update to ABS Valve Replacement post

Reply #2 – January 26, 2017, 07:48:22 am

Say BillO, I am curious, with your abs problem, were you getting the ABS Caution Light when you started up and began moving the coach, and it then would go out sometime later down the road? Mine does, and I also have an air leak that I just can't find that brings both tanks down within 24 to 36 hours.
Thanks, Mike

Re: Update to ABS Valve Replacement post

Reply #3 – January 26, 2017, 09:05:01 am

So Bill,
How does this system work?
It sounds like you have remove ABS brakes from your front axle?
If the wheel speed sensors are removed from the front wheels how would it know if a front wheel was locked up?
Always something new.

Re: Update to ABS Valve Replacement post

Reply #4 – January 26, 2017, 10:13:16 am

Mike, your big leak down could be a few things.
I found after some searching that the step slide cylinder was leaking badly and changed the set up (as others have now done) and that made a big difference.
Another place to look are the check valves on end of air tanks and the one at Air Dryer. these could be not sealing and air going backwards and out thru dryer which you would not hear. Another small leak has been found in Parking Brake controls. All easy to fix but you should determine which tank and circuit has the big leak and go from there. If you have the air operated step they can cause leaks too past O rings on cylinder shafts.
Lots of known leak points.
JohnH

Re: Update to ABS Valve Replacement post

Reply #5 – January 26, 2017, 10:47:15 am

John, is 5 lbs. overnight considered big?

Re: Update to ABS Valve Replacement post

Reply #6 – January 26, 2017, 11:31:57 am

Quote from: craneman – January 26, 2017, 10:47:15 am

John, is 5 lbs. overnight considered big?

Actually 5 PSI overnight may indicate ZERO leak if ambient temperatures dropped, that alone could account for PSI drop.

And, if it is a 5 PSI drop, that is EXCELLENT.

Re: Update to ABS Valve Replacement post

Reply #7 – January 26, 2017, 02:03:01 pm

Like Brett said that is NOTHING!! I get about the same as in a week or 2 it usually is down to 60 ball park. I found my steps are still the main culprit and keep intending to remove cylinders and rebuild but something elso comes up more important. DW needs me to fix or do something!!!

JohnH

Re: Update to ABS Valve Replacement post

Reply #8 – January 26, 2017, 07:21:04 pm

Both tanks down 50 psi in 4 hours. No pressure on airbags as coach is 'blocked'.
Mike

Re: Update to ABS Valve Replacement post

Reply #9 – January 26, 2017, 08:11:05 pm

Quote from: rbark – January 25, 2017, 10:54:55 pm

Could you post a picture of the valve?

Sorry, I didn't take any pix.

I took in this stray dog back in the summer. It's still very puppyish and friendly so I spent most of the time while they were working keeping her out of the shop and off the mechanics.

This valve did not look anything like the Wabco pix that you posted in the previous thread. It provides the same function but incorporated everything in one big "block".

Re: Update to ABS Valve Replacement post

Reply #10 – January 26, 2017, 08:12:48 pm

Quote from: Yetch – January 26, 2017, 07:48:22 am

Say BillO, I am curious, with your abs problem, were you getting the ABS Caution Light when you started up and began moving the coach, and it then would go out sometime later down the road? Mine does, and I also have an air leak that I just can't find that brings both tanks down within 24 to 36 hours.
Thanks, Mike

My ABS light would go on a start-up but go off immediately as soon as the coach started rolling. I believe that was the normal operation for this system.

In this case the leak in the valve was obviously audible. After I had the step and step-well cover cylinders replaced the tech that did it called me over and pointed out the air flow coming out of the body of the valve. It could be heard by just sticking my head under the coach ahead of the front axle.

Re: Update to ABS Valve Replacement post

Reply #11 – January 26, 2017, 08:25:39 pm

Quote from: John Duld – January 26, 2017, 09:05:01 am

So Bill,
How does this system work?
It sounds like you have remove ABS brakes from your front axle?
If the wheel speed sensors are removed from the front wheels how would it know if a front wheel was locked up?
Always something new.

John,
It is a bit more than that. The complete ABS has been disabled as the remote ECU was shutdown to turn off the dash light. There is no overt way to tell if a wheel locks up other than feel.

As I wrote initially I'm not too terribly bothered my it. My last coach was heavier, had no ABS and drum brakes to boot. I drove that for 6 years without incident.

Re: Update to ABS Valve Replacement post

Reply #12 – January 26, 2017, 08:42:05 pm

BillO,
Thanks for that information.

Re: Update to ABS Valve Replacement post

Reply #13 – January 26, 2017, 11:04:58 pm

I have the same leak down, What did the parts cost?

Re: Update to ABS Valve Replacement post

Reply #14 – January 27, 2017, 12:12:40 am

Howdy from New Braunfels--Just got back from a 500 mile round trip to NAC and spoke with Braxton at FOT regarding my ABS Valve replacement. I believe our coach was the other rig being serviced recently with the same concern. Braxton mentioned the same situation arose on another late 90's coach, (maybe yours?) after ours was resolved recently. I've never ever quoted myself before, but, here's my old post:

Quote from: Old Knucklehead – December 05, 2016, 08:16:25 pm

Trying to get to my Nacogdoches appointments and our brake valve "hung up" at startup. The hissing stops when the service brake is fully applied, but continues to leak air when the pedal is released. I pulled the part tag while muttering bad words: "Midland N4506A 254K"

The FT parts folks dead-ended looking for my obsolete part. Their replacement was installed, eliminating the ABS function. A call to Braxton will give you the cost of RR. (I haven't seen the bill.) Hope this helps! Our valve's photo is glued back on my old post and I am too pooped to pry it off that old post and stick it up here. G'night!

Re: Update to ABS Valve Replacement post

Reply #15 – January 27, 2017, 08:31:43 pm

Paul,

I believe that you were likely the ones in FOT when I first went in to talk with James Triana. We ended up in the shop with Alton who said they were replacing the ABS valve with a standard valve on the coach in the first bay (nearest the parts counter).

I looked up your previous post and the picture is pretty much exactly what I had as is the number (except mine was just a number which came up as Haldex -- likely due to a merger).

For those who asked for a picture, Paul was more thorough than I and has it here:

"Stranded" at Home: Brake Valve Hanging Up

Re: Update to ABS Valve Replacement post

Reply #16 – January 27, 2017, 08:43:52 pm

Quote from: Lon and Cheryl – January 26, 2017, 11:04:58 pm

I have the same leak down, What did the parts cost?

Assuming that your leak down is from the same source, the replacement valve is very reasonable -- around $60 at FOT or ~$100 from a parts supplier. Labor was a little over 4 hours, including pulling out the front wheel sensors and disabling the full ABS function in the coach (i.e. turning off the ECU).

If you are thinking of DIY make sure that you get the right TYPE valve. When I first called Haldex the tech told me informally (avoiding liability issues) to replace with a RELAY valve with a 4psi crack pressure. At FOT the mechanic was talking about a quick release valve and the service writer said they had replaced Paul's valve with a check valve. These terms are not interchangeable at all!! The actual valve they put in my coach was a relay valve.

Re: Update to ABS Valve Replacement post

Reply #17 – January 28, 2017, 12:06:13 am

We may have discovered the mean-time-to-failure on this valve. About 21 years or so? Mine hung up once before failure and I figured that we had snorted that bit of silage right out of the beast- but no. It let me down again.

I will get a detailed, written explanation from our manufacturer, I am sure, before I pay my bill. We can share the results of this new experiment with everyone interested at that time. Sound good?

If I disable ABS, I must be about even with the other SOB high-line coaches, right?

Re: Update to ABS Valve Replacement post

Reply #18 – January 28, 2017, 11:35:11 am

At one time there must have been an overhaul kit for these valves.
Like every thing else, there has to be one sitting on a back room shelf somewhere, probably a valve also!
Another item on the scavenger hunt list!

Re: Update to ABS Valve Replacement post

Reply #19 – January 28, 2017, 01:08:11 pm

Quote from: Old Knucklehead – January 28, 2017, 12:06:13 am

We may have discovered the mean-time-to-failure on this valve. About 21 years or so? Mine hung up once before failure and I figured that we had snorted that bit of silage right out of the beast- but no. It let me down again.

I will get a detailed, written explanation from our manufacturer, I am sure, before I pay my bill. We can share the results of this new experiment with everyone interested at that time. Sound good?

If I disable ABS, I must be about even with the other SOB high-line coaches, right?

I think you're right on the last point. My previous coach was a '95 Vogue Prima Vista, which was certainly another high-line offering, with neither ABS nor disk brakes.

Re: Update to ABS Valve Replacement post

Reply #20 – January 28, 2017, 01:26:09 pm

Quote from: John Duld – January 28, 2017, 11:35:11 am

At one time there must have been an overhaul kit for these valves.
Like every thing else, there has to be one sitting on a back room shelf somewhere, probably a valve also!
Another item on the scavenger hunt list!

I suspect that you're right on both points. However, in a year of searching I could not find anyone that knew about them.

The reason that I ended up back at FOT is that someone else went there and found a referenced replacement valve. However, when it was compared to the valve on my coach the electrical connections were not compatible (old 4 prong connector versus replacement 3 prong connector). I suspect that it might have worked if electrical connection specs for both were still available. FOT did not have the specs and without those specs a conversion harness would have been just a guess and not worth the potential liability. Interestingly, Haldex makes a 4 to 3 conversion harness pigtail, but only in the opposite direction. The techs that I reached there didn't know enough about these old valves to address rewiring.

There is some scuttlebutt around NAC that some years ago FOT sold off a lot of spares inventory to another RV shop there. According to the rumor that inventory was put into containers which were never opened or sorted for contents. If the rumor is true I would not be surprised if there are some valves hiding there.

Re: Update to ABS Valve Replacement post

Reply #21 – January 28, 2017, 02:05:55 pm

BillO...call up Aubrey Lee at MOT. 936-564-1112. He was the electrical engineer guru at FOT and is now at MOT, very glad that he was kept in the industry! A resource if on road and need some help but the electrical things were, I was told, his main area. You can check with him. Very nice fellow.

Encore had lots of decals and such, he tried to get molds from FOT but Bob told me that they were destroyed. Last I knew, some of that inventory was preserved by Bob out at a hanger, but I have not tried to trace that down. If it vital to have, call Stewart Canty at MOT, he may know as he has a hanger.

Hope this helps.....

mike

Re: Update to ABS Valve Replacement post

Reply #22 – January 28, 2017, 02:24:40 pm

Quote from: BillO – January 28, 2017, 01:08:11 pm

I think you're right on the last point. My previous coach was a '95 Vogue Prima Vista, which was certainly another high-line offering, with neither ABS nor disk brakes.

The 96 Monaco Signature had the same Meritor anti-loc discs as my 99 FT.

Re: Update to ABS Valve Replacement post

Reply #23 – January 28, 2017, 05:20:39 pm

John D, when I had my leaking valve issue, for the rear ABS, after many phone calls about doing my own repair, was told you needed to be DOT certified in order to repair them. Fortunately FOT had one in stock that was a direct replacement for mine. I still have my old one, still deciding on what to do with it.

Re: Update to ABS Valve Replacement post

Reply #24 – January 28, 2017, 05:35:32 pm

Quote from: Old Knucklehead – January 28, 2017, 12:06:13 am

If I disable ABS, I must be about even with the other SOB high-line coaches, right?

Not the newer ones, though

. Most of the Spartan-based have the Wabco 6S/6M ABS system. Not familiar with the Freightliner RV chassis specs.

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