Air Brake Leak / Info for 1997 Dynasty?

[RoadTrip2084]

My rig (1997 Monaco Dynasty 36' non-tag) has developed a fairly massive air leak in the front brake system.

On the way back from a recent trip I noticed that both air tanks were cycling between 125lbs and 90lbs fairly frequently, maybe every 10 mins or so, which is not normal. Then when I was making the short trip to the storage lot I started losing pressure in both tanks quickly, below 90lbs. I was just able to roll into my spot before the emergency brake engaged due to low air pressure.

At this point, the leak is continuous whether I apply the foot brake pedal or not. I am unable to build pressure in either tank higher than about 30PSI under fast idle (1300 rpm).

Upon investigation the culprit was found to be a stuck dump valve in the front braking system.







I'm not sure what this component is, it seems to have a bit more going on than I would expect from a simple brake relay valve. I found one diagram for this era of coach that indicated the ABS Modulator could be in this location. According to the air system diagram I have this could be Monaco part #01807254.

Can anyone confirm that I'm dealing with a faulty ABS Modulator?

Also, any idea what make, model, part# I should be looking for for a replacement? I didn't see any writing on mine in the pictures I have taken.

[RoadTrip2084]

Upon further review of my air system diagram, dated 1997, it seems that this component might be the front brake quick release / divider valve, and not an ABS modulator.



Can anyone confirm and or provide ideas on the manufacturer or model #?

[veraken]

Here's are 2 pdfs that may help you.

[RoadTrip2084]

Originally Posted by veraken

Here's are 2 pdfs that may help you.

Thanks for those.

A fellow on the Monacoers forum has found a very similar valve to mine, it seems to be an ABS Relay Valve.



https://www.wabco-customercentre.com..._US/4721950340

Now I need to remove mine and see if I can find a part #. The linked above has the same port arrangements but not sure about actual specs, etc.

[Craig1960]

I will have to look but I have a brand new one if you can't find one. I bought it last year when my mechanic said mine had a slight leak and he couldn't find a new one. Now it turns out he was wrong about the leak.
I will check the part # on mine today. I was just going to keep it in case but if you're stuck I would be willing to help out and live just outside of Edmonton.

[RoadTrip2084]

Originally Posted by Craig1960

I will have to look but I have a brand new one if you can't find one. I bought it last year when my mechanic said mine had a slight leak and he couldn't find a new one. Now it turns out he was wrong about the leak.
I will check the part # on mine today. I was just going to keep it in case but if you're stuck I would be willing to help out and live just outside of Edmonton.

Wow, that's incredibly generous of you!

At this point I should just get it removed, cleaned up, and disassembled to see how it looks. Could be as simple as a small piece of crud jamming up the works. Unfortunately, as you know, the 50-90km/h winds and heavy rain will keep me from that for a few days anyway.

Having the correct part number would be great, so I'd appreciate it if you could look at up for me.

[Craig1960]

Thanks just trying to help out a follow RV'er. I know there are at least 2 different ones so this might not be the one you need but this is what I have.

[Craig1960]

I don't know why but it would only let me add one picture, here is another view of it.

[RoadTrip2084]

Originally Posted by Craig1960

Thanks just trying to help out a follow RV'er. I know there are at least 2 different ones so this might not be the one you need but this is what I have.

Thanks. That one doesn't really resemble mine very much, does your have 4 ports + the drain, or 3 ports and a drain?

[Craig1960]

Mine is a 2 port, the white cap is for the three prong electrical plug and the rubber boot is the exhaust. They must have changed it in 98 on the Windsor.

Edit: Sorry just reread your second post and realize you are looking for the relay valve and not the ABS Modulator valve.

[RoadTrip2084]

Originally Posted by Craig1960

Mine is a 2 port, the white cap is for the three prong electrical plug and the rubber boot is the exhaust. They must have changed it in 98 on the Windsor.

Edit: Sorry just reread your second post and realize you are looking for the relay valve and not the ABS Modulator valve.

Okay, that makes sense. Well thanks again for the offer!

[Craig1960]

Sorry I couldn't help out.

[RoadTrip2084]

Progress report, I got the abs relay off the rig yesterday, such fun crawling around in the mud under the coach.

I was convincing myself that the real problem might be elsewhere, like in the brake pedal valve itself, but sure enough, if I blow in the input port it vents directly out the dump valve.

So the valve is covered in the factory undercoating tar. I thought I'd try to clean it up a bit before cracking it open and made the mistake of spraying it liberally with brake cleaner. Well that softened the tar and partially liquified it, but wasn't able to take it off much. So now I'm dealing with a sticky wet valve that gets tar all over anything that touches it. Oops.

Btw it's a Grau Model 364140121, manufactured in 1996.



A websearch turns up nothing for this, btw. I'm still confident that the Wabco unit (https://www.wabco-customercentre.com..._US/4721950340) is a close match.

After opening it up it's amazing how simple and elegant these valves are. I was also impressed with how clean the inside of the valve was, I was expecting a horror show of grey greasy water all over everything from watching truck-repair videos on youtube.



I sprayed the bottom valve liberally with WD-40 and then rinsed water through it. Bingo, the valve seats perfectly again and will no longer pass air from the input port to the dump.

I noticed that a few of the o-rings are looking rather haggard, could likely be at least one source for contamination, small bits of rubber getting stuck on the valve seat causing it to leak.

I'm currently trying to source either this rebuild kit from Wabco (https://www.wabco-customercentre.com..._US/4721959262), or as many of the individual o-rings that I can find. These are not common metric sizes so will need to contact a speciality fluids place on Monday if the Wabco kit isn't readily available locally.

I'm still concerned about why this leak caused both the front and rear tanks to drain though, there doesn't seem to be a valid reason for that. It's possible I have a failed check valve somewhere as well.

[96 Wideglide]

Seems pretty common for your two dry tanks to drain at about the same rate.

I would just repair that issue, and go from there.