RoadTripper2084

On my 1997 Dynasty with 130 gallon diesel tank, the owner's manual has this to say about useable capacity:

Good point re: tranny fluid expansion with temp, that's why you always check it hot. I guess it could just be that we're finally reaching warmer daytime temps here. I'll follow your advice if it continues to drip.

Okay, it's definitely a breather cap. Not sure why it would just start to leak, perhaps it's cracked at at the base or something. I'm going to monitor it and if it keeps leaking I'll try to remove it entirely and look for a suitable replacement. Something like this https://www.amazon.com/Professional-Parts-Warehouse-Hydraulic-Breather/dp/B088MGGQYH/ref=zg_bs_383872011_2/140-0237624-2839629?pd_rd_i=B088MGGQYH&psc=1 might be comparable.

Well I haven't added any fluid to this tank, and it never leaked before. I also hadn't extended the generator recently when it began to leak. Could warmer ambient air temp. cause the fluid to expand? Doesn't sound like the kind attribute that you'd expect transmission fluid to have. 🙂 The cap seems like it might be meant to act as an air vent, but access is limited so I can't really tell how it's put together, other than it turns when I turn it, and the cap itself can be removed by pulling it straight off.

Yesterday I noticed a puddle of fluid under the front of the coach(1997 Monaco Dynasty) and traced it to the small hydraulic fluid tank used to slide the generator tray in/out at the front of the coach. The fluid seemed to be leaking out of the cap area. What I can't figure out is how the cap is supposed to work. I though I could tighten it by turning it clockwise, but it just turns in circles without getting tighter (it offers medium resistance when turned). Then I realized the plastic cap pulls straight off the top, no threads. Seems to be a small foam patch on the underside of the top of the cap, maybe meant to be a breather of some kind.Can anyone explain how this cap should work, can I tighten it?, and why it might suddenly have started to leak fluid?

Beautiful rig btw! Go team Blue! 🙂

Nevermind, you already answered my question. Both. There is an air line from the wet tank at the front to the governor, which it uses to sense the air pressure. Fills to cutoff pressure (generally 125lbs or so), and then disengages compressor (and triggers the air dryer purge valve), then when it sense a pressure drop of 20-30psi it re-engages the compressor.

Ah, sorry I missed that detail. If your air pressure governor wasn't cutting out at 125lbs you would hear the overpressure valves on the wet tank (1/2 of the front tank) releasing at 150lbs. You would also see 150lbs or thereabouts on your air pressure guage, which you are not. It still seems likely that the air dryer purge valve is sticking, though it could also be the rear brake relay valve in that area, it also has a large purge valve on the bottom of it. My front brake relay dump valve recently stuck open and caused rapid air loss, resulting in continuous cycling between 90-125lbs and eventually made it so my compressor was unable to keep up to the leak at all. But in my case the leak was easily heard when the coach was shut off. I'm just waiting for new o-rings for it and will re-install, though I'm certain the debris that was causing the leak is now gone. Note that I'm far from an expert on this stuff, just another guy learning as I go.

Yes, the regulator disengages the compressor when 125lbs is reached, and triggers the purge on the air dryer. You were seeing continuous cycling while driving between 125lbs and 90lbs, correct? As if the compressor would fill to 125lbs and be disengaged, but then the air would rapidly leak down to 90lbsish and then the compressor would kick back on to refill to 125lbs, etc. ?

I would suspect the purge valve on the bottom of the air dryer isn't sealing 100%. Usually you can tell if you run the motor and stand outside near it so you can hear it when it purges, it will continue to leak after the purge, and not end in a crisp Pffssst! sound. 🙂 I have the same model air dryer on mine, do you happen to know what make/model it is?

Sorry to hear about the rough road, sounds terrible. The compressor is mounted to the passenger's side of the engine, and is gear driven off the engine. On my 97 Dynasty (C8.3 as well) the air dryer/purge valve is mounted behind the passenger side rear axle. If you crawl under the coach behind the rear mud flap you will find it. Make sure you brace the coach first using jacks or some other mechanical means of keeping it from potentially dropping down on you while you're under it. Can you tell if the leaking sound is coming from the front axle area or the rear closer to the engine? You should be able to try fast idling until your air pressure in both tanks hits 125lbs and the air dryer purges, then shutting the motor off and quickly going outside to listen for leaks.

Okay I found another diagram from a difference source that does show there is a 2-way check valve in the mix. So the purpose of the 2 way check valve is to provide air to the abs relay for the front service brakes from either the front (secondary) air tank or the rear (primary) air tank, whichever has the highest pressure wins. Idea being that if one air system fails and loses pressure the other can keep your brakes working. In my case though the front abs relay is stuck dumping air - that just means that each tank takes turns dumping all its air out the relay trying to keep the front brakes pressurized. The reason the rear tank wasn't complely empty (25lbs or so) is probably because the tolerance of the 2-way valve requires higher pressure than that to switch inputs. So my abs relay is either failing in such a way that it: A) Thinks it should be quick releasing the front brake air continuously. In order for that to happen "normally" I think the air pressure from the brake pedal would need to first be present (brake activated) and then release. Since I have little air pressure and am not working the brake pedal (though I did try pumping it a few times, no difference), that seems unlikely. B) Is just fundamentally borked in such a way that the input air is being vented directly out the vent. Sounds like B is most likely. Okay, plan is to pull the abs relay tomorrow (if there isn't 6" of water pooled under the rig after all the rain we just had) and then tear it apart to see what I can see and look for a part number.

So another thing that is bothering my about this leak is that if the leak is in the front service brake abs relay, shouldn't that be solely connected to the Secondary/Front air tank? With this leak I'm seeing both tanks deplete, the primary down to approx. 25psi and the secondary to zero. I am also unable to add enough air at fast idle to gain more than approx. 30psi in both tanks. I do see a line connecting the secondary / front dry tank to the rear primary tank, which also connects to the same outlet that the front service brakes do, via the abs relay which is leaking out the exhaust port (see below). I'm confused as to why/how the primary tank connects to the secondary tank in this manner. It would seem to violate the isolation of each tank circuit. As you can see in the diagram, the wet tank (half of the front tank) connects to the rear tank via the Red 5/8" line that has a check valve to prevent backflow into the wet tank half of the front tank. But there is also the Silver 1/2" line that seem to directly connect the rear tank to the front dry tank at the service brake fitting, with no apparent check valves. This would explain why both tanks are leaking out of the front service brake abs relay, but doesn't really seem like a sound air brake design, I would have expected the rear tank to be reserved for the rear service/parking brakes.

Well that story paints a real horror show scenario for a DIY guy. Point made!

So that certainly is a close match for mine in terms of overall shape and number of ports, etc. Of course I need to remove mine to see if I can find a part # on it to be sure. I have no idea about the actual specs, etc. I did find this model that was 12v instead of 24v: https://www.wabco-customercentre.com/catalog/en_US/4721950340 The explanation of how it functions also matches my own expectations: Thanks for this!

That does look very similar to mine, I guess the thinner top line could be electrical as well. I don't believe I have ATC but couldn't say for sure. It was one of the earlier ABS equipped coaches, back when they still put "ABS" on the back of the coach as a feature badge. 🙂 Can I ask where you found that picture?

You may be correct. Looking at this diagram, it looks like the middle valve that is leaking may be the quick release valve for the front brakes. And that the hoses go from it to the ABS modulator units on each brake can. I had found another diagram earlier that made it seem like it could be the ABS modulator, which I can't seem to locate now. Any ideas on what the brand or model might be?

You are correct, this was my original thought as well. The top smaller line goes from the small valve assembly off of the front tank to the valve, this seems to be the control line from the pedal. The two lines on each side go directly to the brake chambers on each side. There is also the larger source air line from the front tank to the lower center of the unit, and then one more larger line above that and to the right. Not sure where that one comes from. Upon further reading it seemed like this was the ABS Modulator unit, perhaps combined with the function of a normal brake relay valve.

Yes, 30 PSI is when mine engages. So the leak occurs with or without the parking brake engaged. The leak is in the front brake system and the front brakes don't have spring/parking brakes, so it makes sense that having the parking brakes engaged or not makes no difference. It seems like the component I have circled above is failing and simply dumping all the air that goes into it from the tank. But I am wondering if the brake pedal treadle could be the cause, if it was resulting in continuous air pressure being fed to the abs modulator, resulting in the modulator dumping air. But logically, as far as I understand how this system works, the abs modulator should only dump air if the air pressure from the pedal is less than that of the front brakes (when the brake pedal is released after engagement). In my scenario, there is no pressure in the front brakes (brakes are not applied), and the air is continuously being dumped. I will need to remove the leaking valve and clean it up to see if I can figure out what brand or model # it might be. If anyone has any idea which company might have provided this part on a '97 Dynasty I'd be happy to hear it.

Just came back from a very nice weekend of camping. On the way back into town 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. Not the kind of excitement of I was looking for. Things I noticed while driving: - Large hissing sound from under the middle/rear of the cab section of the coach. - Small hissing sound from under the brake pedal itself when holding the brakes in (normally no hissing while holding the pedal at a stop). Now that it is parked, I am unable to build more than about 30lbs of pressure in both tanks at fast idle (1200 rpm). Got under the coach, sprayed around the front tank area with soapy water and quickly found the leak, a lot of air coming out of the purge valve on what I *think* might be the air brake ABS modulator. I'm basing this on the Monaco Dynasty air system chart I have (general location) and the fact that it has: - 2 x lines, one each running to each of the front brake chambers. - 1 x smaller line from the top of the front tank, where the diagram says the brake pedal connects to the ABS. - 1 x feed line from the secondary/front air tank - 1 x another line, or maybe it's an electrical connector, not sure. Too complicated to be much else, no? 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? Is there any chance the problem is actually elsewhere, like the brake pedal unit itself? I did hear light hissing from the pedal while stopped but am wondering if it would do that if the pressure was being bled off by a faulty purge valve on the ABS unit? 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 took (this is for an 1997 Monaco Dynasty, 36', single axle).

...but the DEF! 😉 Wow! That is one beautiful coach. I'm not always a fan of the interiors on the Newells but this one is really nicely done. It must feel like you're driving a spaceship in that thing! 😀 Happy trails and thanks for all our contributions here.

Lol. Correct you are! Sorry I should have been more explicit in my posting, that picture was taken after I remove the bolt. It's all good. Just completed a 3K mile trip without issues, very happy with the steering setup on my rig now. On a related note, my steering wheel has started to squeak from sort of under the horn area sometimes. I don't see any grease nipples in that area so not sure what I should be trying to lube to eliminate the squeak. Thoughts?

3 jack setup procedure is to always drop the front / center jack first to give the coach frame a pivot point, then you can you drop the rear L and R jacks. Always use the front jack even if you're already level front to back. Also, always drop all 3 jacks even if you only need one to level the coach, the load needs to be distributed across 3 jacks for stability.

Mine is a standalone panel in the engine bay at the back (side radiator). I have the start-detect input running from the fuel-start circuit, which was readily available in the panel, seems to work. I'm also happy to report that this solar panel IS keeping my chassis battery topped up while parked, but with the chassis battery enable (not cuttoff). It just needed some more direct southern sun exposure this time of year (southern Utah). My voltages vary from 12.9-12.6 🙂

Well the RRB has a vent port in the bottom right corner and top left corner, so I assume it will vent alright. Also the exhaust fans on the Renogy are at top of the device, so should be pulling cooler air from the bottom vent and exhausting toward the top vent. Though I haven't measured the temps at all.