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Air Drain Valves

MatthewWBailey

MatthewWBailey

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After reading a thread on here about regularly draining the air tanks, I went and open them up. No water in there as expected since it's bone dry here. BUT, after cycling them, they now leak like hell. All three are leaking air thru the handle posts. If I press the handle down it stops. The parts spreadsheet says they're Napa 12110. Anyone tried this replacement?
 
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GeneralDisorder

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That is the pressure protection valve that limits the CTIS and radiator fan to only receive air when the wet tank is above 95 psi. Probably best to just replace it.
 
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MatthewWBailey

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Ronmar said:
The regulator looking thing is the air brake protection valve. Works like a CTIS wheel valve. Halts flow when wet tank drops to ~85PSI.

take it apart and clean and inspect and or replace the rubber disc…

Click to expand...
So there's no seal on the flange? Just the rubber disk?
 
MatthewWBailey

MatthewWBailey

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Ronmar said:
Correct. If it is not cracked/deteriorated, i would add a little silly grease arount the perimeter and re-assemble it.
Click to expand...
Took this apart. The disc looked fine just dry. Greased it and reassembled. It spins freely in the seat now. I put a thin layer of rtv around the outside flange base just in case.
 
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KN6KXR

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For the air tanks I used 90 degree brass 1/4" with stainless seats. The type with the little lever on the outside. On the wet tank I installed a tee with one side a drain and the other side an air fitting. I like being able to plug a hose into the wet tank from the shop and air to 120psi so I can chase leaks and such with the motor off. Also I have point of use air. I don't care about having the OEM style it's more about reliability.

The pressure protection valve leaked when I got it. I cleaned and used Permatex #2 (just on the outside flange) but the other day it was leaking again. So I cleaned again and used some Hondabond #4 this time. If it keeps giving me issues I'm replacing it with a commercial style fixed pressure piece. That part is 3 or 4x the cost, often not in stock anywhere, and why do I need setpoint adjustability?
 
R

Ronmar

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KN6KXR said:
For the air tanks I used 90 degree brass 1/4" with stainless seats. The type with the little lever on the outside. On the wet tank I installed a tee with one side a drain and the other side an air fitting. I like being able to plug a hose into the wet tank from the shop and air to 120psi so I can chase leaks and such with the motor off. Also I have point of use air. I don't care about having the OEM style it's more about reliability.

The pressure protection valve leaked when I got it. I cleaned and used Permatex #2 (just on the outside flange) but the other day it was leaking again. So I cleaned again and used some Hondabond #4 this time. If it keeps giving me issues I'm replacing it with a commercial style fixed pressure piece. That part is 3 or 4x the cost, often not in stock anywhere, and why do I need setpoint adjustability?
Click to expand...
In the case of the PPV used on the LMTV, they may have selected an adjustable to tune its interaction with the CTIS pressure switch. The CTIS switch closes when it passes above 117PSI and opens again when it passes below ~89PSI. Since CTIS can draw so much air, the controller uses this switch input to cycle its fill cycles and force/allow the wet tank to cycle to a high pressure to keep the service tanks topped up and the brakes fully operational…

If the fixed protection valve won’t let the wet tank drop below the 89PSI switch point(the adjustable should be set for 85PSI), the CTIS won’t stop its fill cycle and will steal all the air the compressor can produce until it reaches its set tire pressure or decides to halt to check tire pressure… since CTIS times everything, it may even cause a fault…
 
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KN6KXR

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Maybe. I've run my M936A2 off shop air and not had an issue though. My compressor is a 60 gallon I keep between 120 and 150 and connect a 120psi regulated line to the wet tank of that truck. So it's like an "endless wet tank" and the CTIS works fine. The system does a check then targets the fill/deflate time based on the target and current pressure. I would like to say for certainty what the M1078A0 does but my CTIS is INOP at the moment all the tires flatten I likely have a blown hub seal and/or bad wheel valves. Chasing other things at the moment.....

I've actually been looking this morning in the TM's for the exact pressure setting of this valve and can't seem to locate it. In the CTIS troubleshooting section it just says "if no air comes out replace it". Not too helpful. On here I've seen anything between 70 and 85psi. I'd like to find a procedure in the TM's.

Just replaced the air bags and they wouldn't inflate. Found that I had the pressure adjusting screw in TOO FAR and when I backed it out they inflated. Must have done this when I re-sealed it. I think the one I have is toast it shouldn't behave like that. Looks like new ones are $200 to $250 plus any tax/ship.

I have on hand a Hendrickson B-38941 pressure protection valve it's designed for air bag suspension systems and the cut out is 65psi. Those retail for about $25. The only issue I think might be a problem with this valve is it's a 1/4" NPT and may not allow enough flow for things like the CTIS. I think I'll give it a try and keep that in mind when I get to the CTIS repair.

Still don't understand why there's an ADJUSTABLE protection valve there. The truck has other braking system protection valves that are fixed. Why install this weird one? All I can think of is CFM throughput requirement. If that's the case a set in parallel with one dedicated to CTIS might be the trick. I'd like a better solution it seems everyone has leaks and issues with these and they are pricey and hard to get hold of.
 
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GeneralDisorder

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IDK where the actual f*** you fellas are buying these for $200 - $250, but they are $79 (including shipping):

www.finditparts.com

Haldex 314013005 Air Brake Pressure Protection Valve + Cross Reference | FinditParts

Haldex 314013005 Air Brake Pressure Protection Valve ✓ Order now for same-day shipping on eligible purchases from FinditParts.com, America's online marketplace for heavy duty parts.
www.finditparts.com www.finditparts.com

🙄 🤷‍♂️

And sure the non-adjustable is still cheaper - but you are talking about using two.... so now were down to $30 and I have to modify the plumbing...... Naw I'll just buy one for $79 and swap the diaphragm into the original without even removing it (what I have done on several trucks now). 3 minutes tops aaaannnnd moving on to the next problem.....
 
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K

KN6KXR

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GeneralDisorder said:
IDK where the actual f*** you fellas are buying these for $200 - $250, but they are $79 (including shipping):

www.finditparts.com

Haldex 314013005 Air Brake Pressure Protection Valve + Cross Reference | FinditParts

Haldex 314013005 Air Brake Pressure Protection Valve ✓ Order now for same-day shipping on eligible purchases from FinditParts.com, America's online marketplace for heavy duty parts.
www.finditparts.com www.finditparts.com

🙄 🤷‍♂️

And sure the non-adjustable is still cheaper - but you are talking about using two.... so now were down to $30 and I have to modify the plumbing...... Naw I'll just buy one for $79 and swap the diaphragm into the original without even removing it (what I have done on several trucks now). 3 minutes tops aaaannnnd moving on to the next problem.....
Click to expand...
That's a slightly different part but might be the same with the exception of the end adapters which can probably be used on the one in the link. Thanks for that I went ahead and ordered one it was $91.12 after ship and tax. Oddly I did search for that part on the US Haldex website and came up with nothing.

The stock part number is N30261B and a search for that gets you MME at $220, Memphis at $210 and fleabay at $250. That's where those numbers come from.
 
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