Air system relief valve opening on M925...Frozen air lines/valves?

Started the M925 up yesterday, jumped out of the cab to move some snow while it warmed up.......and came back to what could only be the emergency relief valve opening on the system (very distinct sound....like letting the air out of a balloon). I jumped in the cab, looked at the gauges, and both the primary and secondary were showing 150+. I shut the truck off, opened the 4 petcock valves at the air tanks, and restarted. The air system built back up to 120 and didn't stop, so I shut it down again. I also noticed the manual front axle switch has no pressure, nor the wipers.....and when I went from high to low transfer.....it will not go back (air switch stuck?)

Instinct would tell me the lines are frozen, though it has air drier in it (ABS modification). The governor would be my next step after checking the air drier. I don't have the ability to bring it into heat....but could set a salamander with about 100K btu in front of it (when the wind stops a little).

Is there a winterize kit on the M925 (didn't see an evap bottle anywhere) that I might of missed?

Thank you

Hmmm,


I am no mechanic but I wonder if you have frozen water in your air lines
someplace. The govenor is suspect IMO. How hard is it to pull it, bring
it inside and let it thaw and examine it or how old is it? How about
just pick up a new one? I know throwing parts at a problem is
not real professional but the first 4 words of my post are?

If you add a QD so you can pump the system w/ air and if all
works well I "THINK" that ponts harder at the govenor.

Keep us posted ...

I would also check the governor.

I just had the very same issue(one day after Wheelspinner said he did also).

I simply let it run for 20 minutes and all was well.

Did some more research in the TMs. Everything points to a defective/and-or frozen pressure protection valve. This valve assures full brake tanks before any accessorie including wipers, horns and governor receive air. I plan to heat it today with a heat gun. DH, running at overpressure for 20 mins is not a real good idea for many reasons.

Thank you gents.

I'll try a heat gun at the protection valve. I use to use it for R/C modeling (when applying covering to wings)......should work for this application.

Merry Christmas!!

It worked!!! A heat gun applied to the protection valve for about 5 minutes and it did the trick. The protection valve is on the front of the wet tank just to the right (when looking back towards the drier). I plan on changing the desiccant canister (the black can in the background of the picture) to be safe.




Thank you

Bob

p.s. I called S.S. member JBL to verify what happened here......common problem with "winter going 5 tons".

Bob, glad to hear. I still haven't had a chance to go out and thaw mine out.

I've got 1 more those new somewhere. if you want it let me know and I'll send it your way. My 900 was missing them when I got it and I bought too many of them.

jwaller said:

I've got 1 more those new somewhere. if you want it let me know and I'll send it your way. My 900 was missing them when I got it and I bought too many of them.

Click to expand...

Darn!!! I just picked one up on E-pay. Next time, I'll put a "want ad" in before buying outside of the "family". Thank you for offering.

Oh.....a side note on my heat gun: it goes up to approximately 350 degrees. Anything more (such as a blow torch or the like), I would worry about damaging the valve or the line (that would be a whole new level of "fun" while lying in the snow to work on the truck).

Neophyte said:

Darn!!! I just picked one up on E-pay. Next time, I'll put a "want ad" in before buying outside of the "family". Thank you for offering.

Click to expand...

Can you PM me that link please?

Pm'd link Artisan

Sounds like the desiccant in the dryer needs changing.

Years ago when I worked up north, NWT area we had fittings on the trucks so we could put methyl hydrate in the air line at various plaices. I don’t know if this would work in this case but it would be something to look into. Worked fast to thaw out a frozen spot. I don’t know if the newer air systems would except it or not so asking around would be a good idea.

Roger that and Thank U

Neophyte said:

Pm'd link Artisan

Click to expand...

put methyl hydrate in the air line at various places

Click to expand...

I was going to suggest Methanol however there are concerns with using alcohol in the air system. Particularly in those that don't already have a alcohol tank, because the system was designed without one.

Alcohol is bad for the air lines, and dampeners in the ABS system, it also reacts poorly to the desiccant in the air dryer.

If we are talking one time use then I see no issue but we tend to forget people begin to rely on what works. Then the unknown on where it's best to add the alcohol to. There are those that suggest adding it to the wet tank, but with the concerns of what desiccant is in the dryer, and how it would react. It's probably best to add it to the dry tank to polish off any moisture the dryer missed.

Which brings me to my point, if the dryer was working properly and the air system was purged regularly. This wouldn't be an issue.

Cheers

It's likely the drier as the wet tank is the first to get air from it, then the protection valve. Petcock #3 has never let water out after each run (unlike my M817 which spits like Daffy Duck). I'll change the desiccant and report back.

Desiccant canister installed.......not sure of quality of product from supplier

I received the desiccant canister yesterday and found an issue. I purchased the canister from E-pay and the surplus supplier had a 99.7% satisfaction rating. The problem is the aluminum sealant bag has a hole in it......not something I would of thought about, and likely he didn't look at it before shipping (was boxed up in OEM packaging). The date is 2007, so likely wear and tear moving it around over the years. The canister feels "heavy", even when comparing to current canister, so likely I'll need another. I read his return policy, and as a surplus supplier, no returns (understandable).

Moral of the story......buy these canisters new (not NOS) if possible, or from someone you know that has inspected it. I will seek to buy from our members as I've had nothing but success (though this product didn't strike me as being shelved by many on S.S.'s); do not buy these from E-pay.

As a side note, my "just replaced" canister was not screwed down tight (was loose by a full thread)....letting moisture in (see pictures).

Having fun....for this isn't work.

Neophyte, can you tell me the part number on the desiccant and the filter for the air dryer?