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thebaz

R Model Air start losing air over two days

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i have an R Model Mack with a 350hp motor and ingersoll Rand air starter. I have had the truck close to 30 years and have really not had much trouble with the air start at all. I replaced the seals in the Sealco 14900 starter valve many years ago for reasons that escape me now, but I have never really had any problem with losing air from the start system. I have checked all the fittings for leaks and found nothing.

I am suspicious of the check valves and the starter valve. Are the check valves anything special? The ones fitted have "closed  U" and "5      76" stamped on them but no other markings i can see.

The tank has two check valves, one after the supply line from the wet tank and one before the female fitting for refilling the tank from a compressor or the like in the event of air loss.

I am hoping to replace the valves and re-seal the start valve and see if that fixes the air loss. The truck used to start no pr0blems even after 45 days or so of not being started.

Any advice is very welcome.

 

Baz

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Baz I think your onto it the air starts out here I have seen all have to non return valves (check valves) in series on the fitting you hook a air line to on the air start tank it's self and these are the ones I have had to change

I could pour a little bit of water down the inlet and watch the bubbles slowly form

But if that didnt fix it I would try everything you have mentioned and also check the air lines for any damage or chaffing

Maybe a little squirter bottle with some very soapy water might help

 

Paul 

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Hey Paul,

I did the spray bottle thing and sprayed everywhere I thought there was possibility of air loss. I even disconnected the supply line at the check valve to see if air was leaking and it appeared not to be.

It later occurred to me that when the air lines were in situ, there would be equal pressure on either side of the check valve meaning that there would be little pressure on the rubber disk and seat so it could lose pressure from the start tank as the whole system lost pressure, whereas if the supply line was disconnected there would be 125psi pressure on the disk and seat and the check valve would be less likely to show a leak. When I replace the check valves, I will fill the tank and see if any air escapes trough the port on the start valve going to the starter which is what I suspect will be the culprit.

Unfortunately, when I tried to remove the check valves the T fitting broke off the tank. I have managed to remove the broken 1/2" fitting, but figure I will re-assemble it when I get new valves.

 

Baz

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 I just put a kit in my Sealco 14900 valve.  Kit #109-5.   Mine lost air in hours, it seems better now, only dropping a few pounds over night.  I hope it is just the cold(it's 45 in the garage).  I'll check it later today to see if it is holding steady.

I plugged the tank using a gauge in one fitting and a air line fitting in the other with a 1/4 turn ball valve.  I'd like to put a balloon on the output side of the starter valve to determine if it is still leaking.  I want to make sure it is pretty tight before I get all this stuff installed on the truck.

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Does your tank have a pop off?  I just realized mine did and think that was my leak.  I plugged it and retesting.  I also found the drain plug was a bit loose too.  

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I had a look for it and didn't find it, I have to take another look as I have seen these leak before. I did give every fitting i could find a good dose of soapy water and nothing showed a leak including the drain tap.

 

Edited by thebaz

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Soapy water is good but if you will go to a store who sells propane or supplys and buy some propane detector and put in your spray bottle you will be happy with the way it bubbles forever when it finds a leak.I used it years back when i worked on propane powered trucks and you dont have to spay very much on and hors later its still bubbling.

Edited by theakerstwo
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1 hour ago, theakerstwo said:

Soapy water is good but if you will go to a store who sells propane or supplys and buy some propane detector and put in your spray bottle you will be happy with the way it bubbles forever when it finds a leak.I used it years back when i worked on propane powered trucks and you dont have to spay very much on and hors later its still bubbling.

I have never heard of that before, thanks for the heads up.

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The pop off on mine was not the typical big external model.  It looked just like a pipe plug, til I unscrewed it and saw the spring on the inside.  This is an aluminum tank.  I have a couple steel tanks and they have no pop off valves?

I rechecked mine this morning and it was not down at all from yesterday, so I think I found what was wrong(loose drain plug and maybe the pop off).  I have a few new pop off valves so I'll replace the original.

Edited by Freightrain

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I replaced both check valves and used all new fittings for the tank supply. Sealed the threads with Loxeal 18-10 and fitted a seal kit to the starter valve.

I am going to give it a day for the sealer to really go off and see how it goes.

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I looked at mine this morning, still hasn't moved from Sunday.  Guess mine is doing okay. 

I hope you got yours fixed.

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Put the truck back together on Friday, started straight up Monday afternoon. So far so good.

Anyone recognize this check valve on the brake tanks?

DSC_4074.JPG

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Could be Sealco?  That is what my starter tank had and was similar 90* set up.  Could not find one online looking at their website(they dont list anything 90* anymore).  Going to replace with something else.

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Yeah, I think I may have to go with a straight one and just fit an elbow to it.

 

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Thanks Freightrain,

I did come up with that myself in a search, but it would not be cost effective compared to using a straight one and an elbow by the time I had it ship to Australia.

The threading is the right way around BTW for my truck.

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Aye Mate....I see your point.  :thumb:

(I didn't realize you were from down under.  The air starter wasn't a big enough clue for me :lol: )

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Well, an update. The check valves on the brake tanks seemed to make no difference to the air loss on the general system, but the starter system is now working well and holds air like it used to and I no longer have to drag the compressor out to start the truck.

I will start searching with a spray bottle for the air system leak and see what comes up.

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1 hour ago, thebaz said:

Well, an update. The check valves on the brake tanks seemed to make no difference to the air loss on the general system, but the starter system is now working well and holds air like it used to and I no longer have to drag the compressor out to start the truck.

I will start searching with a spray bottle for the air system leak and see what comes up.

Just a thought, have you checked around and under the straps that hold the air tanks to the brackets for pin holes caused by rust or corrosion?    Paul

Edited by 41chevy

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I will check that out Paul. The truck dropped from 125PSi to 100psi in around 8 hours which is not bad but it used to be better than that.

It is nice if I can hit the starter and idle out of the driveway within minutes to keep the neighbors happy if possible.

 

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What kind of start button?  Air control or electric?  Might be the valve that is draining air off the system.

I have my system on and working.  When I was testing the tank, I only had the big valve on it and it held for a week with only a dropping a couple pounds.  Now with the system installed, it seems to loose more, but not horrible.  Almost 20# in a week.  I removed the pressure relief valve to see if that helps.  It did.  My assumption is that being so close to "pop off" that it actually is loosing ability to hold the pressure fully.  I have a relief on the wet tank so this was just a secondary(tank had one on it when I got it).  It is still down a few pounds, but not 20#.

I have a brand new air button on the dash, so likely it is not he reason for my losing pressure.  Even with new check valves, I bet they are the reason for my small loss.

 

Edited by Freightrain
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I am not losing any air now from the start system, only the brake/air supply side of things. I didn't need the truck for a few weeks and it started up easily, but the brake side is down to 60psi after 24hrs.

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Ah, my main side dies off in a few hours.  I'm thinking it is the air wiper switch(again).  Used to last a day or so.

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Went to start the truck today, out of air in the start tank. Grrrrrrr!!!

Will have to investigate further now.

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