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Fix for air leak - M35A3

Rustygears

New member
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Location
Ramona, CA
I'm passing this on because I see threads for the A3 regarding both air leaks and PS issues.

I noticed the air dryer cycling fairly rapidly and the gauge pressure dropping on my A3 when just sitting and idling. Since there aren't many other items that consume significant air aside from brakes and PS, I figured something was wrong. I started checking around and thought I heard air leaking after shutting down the engine in the engine area around the compressor unloader valve. Before replacing it, I looked more closely and found the PS regulator neatly tucked up in the frame rails immediately below the compressor. It has a little cylindrical cover on it with a small hole in the bottom. By pressing my thumb over the hole, I could feel the air escaping it and the slight hiss that I had previously heard change sound. After then finding the PS air shut off petcock on the firewall and isolating the PS system, the truck guage bleed down stopped - found it!

I bought a replacement reg on ebay and in order to figure out the proper setting for the PS pressure, bought a schrader valve (tire valve stem type valve) having a 1/8" pipe fitting at Napa for $3 and installed that in the old regulator monitoring port (hex cap screw at the to of the reg in front). I then used a tire gauge to measure the pressure at the reg output via the schrader valve. The system was set too high (over 100psi), but reducing the pressure setting it didn't stop the leak. The reg was still working, just leaking from around the pressure adjusting know area.

I installed the same schrader valve on the new reg and replaced the old reg in the truck. Using the schrader valve, I set the pressure on the PS for 60psi on the new reg and then capped the schrader with a metal/gasketed valve stem cap to seal and to also keep the crud out.

Needless to say, the truck now holds air for days and the dryer cycles very infrequently when idling with no brakes or PS being used. This will save needless wear and tear on the compressor, unloader, dryer, etc. and the truck system keeps a constant 120psi now.

The schrader now remains as a permanent part of my PS air system and I'll use it to monitor/troubleshoot future issues should they arise. I figure the $3 spent on it is a lot more cost effective than buying and mounting a gauge on the reg, especially considering the gauge will get gummed up, etc. in that mounting location and likely not be working when I really need it. I always have a working tire gauge available! Total repair investment: $32.
 

Rustygears

New member
394
6
0
Location
Ramona, CA
I'll snap some tomorrow and post.

Hope folks find helpful. This is my attempt to 'give back' since I've found so much useful information at this site that helped me learn and repair/avoid issues.
 

mktopside

Banned
467
6
0
Location
Gainesville, Va
I hate that F'ing regulator. One day when I take it off I'm going to baseball bat it into the next state.

Welcome to the A3 distributed terrorist network. We get made fun of a lot, and we have to bounce from A3 thread to A3 thread to stay one step ahead of everyone else. Remember, every A3 thread is an "A3 General info" thread.

You'll learn the secret hand shake in the next thread.
 
365
3
18
Location
Anderson Creek, NC
So, have you experimented with different regulator pressure on the PS performance? Some have suggested that 120 psi is ok. Anything in the manuals about that?
 
Last edited:

Floridianson

Well-known member
Steel Soldiers Supporter
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Location
Interlachen Fl.
yea I thought there was a thread or post about not putting the reg. in line when you install the new units just run them at what you got for pressure.
 

rchalmers3

Half a mile from the Broad River
Steel Soldiers Supporter
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Location
Irmo, South Carolina
Rusty,

Thanks for the post with your diagnostic routine and solutions. I appreciate the contribution even though I don't have an A3. Someday I'll make the switch.....

Rick
 

rwoods

Member
258
4
18
Location
Greeneville/TN
My first A3 leaked like crazy at the regulator. Took a lot of time to find the leak as it was so bad it would empty the tanks before you get under the truck to find it and you couldn't hear it with the engine running (the NG had simply shut the valve at the firewall which eliminated the leak and the air assist). Long story short, I took it apart and lube the diaphragm with spit as I had nothing else handy. This fixed the leak and it continues to work after almost two years. Ron
 

renovate7

Member
422
7
16
Location
Florida
Thanks for the pic. Great idea. Just want to confirm the pressure reading at the schrader is the out put pressure to the steering system.
 

Rustygears

New member
394
6
0
Location
Ramona, CA
Yes, the measured pressure is the regulator output. If you pull out the hex setscrew used as a plug , you can see the passage to the output port. There is a similar screw on the opposite side of the reg that also taps the output port. I was originally concerned that one side measured input and the other the output so I removed both and confirmed that both monitor the output port.

Have fun!
 

Derrickl112

Well-known member
Steel Soldiers Supporter
2,655
84
63
Location
Southeast MI
My first A3 leaked like crazy at the regulator. Took a lot of time to find the leak as it was so bad it would empty the tanks before you get under the truck to find it and you couldn't hear it with the engine running (the NG had simply shut the valve at the firewall which eliminated the leak and the air assist). Long story short, I took it apart and lube the diaphragm with spit as I had nothing else handy. This fixed the leak and it continues to work after almost two years. Ron

i used an air compressor to fill the tanks on my 5ton so i could listen for leaks. worked great.
 

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