Seneca - Air Tank Bendix Drain Valve

[Crossingover]

The front drain valve on our forward air tank is not sealing properly and leaks air. Not a lot of air and not all the time, but enough to hear when walking past the tank. I can manually re-seat the drain port by sticking a screwdriver against the valve stem. Has anyone rebuilt theirs, and if so, what was the difficulty level? Don't know if it matters, but our rig does not have an air dryer.

[SloPoke]

Last winter, we had a similar issue. I let the air bleed down and then pushed in on the valve to release a large amount of air. It blew out a chunk of crud, sealed back up and I have not had an issue since.

I did research replacing it, rebuilding it and other options.... Since It has not acted up since - It's fallen low on the list of things to do now.

[javamon]

Originally Posted by Crossingover

The front drain valve on our forward air tank is not sealing properly and leaks air. Not a lot of air and not all the time, but enough to hear when walking past the tank. I can manually re-seat the drain port by sticking a screwdriver against the valve stem. Has anyone rebuilt theirs, and if so, what was the difficulty level? Don't know if it matters, but our rig does not have an air dryer.

The rebuild kit is Bendix 282134 and consists if a new rubber diaphragm, diaphragm support cage, and gasket. It looks very simple and according to the directions you can replace it by just removing the valve cover.

https://www.ebay.com/itm/MAINTENANCE...-/303103786380

I have not changed one yet but I carry the repair kit just in case. Once you have a repair kit, you may try just taking the valve cover off and cleaning the entire diaphragm and spraying it with silicone (do not use WD-40). As long as there are no tears and the pintle is OK, a good cleaning should do the trick.

I also carry a pull-drain with a 60" lanyard as an emergency back-up. With this, I could pull the valve entirely, replace it with the pull-drain, and be on my way.

https://www.amazon.com/dp/B00BBZGWIC...v_ov_lig_dp_it

If you take yours apart, please post some pictures. It would be good FYI for the rest of us.

Good luck with your repair!

[SloPoke]

Back when I was contemplating a rebuild... I talked to my buddy Ron (diesel Fleet Service Manager) who cautioned me to get the part number off my valve. He says there are some variations between these, and you have to get the right rebuild kit for your part number. He said his part book shows they used different valves on different year M2's

[javamon]

Originally Posted by SloPoke

Back when I was contemplating a rebuild... I talked to my buddy Ron (diesel Fleet Service Manager) who cautioned me to get the part number off my valve. He says there are some variations between these, and you have to get the right rebuild kit for your part number. He said his part book shows they used different valves on different year M2's

I've only been able to find two part numbers: 28134(Bendix) and 28134K(Haldex) and they are supposed to be interchangeable. I think I'll take one of mine apart soon and check it out. I'll update this thread when I do. I don't like to learn about this stuff on the road and I damn sure don't want to burn up my compressor.

[SloPoke]

Originally Posted by javamon

I've only been able to find two part numbers: 28134(Bendix) and 28134K(Haldex) and they are supposed to be interchangeable. I think I'll take one of mine apart soon and check it out. I'll update this thread when I do. I don't like to learn about this stuff on the road and I damn sure don't want to burn up my compressor.

I hate on the road repairs too... Ron told me that even if the valve was stuck in the wide open position, it will not allow enough air to bleed off of the air system to cause a "low air" situation as there is a mechanism in it that limits the amount of air-flow to be a fraction of the compressors capacity.

How he explained how it works, when the air pressure builds up to the point where the compressor is going to shut off (pressure is built up) then the drain-valve will purge for a second and flush out any moisture. Since the air pressure is constantly going up / down due to brakes / fan / suspension and that kicks in the compressor - the pressure reaching the top of the range is when the condensate valve will actuate.

[LoveLife]

I have those auto drain valves on my 2016 and had the front valve leak too on trip to FL last year. It was totally plugged with crud/sediment. Diaphragm was in bad shape. I had the front one replaced at small truck stop in SC off I95. When I got to Jacksonville I had Freightliner dealer change the rest of them out with all new valves. New valve assembly is about$60-$80 each. I believe this to be a common flaw on the auto drain set up. Bendix does not want to fix as they make money on dryer systems. I will likely install a dryer soon.

[javamon]

Originally Posted by SloPoke

I hate on the road repairs too... Ron told me that even if the valve was stuck in the wide open position, it will not allow enough air to bleed off of the air system to cause a "low air" situation as there is a mechanism in it that limits the amount of air-flow to be a fraction of the compressors capacity.

How he explained how it works, when the air pressure builds up to the point where the compressor is going to shut off (pressure is built up) then the drain-valve will purge for a second and flush out any moisture. Since the air pressure is constantly going up / down due to brakes / fan / suspension and that kicks in the compressor - the pressure reaching the top of the range is when the condensate valve will actuate.

As part of my pre-trip ops check I always get underneath and have the wife pump the brakes to ensure I feel air coming out of each valve and that is seals correctly. I'm going to get under there with the engine running and manually open one of the valves, wait for the compressor to kick in, and have the wife check how low the air pressure gauge gets to with the valve open. Can't help it...curiosity always gets the best of me.

I've attached the DV-2 Service Data document for those who might be interested. Not sure what your friend Ron is explaining when he said "...the pressure reaching the top of the range is when the condensate valve will actuate." He may be referring to what happens when the tank is initially charged to capacity. However, as detailed on page 2 of the attachment, the valve(s) is (are) supposed to open every time air is used and results in a pressure differential of approx. 2 psi. between the tank and the sump chamber.

Would I rather have a dryer than these valves? Absolutely ... but not at my expense. Based on what others have paid to have one installed and my situation, I personally don't see a return on investment. The valves are a clever, simple design; they just need occasional maintenance like anything else. Also, I recc. carrying a maint. kit or a spare valve.