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Old 05-21-2020, 12:47 AM
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crystalworks crystalworks is offline
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Join Date: Jun 2014
Location: SA, TX
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Solved... Hopefully

Update: So, I think this is solved? Truck has been aired up at normal ride height for 2+ days now and is holding. Was waiting a bit before posting this to be sure.

Symptoms: Both front air springs will slowly deflate over time. When the problem started it would take a week of being parked to fully deflate the front end. By the time I made the repair it would only take 6-10 hours (overnight) before the front fenders were both sitting on the front tires.

So, in my case, the valve seems to have been the problem. I focused on it as it is the only thing that ties the two front air bags together at one place, in one component. I used my original accumulator/pressure sensor and paired it with the replacement used control valve that I bought off Ebay. The build date of the replacement was newer than my "failed" valve so at least it's a few months younger.

Valve part number: 37246779713



Replacement was not overly complicated but a bit tedious due to the giant plastic windage tray that covers the accumulator, lines, and control valve. Once you get that off (be sure to order replacement rivets and single use push pins) it's 6 bolts to remove the accumulator and valve combination. And trust me, you have to remove it to be able to remove the control valve. The fasteners will be seized on there and you WILL break the rubber vibration isolators if you try to remove it in place. Ask me how I know. Glad I had extras on the spare unit I ordered.

Follow the TIS procedures before removing the air lines as far as pulling fuses and lines/depressurizing the system so as to not damage anything. After getting things swapped over and reinstalled, follow TIS for repressurizing and inflating the bags. You'll need a Foxwell or ISTA/autologic/similar to do it.

TIS Air Accumulator Removal

TIS Air Control Valve Removal

TIS Draining and Filling the System

I disassembled the old control valve and it appears the gasket between the two sections on the front bag control valves has flattened to the point of a slight leak. I think if I resealed it with gasket maker it would be perfectly functional again. The 2 o-rings around the pistons looked fine. That's my theory anyway. I originally thought the vent valve might have been stuck or something for the front bags, but after dissection think it's the gasket. Looked around for replacement gaskets & parts from Wabco, but it appears they only sell the entire valve.
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Last edited by crystalworks; 05-21-2020 at 10:03 AM.
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