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Changing air dryer 1991 gv u300

June 28, 2019, 06:27:17 am

Why do you need to drain front 2 tanks not just the wet tank. Isn't there valves that keep air from going back to wet tank?

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Re: Changing air dryer 1991 gv u300

Reply #1 – June 28, 2019, 06:36:13 am

Because the check valves may not work and you don't want to be working on a system with pressure in it for safety reasons.

Rich

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Re: Changing air dryer 1991 gv u300

Reply #2 – June 28, 2019, 09:36:37 am

If the check valves on a 1991 GV are original, there is very good chance they don't work (fouled with trash/corroded/broken spring).

You could take this excellent opportunity to test your front and rear brake tank inlet check valves.

With engine off, normal air  (100-120) on the system, drain your wet tank pressure down to zero.  Then go look at your dash gauges.

If they are both holding pressure - CONGRATULATIONS - your inlet check valves are still working!

If one or both tanks show loss of pressure, then you need to replace the corresponding check valve.

Part Number Collection

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Re: Changing air dryer 1991 gv u300

Reply #3 – June 28, 2019, 10:18:03 am

Good opportunity to change to a spin-on dryer. I just needed one $9 fitting. R&R is only 5 minutes at the most. See my old posts if interested.

Pierce

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Re: Changing air dryer 1991 gv u300

Reply #4 – June 28, 2019, 10:39:46 am

Thanks to  all who answered. Will check valves and read post about going to spin on dryer

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Re: Changing air dryer 1991 gv u300

Reply #5 – June 28, 2019, 11:02:46 am

Here are the photos of the installation. You can see the shiny 45 degree fitting in one of the photos. Think I paid a little over $100 for the unit. You need a HD strap wrench to change as the rubber belt models at HF don't work. Still, it's a spin on and easy to R&R in the location we have. Extra cartridges are about $25 delivered. I purchased a clone made in Poland not German OEM. Quality was excellent. spin on air dryer meritor | eBay

Sticking the mount in the powder coating oven is not necessary, any bracket will do. I just filed a bit on mine. Don't know how earlier rear radiator models have their dryer mounted. Getting a "Crow's Foot" ahead of time saves a LOT of work with the big air fittings. Any truck store will have the fittings. They are cheap.

Pierce

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Re: Changing air dryer 1991 gv u300

Reply #6 – June 28, 2019, 11:18:21 am

I changed my air drier to an adsp also. Mine is a rear radiator coach, I wasn't able to find a cool little mount like that. I had to build mine, it was no big deal. Then the hose from the drier to the wet tank was 6" short. Ended up buying some new aeroquip air line.  I really like the thought of spinning the filter off and spinning a new one on.  My opinion, well worth it.

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Re: Changing air dryer 1991 gv u300

Reply #7 – June 28, 2019, 12:08:12 pm

I think I salvaged the mount from the old dryer but not sure. Yes, getting stuck on the road with a bad dryer could hang you up for a while, while a rest stop and a strap wrench make it fast. The Snap On tool came from a used tool store for about a buck or so. Good to have one that fits the hydraulic hoses for the later coaches. As I remember, most are 1 inch but I had one 1 1/16" or perhaps it was 1 1/8". Make changing/repairing hoses much easier.

Pierce

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