2002 U320 ISM 450
Couldn't build air pressure in both tanks above 60 psi. Found an air leak from what I think is a purge for the air control for the hydraulic accumulator. Tapping on it seems to make it function ok now and get good pressure. I couldn't find anything on the forums for this. Anyone with info on this solenoid valve. FYI. On my way to Albuquerque for over night and maybe find the part. Thanks
This might help you out:
Allison retarder air valve (https://www.foreforums.com/index.php?topic=31477.msg277542#msg277542)
Most places won't have one on the shelf. I will have to hunt around and find a part number as I cant remember everything these days.
Mike
Once the solenoid is closed, he should be able to leave the retarder off and proceed without it though, no? Otherwise just cut and cap the line until a replacement can be found.
Andy,
On an '02 you should need an Allison # 295-52377
Mike
Correct on both points Elliott
Mike
Hey thanks. Yes, that looks like the retarder accumulator valve. I was searching for the wrong thing. The system has been working fine for the last couple of hours after a little tap tap. We'll see what the morning brings.
Excellent write up link on servicing the valve. Google doesn't know what that part is so maybe some phone calls, but I'd rather do the cleaning next week.
In addition to Mike's great write-up, here's some prior info
Replacing transmission retarder valve (split from What did you do to your coach) (https://www.foreforums.com/index.php?topic=17318.msg114994#msg114994)
Air leak (https://www.foreforums.com/index.php?topic=36410.msg345906#msg345906)
Help Air leak from top of the transmission (https://www.foreforums.com/index.php?topic=42427.0)
I did finally find it on line, no dash in the number. Looks like it may have been superceded a few times and now could be 29557354. Price was enhanced along the way too. :-\
Went through POs box of spare parts and found this. Now I know it goes to the retarder valve.
That part could be a plunger/seat for a 6 pack solenoid valve so check the size to be sure. They look the same but are different size.
Mike