Ride Height Valve - Dump at zero pressure or bad idea?

[Mike Gineris]

1999 Contessa Naples. I discovered that my Haldex Valve (driver side) does not dump air at zero pressure but the valve on the opposite side (passenger) does.  The passenger one I'm sure has been replaced.  So if I dump the air manually at the service panel, the passenger side drops and the driver doesn't.  I plan to replace valve(s) but am not sure what the right choice would be.  To dump or not to dump at zero pressure?

[Eric Maclean Co-Admin]

The ride height valves and the dump valves are two separate items the ride height valves only add or remove air to maintain the ride height at a predetermined height mechanically where as the dump valves are an electric solenoid valve operated by the dash switch to dump air only.
If one side of the coach doesn't go down when dumping air it's likely you have a defective dump valve on that side rear or you have a suspension torque rod seized up.


Eric

[Mike Gineris]

Eric.  I'm aware.  I've fixed the Dump Valve issue by replacing the Relay.  All the dump valves work great.  When I manually empty the wet/dry side of the tank using the petcocks at the rear hatch, the Passenger Ride Height Valve dumps (once I get to zero pressure) and the bags on that side deflate but the driver side doesn't.  I looked it up and these ride height valves have the option to be a normally closed or open (auto dump at zero pressure).  I have both because the passenger side was replaced with something different.  I believe the Driver side is the Stock Issue (normally closed) which doesn't dump when you manually drain the tank.

[Eric Maclean Co-Admin]

Mike
There are two electric solenoid dump valves above the rear axle one for each side they are plumbed into a manifold for each sides rear air bags when the you push the dump button up front it activates all the dump valves .
These dump valves bleed off the air from the air bags but at the same time the ride height valve try to add air toaintain ride height the coach doesn't actually go down until the ride height valves deplete all the air from in the air supply tank.
There fore if the air tanks are empty and one side of the coach doesn't go down the dump valve for that side on the rear axle must not be dumping the air from that sides air bags.

[Eric Maclean Co-Admin]

Mike
Ifim reading your post properly what your telling me is without operating the electronic dump valves and just dumping the tanks manually at the tank drain / purge valves that the air bas deflate once the tanks are empty.
Theoretically you should be able to empty all the tanks and have the vehicle stay at ride height because the ride height valves have a check valve in their inlet port that prevents a back flow .of course this is in a utopian world the truth is these systems at the best of times will leak down over a period of days because of small leaks at connections, air bags and eben the ride height valves.
If the coach goes down immediately on one side it is an indication that the ride height valve on that side has been installed wrong or the check valve in it is defective.


The original haldex valves had plastic housing with an aluminum insert for each air fitting to screw into these aluminum inserts where sealed with O rings and as they get older the aluminum corrodes causing the O rings to leak between the plastic and the aluminum insert.

There are .any manufacturers of this ride height valve with lots of different prices .
As you noted the original valve s where Haldex  part number KN 2700 but the Chinese had lots of knock offs of the very same valve right down to the part number all over Amazon however the quality may not be as good.

https://www.finditparts.com/products/368746/haldex-kn27000?srcid=CHL01SCL010-Npla-Dmdt-Gusa-Svbr-Mmuu-K368746-L134&srcid=CHL01SCL004&utm_medium=cpc&utm_source=google&utm_marketing_tactic=broad&utm_paid_search_intent=pmax&utm_campaign_id=21647308742&utm_ad_group_id=&utm_ad_id=&utm_platform=x&utm_placement=&utm_keyword=&utm_target_id=&utm_match_type=&utm_feed_item_id={feed_item_id}&utm_extension_id={extension_id}&utm_location_interst=&utm_location_physical=1026456&utm_product_id=368746&gad_source=1&gclid=CjwKCAiA-ty8BhA_EiwAkyoa30XMrnJ3sKArGXwe1De5A0Lv3LGprKF5HZFCrOOgr4cr02lzjjpWlxoCe2AQAvD_BwE


Eric

[Mike Gineris]

Thanks for the detail!

Before I reached out I discovered that there are Ride Height Valves that dump air when pressure drops to zero (no internal check valve to hold pressure).  The side that dumped air is clearly not the original valve.  When I manually purge the tanks, I can hear the Passenger side bleed out (sounds like the electric dump valve but it's not) after the tanks near complete emptiness. Yes I noticed the crazy low price on Amazon and it scares me to go that route.  I will definitely go with the original design and get a valve(s) that hold air even when the tanks are emptied. 

Because I changed everything (bags and manifolds) the system "should" hold air for at least a day or more.

https://www.fleetpride.com/parts/hadley-height-control-valve-h01502unc?srsltid=AfmBOoqAIBdB03KafNcXt28GoVKVd9vlUFhVGpFRzcHq9V6L850oMzFf