Hi, about two months ago, I was looking for the source of air leak
Found the leak was from pressure regulators of entry step and step cover which I replaced
Then iI realized there must be another leak
Searching for it I heard leak noise on the rear right leveling valve
When I was pushing on where the leveling arm is connected to the valve , leak noise stop
Yesterday i replaced the valve with a new but aftermarket one by keeping the arm adjustment unchanged
The Haldex ones were around 200.00 and the aftermarket one was 80.00
A- are all leveling valves the same
B- is it ok if I used the aftermarket
C- do I have to replace the rear left as well
D- is there only one on the front, do i replace that
As well
Or , if it ain't broken don't fix it
I was wondering how the leveling system work with only these three valves?
Please advice lets learn more about the leveling system
Edmond
That is a couple of mostly not related questions.
Yes, two ride height valves on the rear axle and one in the center of the front.
Any time a valve is replaced, it is a good idea to check ride height. Do rear first, then front as front side to side is really an "average" with one side being slightly higher, one slightly lower. But rear has to be done first as it also affects front side to side dimensions.
As far as quality-- NO IDEA. Have seen some good knock-offs and some with terrible QC.
Other issue ( I believe-- have not used non-OE ride height valves) is that I believe some ride height valves are "instant reacting" and some are "delayed/slower reacting/ long delay valves,". Hopefully someone with more experience with the various ride height valves will chime in on this.
A little suggested light reading:
https://www.foreforums.com/index.php?media/item/hwh-leveling-system-text-book.5524/
https://www.foreforums.com/index.php?media/file/haldex-hcv-troubleshooting-guide.5178/
Some years ago 14 I replaced my ride height valves with intermediate response valves. I'm going to replace them with immediate response valves better ride I think and better cornering. As far as after marketwho knows the quality. Those valves can be repaired nothing but o rings.
Link below to an old Forum thread with discussion of "old" original style metal ride height valve versus the "new" plastic replacements.
Ride Height Valve by Torque (https://www.foreforums.com/index.php?topic=34497.0)
I had two of three orginal plastic RHC valves fail internally the same way. I would suggest if you have original I would replace. I believe our coaches came with immediate response valves.
"The primary difference between immediate response (IR) and standard (or delay) ride height valves is the speed at which they react to changes in the vehicle's height. IR valves act instantly, while standard valves have a built-in delay to ignore minor fluctuations.
Immediate response (IR) ride height valves
Reaction time: An immediate response valve starts adjusting the air springs as soon as its activating lever moves, with no intentional delay.
Behavior on the road: Since they react to every movement, IR valves are constantly inflating or deflating the air springs to maintain a perfectly level ride height. They do not ignore the up-and-down motions that occur when the vehicle hits bumps.
Ride quality: The rapid response results in a stable and comfortable ride, as the suspension is continually adjusted. This makes them particularly suitable for high-end buses and passenger vehicles where passenger comfort is a top priority.
Air consumption: Because they are constantly working, IR valves use more air and cause the air compressor to run more frequently, which can reduce the compressor's service life.
Standard (delay) ride height valves
Reaction time: Standard valves, also known as delay valves, have a built-in time delay before they begin to inflate or deflate the air springs.
Behavior on the road: This delay is designed to ignore the normal, short-duration movements of the axle while the vehicle is driving, such as hitting a minor bump or pothole. The valve will only activate if a major or sustained height change is detected.
Ride quality: While still providing consistent ride height, the ride on standard valves is not as smooth as with IR valves, as the suspension is not constantly correcting for every road imperfection.
Air consumption: The delayed response significantly reduces air consumption and air compressor runtime, which is beneficial for the longevity of the air system. This makes them an economical and durable choice for heavy-duty applications like dump trucks and semi-trailers."
To answer Edmond's "I was wondering how the leveling system work with only these three valves?" Single front leveling valve controls whole coach front to back level Dual rear leveling valves controls whole coach side to side level
I was under the impression that the air compressor ran continuously as long as the engine was running. I thought that the D2 valve just directed the compressed air toward the air dryer or just dumped it overboard. Is this incorrect?
Thanks
Your understanding is correct (except for the "dumping overboard" part). The gear driven engine air compressor "runs" all the time the engine is running.
It only does actual work (sending compressed air to the air dryer) part of the time, when directed by the D2 governor.
The Bendix D2 governor controls the air compressor by using system air pressure to signal the compressor to stop or start pumping air. When air pressure in the wet tank reaches a preset cut-out pressure (e.g., 125 psi), the governor sends pressurized air to the compressor's unloader mechanism, which holds the intake valves open, stopping compression. When pressure in the wet tank drops to a cut-in pressure (e.g., 100 psi), the governor vents this air from the unloader mechanism, allowing the valves to close and the compressor to resume pumping.
Yes, the UNLOADER VALVE on the compressor is controlled by the D2. When air pressure reaches cut-out PSI, the valve(s) open, so, while the air compressor piston(s) continue to go up and down, there is no compression and no air PSI built and no or very little HP taken.
Thank you Chuck and Brett for the clarification. I now have a better understanding of how the system actually works. It is always nice at my age to keep learning new things. However, I can't figure out what "HP" stands for.