What are the functions of a Soft Check Valve?
- One-way sealing: Prevents air that has entered the bellows from escaping, preserving suspension pressure.
- Fast response: Reacts instantly to pressure differential, seating against or lifting off the valve seat, so the system operates without delay.
- Flexible sealing surface: Makes full contact with the hard valve seat through its soft surface, sealing even microscopic surface irregularities.
- Resistance to pressure fluctuation: Continues to function while keeping its shape under the suspension system's constantly changing load and pressure conditions.
What are the symptoms of a failed Soft Check Valve?
- Drop in suspension level: One side or the whole vehicle settling lower over time while parked.
- Frequent compressor cycling: As the system loses air, the compressor engages more often than expected to top up pressure.
- Air leak sound: A hissing or leaking sound from the check valve area, especially noticeable once the vehicle is stationary.
- Harsh or overly soft ride: Pressure imbalance prevents the suspension from delivering its designed comfort level.
- Delayed level recovery: The vehicle taking longer than normal to return to level when loaded or unloaded.
How is a Soft Check Valve checked?
Inspection first uses a soapy water test with the system pressurised; if soapy water applied around the check valve body foams, there is an air leak. When the valve is removed and the internal structure examined, look for cracking, hardening, deformation, or a lost seating mark on the soft seal's surface; a healthy seal should stay flexible and make full contact with the seat. Leaving the vehicle parked overnight and checking level the next morning is a practical way to detect slow leaks. When working on pressurised air systems, safety rules must be followed and no component removed before the system has been fully vented.
What should be considered during replacement?
- Correct material and size: The elastomer seal's hardness (shore value) and size must match the valve body exactly; different-hardness material breaks the seal.
- Clean installation: The valve seat and seal bore must be cleared of dirt, moisture, and old seal residue.
- Direction check: Since a check valve is directional, installation orientation must be correct; reversed installation results in the system holding no pressure at all.
- System test: After installation, the system should be pressurised and sealing confirmed with a soapy water test.
- Other seals: Auxiliary seals such as O-rings on the check valve body should also be renewed if worn.
How should a Soft Check Valve be selected?
Selection should be based on the valve body model, elastomer material type, and hardness value. It is recommended to confirm that the material retains its flexibility across the air suspension system's operating temperature range, using the OEM part number.
Check valve soft seal selection criteria| Criterion | Description |
|---|
| Material | Flexible elastomer resistant to pressure fluctuation |
| Hardness (shore value) | Correct hardness for full, sustained contact with the valve seat |
| Size | Matches the valve body and seat exactly |
| Temperature range | Must not lose shape across the vehicle's operating environment temperature |
| Pressure rating | Suitable for the system pressure specified in the vehicle's current OE service manual |
Maintenance and service life
A check valve soft seal lasts a long time in systems that run clean, dry compressed air. Moisture or dirt entering the system causes the seal to harden and gradually lose its seal. During routine suspension maintenance, the air dryer's condition and system moisture level should be checked, and the check valve area should be regularly tested for leaks with a soapy water test.
VADEN Soft Check Valve
VADEN manufactures OEM-matching check valve seals for heavy-duty commercial vehicle air suspension systems, built with the correct elastomer material and hardness value, with the goal of preserving the vehicle's original level-holding and ride comfort performance.
Frequently Asked Questions (FAQ)
Why does the vehicle settle lower when the check valve soft seal fails
Once the seal loses its sealing ability, air that has filled the bellows escapes back out, dropping suspension pressure and causing the vehicle to settle.
How is an air leak detected
With the system pressurised, soapy water is applied around the check valve body and foaming is observed; foaming indicates a leak.
What happens if the check valve seal is installed backwards
Since a check valve is directional, reversed installation causes the system to hold no pressure at all or to operate in the wrong direction.
Can moisture damage the check valve seal
Yes, moisture entering the system causes the seal to harden and gradually lose its seal; regular checks of the air dryer are important.
Is frequent compressor cycling a sign of check valve failure
It can be; when the system continuously loses air, the compressor engages more often than expected to restore pressure, and this warrants inspection.
