We have a Stay N Play Duo system installed in the Wrangler. While driving today, I pulled into a parking spot at the mall and experienced a very hard brake pedal with little braking action...pucker time!! This is the third time we've had the system's vacuum check valve fail in a year's time.
The above check valve keeps the vacuum supplied by the Duo's controller from escaping back into the engine's engine vacuum system while in tow. When not in tow, the check valve allows the engine's vacuum to operate the Jeep's brake booster as normal. The Duo's check valve is becoming blocked both ways and causes the 'no brake' condition I had today. Simple fix...take the check valve out of the picture and the Jeep's brakes return to normal...install the valve back into the system while towing and the auxiliary brakes operate normally as well.
I took the last two valves apart to find the rubber diaphragm swollen and that is causing the blockage. There was also an oil residue throughout the valve's interior. I use dino Castrol 10W-30 and SMI says they have never had this type of problem with their system's check valves.
I've changed the routing of the engines vacuum source line to maintain an 'uphill' angle to help keep the oil mist out of the check valve(this seemed to help the most...longer service). The V6 engine's compartment gets extremely hot to the touch, so I've even insulated the check valve from the heat hoping that would help. Like I said, this is the third failure and I'm at wits end...I am thinking of going to Mobile I to see if synthetic has any effect on the rubber diaphragm???
I am going to contact SMI, but in the meantime...has anyone with the Duo system had any similar experience or am I the lucky one? Thanks and sorry for the long history report.