Solenoid problems: Wear

Wear

Wear Issues:
Wear is the second leading cause of solenoid failure.

Two types of wear:
Abrasion
Caused by repeated pounding of solenoid components. Accelerated by contamination, and material changes due to heat and chemicals in ATF.
Shows up in Seat areas. This solenoid face was originally flat. After 1 million PWM cycles the seat is badly worn. (3000 vehicle miles). A poor material selection was made by the MFG of this solenoid.
Spring pockets and areas of contact with the spring see considerable wear. Springs twist as the are compressed. This rotating, grinding action, as well as the repeated loading will cause the spring to dig its own pocket. Spring loads change, solenoid may loose it’s holding or closing ability.
Sealing faces, especially in EPC type solenoids. Spool valve edges get rounded pass too much oil, ability to regulate pressure goes south. Nissan EPC solenoids can wear out in as little as 40,000 miles. A lack of armature guidance causes the armature to hit not square wit h seat. Allowing for excessive oil leakage.
Fatigue
Seat areas, especially plastics, subject to creep, a gradual deformation and movement of plastic due to loss of material strength, from repeated loading. E40D on/off solenoids suffer this. Large ball, much surface area.
Springs loose their load handling ability with repeated cycles. Special materials should be used.

Some wear is normal.

Contamination will greatly increase wear.
Heat influences wear, especially in plastics. Impact resistance goes down with increased temp.
Proper material selection is required.
Solenoid testing in the shop can not determine the wear, or life expectancy of the solenoid.
Photos illustrate before and after shots.
Poor workmanship, tool drag mark on seat, gives a poor seal to begin with.
Same seat after cycling. Note out of round hole. Poor armature guidance, note wear, up to .015 a soft steel was used, good for magnetics, awful for seat wear.
Plastic vs metal
Plastics work well for on/off applications, not too good for PWM. Special hardened magnetic steels should be used in seat areas for best life. Also synergistic coating works well. Polymer impregnation into first few thousandths of metal
On/off 500,000 clean cycles…. 80 thousand miles
PWM 300,000,000 cycles… 80 thousand miles
Wear will result in:

• Increased armature stroke
• Longer solenoid response times
• Sealing problems
• Changes in solenoid performance

Solenoid failure analysis graph

The graph shows how excessive wear changes the solenoids ability to control output pressure. Poor material selection, and improper machining were the cause.