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On-off soleniods: failure due to wear

On-off soleniods: failure due to wearn 4

1. Abrasion. Caused by repeated pounding of solenoid components,accelerated by contamination and material changes due to heat and chemicals in ATF. Seat areas and areas of contact with the spring see considerable wear. Springs twist as they are compressed. This rotating and grinding action, as well as the repeated loading, will cause the spring to dig its own pocket. When spring loads change, a solenoid may loose its holding or closing ability.

Seat areas, especially plastics, are 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 due to their large ball,and much surface area.

2. Fade

Springs lose 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. Unless you knew the original stroke of the solenoid when it was new, you would not know how much stroke it has left before the seat starts to leak. The best way is to estimate by vehicle mileage.

3. See the enlargement of the slide. It shows poor workmanship, (tool drag mark on seat) which gives a poor seal to begin with. You can also see the same seat after cycling. Note out-of-round hole, poor armature guidance. Note wear up to .015. A soft steel was used. This is good for magnetics but awful for seat

Spring Fade: Spring fade will occur in every solenoid. This is predictable, Gradual breakdown of spring loading reduces the springs ability to hold and close. Spring fade can be pre determined, and solenoid springs must be over designed to work when it has faded.

4. Signs of wear

There are none!

Nothing apparent on outside. Take some defective solenoids apart, look at seat areas etc. get the feel of what a worn out solenoid looks like.

Vehicle mileage.
Driving conditions. (Stop and go driving, multiple city shifts)

Assume for the life of a vehicle 2 shifts per ¼ mile, 2 energizations of each solenoid.

Click on an illustration to see an enlargement.