Taking apart Constant Speed Solenoid (CSS, Lift Magnet)

[Thierry du Laos]

Ho Meyer sorry I didn't read for a long time this forum.
Yes I opened my CSS a while ago. I had to cut the side on my lathe, where the shaft comes out. It is glued and couldn't open. I cut the minimum to open, and made a little ring similar to what I cut out, to re-assemble and glue again.
I used the lathe also to pull strait the piston out of the solenoid.
The problem is that as it is always energized, it warms up and humidity condensate and stays in. This brings corrosion, and get all stuck.
attached are some pictures.

[Thierry du Laos]

Hi Chris,
The CSS is still working as of today. But now I have a problem with the injection pump!!
Wouldn't start anymore after she has been left a while parked...!
I just raised a topic.
Best

[Marc]

Salut Thierry,
Nouveau sur le forum je m'attache à remettre en état un 280 SL de 69
Merci pour ta publication sur le CSS, très instructive
Quel est le débattement (en longeur) de la tige du CSS lorsqu'elle est actionnée pour appuyer sur la tringlerie et ainsi augmenter le régime moteur ?
Une idée de la force exercée ?
Je trouve mon CSS un peu "faiblard" même si la tige semble se déplacer librement (sans trop de corrosion donc)
Le débattement de la tige que je mesure aujourd'hui est de l'ordre de 15/18 mm et je ne suis pas sur que ce soit suffisant.
Bonne soirée
Marc (région lyonnaise, bien loin du Laos...)



Hi Thierry,
New on the forum I am trying to refurbish a 280 SL of 69
Thank you for your publication on CSS, very informative
What is the travel (in length) of the CSS rod when it is pressed to press the linkage and thus increase the engine speed?
An idea of the force exerted?
I find my CSS a bit "weak" even if the stem seems to move freely (without too much corrosion)
The deflection of the rod that I measure today is of the order of 15/18 mm and I'm not sure it's enough.
Good night

[stickandrudderman]

Nice idea!

[JIMV]

I was having trouble with the CSS on my 69 280SL without AC. The thing would energize and stick in the extended position after the 12 volt signal was withdrawn causing a fast idle due to the linkage being pushed forward. . All connections were correct with senders from the tranny appropriate. I took it to the bench thinking it was dirty and lubed it. It spun freely and would not stick when pulling it to extension.  I energized it with a 12 volt  power supply and it once again stuck with 12 volts withdrawn. It was stuck so firmly that the throttle linkage springs could not defeat the extension.

From reading the forum I figured it was magnetized due to metals being exposed long term (sort of a memory) to the electromagnet.  I then placed a clamp around the device preventing full travel of the piston by 1mm or so preventing mating of the piston surface against the inner housing surface. This resulted in no sticking and smooth piston retreat when the power was removed. This seemed to confirm the theory.

The housing seems very unforgiving to break open and repair.  I decided to tap a half inch 4-40 stainless screw next to the piston rod allowing for the head of the screw to fit in the recess between the shaft and the rubber boot ring (a 3mm machine screw head was too large).  I adjusted this screw in the car to not allow the piston to mate to the underside of the housing setting the maximum extended piston travel to within 1mm or so. This seemed to eliminate any effect of magnetism on the retreat of the piston.  The result was a once again functional CSS.  It does have about 1mm less travel which is workable. The hole allowed for extra lubrication. I was cautious drilling the hole to minimize any metal shavings from entering the housing.  Placing a new rubber boot will require a bit of thought. I'm not sure how long this work around will function correctly, but I'm glad to not drop 1K on a new one just yet.

I have a photo and will try to post it. Happy to email it if it fails to load

Jim