These pictures show the valve, and open and close position for the cap and the cam. The problem in this valve is that the stem that joints the cap with the cam gets dirty of soot from the smoke and gets stuck, leaving the valve always open. The easy and fast solution is to grease the stem with oil, but it lasts for a short time. The right solution is to disassemble and clean the stem, and only requires good skills on welding (you, a friend, a workshop or anyone. It's a 10min, operation for somebody who knows how to do it).
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Step 1: Begin to Disassemble
After removing the valve from the car (very easy, you can google a little and find it), the first to do is to remove the plastic cover of the cam. Then remove the module that controls solenoid, being carefull with not breaking the little pins that hold it. Before continuing we have to mark the position of the rotor, in order to put it in the same position at the end of the process. I've marked a red point between the two pins of the solenoid.
Step 2: Removing the Cam
Pass the grinder on the end of the cam shaft, taking care in not to pass it over the lane of the bearing of the stem.
Then, with a screwdriver push up the cam. It wil bend a little, but with a couple of magic kicks becomes straight again.
Now remove the three nuts that hold the solenoid to the body of the valve.
Beware not to lose the spring.
Step 3: Removing the Plug
Pass the grinder over the end of the stem, and then hit in the center of the cap with a big nail or something similar.
Step 4: Cleaning the Stem and the Stem's Hole
Never sand or scrap the stem or the hole. Doing so will facilitate the accumulation of soot. You have to clean both the stem and the hole with some solvent. It will take some time, but it's the only way not to scrath the parts.
For the hole I used a little cloth soaked in solvent and a thin stick (the handle of a brush).
Step 5: Reassembling the Plug
Just get the stem through the hole and fit the cap. Be careful with the bearing. Hitting on the cap resting the stem on the bearing can break it. You can rest the stem on one of the two sides where the shaft of the bearing is inserted.
Now you have to weld the cap to the shaft, then pass the grinder, and then sand the cap, in order to smooth the surface
Step 6: Reassembling the Cam
Protect the lane of the bearing and the bearing from sparks of the solder.
Put the solenoid in the original position and hold it with a toothpick.
Take care on the position of the stem. It has a larger gap than another. The cam enters through the bigger one.
The cam has to be 90º from the shaft. The picture shows a wrong position of the cam.
Solder, reassemble the cover of the cam and the module of the solenoid and ... YOU'RE DONE!!!
(...and with a lot of extrra money in the pocket, to spend with your family and/or friends, instead of giving it to your car's make).