Yet another issue that was discovered on the car was that there were signs of oil leaking from the bottom of the vanos solenoid cover. This is a clear indicator that the solenoid seals are beyond their useful life.
The other issue I noticed was that one of the bolt heads was missing from the cover, so that needed to be addressed. They are common for breaking over time, so I made sure to have some replacements on hand.
I ordered a whole vanos rebuild kit, including new M5 seals (as per a very useful guide) but decided as I was limited on time, and the vanos appeared to be working OK now it was plugged in, I didn’t want to take the time to rebuild the whole thing yet. It also didn’t help that my fan clutch tool hasn’t arrived, so I couldn’t remove the fan to access the vanos unit.
The solenoid seals are the most common point of failure anyway, and with mine leaking, it’s a fairly easy thing to replace.
First is to remove the solenoid cover. Its held on by 4 screws, with either a hex head (if original bolts) or torx (if replaced). The broken off bolt was still there, just with no head. I used some vice grips to slowly turn it until i could spin it out
The cover was missing one half of the gasket, and had evidence of the bottom solenoid moving in the housing (the black circle on the cover is from the solenoid pressing against it). The bottom of the cover was caked in old oil
The gauze filters were still fitted (usually removed when serviced), although most of the gauze was missing, like the last lot I serviced. Using a small screwdriver I broke off all the brown plastic for the filter, and removed it. I also used a scalpel to cut off the old seals. The old seals were hard as plastic, well overdue for replacement
As with my last guide I used a 9v battery and brake cleaner to clean out the solenoids. They were surprisingly clean though, with nothing gross coming out of them like the ones I did on my old M3. Both give a nice solid click when powered.
The cover was then refitted, with one new bolt (I can’t fit my Torx driver in the space with the fan fitted). I will fit all new bolts, and join the solder points on the solenoids, when I remove it all to refresh the vanos later.
I noticed when I had the valve cover off that the intake cam sensor had a very big air gap. I know from INPA that it appears to read OK, but I wanted to look further into this. It turns out, looking at the sensor, the previous owner had pinched and hulk smashed the O-Ring on the sensor so it was sitting out quite a bit. The screw was finger tight too.
It turns out you can order these seals separately, but I didn’t know I needed them so dug through my viton O-Ring kit and found one that fit well. The one in the photo was too big, but I did eventually find one that sealed well
The sensor now sits flush with the head. It probably isn’t making any difference, but it bothered me as it was.
One last test needed to be done before I could go give it a try, and that was to fire up the old beast and run the DIS vanos leak test. This test is used to see if the vanos solenoids can keep the cam at a certain degree over a certain period of time or if the seals leak, resulting the cam angle slipping. There is some allowance for variation, up to about 5 degrees off target over 10 seconds if I recall correctly.
I didn’t test beforehand, I should have but I forgot, but after the seals my solenoids can hold the cam at about 3-5 degrees off target for as long as you want. That’s pretty good in my books, for a vanos unit that has done almost 300,000km and never been rebuilt. I’ll be interested to see if there is as much variation after rebuilding the vanos unit.
So, after all this work, there was only one thing left to do. Hoon.
The car runs and drives very well, with plenty of power. It feels much more like my old one, pushing you into your seat when you put your foot down. There are still some issues, like the misfire at idle, but overall it’s significantly better than when I got it.