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gzig5 24th July 2011 02:34 AM

Vanos Solenoid Repair
So for a couple weeks I have been occasionally getting the 4A and 4B codes which indicate a problem with the Bank 2 Intake Vanos control. I reset the light a few times and never really saw any performance issues. This week, the car started running rough, and the SES light came on. I had the 4A and 4B codes as well as 71 and every misfire code for cylinders 5-8. These were identical symptoms that I had two years ago and I found I had a broken wire on one of the Vanos solenoids. I didn't document it then, so I am doing it now. I'll leave the solenoid removal "how to" to others who have documented it well. I will add that I remove the entire filter box to get better access and leave the coolant hoses in place.

Time to do something about it so out comes the driver's side Vanos board. I immediately see that there is a cracked solder joint on one of the leads that goes into the coil from the little board.

So, I clean the board up, re-solder that joint and all the others ones, adding additional solder to reinforce the weak little trace between the pads.

Back into the car, clear codes, start it up...still the same. FARG! Take the board out, I must have missed something. Now I break out the meter and my power supply. I thought the cracked joint was a slam dunk but I was mistaken.

I found the coil that did not respond, right away. This wasn't the case last time, I had to wiggle connections to get it to fail then. Desolder the little board and my problem becomes apparent. The lead has broken off flush where it enters the coil potting. Just like last time.

So out comes the Dremel, files, and X-acto knife and I start carefully hacking away to expose the wire. This is tedious and the epoxy is tough. You must be careful not to damage the lead wire more than it already is. I exposed about 2mm and stop because I don't know how deep I can go before hitting the winding. It doesn't show well in the picture, but it is there.

I then took a section of solid core wire that is 1mm(.040") thick and using a small drill bit as a mandrel, I bent a tight loop on the end and then put a curve in it to match the other one. The hoop was pushed over the stump and soldered on. When I did this the last time, I threw away the little board and soldered the wires directly to the solenoid leads. The unbroken one was no problem because it was long enough but the short bit of wire was difficult to connect the wire to. The first attempt broke after two weeks and I had to redo it with a bigger blob of solder and that repair has lasted over a year and a half. So this time, I decided to fix it so that it was stronger from the start. The loop of wire provided much more surface area and I think this will be a good repair.

Now the little and big PCBs were prepped for assembly by using solder wick and a solder sucker.

The parts were then fit together and I started by soldering the wire lead that wasn't broken to the little board. I then soldered the wires back into the main board and finally the repaired wire lead. I felt that in this way, I would have the least stress on the repaired lead and the repair wouldn't move if it re-melted when soldering the wire to the small board. It seemed to work. A little bit of shrink tube was used to repair the insulation on the yellow wire. And that is it.

The board was tested and installed with no problems. The car once again runs like it should, or at least as well as it ran before. In this case, the board failed in two ways. First, the solder joint broke on the black wire and then all the mechanical load went to the other wire which finally broke. This solenoid board is a pretty poor design execution and invites failure. I'm afraid it's not the last time I'll be in there. The newer solenoid cover with the screws may reduce the movement of the solenoids and the have fewer failures like this, so I may have to look into that. Everything I did here could be done by anyone with basic skills, so don't be afraid to give it a shot and save yourself $1500 in parts and labor.

68FB 24th July 2011 03:36 AM

Great write-up, gzig5. Thanks. I resoldered the obvious joints a while back but now I have a 71 code, so this may be my problem.
I have a early 2001 and the solenoids are firmly clamped in place by setscrews. Are you saying they are loose on yours and can move around?

gzig5 24th July 2011 04:39 AM

I don't know when they did the change, but the early cars don't have the set screws. So the coils are free to rattle around on the end of their tethers, which are the wires. I think this is why they are breaking. The upgrade is probably as simple as bolting on the new covers, but I may modify my existing covers if there is enough meat for the set screw threads.

Sailor24 24th July 2011 07:06 PM

Nice job! The extra surgery is excellent! I think if I had found that I would have been forced to buy a new noid, not any more.:cheers: thanks much

BrendanSC 24th July 2011 08:08 PM

Nice work. I gave myself a good fright when I broke a wire off mine but work like this helps everyone to see it's not brain surgery if you can solder a bit and have the right tools. What power supply were you using there btw?

jdb884 24th July 2011 08:56 PM

So for an early model year is it as simple as buying the updated cover so they are not loose? Anyone know the part number for it?

BrendanSC 24th July 2011 09:14 PM

gzig5 24th July 2011 10:20 PM


Originally Posted by BrendanSC (Post 2121168)
Nice work. I gave myself a good fright when I broke a wire off mine but work like this helps everyone to see it's not brain surgery if you can solder a bit and have the right tools. What power supply were you using there btw?

It's made by Power-One and has +12, -12, +5, and +24 VDC outputs. I can't remember where I got it, but probably from a machine retrofit years ago. Lot's of supplies like this at salvage shops and online. Another good source would be a 12 VDC wall wart from an older printer or something like that. You can use a car battery, but there is a lot of current capacity there and one of these little supplies will fold back if there is a short.

bimmerule 25th July 2011 05:38 AM

413 Attachment(s)
Great write up, especially the level of details, and nice to see circuit diagrams used in practice.

bimmerule 30th January 2012 05:54 AM

413 Attachment(s)
What wattage soldering iron should be used for this repair? I have a 35 watt kit that melted the usb port when I tried it on my HTC cell phone.

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