I recently replaced my head gaskets (2.5 STI Hatch) so had to remove the camshafts. I don’t have the special tool to lock the pulleys. Internet lists tools that hold the AVCS body or tells you to lock the pulley’s using the old cam belt. If you have AVCS, DON’T USE EITHER METHOD. The cam bolts are V tight and holding the outer part of the pulley while undoing the bolt through the inner part breaks the AVCS system. The inlet will take it but not the exhaust. There’s an explanation on YouTube . I’m not convinced he fully understands how they work but he shows the broken bits well

Long story short, I bust my 2 AVCS units. I’m told parts are not available and new ones cost £££. The good news is they can be repaired. Here’s how…

Easy way to tell if they’re damaged is the ends of the big spring should be 180 degrees apart.

Be careful not to damage or lose anything. Remember, spares may not available.

Obviously the first step is to dismantle them. You need 5 point Torx bits. I got a set from Screwfix.

Remove the spring and the washer underneath

Undo the bolts. There are 2 different sizes. They are soft so be careful not to damage the heads

Remove the pulley and the steel cover

Remove the O ring

Now the difficult bit. The rotor is a press fit into the cam drive (top right in pic) and they both sit on opposite sides of the housing (bottom left).[img]file:///C:/Users/John/AppData/Local/Temp/msohtmlclip1/01/clip_image002.jpg[/img]
There is a 3mm pin through the rotor into the cam drive. This is what shears and damages the rotor. To split the rotor/cam drive is difficult. Support the housing and gently drift the broken pin towards the cam drive. It should separate from the rotor

Carefully separate the rotor, housing and cam drive. The rotor contains 6 sprung seals (top left and right)

The rotor will be damaged where the pin sheared. The cam drive less so.

Don’t remove the old pin from the rotor.

With a dremel, remove any high spots on the rotor. It doesn’t have to be perfectly flat, just not have high bits as they stop the cam drive seating. You can see where I’ve done that in the picture. My cam drive also has an extra hole in it, more on that later.

The cam drive will be almost undamaged. I put some fine wet and dry on a flat surface and lapped it smooth.

Now you need to replace the pin. The new one doesn’t have to be in the same place. The rotor has oil holes through it in various places and directions so choose a place away from those. I drilled a hole through the steel cam drive, then reassemble the cam drive through the housing into the rotor. Make sure the rotor and cam drive are as closely aligned as possible and the rotor is in the housing the right way. The spring holes must end up 180 degrees apart. You can sight the old pin through the cam drive. That’s why you shouldn’t remove it. Press the cam drive fully home (I used a vice). I then drilled through the new hole in the cam drive into the rotor. This way, the holes are perfectly aligned. I had some 4mm ground stainless rod so used that to make a new pin. You could sacrifice the drill you used for the hole and cut some off the shank. The pin can’t come out with the cam bolt in place but a dab of Loctite adds confidence.

Carefully assemble the rest of the AVCS taking care with the rotor seals and O ring. It is imperitive that the rotor and steel plate are perfectly lined up. I made a dummy cam end to help but you can use the camshaft itself. It's just more fiddly. The rotor and plate must both be free on the cam. The plate has to rotate to vary the valve timing. If it's not free to move, it won't work. Get this right!

I replaced the original Torx screws with normal cap heads 25mm long. Watch the clearance between the heads and the plastic belt guard. It’s only an issue on one side, LHS I think. Cap heads are bigger than the Torx ones and mine rubbed. I took about 0.050” off the top of the head. Don't overtighten the cap heads. They're only into aluminium.

The spring is a bit tight but can be fought on.



Hope this helps folks NOT break their AVCS or to repair them if they have.

 

In my experience of the exhaust avc's pulleys, once they have been apart or messed with they never function correctly, I presume you have logged the performance of them now you have refitted them, especially there static position, I always fit new, they are not expensive £160.00 in the bigger picture of an engine build, & especially if there has been any bearing material floating around it always seems to end up in the exhaust avc's solonoid & pulleys.

 

Not logged them yet.
New is always an option of course.
I tried this as much out of stubbornness and curiosity than anything. I did keep in mind that it's not a big job to replace them if they didn't perform.
The embarrassing thing is that I had to do this at all because I locked the pulleys when removing the bolts.

 

Yes, worth trying, just be care full they are not over advancing, although if they were, you would know about it by now.

 

That surprises me as the oil supply to the heads are through a filter in a banjo bolt. I thought that also fed the AVCS via the solenoid valve. These banjo's are identified by a lump on the banjo's hex head. Someone didn't know that when they worked on my engine. I found one of my filtered banjo's in the turbo water supply pipe. The matching oil supply was unfiltered.

 

Bearing debris will pass through the banjo bolt screen filters and collect inside the AVCS pulley quite easily - you want to see what gets trapped in the
cylinder head oil gallery's and behind the oil restrictor in the heads after a big end has spun.

 

The proper tools to hold the pulleys is available and it holds the inner part of the pulley as per the Subaru manual this is the one I bought on Ebay 173718796715.

Holds the inner parts so don't sheer the pin,also even advised not to open up as to re align without a made up tool is very difficult and due to these being an absolute **** for remove not worth the hassle.