gnosis

Can someone explain to me where exactly the variocam unit's check valve (part 944 105 508 00) goes? I know that the variocam solenoid pushes on a spring-loaded valve, but is this the check valve in question, or is the check valve something else? If so, it is supposed to go in the J-tube that leads from the head to the variocam unit? Some photos of the part would be nice if someone has them.

I'm in the middle of an engine rebuild, and I have this fear that I've lost this part.

Thanks,

Clayton

RajDatta

It is a small metal ball that allow oil to run into the variocam unit but stops it from flowing out. This way the system remains pressurized.
I will see if I can get you a picture.
Raj

gnosis

Okay, a picture would be excellent. Perhaps it'll jog my memory, but to be honest I'm pretty sure there was nothing in there where I removed the J-tube. I have a photo of the tube sitting in the installed position on the head along with the hydraulic unit (the mounting bolts are removed but the tube is still in place), then the next photo shows the whole assembly including cams on my bench with the tube still in place. Only then does the tube come off, and I can't imagine how I wouldn't see this part if it fell out.

But is it feasible that it might not have had the part in there in the first place? What would it run like if it kept losing pressure? I presume it would slacken the chain and/or lose effective cam timing control. I haven't noticed anything like that from the car's performance.

RajDatta

It would sound like a lot of chain noise on startup but would go away as soon as the system is pressurized.
Raj

gnosis

And would reappear again if oil pressure dropped, I guess. Kinda like starting the car after it's been sitting for a few months each time you go below the oil pressure the check valve is set to operate at?

The reason I ask is that this part is special order, and insanely priced if Pelican are anything to go by, and I'm rushing to get this engine back together. I don't want to be held up if I can get it running and come back a few weeks later and put this part in. So long as I can run it without damaging stuff, I can get by for a few weeks.

gnosis

Okay, I've found my missing check valve (would you believe I found it in a bag that I labelled "Variocam mounting hardware"?).

I've also sorted out my confusion over where this part goes, and whether there's a separate spring involved. It goes in the Variocam hydraulic unit, where it sits neatly in a countersunk hole, surrounded by an o-ring. The J-tube bolts down over this assembly. This means that oil going into the hydraulic unit pushes past the check valve, which contains a ball bearing acting as a one-way valve. When oil pressure drops (below 3 bar, I've heard), the check valve prevents the pressure in the Variocam unit from also dropping, thus keeping pad pressure on the cam chain during idle. There is no spring to hold the check valve in place, as was rumoured, because the J-tube clamps the check valve into the Variocam unit, from which it cannot escape. However the check valve itself probably has some sort of spring mechanism within it, since the valve is forced open by oil pressure.

I believe the confusion about the spring comes from the fact that there's a ball bearing and spring contained in the cylinder head that acts as a pressure valve. That's a totally different place and purpose, which has nothing to do with the Variocam unit.

The check valve is small, and very easy to lose if you're not careful when putting pressure on the Variocam pads during maintenance. This is why I feared I'd lost it. I'll be posting detailed photos of all this stuff when I finish my rebuild in the next few days.

Clayton

MacinTek

... and Pelican wants $127 for a little steel ball?

savvas944

it is from Porsche the cost.
i guess they found a niche in the market for some cool overcharge.