I recently lost turbo boost on my JDM Series 8. Off comes the upper intake manifold to find a simple cause – the main hose from the manifold to the Solenoid Box was not clamped and had blown off. While I had things open I started checking out the vacuum lines. Straight up leaking check valves, not enough to stop things working but a sign that they were on their way out and there might be other issues.

There is already a truly excellent guide over on Ausrotary that about says it all about getting the valves out of the black box: https://www.ausrotary.com/viewtopic.php?f=16&t=192188 There are a few dead links there, the one at the bottom of the first post worked for me and I think is the latest.

I also wanted to use the Dale Clark viton check valves. Dale was not aware of any issues fitting them to the solenoid box but I could not find any solid confirmation that they fitted. I can confirm that they will fit but I think that it would be wise to take a couple of additional steps to ensure reliability.

The valves in the “black box” are sandwiched between a top and bottom housing with rubber grommets sealing the nipples where they enter the housings. The assembly is held together by the friction of these grommets with a bit of assistance from the vacuum – no screws.

The stock check valve body is 20 mm long and is neatly sandwiched by the grommets top and bottom. The nipples either end have a constant 5mm diameter.

The Viton check valves are 5mm shorter overall, have a shorter 9mm long body. The 5mm shaft has a very sharp 6mm barb.

I was concerned that the extra diameter of the barb would either cut into the grommet as the gromet has nowhere to expand. It could make a difficult to safely separate assembly even more difficult to get apart. So, first thing – carefully trim off the barb using a sharp utility knife.

Second thing, the guide mentioned above recommends using silicone spray lubricant to aid separation. I also think that it is a good idea to keep things lubricated during re-assembly in the hope that it will make things a little easier for disassembly next time. There is a danger that the boost/vacuum cycle will cause the unrestrained check valves and grommets to slide up and down in the housing leading to a leak? While I’m not sure but there is enough force on an 8mm diameter grommet to be concerned, the forces will not be insignificant, and I don’t know for sure that it won’t be a problem. My solution - install 5.5mm plastic spacers top and bottom just to be safe.