HermanH's PASSAT Site

Tools Required

Forge Diverter Valve Replacement

The Diverter Valve ( number 19 in the diagram below ) functions as the turbo's "blow-off valve" (BOV) or "dump valve". Unlike the conventional BOV, which disperses excess charged air pressure into the atmosphere, the diverter valve (DV) redirects the excess back into the instake hose ( number 1 in the diagram below ); essentially recirculates the air back to the turbo. Just an FYI, the number 6 component in the digram is the "Pressure Regulator Valve" and is in essence, a PCV. The crankcase breather air (number 4) vents excess presure from the valve cover back into the turbo as well. And number 3 is from the EVAP canister. One begins to think the turbo is garbage disposal!

The reason a diverter valve would need to be replaced is varied. Older model Passats had some faulty Bosch DV's while others failed due to boost increases via chip tuning. Some of the DV's will simply fail over time/milage. The typical symptom of a failing DV is a "surge" in power as opposed to a crisp increase in power. If the DV's diaphram is torn, you may get inconsistent boost (if you have a gauge), lack of power or studdering under boost.

Inevitably, replacement of the DV must be done; newer Bosch units have been upgraded but some people have opted for the DV's found in the Audi TT Roadster since the DV is used on a 225hp 1.8T motor. And the price is very good at about $35. However, I have opted for the Forge DV from Stratmosphere. The unit is made out of billet aluminum and unlike the diaphram style Bosch units, Forge utiizes a solid aluminum piston with dual O-rings. The unit is 30% larger than stock. And it's rebuildable so only O-rings would require replacement!

Another company, Bailey, can also be purchased. It is reported to be the same "quality" as a Forge and about the same price but it's not rebuildable. And some adventurous souls have tried DV's from Saab and Porsche with good results.

A ClubB5 member, "mistertam" has provided some information regarding various DV's. He has tested the stock DV against the Stramosphere and Forge units. Read his findings on "The Great DV Face Off".

INSTRUCTIONS:

1. Jack up the front of the car and put on jackstand or ramps.

2. Remove the belly pan; there are 2 plastic desus clips in each fender well which need to be removed, and 5 more desus clips directly under the belly pan perimeter, and a single 10mm nut. Once all of the fasteners are removed, the belly pan slips out.

3. Locate the DV; it is attached to the inlet tube that runs across the bottom of the radiator, close to the AC pump:

4. On some of the older Passats, you will need to literally cut or destroy the one-time use crimp style clamps. Otherwise, a screwdriver is all that's needed.

5. Double check the hex bolts on the Forge unit, prior to installing; while Forge does a good job, it's always possible one of the hex screws might be loose. If they are loose, I'd recommend getting some Permetex "Blue" thread lock and apply to the hex screw before retightening.

6. Install the DV in the same orientation as the OEM DV. The small 1/8" ID tube may kink since the nipple on the Forge unit is fairly long. I cut one of the tie-wraps which restrained the tube and allowed it to relax. I used another tie-wrap and loosely bundled it back a bit. The 1/8" ID tube may be rather tight; use some veggie oil to help ease it onto the DV's nipple.

7. Start the car and check for any possible leaks.

8. Bolt the under belly pan back on and lower the car.

10mm 3/8" socket
3/8" drive ratchet
small flat blade screwdriver
A quarter or nickle (to remove the desus clips)
Needlenose pliers

Misc. Items:
soap or veggie oil.