jpurban

Quick question... Is the Venturi tube (#9 in diagram) that is part of the intake manifold vacuum piping reliable?

I know it has an internal check valve. So, I thought I'd ask to see if it should be replaced opportunistically.

My intake is already disassembled to repair the dreaded #16 check valve failure. Since I'm in there, I'm wondering what else I should do. It ain't a fun task to deal with #16, especially with the stock position of the clamps, and I don't want to go back in there again any time soon.

While I'm at it... Damn the factory position of hose clamps on the #16 valve. I broke the nozzle/tube on the intake. $180 mistake due to the combination of hose clamp position and a low cost (poor) plastic design of a small "nozzle". As has been said by others before me, be very careful the first time you replace #16.

pfbz

My #9 Venturi had a small leak when I pressure tested the system, I replaced it. 996.110.652.70, about $40.

It's shutting the barn door after the horse has run off, but a good way to NOT break your plenum nipple when replacing #16 is to use something like a drywall saw and just completely cut through the small piece of hose between the check valve and the plenum (#8 in the diagram). Once the check valve is free and completely removed, it's much easier to get to the clamp ears on the back-side and remove the bit of hose still attached to the plenum. Then just use a new piece of hose when reinstalling...

Picture below shows the cut hose that finally got my check valve off without breaking anything, along with all the replacement parts. I also replaced both small check valves ( 964-110-950-02), one had a small leak and the N75 valve. The N75 valve was working fine but the mounting ear was broken off, so I replaced it.




This is the kind of drywall saw I used to free my check valve! I don't think you'll find this method in the factory service manual, but it works wonderfully...

dos531

Mine exploded recently. I would replace it while you're there.

"02996ttx50

#16 is a bitch, indeed lol.

jpurban

Thanks for the confirmation... I'll order a new venturi.

Anyone ever researched a higher quality check valve for #16? That thing feels quite cheap -- almost no weight to it. Shouldn't really be surprised that the lightweight spring/flapper in it fails routinely.

Along the same lines... Do we really need the venturi for the brake booster? I'm guessing the venturi ensures vacuum is available to the brake booster when under boost... Certainly a lightweight solution, but seems overly complex since we're not really going to brake often (or for very long) under boost. Strikes me as similar to the boosted, overly complex OEM clutch slave that most of us just convert to a GT2 like arrangement for higher reliability. Am I missing something here?

Maybe we should consider less complex, more reliable, higher quality check valves to replace the venturi as well as the #16 check valve. I mean, who wants to do the #16 valve replacement more than once? I'll bet somebody on the forum already came to that conclusion...

pfbz

Member Powdrhound converted his uber 996 GT2 (same stock venturi setup as the 996 turbo) to the 997 GT2 vacuum pump which eliminates the need for the venturi... Not sure it 'simplifies' the system very much but evidently has a positive impact on brake feel, especially on the track. I'm sure the conversion is also quite expensive.

Link:

As for check valves, I've seen quite a few threads mentioning potential afermarket replacements for the #16 check valve, but nothing definitively better.

"02996ttx50

it all comes down to plastic parts. for as long as they are important? think r&r on occasion.

atlzhp6m

Here's a video of my venturi under slight air pressure. Replacement is on the way.