Hey everybody -

I cut open 2 check valves this weekend to see how they work, and why the OEM valves fail.

First up was one of the green/white check valves. I can see how the design fails - there's a disc of VERY thin red rubber that's bonded in the center of the disc. The edge of the disc covers about 4 pinholes in the plastic. Air coming from the bottom pushes up on the flap through the pinhole and continues on its way. Air going the other direction would push shut the flap and not continue through.

Well, time, heat, and oil will erode the rubber flapper, making it stick open. With it open even a little bit and the flapper turning hard and plasticy (like the vacuum lines) it can't flex back to seal the holes up. Once this happens, air can pass both ways and the valve fails.

The second valve is the metal check valve that comes from the purge control solenoid. This valve keeps pressurized air from blowing into the fuel tank and charcoal canister.

Surprisingly, this is actually a pretty well-designed valve. It uses a plastic ball with a return spring. Unfortunately, I couldn't see exactly *how* it failed since I had to cut the case open. It may have been repairable by cleaning it out with carb cleaner and using something thin to work the ball against the spring. Good thing is there's only 1 under the hood and it's $16. I may have to find a Viton valve and see if it will work in this application .

Anyhow, thought you guys would be interested. It always helps to understand the design of the stock parts!

On the second pic of the green/white check valve, I'm raising the rubber flap up to reveal the pinhole - you can just see it in the pic.

Dale

 

you were bored while the forum was down huh! Time well spent substituting tedious work for forum talk At least you kept your mind focused on the car!

 

Interesting pics. Have you done a vivisection on one of your new viton check valves yet?

 

You can almost see through the kynar/viton ones. Same design, but better materials.

Dale, did you cut open a green/black one? I'm curious if they have the filter they were rumored to contain. In fact I might have one around if I can find it.

Dave

 

Where do you get these? I need a check valve for the brake booster vacuum line.

 

I sell the small Viton check valves - I don't have any large enough for a brake booster. I might be able to source a larger one - let me do some digging.

Dale

 

I checked, and I can't get any check valves anywhere NEAR big enough for a brake booster. Sorry, Jim!

Dale

 

Jimlab, Try McMaster Carr.
They might have something for your application.

http://www.mcmaster.com/

 

jim, If you just need the hose that has the valve in it. Ray @ Malloy has the "booster hose kit" in stock all the time and it is only like 6 bucks. comes with both sides hose. The valve is in the booster side hose in all the kits I have gotten from him.

If you are just in need of the valve itself then Mcmaster as stated above

 

I don't want the stock formed hose, or the tubing that used to run across the firewall to the backside of the intake manifold.

Are these the type of check valves being discussed (they list a Viton valve seat as an option) on page 387 of McMaster Carr's catalog? They have a spring loaded ball type valve.



Or these?



They say these are available with a Viton diaphragm and Nylon body (translucent white and black or translucent white and gray) or Viton diaphragm and PVDF body (translucent white). Page 389.

 

I'm getting the check valves straight from the manufacturer - the ones I sell are similar in design to the bottom valve. Problem is I can only get them in sizes up to like 1/4" or so nipples.

If you want a quality in-line check valve, the '87-91 TurboII used an external check valve for the brake booster - it's not integrated in the vacuum line like the FD. Sized properly, works well, and I've NEVER seen one have any problems. It has the right sized hose barbs for in and out, too.

Dale

 

Hey Dale,

Do you still offer the VITON check valves?

 

Sure do, just got a whole new batch in last week. I'll send you a PM.

To add to this thread, the Viton valves I sell have a fail-less design. The stock check valves depend on the diaphragm flexing up and down to work properly. The Viton ones I sell have a floating disc inside, it seals on the bottom of the valve with vacuum/pressure shutting the nipple off. Hard to explain, but it works great. I warranty the Viton check valves for life, and so far I've only replaced 1 or 2 out of the thousands I've sold.

Dale

 

Replied and payed.

If anybody else is thinking about this, do it.

DALE'S PRICES ARE AWESOME!!!!

 

Dale, do you have any online documentation you can share regarding your check valves? I may have to pick some up. Please post a link, thanks Did you ever get a hold of a viton valve for the purge control?

 

pm sent

 

Good job cutting that check valve apart. I have learned so much about cars by tearing down/cutting up/disassembling OEM pieces from various cars. I cut an ISC valve in half once and after I finally understood fully how solenoid valves work. I disassembled an ebay external wastegate and I learned a lot. Rotary engines finally made sense to me when I had to put one together myself.

 

the bottom of this page has someintersting check valves we might be able to use

http://www.mcmaster.com/#plastic-check-valves/=4raai0

 

Does anyone know what the "cracking pressure" or the original green/white valve is. According to the websites, the non-oem valves crack at 1 PSI.

It would be good to have a comparison

 

i just got the vavles today
looks strong lol

so where are all the check valves located ?

 

If you remove the black pressure tank behind the alternator, you can see/get to at least 2 of the stock check valves, maybe 3. One is in the back under the upper intake manifold and you really need to pull the intake manifold to get to it.

But, the ones up front are the ones for the turbos - those are the ones that really need replacing.

My check valves "crack" at pretty much no pressure. It's a floating Viton disc, takes very little pressure to move it. By the same token, it takes very little pressure for it to seal and start working.

Again, I've sold literally THOUSANDS of these check valves all over the world. I've had maybe 2 or 3 fail (the plastic case broke, could have been through rough handling or a manufacturing defect). I warranty them for life, so I'll be happy to replace them if they fail, but they won't . This is just one of the best bang-for-the-buck things you can do on the FD.

Dale

 

Sorry, I was asking the cracking pressure/suction of the original green/white check valve. Has anyone tested these to see when they open?