Vacuum leak assistance needed (pic)

chapstic2001 · 11-26-2005, 11:55 AM

I have a nasty boost hesitation that I am trying to resolve. I have lifted up the hood with the car running and I can hear an obvious vacuum leak I have narrowed down the leak to be from the BV to the connection bettween 3 and 4 intake manifold, see picture. When I pinch off the line at the intake, or at the BV, the hisssss goes away. I have zip tied all the connections to no avail. Is it possible that the threads that are welded in to the intake manifold is leaking? If so, why does it stop once I pinch off the line?

Any assistance is good assistance.

AaronM · 11-26-2005, 01:28 PM

Sounds like the BV itself it leaking...

ae1969 · 11-26-2005, 02:05 PM

Quote:

Originally posted by AaronM
Sounds like the BV itself it leaking...

DING DING DING...

Chap check out that valve you will probably notice that the diaphram has a tear...

IanS · 11-26-2005, 04:45 PM

And yes, those lines going into the manifold can leak. My center line was actually loose when I bought the car, so I'm sure it was a vacuum/boost leak.

chapstic2001 · 11-28-2005, 07:01 AM

I took the vacuum line off where it goes into the manifold and physically blew into it. I could hear the BV blowing right through. Is that the tell tail sign of a shot BV? Also, Ian, you mention that the center line was loose. Are you refering to the acutall bung or the bolt? If it was the bung, I assume the intake has to come off and have it re-welded.

IanS · 11-28-2005, 10:18 AM

The actual bung was loose and could be slid completely out. I fixed it with jbweld, and pressure tested it afterwards with no problems. I don't think it was originally welded in there, I believe it was some type of epoxy/adhesive.

The best way to check a DV is to use a vacuum pump and see if the small nipple holds vacuum. It should. If you don't have a vacuum pump, take off the DV, push the valve open, put your finger on the small nipple, and the DV should stay open. This is a bit less reliable since it can be hard to get a good seal with your finger.

chapstic2001 · 11-28-2005, 12:53 PM

Thank you IanS. I will try the JB trick. It appears that there are small gaps to the left and right of the bung, not visible in my picture. I will try that and see if the DV is holding or leaking.

Cali56 · 11-29-2005, 12:47 AM

Quote:

Originally posted by chapstic2001
Thank you IanS. I will try the JB trick. It appears that there are small gaps to the left and right of the bung, not visible in my picture. I will try that and see if the DV is holding or leaking.

that part is actually threaded into the manifold, the gaps are for the wrench used to tighten the bung into the manifold, the other parts that hook into the breather and brake vacuum are actually epoxied in. Maybe there is a threaded insert epoxied into the manifold but it wasn't that obvious to me when I was looking at mine. If there is a leak in the bung that accepts the vacuum lines it could be loose threads, mine was loose in the manifold but the banjo was tight on the vacuum fittings. It's an easy fix if the threads are not stripped you can remove it, loosen the banjo, re-install the threaded bung with a sealant and tighten it with an open end wrench or an adjustable but they get in close to the manifold metal, I just used my fingers and then some needle nose with the sealant and positioned the banjo fittings so that as I tighten the banjo the whole lot twists into place nice and tight with the vacuum lines pointing in the right direction. as for the bypass/recirculation valve, it should be held close with spring pressure up to a certain air pressure before it opens and should take considerable vacuum on the small fitting to pull it open.. If you can blow through it without any force it's not doing what it was designed to do..

chapstic2001 · 12-05-2005, 03:08 PM

Yup, shot Diverter Valve. You can see by the picts that the diaphram in busted, but to double check, I tried the vacuum method. Any suggestions on where to get a quality replacement? I have seen a LR DV that does not have a diaphram which leads me to the impression that it would be a piston based system. Any thoughts? What are you running with that is not diaphram based? I do not do any racing so SCCA or PCA stock regulations are not a concern. Function is.

IanS · 12-05-2005, 03:15 PM

I'd get an 'improved' Bosch one from Paragon or Pelican. They work fine and are relatively cheap. You may have to replace them every 100k miles, but no big deal.

Zero10 · 12-06-2005, 10:08 AM

996 BOV, ~$30, and a direct drop-in replacement. Supposed to be better than the original.
I just experienced exactly the same failure, and am going to replace mine this spring.
I'm getting ready to put the car away for winter, and am in the midst of breaking in new rings, so it's not high up on my priority list right now, since I can't get on boost much right now (2-3psi tops, don't want to mess up my rings...).

Karl2bdc · 12-06-2005, 12:42 PM

Might as well drop in a billet diverter valve (you can get them at Evoms.com, they have the billet piston that will not fail like the standard one. They can be had for around 100-110 bucks.

ae1969 · 12-06-2005, 05:43 PM

......... as you can see yours has a rubber diaphram (original)..... the updated one is cheap as has been mentioned....The 993 part number one has a metal diaphram and it will work great

I went for bling and I use an HKS ssqv. Actually my 993 bov would gobble gobble under extreme use........ but the HKS is one tough cookie.....

chapstic2001 · 12-07-2005, 09:56 AM

I will probably go with the billit DV from Lindsey. Merry Christmas to me.

To continue the saga, I went back to the basics trying to isolate the hissssssing leak. I took the vacuum line from the DV and blew into it. There is still a leak somewhere. This is the strange part, when I pinch of the line, snicker snicker, at the intake manifold the leak stops. Riddle me this, does the air flow from the manifold to the DV or is it the other way around?

chapstic2001 · 12-15-2005, 01:21 PM

Well the billet DV from Lindsey did the trick. The hissing is gone. Unfortunatly it is sleeting here in NoVA and I won't be able to take it for a spin. I am still planning on going over the car with the air compressor and soapy water to see if there are anyother leaks robbing me of HP.

Thank fellas