Impossible Intake Seal
Thread Starter
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Road Warrior
Joined: Dec 2015
Posts: 1,416
Likes: 317
From: CA
Impossible Intake Seal
Hi, I have a 2003 Wide Glide with carb. Replaced the intake seals on it and they were fine for some time. However, it started to pop through the carb and backfire on decel showing signs of lean.
A spray test with brake cleaner strongly shows that there is a leak on the left (non-carb) side of the seals.
I replaced the seals again to eliminate that as the issue but there's still a leak. I pulled off the intake to check for hairline cracks or warping. Could not detect any. I checked the air sensor for leaks as well to the best of my ability (hold the ends of the intake and exhale into the intake. Seemed rock solid.
Can an intake manifold warp or otherwise become damaged? It looks pretty solid. The seals seem to install fine. I have the install tool as well as the intake alignment tool. I took it very slow and methodical on install. The carb to intake seal is new and good. Yet there's still a leak. Very strange.
Thanks for any suggestions.
A spray test with brake cleaner strongly shows that there is a leak on the left (non-carb) side of the seals.
I replaced the seals again to eliminate that as the issue but there's still a leak. I pulled off the intake to check for hairline cracks or warping. Could not detect any. I checked the air sensor for leaks as well to the best of my ability (hold the ends of the intake and exhale into the intake. Seemed rock solid.
Can an intake manifold warp or otherwise become damaged? It looks pretty solid. The seals seem to install fine. I have the install tool as well as the intake alignment tool. I took it very slow and methodical on install. The carb to intake seal is new and good. Yet there's still a leak. Very strange.
Thanks for any suggestions.
Thread Starter
|
Road Warrior
Joined: Dec 2015
Posts: 1,416
Likes: 317
From: CA
I've watched that and a few other vids several times. Goods stuff.
I was working on it this weekend. It is not fixed but the answer to the impossible seal problem is that it's not a seal!
I tried using a precise spray bottle of water instead of brake cleaner. I sprayed all around the manifold seals. No change in RPM. When I aim brake cleaner in just the right place, it looks like it's hitting the seal but what I think is happening is that it's going to a leak in the carb. When I spray from the side opposite the carb and then spray toward the carb, it revs higher. As a test, I sprayed brake cleaner directly into the carb and it stalls it.
So what I want to do next after buying more brake cleaner is use a longer tube and use more precise shots at the carb and seals to try to pinpoint it.
The carb has a brass fuel elbow so that's not a problem. I'm on a 3rd carb to intake seal boot to eliminate that so I don't think that's the issue.
If anyone has any suggestions on how to troubleshoot an intake seal leak that isn't an intake seal leak, I'm all ears.
PS - I did replace the map sensor seal as well and have eliminated the vacuum petcock tube as a possible culprit.
Thanks.
I was working on it this weekend. It is not fixed but the answer to the impossible seal problem is that it's not a seal!
I tried using a precise spray bottle of water instead of brake cleaner. I sprayed all around the manifold seals. No change in RPM. When I aim brake cleaner in just the right place, it looks like it's hitting the seal but what I think is happening is that it's going to a leak in the carb. When I spray from the side opposite the carb and then spray toward the carb, it revs higher. As a test, I sprayed brake cleaner directly into the carb and it stalls it.
So what I want to do next after buying more brake cleaner is use a longer tube and use more precise shots at the carb and seals to try to pinpoint it.
The carb has a brass fuel elbow so that's not a problem. I'm on a 3rd carb to intake seal boot to eliminate that so I don't think that's the issue.
If anyone has any suggestions on how to troubleshoot an intake seal leak that isn't an intake seal leak, I'm all ears.
PS - I did replace the map sensor seal as well and have eliminated the vacuum petcock tube as a possible culprit.
Thanks.
Thread Starter
|
Road Warrior
Joined: Dec 2015
Posts: 1,416
Likes: 317
From: CA
Yep - the rubber is good. Accel diaphragm and main dia are in great shape. I think I have found an issue but will need to get back at it on the weekend. Not counting chickens yet.
I also ordered parts to return the Dynojet parts to stock. CV Performance should literally sell an "un-f*ck" kit for that POS. No offense to those who actually like that stuff.
I also ordered parts to return the Dynojet parts to stock. CV Performance should literally sell an "un-f*ck" kit for that POS. No offense to those who actually like that stuff.
Tourer
Joined: Jul 2007
Posts: 250
Likes: 7
Be sure the plastic knurled nut where the enricher cable goes into the carb is clean and snugged up good. Careful not to over tighten though. I remember seeing a youtube where it was pointed out that this can be a source of air leak.
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Seasoned HDF Member
Joined: Apr 2010
Posts: 9,586
Likes: 7,969
From: Long Island, New York
Old school suggestion, intake leaks have been an issue forever. For my Flathead I take off the carb and then built a simple metal plate that I can attach to manifold that has a tire inner tube valve attached. With an air compressor, air gauge (HF has ones to regulate it very precisely) you pump it up to 14.5 PSI. 14.5 has something to do with atmospheric pressure. Let it sit for about a minute maintaining pressure then spray everything with soapy water and wait for the bubbles. Then you know where the leak is, not sure how this translates to an Evo but it is low tech and easy to do. Good luck.
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Road Warrior
Joined: Sep 2014
Posts: 1,872
Likes: 1,325
From: DeLand, Florida
Sounds like you may have a porous intake manifold. Only way to know for sure is to take it off and paint the outside to seal it or get a new one. BTW I use starter fluid to check for leaks as it doesn't stain. Never thought about brake fluid. May give it a shot to compare next time I am looking for an intake leak. Anyway. Good luck.
