8 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHEarly 996 C4 brake booster hose vacuum leak
Leading reported evidence
Repair very easily vs
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
The elbow can be repaired very easily vs replacing it.
Leading evidence: 'Repair very easily vs' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'resonamce flap pivot in the rear crossover tube' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Repair very easily vs' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Discussions that suspect a cause
1
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Suspected cause
The leak behind the tb is probably the resonamce flap pivot in the rear crossover tube.
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Suggestion · Original poster
I tried replacing both the C clamps and O rings with new Porsche genuine ones and I'm still getting the leak and other symptoms.
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Suggestion
The rubber "elbow" replaces the plastic " elbow" ..
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Suggestion
I'd probably replace the old plastic pieces before trying grease or making a gasket.
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Suggestion · Original poster
Do you put the straight adapter inside the Dorman elbow, clamp it off on both sides and then use the existing metal bracket to connect the adapter to the manifold?
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Suggestion
It is a high quality thick rubber that is oil resistant and can hold 29 inhg vaccum because that is what it is designed for to use on FoMoCo Modular engines..
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
8 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
1 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
I tried replacing both the C clamps and O rings with new Porsche genuine ones and I'm still getting the leak and other symptoms.
Hey all,
My car recently got check engine light codes P1128/P1130. Since I got the car, Ive been noticing hesitation or jerky throttle response at lower RPMs especially during the cold start cycle. I did a smoke test and found a leak from the brake booster hose on the engine side where it connects to the intake manifold.
I tried replacing both the C clamps and O rings with new Porsche genuine ones and I'm still getting the leak and other symptoms. My car has the early 99 design with the 90 degree plastic elbow and the straight adapter. I took the adapter out and did a smoke test on it and it didn't have any leaks. The leak seems to be coming from the manifold side of the connection more than the hose side of it, though Im not sure if its leaking where elbow connects to the adapter or where the adapter connects to the manifold given how small the parts and how close they are to each other.
Wanted to get some advice for how I should proceed:
1) Is there a trick to properly fitting the straight adapter and C clamp to the 90 degree elbow so it's air tight? I couldn't find anything in the workshop manuals or google search about this.
2) Could the issue be that the adapter has shrunk and so it's unable to make a flush connection with the manifold? I saw "Man in a Garage" made a home made gasket for his and have seen other forums say they added petroleum grease around the O-ring to ensure an air-tight fit.
3) I saw a thread where it was suggested to just replace the Porsche 90 degree plastic elbow for a PVC elbow from auto parts store (Dorman 46051). The design of this connection seems over complicated and prone to leaks so Im wondering if its even worth trying to fix it using the original design parts vs. just going for a simpler but not "proper" fix?
The Dorman 46051 is my discovery to solve this problem. It is a high quality thick rubber that is oil resistant and can hold 29 inhg vaccum because that is what it is designed for to use on FoMoCo Modular engines..
I also include this in the 99 model years UAOS System because this leak is so prevalent...
The OEM plastic elbow has two "internal" O-rings (
99923049840 ) it may still be available if you want to use it and can find one..
Do you put the straight adapter inside the Dorman elbow, clamp it off on both sides and then use the existing metal bracket to connect the adapter to the manifold?
Alright the Dorman elbow is in. I used the 120 degree one out of the 2-pack and a couple of these clamps I found at O'Reillys. No more smoke coming from there. I did notice a smaller leak from behind the throttle body which I hadn't previously but I'll chalk that up to being tunnel visioned on this brake booster hose leak . Drove the car the check engine light is still there but the throttle response felt better and the car felt smoother at lower RPMs.
I had the same thought about the adapter shrinking with age. If the smoke is clearly coming from the manifold side and you've already replaced the O ring and clamp, I'd suspect the plastic adapter or the sealing surface more than the O ring itself. I'd probably replace the old plastic pieces before trying grease or making a gasket. The Dorman elbow seems like a reasonable fix if you're not concerned about keeping everything original.
The elbow can be repaired very easily vs replacing it. Once you remove the plastic ends that are held out with the grey clips (locks), you can pull out the oring at the bottom(pick tool). It will be very hard and brittle (probably wont come out in one piece) and certainly is no longer sealing (hence the leaks). The o-ring is a 20mm OD x 14mm ID x 3mm cross section. You can buy some silicone ones on amazon for like $6 for 20 of them. Just push the oring back to the bottom stop and re-insert the plastic piece. It will reseal like new. The original o-ring is buna rubber and they get hard with age and temperature, so the silicone one will last quite a bit longer. Alternatively, the replacement fitting(15mm acetal fitting with buna rubber oring) is available on Mcmaster-carr for like $6, but you will have a $10-12 shipping charge.
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