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I finally invested in a small smoke tester and I immediately detected 3 sources of leakage. Both joints for the AOS connector to the intake plenum are leaking. The gray spacers/locks have been removed for disassembly prior to taking the pic. I’m guessing that replacement of this elbow assembly is the only fix?
Also, there’s a leak on the forward plenum boot (forward of the throttle body) from this circled area. What is it? Does it look like it’s missing something? It appears to be threaded but I can’t quite tell.
A Dorman 46051 rubber PCV elbow makes a nice fix for this if also use two appropriate spring clamps. (oil resistant and vacuum rated).
The leak at the crossover plenum is where the "resonance flap" shaft extends through the housing. I don't have a good fix for this other than replace it with a non-leaking one...
A Dorman 46051 rubber PCV elbow makes a nice fix for this if also use two appropriate spring clamps. (oil resistant and vacuum rated).
The leak at the crossover plenum is where the "resonance flap" shaft extends through the housing. I don't have a good fix for this other than replace it with a non-leaking one...
Brilliant. My Autozone has the Dorman elbow in stock.
As to the resonance tube, would some RTV over the port/threads make for a temporary fix until I have time to dig into it?
Here it is with the Dorman piece and two 13/16” spring clamps.
This pipe lube is some magical stuff and I would have really struggled today without it. It definitely helps when dealing with old cars (and potentially brittle components). It’s saved me quite a few times with the 996 and with my prior 928.
That Dorman 46051 elbow make a nice replacement for the plastic o-ringed factory elbow. Only used on the "early '99" and I include the Dorman piece in the UAOS kit for "99 models.
That Dorman 46051 elbow make a nice replacement for the plastic o-ringed factory elbow. Only used on the "early '99" and I include the Dorman piece in the UAOS kit for "99 models.
You da' man Skip.
On a side note, I can't figure out why people keep telling me that my 9/98 build isn't an "early 99" yet I keep finding details about it that only apply to "early" cars?......
On a side note, I can't figure out why people keep telling me that my 9/98 build isn't an "early 99" yet I keep finding details about it that only apply to "early" cars?......
Don't pay no mind to what "people say", they always try to split hairs make concrete rules. One thing is for certain when it comes to Porsche, there are no concrete rules and there is always an exception .
Don't pay no mind to what "people say", they always try to split hairs make concrete rules. One thing is for certain when it comes to Porsche, there are no concrete rules and there is always an exception .
By the way, here’s what I came up with for the leak in the resonance pipe. The OD of the nipple appears to be almost exactly 3/4”. I found these vinyl plastic caps at my local hardware store. I had to lower the engine on the mounts in order to have room for my hand to get in there. This cap has an incredibly tight fit on the nipple so I’ll test this for now and see if I can get by without applying any adhesive. Fingers crossed!
EDIT: Smoke test passed with zero leaks on the motor.
Last edited by islaTurbine; Apr 1, 2022 at 08:58 PM.
I have a suspected vacuum leak too, despite changing out most of the skinny vacuum hoses, as well as the U and I rubber couplings on the various components.
@islaTurbine what smoke machine did you get? How is your “chair leg cap” fix holding up?
I have a suspected vacuum leak too, despite changing out most of the skinny vacuum hoses, as well as the U and I rubber couplings on the various components.
@islaTurbine what smoke machine did you get? How is your “chair leg cap” fix holding up?
While maybe not the direct subject of this thread - would a loose intake pipe cause a sporadic rough idle? This would be the soft rubber pipe that connects the throttle body to the air filter housing. I tightened the pipe and went for a drive where I reached operating temp and it seemed to be more stable but sometimes it’s stable anyway.
My symptoms so far are:
1. Rough idle on startup (sometimes it happens, sometimes it does not)
2. Stable idle during warmup
3. Sporadic idle drop when warm - drops to about 400 and bounces back when clutch in while slowing down.
4. Engine stalled twice in 900 miles, when the idle didn’t bounce back after clutch in coasting to a stop. Engine was at operating temp both times.
5. Had a pending code for O2 Sensor Oxygen Sensing Range 1 Below Limit Value. I changed all 4 O2 sensors, cleared the fault code memory, and it hasn’t come back yet after about 200
miles. The idle problems remain. No other codes.
I’m reluctant to throw parts at this beyond the O2
sensors I changed because I’m not convinced they cured the issue. What other numbers can I read from Durametric (and at what time - cold start, warm, hot, etc.) to help diagnose the issue?
While maybe not the direct subject of this thread - would a loose intake pipe cause a sporadic rough idle? This would be the soft rubber pipe that connects the throttle body to the air filter housing. I tightened the pipe and went for a drive where I reached operating temp and it seemed to be more stable but sometimes it’s stable anyway.
My symptoms so far are:
1. Rough idle on startup (sometimes it happens, sometimes it does not)
2. Stable idle during warmup
3. Sporadic idle drop when warm - drops to about 400 and bounces back when clutch in while slowing down.
4. Engine stalled twice in 900 miles, when the idle didn’t bounce back after clutch in coasting to a stop. Engine was at operating temp both times.
5. Had a pending code for O2 Sensor Oxygen Sensing Range 1 Below Limit Value. I changed all 4 O2 sensors, cleared the fault code memory, and it hasn’t come back yet after about 200
miles. The idle problems remain. No other codes.
I’m reluctant to throw parts at this beyond the O2
sensors I changed because I’m not convinced they cured the issue. What other numbers can I read from Durametric (and at what time - cold start, warm, hot, etc.) to help diagnose the issue?
I’d say the first step is to smoke your engine and see if you have any air leaks. I’d also simultaneously take a screen shot of all the Durametric parameters and start a thread with that info posted there. I had a lot of small issues that were culminating into a bigger one, so I had to slowly and methodically fix them one at a time. At first it seemed like nothing worked but then it turned out that every little fix was definitely making a progressive different.
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Engine Vacuum Leaks - help with analysis
