Found the leak, cannot I.D. the part!

After quite a few premature declarations of victory, I believe I have finally found the cause of the high idle (sticky throttle) on my 1999 C2. I bought a "Stinger" smoke generator (highly recommend) and in about 30 seconds found a monster vacuum leak....two actually. Now the issue is, what is this part called, and what is the part number. It seems embarrassingly easy to identify, but I just spent an hour at my local dealership, and they couldn't identify it - largely 'cause the Porsche parts drawings on vacuum system show the pieces in isolation, not relative to the engine around them. Also, any model built before the 991 series seems to be an antique to them. Here are the photos. I am hoping the hose is a two piece and that where it transitions from "accordian" style to smooth is a connection point, otherwise the engine will have to be lowered to get my arm in there. At the 90 degree connection, I assume that is a piece that can be disconnected from the hose..... Close up shows hole in hose, and the 90 degree connector that is also leaking. leaking hose and 90 degree connector are within this purple box I am so excited to have found this problem, I just hope someone out there can ID the parts! Thanks

Unless I'm mistaken, that's the return vacuum hose from the AOS to the intake manifold. Those two 8mm bolts are also holding a vacuum solenoid. The hose should be found on the parts diagram for the AOS. I'm surprised the dealership couldn't assist.

Well, It's a Saturday.... They seemed to think it is the brake booster vacuum. I asked if the mechanic could just look at the picture I took, but they were going to charge me for it! I have looked at the drawings for quite a while, and while I hope it is the AOS line, i cannot be sure....

No its the vac line for the brake booster. Its the other side to #10. Not sure if one hose runs the full length. I know the elbow is sold seperate. I just cant find the pet pic. http://www.autoatlanta.com/porsche-p...section=604-00 maybe #14? http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996-99-05&section=604-15

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I can't be 100% either. I've replaced brake boosters on my Volvos, but never the Porsches. Maybe some of the Porsche techs will chime in here.

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Ok... so if it's a brake booster vacuum line, wouldn't the hose connect a coupler. I'm sure it runs the length of the car to connect with the master cylinder, correct?

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It's the vacuum line for the Power Brake Booster. The corrugated part is made into a long metal hose that goes over the engine and will be a bitch to replace. I would suggest getting some Marine Adhesive shrink tubeing and repair it. Cover the leak area with some black silicone sealer then shrink the heat shrink tube over to create a very sturdy leak-proof repair. The plastic elbow is available separate,and is only used on early 99's, so make sure you get the right one, the late 99 and up use a 1 piece..

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Skip, how does Porsche service handle this type of replacement? Does the engine need to be dropped a little to gain better clearance to remove the hose? (see picture) is this the correct hose for Craig?

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Yes, that is the correct hose. There are two different ones, an early 99 version and a late 99 and up version..The early version hose uses a 90* elbow and a straight intake connection adapter, the late 99 and up version uses a 1 piece 90* intake adapter. Yes you will have to lower the engine and snake it up over the engine and clip it into the brackets..

Looking at PET, it looks as if the early version like he has is discontinued, so he will have to use the later version and use the later 1 piece 90* intake adapter part number 996 110 151 52

early design hose with 90* separate elbow and straight intake adapter Later design brake hose with 1 piece 90* adapteralso fits better to the UAOS kit

Thanks guys. I figured if the hose does not disconnect at a second point before it disappears over the engine, I would try to patch it. I disconnected the elbow from the hose and the body it connects to. I was hoping the silver ring at the back end of the accordian hose was some sort of connector that could be used to remove the damaged hose, but I guess not. Will the new design elbow still connect to the aluminum end of the leaking hose?

The leaking hose is now also covered with mineral oil from the smoke machine. Should I use Carb cleaner, Brake cleaner, or something else so the silicon will stick to it?

If you are going to repair the corrugated hose, you can use your existing 2 piece elbow and straight intake adapter, or replace them if necessary (Leaking), they are still available (but the early design hose is no longer available).. The later design 1 piece intake adapter will NOT work with the early design hose, which is what you have..

I just had it confirmed by porsche the the early adapter, which I have, is no longer available..... Is this the adaptor you say i can still purchase?

Are you certain the original hose won't fit into the new adaptor?

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Yep, that is the two piece early design part numbers 996-110-151-51 straight intake piece and 999-230-498-40-----90* elbow... the elbow part # 999-230-498-40 is what usually leaks, I have recently bought them in the last few months, if they are discontinued, it only happened recently.. Yep, if you look at the examples I show, the early design comes in at an 10 o-clock angle and only the 2 piece design will swivel to that angle. The later 1 piece design comes in at 12 o-clock.. and does NOT swivel.

Porsche tech - you are super helpful! I think the reason I had a leak at the swivel point as well as the hole in the hose is that the c-clip is missing, allowing the joint to loosen (see photo) You wouldn't happen to know the part number for the c-clip would you? It is not on porsche drawings that I can find... I assume there is supposed to be a c-clip here as well as at the hose end. If so, it is missing, allowing the coneection to be loose and leak

Plastic "c-clips" part # 999-230-512-40

What a coincidence, I had a separate thread asking what that hose was all about, as I too am missing that clip. Along with the clip, it has been suggested to get the accompanying O-ring (999-701-163-41 I believe) so everything seals up nice and tight.

I think the problem with mine was simply the missing clip at elbow joint (there are 2) allowing the compression fitting to leak. PORSCHETECH3 was invaluable help, turns out all the original parts are still available from Porsche. Also get the small o-ring, old one may be intact but brittle. New parts arriving tomorrow....cannot wait

You have got to be kidding me... This is the same issue that I've been dealing with for months and lo and behold my elbow is missing the c-clip and probably the o-ring as well. The elbow can be smoothly removed from the intake manifold adapter with a gentle pull.

That's 3 of us. Sounds like a conspiracy to me, except an O-ring + clip is less than $5 at my friendly local Porsche parts counter. If this is the only vacuum source to the brake booster, I wonder how much is actually leaking through there.

The missing clip shouldn't impact the o-ring, it's behind the mounting plate with the two screws in it.... There must have been a lot of failures since porsche re-designed the elbow at the end of '99

There was quite a wisp of smoke coming out of my clipless elbow joint....not as much as was pouring out of the hole in the hose, but enough to cause a problem. I am interested to see what the brake performance will be when I get my parts tomorrow

Well, the new parts are on and, unbelievably, the car is worse than ever! A spirited drive and the tachometer wouldn't drop below 2300 under load. If I applied the brake with the car in gear, I could drag the rpm down to 1000, go into neutral, and the car would idle normally. But any time I go over 2300 in gear, the engine would never drop below that point while shifting, or if i just put it into neutral at any speed from any gear when the engine was running at 2300 or more. When I returned to my driveway, I dragged the rpm down by braking. Then I put it into neutral and repeatedly reved the engine over 3000 rpm. Each time the car returned to normal idle. i have no idea what to check next.

What happens if you encourage a bit of a leak somewhere? Brake booster probably isn't the best place for that. Just wondering....

Is it possible that this is a "learned" behavior? Can you reset your ECU by disconnecting the battery for a while? I wonder if somehow the computer has adapted to the leak and now that it's fixed it's still acting as if it was there.

Thanks for that, wiggle puppy, i will try that first thing tomorrow!

Wiggle puppy rules! I couldn't wait 'til morning....disconnected battery for 1/2 hour, went out and tore it up! Never once had the high idle! Finally....it just needed the ECU reset after the numerous repairs. Thanks to all!

Excellent! Good call Pup!

When you added the clip, did it make the elbow sit tight? I did mine yesterday and the elbow still slides off with only a little persuasion.

F-Lambda, my elbow sits tight on the intake manifold now. It didn't really "clip on" in a way that assured me but it seems to be alright. I still have the 2200 RPM hang after replacing that part so I guess buying a smoke tester is my next step.

Thanks wiggle_puppy. Did the clip and the o-ring and it seems fine, just isn't as secure a fitting as I would like. I did the home-brewed smoke tester with a soldering iron and baby oil. Made enough smoke that I think I'm good.

On the pipe elbow there is a white plastic clip like a I shaped thing which slots into the ends of the elbow to stop the ends sliding back like when you push them back to remove the pipe from the elbow, it's like a lock piece, I didn't even know about it and it wasn't on the diagram I ordered from but when the parts came they were in there , they seem to lock out the elbow and make it fit better, I will get a picture

So both ends of the elbow are compression fittings, as you know. You compress the female ends of the elbow into the elbow, and install the male hose/straight piece. Then you pull the tip of each end of the elbow away from the elbow toward the hose/manifold, creating a space that is just wide enough to install the clip. Installed clip has pieces of the elbow on both sides of it. The clip forces the compression of the joint by pushing the tips of the elbows TOWARD the hose/manifold. Counter-intuitive perhaps. I found that my original remaining clip seems to have shrunk, and was very sloppy, and easily rotated around the circumference of the elbow; whereas the new clip seemed to be wider and was much tighter - forcing the compression joint to be tighter. They also were different colors, suggesting that the original clips may have been made from a material that could shrink from the heat of the engine compartment (as PVC and other petroleum based plastics can) You might also clean the straight piece and the aluminum hose tip with a little alcohol soaked rag first, there was some soot on mine which could cause slippage. Don't give up the fight! If your problems continue I am sure you will find a vacuum leak somewhere. The "stinger" smoke machine I bought was only $150., much cheaper than a shop to test the car, and produced smoke like a battleship. You will need a compressor....you need to pressurize the system to force the smoke through all the lines.

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I chased vacuum leaks yesterday too. I built a home-brewed smoke machine too, with a large mason jar. Drilled three holes in lid, one for soldering iron, and two for brass spigots (threaded at one end, barb at other). Epoxied them all in place, old bit of cotton towel in bottom and soaked with mineral oil (baby oil). I simply used a bicycle pump to produce pressure, it�s very easy to regulate and clips straight onto the barb connector. I replaced my brake booster elbow, and o-ring, but was still getting some leakage around the hose connection (**** poor system to try to seal air IMO). I also had some leaks around my AOS connector, where it connects into the intake. A little grease on the o-ring seemed to solve that. Out of frustration, I actually used some electrical sealing tape (made to create water tight connections)...that fixed the leaks but good.

I'm thinking there's some wear and tear on the elbow joint. I can see how it's trying to compress but there isn't much action there. Another trip to the parts counter for me .

It cannot be happening again! After resetting the ECU as per Wiggle-pup's advice, and enjoying a normal engine performance for a nice long drive, day two brought me right back to where it all started, but perhaps worse. The car is now stuck at 2500 RPM, and will actually climb to that RPM if I put it in neutral at any RPM below that. Do you think the ECU is toast? I cannot imagine any other mechanical problem causing this - It has to be an electrical/sensor issue. I am at a total loss at this point.

I have a fabspeed exhaust with an x-pipe and no cats....could this be an issue?

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Resetting the ECU just takes it back to factory defaults. It doesn't really indicate that the problem is fixed, it just forces everything to work at some default setpoints. Over time, the ECU changes these values to 'optimize' something...Air to Fuel ratio? Sorry I don't know what it is. But, it does indicate that you still have some type of leak. It must not be too severe as the car runs OK when the ECU is reset. If it was a big leak, it would run horribly. Sorry, not a lot of help. It seems you need a Durametric to figure out which sensor is off and forcing the high idle. I learned about this on our old VW Passat wagon. The fuel trims would wander out spec and throw a code. Many days later using the Vag-com (Durametric equivalent), I figured out the pre-catalyst O2 sensor was 'lazy' and not responding fast enough to feed the computer the correct information. The ECU's response was to up the fuel trim... Good luck with the continued search.

Could be as simple as the TPS showing a tenth or so more volts than it should, causing the DME to keep the ISC open. You need a Durametric or some OBDII tool that can show sensor values.

Do the cable throttle cars have a TPS? IF it were to go bad, would it cause a CEL? Thanks

Is it part # 996-606-116-00-M14 ?

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that is a throttle position switch but before u throw more money at your car because of internet guesses get some proper diagnistics done. A durametric would have paid for itself by now. As said above u need to see what the individual values of the tps, map, o2, fuel trims and several others ti figure out which one is screwing up. U can easily spend thousands of dollars replacing them one at a time.

I agree wholeheartedly with your position on not just throwing parts at a problem. I don't have much confidence in my diagnostic abilities when it comes to automotive electronics. Nor do I have the patience for the learning curve of a software package relating to the durametric. And I don't even have a laptop. So....I can take the car to an independent to do that for me, I suppose, but that's close to $100 an hour and lost work time for me; or $105 to Pelican for a Bosch part, while a shot in the dark perhaps, seems to be a low risk high reward proposition. I will give it some thought.

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Cable cars do indeed have a simple TPS. Going BAD ,is kind of a relative term. If the value goes "off scale" above 4.5 volts or below 0.6 volts it will flag a CEL fault. Any value between 0.6 volts and 4.5 volts is considered g ood whether accurate or not.The TPS is a simple wiper type rheostat, if the wiper becomes worn or dirty it can become very inconsistent. The DME learns the "closed throttle" setpoint (usually around 0.9 volts) and keeps this as the absolute value for closed throttle. IF the value is not consistent then the DME will not be consistent at performing idle functions. You really need a tool to show values and stop guessing or asking for guesses. You can get an OBDII dongle and a phone app for less than $20 bucks. Sometimes I don't mind using the SWAG method (Scientific Wild *** Guess) to help someone, but had much rather have accurate data, to give a positive concrete diagnosis, so that I am Right and not Wrong..

Thanks Porschetech3 - this will be the final effort for me to correct this problem, then it's off to a professional with the equipment to solve the problem.

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What�s the part number on that line for 2002 C4S manual? Looking to replace it while the engine is dropped down some.

99610714759 Use autoatlanta to find all your parts https://www.autoatlanta.com/porsche-..._911_parts.php

Oh yea i do! I was just having trouble finding the right one. Also you sent the incorrect part number yourself. You send the AOS/Crankcase breather hose.... the one mentioned here is the brake booster hose that attached to the Intake manifold via the 90* elbow....

My bad....i didnt read through the 4 yr old thread and confused it with another. The booster hose parts r in there too.

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You need this one..... 99635557506

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thank you skip!