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Thread: Evap Leak, but no codes showing

  1. #1
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    Evap Leak, but no codes showing

    Hi everyone,
    First post here due to a recent headache on trying to find a EVAP leak somewhere on my 1990 E32 735i.
    I recently took the car to get it smogged and everything passed besides the EVAP test. I took it to a shop to get a smoke test done to find out where the leak is coming from and they were not able to find it, there are no CEL or codes given to show there is a EVAP leak anywhere and I have been searching through forums to try to see if anyone else has had this problem but I have no found any, so I am not sure what to do at this point.
    Any help is greatly appreciated!

    -R.M

  2. #2
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    Wait...................the only evaporator I know of on our car is for the A/C. Is that what you're talking about??

    OK I was just thinking. Maybe you mean a leaking purge valve? That would be the valve hanging on the intake manifold. It has one hose coming from the charcoal canister and on the inside of the purge valve there's a hose that plugs into the back side of the intake manifold. I'll post a couple of pictures in a minute.

    OK Here's a picture we use to see where the vacuum hoses go. You can see a place on the rear of the manifold where the purge valve hose goes



    Here is the hose and the purge valve





    Here are two pictures. One of the canister. One of the hoses goes to the purge valve and the other I have the purge valve circled so you can see where it is.





    So if this is the problem it's the hose from the charcoal canister to the valve and then on the other side of the valve the hook shaped hose pushed on to where it belongs on the rear of the intake manifold. All these parts are available and not expensive. Hope I have this correct.
    Jeff
    Last edited by CroughtonE32; 06-22-2019 at 04:33 PM.
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
    https://1drv.ms/v/s!Av20xCMMocSsyEpl...h_oOk?e=ekIcAT







  3. #3
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    I had the same theory about the valve being faulty as well but if it truly was faulty wouldn’t it at least throw a code ? I don’t think it’s the purge valve, when doing the smog test, the technician pinches off the hose going to the charcoal canister which means no EVAP vapor can even get to the purge valve. Which really throws me for a loop because every other line seems to be intact and not torn or cut to release any vapor pressure.

  4. #4
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    We don't have inspections here in Florida any longer. I remember back in the day, the last thing they did was stick that sensor in the tail pipe and they got I think four readings. Is that the part of the test you failed?
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
    https://1drv.ms/v/s!Av20xCMMocSsyEpl...h_oOk?e=ekIcAT







  5. #5
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    In California the test is sticking a gas cap with a hose attached to it and putting pressure though the gas tank to see if there is any EVAP leaks through the system, if the machine detects a loss pressure then there is considered a leak somewhere throughout the vehicle. Oh and that pressure valve is around 100$, or 30$ used.
    Last edited by RyMcFly; 06-22-2019 at 07:33 PM.

  6. #6
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    Eventually there are people here who will know a lot more about this than I do. A non mechanic. But, I just called a buddy who has been retired from BMW for a long time. Actually, he's not well and I think I brightened his day forcing him to talk E32's for a little while. I told him everything you said and all he can think of is, there might be a small crack on the top of the tank that could cause vapor to escape, the canister itself might have a leak (but it would be the first he's seen), the long line that leads from the gas fill spout to the canister so the canister can do its job of picking up the spillage we make when we over fill the tank, or and most important, the equipment they used at the inspection station could have been faulty. He said he would drive through another lane, or a different inspection station. He also said there would be no code he knows of for this kind of vapor leak. Said at VISTA BMW they would call this one a "Hot Potato".
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
    https://1drv.ms/v/s!Av20xCMMocSsyEpl...h_oOk?e=ekIcAT







  7. #7
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    Inspect the hoses between engine, purge valve, charcoal cannister and till it goes into a pipe, back to the tank. The purge valve maybe o.k., but the hoses are often brittle, so even if he pinched the hose, there might be a leak further towards the engine.
    what we found http://2.bp.blogspot.com/-3yf8sOJPuW...0/P1160664.jpg
    http://bmwfans.info/parts-catalog/E3...filter_tubing/
    to test the valve:
    The tank breather valve should have a resistance of 45 ± 20 Ohm and is closed without volts/connector not attached. When it works, you can feel it clicking when touching by hand.
    I disassembed such a valve and we tested it, see here on an M70 engine http://e32b12.blogspot.com/2012/09/m...ble-fix_5.html

    from a German test instruction:
    Aus Pruefanleitung DME 1.1: Tankentlueftungsventil (TE-Ventil) pruefen:
    Das TE-Ventil wird im Sekundentakt angesteuert. Die Taktung ist mit der Hand fuehlbar.
    Dichtheit pruefen: Unterdruckversorgung vom vom Service-Tester am 8-mm Anschluss anschliessen (Durchflusspfeil beachten). Unterdruck auf 600 mbar einregulieren und TE-Ventil mit 12V versorgen. Unterdruckpumpe abschalten, nach 20 Sekunden darf der Druckabfall 50 mbar nicht uebersteigen. Im stromlosen Zustand ist das TE-Ventil durch ein Rueckschlagventil bis zu einem Saugrohrunterdruck von 20 mbar geschlossen.

    Ansteuerphasen pruefen: Das TE-Ventil wird im Leerlauf angesteuert (Anzeige EIN) und ist somit geschlossen. Sobald die Lambdaregelung aktiv ist und die Drehzahl bis ca. 1600 UPM erhoeht wird, kann die schrittweise Oeffnung beobachtet werden (Anzeige AUS).
    google translate:
    From Test Instructions DME 1.1: Tank Vent Valve (TE Valve) Check:
    The TE valve is activated every second. The timing is palpable by hand.
    Check for tightness: Connect the vacuum supply from the service tester to the 8-mm connection (observe flow arrow). Adjust negative pressure to 600 mbar and supply TE valve with 12V. Switch off the vacuum pump, after 20 seconds the pressure drop must not exceed 50 mbar. When de-energized, the TE valve is closed by a check valve up to a suction pipe vacuum of 20 mbar.

    Test drive phases: The TE valve is activated in idle mode (display ON) and is thus closed. As soon as the lambda control is active and the speed is increased up to approx. 1600 rpm, the stepwise opening can be observed (display OFF).
    Shogun tricks and tips for the E32 series are HERE!

  8. #8
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    @croughton was your friend talking about checking the top of the gas tank ? Or the evaporative expansion tank the rear passenger side ?

    @shogun I will check for those plastic t connections when I get off work and any other of the rubber lines connected to the pipe connection at the start of the engine bay.

    My theory right now might be the evaporation expansion tank, maybe it’s a small crack at the very top where I can’t see it, I can perhaps try taking it off, just scared of breaking the 30 year old plastic.



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  9. #9
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    I will check over the car when I’m out of work, and I will update you guys and try to post pictures also.

  10. #10
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    @croughton Btw is the vapor expansion tank the tank your friend was referring to ?


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  11. #11
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  12. #12
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  13. #13
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  14. #14
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    The third image with the yellow highlighted line goes from
    A metal pipe from the rear of the car to the charcoal canister near the front of the car, don’t really know where else to look from here.

  15. #15
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    The pic in your post 10 is the fuel expansion tank next to the tank under the left rear fender, here you have all the systems in drawings shown http://bmwfans.info/parts-catalog/E3...se/fuel_supply
    The Activated Charcoal Filter is also not hermetically closed, there is a moisture drain hose at the bottom, see here , so check the breather valve Nr 17 as I mentioned above http://bmwfans.info/parts-catalog/E3...filter_tubing/
    Shogun tricks and tips for the E32 series are HERE!

  16. #16
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    He was talking about the expansion tank. I would also say that in your picture of the charcoal canister and the purge valve, you should check that hose on the back side of the breather valve. When I replaced mine (for no reason, just because I had the intake manifold off) it fell apart in my hands. That little L shaped hose had spent 165,000 miles in Florida's heat and at the time 26 years. I have no doubt if my car had to go through your California inspection with this Evap pressure testing, it would have failed because of that hose alone. It's number 16 in Shoguns picture where he shows you the purge valve as number 17. I hope it's not the metal piping that leads to the rear from the canister. Looking forward to hear this outcome.
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
    https://1drv.ms/v/s!Av20xCMMocSsyEpl...h_oOk?e=ekIcAT







  17. #17
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  18. #18
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    Ok, I’m back after finding time to take a look at the car to find this leak, I lifted the car up fully to follow the main EVAP line and couldn’t visibly see anything damaged that would cause some sort of leak, so I took the hose that goes to the charcoal canister and put my DIY Smoke machine, I had it hooked up for about 15 mins and was constantly pushing smoke back towards the rear of the car and didn’t see anything.

    So phase two, I went to the rear passenger side of car and removed the tire to access the expansion tank next to gas take, i cut the hose that when directly fed to the expansion tank and then hooked the smoke machine up to there and still nothing, so I hooked it up to the other half of the hose I cut that feeds to a metal pipe that goes towards the front end of the car and STILL nothing. I’m scratching my head at this point bc I don’t know where else to check.


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  19. #19
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    How much would it cost you to drive through a different inspection aisle just to see if the guy who failed you screwed up. Maybe you have no leak. Maybe they're looking to make a little money by having you go crazy with this and then have to pay again for a redo. If it's only a few bucks I'd get rechecked not just at another aisle but maybe another inspection station. Good luck with this. Great diagram by the way. Just filed that.
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
    https://1drv.ms/v/s!Av20xCMMocSsyEpl...h_oOk?e=ekIcAT







  20. #20
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    I was thinking it was just the local smog place also, but when I took it to get the smoke test done at a auto shop they were just as stumped as I was and even took it to their own smog shop right next door and it failed for the same reason, and thanks for the diagram compliment I was hoping it would be easy to understand.


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  21. #21
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    did you check the breather valve as I mentioned above?
    to test the valve:
    The tank breather valve should have a resistance of 45 ± 20 Ohm and is closed without volts/power/connector not attached. When it works, you can feel it clicking when touching by hand.
    Shogun tricks and tips for the E32 series are HERE!

  22. #22
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    Quote Originally Posted by shogun View Post
    did you check the breather valve as I mentioned above?
    to test the valve:
    The tank breather valve should have a resistance of 45 ± 20 Ohm and is closed without volts/power/connector not attached. When it works, you can feel it clicking when touching by hand.
    Where is that located ? Gas tank ? Close to the intake on the engine ?

  23. #23
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    insside engine bay, between throttle valve and carbon cannister, it has a power connection, # 1 http://bmwfans.info/parts-catalog/E3...urb_air_valve/
    This is a diagram for the older BMWs with M30, but will help https://blog.bavauto.com/wp-content/...uting-0061.jpg
    Shogun tricks and tips for the E32 series are HERE!

  24. #24
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    Were did they apply smoke with the smoke machine ? Do yourself a favor and buy a cheap smoke machine

    https://www.amazon.com/STINGER-Smoke...90603233&psc=1

    you wanna get fancy they make cone adapters to go though the fuel filler too.
    Me E30 87/ 325i + F25 12/ M-Sport + E32 94/ 740i

    G/F’s E34 92/ 525iT + F48 18/ X1

  25. #25
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    Sorry guys been super caught up with life lately but I’m pleased to announce that I have finally found the leak, there were two leaks, from two hoses, found them by take a air compressor and adding about 8ft pounds of pressure through the EVAP system and taking a bottle full of soapy water and spraying throughout looking for bubbles. First leak was the hose going to the charcoal canister, the second leak was from the hose that connects to gas tank to the expansion tank. Took it in the following day after replacing the hoses and it successfully passed smog !
    Just wanted to thank everyone for advice and input throughout this headache.

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