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  1. #1
    mookie's Avatar
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    Unhappy Is a dreaded plenum chamber blockage the cause of my problem?

    I've owned my B6 1.9tdi for almost a year now, faultless driving with no problems... until we returned from a 2700mile European holiday.

    The car essentially lost all engine activity doing 70mph on the motorway, completely out of the blue. All electrics still on, lights, radio etc not affected. But the revs dropped to zero as the engine turned off, lost PAS and obviously the brakes went very heavy etc. Managed to bump the car onto a grass verge and into thick undergrowth as we were on a stretch of motorway outside Grantham with no hard shoulder A very scary experience indeed.

    AA attended, checked all the usual areas with nothing amiss. Car would turn over but not start. Sprayed some equivalent to 'Start Ya B*****d' in, engine started and immediately died. Tried to run diagnostics and he said it wouldn't return a fault code or he was having problems getting his tool to communicate with the car. Long story short, it's back outside the house but dead as a doornail. AA man said he was clueless, but suspected fuelling as the car would start but not maintain revs. He said ECU or injectors.

    The sudden cut of power, got me wondering about a cause considering how sudden it was. Now on Saturday driving up from Dover, we drove through some insane rain storms (not to mention the Austrian thunderstorms we drove through previously). So a quick google brought up the plenum blockage problems. Sure enough when I removed the battery surround etc, I found water. Took out the battery and this is how it looked:

    https://dl.dropboxusercontent.com/u/...825_191735.jpg

    That was 24hrs later. There was muddy gunk up to and over the plastic battery shelf, with a tidemark about another inch about that. Now I don't know how high the water was when the car broke down, but this seems to suggest I've had deep water in there for a while for there to be so much stuck on mud. Possibly even higher with fresh rain water on Saturday? I've now drained it and WD40'd every pipe and cable and gaasket I can see to try and drive out any moisture, and the car is now sitting for a day or two to fully dry out.

    My big question. Is the water issue something that could cause my sudden cut in power? If so, what components could water at that level be in contact with to cause it? The ECU box seemed high and dry, i couldn't see in properly just peeked as I didnt removed the wipers but it didn't look wet?

    Any help would be massively appreciated.

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  3. #2
    bez101's Avatar
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    not realy at that side it woud kill your locks windows etc
    is your pass side carpet wet ?

    also on the ecu side (drivers side) you can take the lid off the ecu and check for water in there now in there can stop the car starting

  4. #3
    mookie's Avatar
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    No passenger carpet is bone dry. Funnily enough my remote locking stopped working a few weeks ago... central locking works though off the key. I tried to look in the ECU box but didnt have time to take the wipers off first...

  5. #4
    bez101's Avatar
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    so forget the water problem under the batt

    open the ecu box to make sure the relays are dry ect

  6. #5
    mookie's Avatar
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    Right been out again to try and get the wiper arm off, can't move it. Managed to prise open the box from the four screws I can see, enough to put my hand in. It's wet to the point of my fingers being damp on the right side of the box about halfway down, and the black bound wires in the woven sleaves are slightly damp too. I can't see right in though. Upper couple of inches of the box looked bone dry to the point of dust still being visible so I don't think it filled up, but it's defo been wet in there. Left the wiper arms soaking in WD40. So frustrating!

  7. #6
    bez101's Avatar
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    the arms are a PITA to get off

  8. #7
    mookie's Avatar
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    They certainly are... I'm scared to be too rough and either bugger the mechanism or crack the screen :/

    Damp ECU box suggests bad times, yeah? How durable are they to getting wet? I just googled the potential cost (am I right it's a maindealer job to get a new ECU coded up?) and it's running to half the value of the car!

  9. #8
    bez101's Avatar
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    it wont be the ecu
    theres 2/3 relays in there aswell and once damp wet they rust up over time and cause all sorts of problems
    now im not saying this is the case with you but its worth a check before you start shelling cash out for a fix

  10. #9
    mookie's Avatar
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    OK cool. Well once I've wrestled off the wiper arm I'll have to have a proper inspection.

  11. #10
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    Try and source a puller, I got one from Halfords and modified it with a file to fit. Screwed the bolt in and pulled the arms off no probs.
    B6 S4 4.2L V8 Cabriolet Black Manual Quad Milltek Non Res

  12. #11
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    There are two rubber grommets which get blocked (i put a post up not long ago on the b7 section) causing water ingress into the cabin which can cause electrical issues. Check passanger carpeting area as thats the area prone for water ingress.

  13. #12
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    i've checked thoroughly round both footwells, no water at all in the cabin I can find. I removed bother the rubber grommets under the battery. I know they're meant to prevent splash back but I'd rather risk that than the tray filling up again.

    I tried jumpstarting the car as the battery has been flat since it happened, and figured a few days in the sun would have dried it out a little by now - inside the ECU box feels dry after I left it slightly open over night.

    It turns over, but won't start. Dash light for the engine management warning doesn't stay solid with the key turned without starting the car, it flickers very slightly? I ran the Check function and it just reports the oil/coolant levels as low but they're not so I'm guessing a side effect of the main problem.

    With the key turned and the car turning over, and even with it just at the final position without it turning over... there is a really strange noise coming from the ECU box. I can only describe it like a jumping CD stuck on one note. It gets louder and higher the longer you leave the key in! Sort of like a loud screech crossed with a click. A stuck relay?

  14. #13
    bez101's Avatar
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    sounds like a relay in the ecu box

    as per my post about looking in there

  15. #14
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    I had this on my c5 a6 about a year ago and had the gearbox ecu (pasenger footwell )and also the pleanum chamber flooded BAD times but managed to dry them out with rice in the end having to open the gearbox ecu and cover with RICE it worked a treat took a few days in the living room though.
    I then took the relays out and cleaned them up with WD40 cleaned the contacts also with WD40 and it all seemed to go OK.
    The plenum chamber is probably the achillies heel in the audi range but hey we cant all be perfect ?
    Tookthem out a few months back just to bake sure the circuits have not rusted over and before replacing them this time double bagged them in plastic so if it does happen again it wont flood .(shouldnt happen now though)
    I have made cleaning the chamber out part of my 6 monthly cleaning routine .
    Hope you get on ok
    genuine parts =genuine service
    Treat it right it'll keep you on the road .

  16. #15
    mookie's Avatar
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    Right FINALLY got the wiper arm off with a puller, opened the box up, and sure enough there was a centimetre or so deep pool of water in the bottom of the ECU box front section, where the two relays sit at the lowest point. Both relays were sitting in the water and were very wet.

    Here's the relays

    Relay 219




    And relay 202


    I dried out the box, dried the relays and WD40'd them both, emmery papered the corrosion and rust off the 219 contacts.

    Engine still won't start (battery very flat but jumpstarting off another car), but it still turns over. However now the weird noise from the ECU box has gone, and the radiator fan is not coming on full blast like it would before. I'm assuming the next best thing is to replace the two relays? How sealed are they to resist water getting inside? Google seems to tell me 219 is the fan control relay, 202 is glow plugs?

  17. #16
    mookie's Avatar
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    Well I've replaced the 202 relay with no difference. Couldnt find anywhere on a Saturday with the 219 for sale. Google seems to suggest the 219 only controls the fan... worth trying it or a waste of time?

    Water in the ECU box, relays manky, car won't start. Suggests the relays. But I'm worried this has all been a wild goose chase. Grrrr.

    EDIT: Just stumbled over this on the TDIClub forum:

    "This is the main power relay to the ECM. and also supplies power to the in-tank fuel pump relay. The ECM power feed also goes to the heating element of the oxygen sensor (via the nearby 10A fuse), and via the nearby a power feed to the glow plug relay (not for the glow plugs themselves, just the relay), and via the nearby 15A fuse: the N75, the intake flap motor, the PCV heater, brake pedal CC switch, clutch switch (if the car had a manual transmission), CC switch, and a radiator fan relay (used if ECM thinks the engine coolant is too hot after shutdown).

    If this relay fails, your GP light will not light when you first turn the key to on, and your car will crank but won't start. If it fails while the car is running, the engine will stop running. "

    Sounds exactly right then. Just need to get another relay then.
    Last edited by mookie; 31st August 2013 at 15:26.

  18. #17
    666markyboy's Avatar
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    Keep us posted...... it's all good info for future reference.... just not so good for you ;(... hope a new relay sorts it for you
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  19. #18
    mookie's Avatar
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    I'm waiting on the 219 relay to arrive, so fingers crossed! I'll update if anything changes.

  20. #19
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    My ECU has been getting wet as well, I've caught it early enough and dried it out each time..

    I've just had a few drips of water in mine, it tends to collect in one of the ECU plugs and doesn't seem to affect the relays.

    I still haven't figured out how the water is getting in, I've removed the one rubber bung I could find under the battery, I couldn't see a second one at all I'm expecting it to be under the brake cylinder, but haven't managed to find it. I'm not sure if it's present on a Cab..
    2005 A4 Sport Cabriolet 2.5 TDI
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  21. #20
    mookie's Avatar
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    I wish I had a positive update, but I don't sadly

    The 219 relay finally arrived, popped off the cover of the old one to check and it was minging


    Put the 2nd hand replacement in, which by contrast looks brand new inside, and...

    ...the car still won't start.



    All the signs were there that it was relay 219 but it appears to have been a red herring. Or else has caused a problem somewhere else if that manky interior has been a problem.

    All it leaves in the ECU box is the 365 little relay. I've prised that open and it also looks brand spanking new inside so can't see a reason to replace it to be honest. Without access to VAGCOM I'm stumped tbh.

    I've checked all relevent fuses in the fuse box, I've checked those in the ECU box, I've cleaned and WD40'd the relay holders and connections... the car turns over healthily when jump starting so is willing but not able! Engine check light and the traction light stay on permanently though, as does the battery light.

    Incidentally, any reason jump starting a 1.9 diesel off a petrol Honda 1.4 might be an issue? Voltage drops quite low across the battery (hovers round the 14v mark when not) when turning over although the startermotor sounds like it's turning at the right sort of speed?

  22. #21
    bez101's Avatar
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    have you opened the ECU yet

  23. #22
    mookie's Avatar
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    Crikey no... the metal casing and such? What would I be looking for, water damage etc? It honestly doesn't look like water got that far... but sounds worth a look. Should I disconnect the battery before removing it?

  24. #23
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    VCDS scan needed. Pointless throwing parts at it.
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  25. #24
    bez101's Avatar
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    as above you really need to get it on VCDS

 

 

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