ATQ Oil Pressure -Zero-

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Thread: ATQ Oil Pressure -Zero-

  1. #1
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    ATQ Oil Pressure -Zero-

    Hey all, I'm a long time lurker but given that searching yielded nothing that seemed to mirror my issue, I'm no a noob poster.

    The Story:
    I have been having an issue with the oil dummy light coming on intermittently and rarely for about 6 months at this point. As a consequence of the first time, I immediately pulled over and checked the oil level (OK & Clean) and then had the car towed home just to be on the safe side.

    Once at home, I tested the oil pressure with my home brewed VAG1342, both the pressure and the sensor checked out okay. Since the engine had no secondary symptoms of oil starvation (valve and bearing noise etc) I suspected a bad connection somewhere between the instrument cluster and the sensor so I put it all back together and resigned to trace down the electrical problem when I had more time to sort it out. with everything put back together, I started it up to warm the oil and move any crud I may have dislodged while messing with the oil pressure switch down into the filter, no oil pressure light. Feeling like this lent more credit to the theory of electrical issue, I changed the oil and filter, and replaced the switch with a new one (just to be on the safe side) and moved on with my day.

    After that day, the problem occurred at random and checked out okay for another few weeks, each time resuming normal no light condition after the sensor was replaced. Concerned that it might just be crud in the oil pan intermittently clogging the pickup screen, I pulled the pan and inspected all of the pump connections and screen, all were remarkably clean and showed no signs of crud roaming around in the engine. Given that everything seemed to be checking out mechanically fine, I felt pretty confident that it was in fact an electrical issue. This car is after all no stranger to random electrical issues that seem to come and go with the wind.

    Fast forward to a few weeks ago the light started to come on more and more frequently, so given that I had planned to have the car out of service for a week to rebuild the suspension and install a new timing belt I figured I'd check out the upper valvetrain to make sure that i didn't have any problems with the cam chain system and inspect for signs of sludge or other debris cruding things up, everything checked out remarkably clean and with little wear, which was to be expected in a car with 136K on the clock and religious 3-5000 mile oil changes with Mobil One 5-30 or 40 (winter/summer).

    I got everything put back together and and started it up, runs smooth and quiet as always, but the oil light is now on constantly. So, I hook up the oil pressure gauge and double check that the pressure is fine and prepare to order an aftermarket pressure gauge but this time zero, zilch, nada. Absolutely no oil pressure... That can't be good... Given that I've never had an oil gauge stay at absolutely zero, I suspected the gauge took a crap on me so I pulled it apart, tested with pressurized air and it worked a-ok. So still doubting the probability of absolutely zero oil pressure, I pulled the sensor plug and cranked the engine over a couple times expecting oil to shoot out of the hole with great exuberance, nothing....

    So, the question is, if you were betting people, and it wasn't your money, what would you bet on and why?

    Given that the sensor port is the first stop after the oil pump, logic seems to suggest that the issue is likely to be an oil pump that is toast, but what I can't get past is that a) the problem has been intermittent b) up to this point the pump pressure has tested out okay and not given any indication of a weak pump, c) the engine has not demonstrated any other common symptoms of oil starvation (thank god) and d) I'm not really aware of any condition that could exist in an oil pump that would lead to both intermittent function AND absolute failure.

    What are your thoughts.

    D

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  3. #2
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    I think that a lower pan drop will be advised. I would be looking for any way that air could be entering the pump, although I've never had the sump pan off of either V6 I've owned. If there were any way that the pickup pipe could have gotten loose, and I don't know whether there is, that could explain a gradual loss of pressure culminating with a total loss. Perhaps AndreasPassat will be kind enough to offer his opinion, as he has done some remarkable work on the 2.8 engines. Another thing to check might be the oil pump drive, although again I don't know if there is any way that could slip.

  4. #3
    PZ
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    I thought the V6 had a chain drive like the AWM, but I never paid too much attention when I had the pan off of one. The chain drives did have tensioner failures.
    I do expect the pump is toast. I've only had 1 non-sludge pump failure and it was on a 1.8T. I have never replaced a V6 oil pump, but I have a dead V6 sitting in the garage with the pan off....

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  6. #4
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    I would pull the lower pan and see what is going on in there.
    The oil pump on the V6 is chain drive like the AWM. There are however segments of the oil feed tube that supply the engine with oil. Those segments have O-rings on them. One of the O-rings might have failed. The tensioner might have failed. Oil pick-up screen could be plugged. Oil pressure relief valve might have failed. It's a crap shoot without getting inside there to see exactly what's going on.


    Lower and upper oil pan removed.
    Green plastic pad is the chain tensioner with a metal spring steel piece.
    Also visible, the pressure relief valve right above the (2) zinc mounting screws.




    The metal tubes are what send the oil to the engine. Upper oil pan installed.




    axenstar likes this.

  7. #5
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    Thanks all for the input. I'm ordering seals and gaskets right now before I crack open the pan but can't seem to find the Orings for the oil feed tubes. The Bentley seems to suggest that there are three, maybe four of them. Three are identified as number seven while the fourth, shown at the junction between the filter to engine tube and the engine block is unlabeled but appears as through it may just be another number seven. Does anyone know what size and type of oring these should be or an Ekta number that I can search for replacements with?

    Additionally with the oil pump itself, the pressure control valve appears that it may in fact be serviceable as the Bentley prescribes a torque value for the valve guide/plug. My question is, what exactly is the function of this valve? I ask because I suspect that it may just be bypass for excessive oil pressure at high RPM and as such could also possibly be sticking in the open position.
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  8. #6
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    Quote Originally Posted by PiedTyper View Post
    Additionally with the oil pump itself, the pressure control valve appears that it may in fact be serviceable as the Bentley prescribes a torque value for the valve guide/plug. My question is, what exactly is the function of this valve? I ask because I suspect that it may just be bypass for excessive oil pressure at high RPM and as such could also possibly be sticking in the open position.
    The pressure control valve is universally used on engines, because without one and at cold temperatures, there's a possibility of dangerously exceeding the allowed pressure. That also puts a severe strain on the pump and its drive, oil filter and gaskets, etc. I suppose it's possible for the thing to stick or spring to break, but not likely in my opinion.
    axenstar likes this.

  9. #7
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    The pressure relief / control valve is set to the oil pressure spec the engineers/designers came with to properly lubricate the engine.
    With out that valve the oil pressure inside your engine would be beyond comprehension. This is a hydraulic system by all rights.
    It is a possibility the valve is giving way or stuck, but not likely.

    Just as an example, when I was still in high school, we took an old Ford engine that had major main journal bearing wear (crankshaft bearings) and we stuck a spacer behind the spring on the oil pump to give it 'extra pumping' ability. Trying to get more life out of the engine. We kids were BROKE.
    The oil pressure was so high it blew the oil filter right off the engine as soon as somebody turned the key.

    As far as O-ring part numbers, I probably still have some laying around, I'll check and see. I'll post if I find anything.
    Last edited by AndreasPassat; 06-12-2019 at 07:29 PM.

  10. #8
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    I'm pretty sure this is the part for those steel tubes that connect to the oil pump.


    https://www.ecstuning.com/b-genuine-...ach/n90613201/

  11. #9
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    Does oil go through the filter before the oil pressure sensor, or after it? If after, I would pull the filter and do the oil check there too.

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