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A Mechanic's Life - Tales From Under the Hood

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  • thecardoc3thecardoc3 Posts: 1,521
    Ah, that makes perfect sense---MORE than one problem---of course!

    It's all speculation at this point, but I suspect someone likes to top off the fuel tank. The vapor separator's do fail on occasion but most people never notice it. The purge valve leaking fuel is strange, it should be completely sealed except for when the computer commands the system to purge, and then it should allow vapors (or in this case fuel) to be pulled into the engine.

    The vent valves can cork closed in the event of excessive system pressure and will sometimes do that little trick when we are leak testing with the smoke machine. If they stick when we command it closed and put pressure into the system then that's not a concern and we simply need to bleed the pressure off of the tank and that allows the valve to open and vent again. In his case it has to be stuck closed or the filter clogged with dirt or maybe a cocoon if some bug got in there. If the vent valve was open like it should be except for when the PCM is testing the system, he should never build any pressure to force the gas out in the first place.

    I few posts ago you mentioned a question where numerous repairs were done, and yet the car still had a problem. I saw that post as I do this one. This car easily is presenting with multiple issues and the "cause" is likely routine topping off of the fuel tank, plus the separator failed. I could see someone finding the purge valve leak (obvious), and maybe even also finding the clogged vent valve. But miss the bad vapor separator only to have the system fail again in the future. I didn't bother to comment on that earlier question that you quoted one because people can't tell the difference between talking about the technology and what it takes to diagnose and fix things like that from people thinking that I'm just making excuses.

    Oh well, that's what this career has always been like anyway, maybe this will eventually allow people to see what I've been talking about.
  • roadburnerroadburner Posts: 6,020
    It's all speculation at this point, but I suspect someone likes to top off the fuel tank.

    You do that on my son's X3 and you'll get an intermittent tip-in stall for the first couple of minutes after a fill-up...

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

  • thecardoc3thecardoc3 Posts: 1,521
    I looked around the answers for that post to see how it was working out, and while I was there found this one and the following response.

    I have a 2006 Toyota Prius. When I get the oil changed they fill it 1/2 inch over the fill line. Should I drive it like this?

    I take it to Prius dealers. One has said NOT to drive it with too much and another says it won't hurt anything. Who do I listen to?


    1/2 inch on the dipstick? I'd have it drained off.

    She needs to have that done right away and make sure that who-ever services this in the future puts in the correct amount of oil. (iirc about 3.9qt)

    What can happen is that the oil can cavitate (foam by mixing with air) or it can create too much pressure in the crankcase and put stress on engine seals.

    Foam up, (aerate) the oil, yes. Stress the seals by creating excessive crankcase pressure, no, it won't do that. What it can do however is damage the transaxle.

    That should get a few "Say Whats?" Yes, overfilling the engine oil can result in a damaged transaxle. I'll explain in a bit.

    I dont' know how much 1/2 inch represents in oil volume so my answer is on the safe side.

    The correct fill level is 1/4" below the top mark on the stick. The top dot is the maximum level and should not be exceeded.


    A couple ounces over, no problem. 1 quart over----marginal. More than a quart, could be some trouble.


    While traditionally there is room to overfill, the Prius isn't a traditional car. It's Atkinson cycle engine and low tension piston rings are very intolerant of over-filling. The rings can hydroplane on the excess oil allowing it to get into the cylinders, and the Atkinson cycle allows for some of the intake charge to be blown back into the intake. That means that engine oil that makes it past the rings gets blown into the intake as well. Eventually if you get enough of it, the engine can ingest some of the oil and fuel that collected in the intake and that results in fouled spark plugs and a misfire.

    I wouldn't fret about it but I'd get it to them at your earliest convenience.

    She needs to deal with it now. If the engine inhales the reversion residue and fouls some of the spark plugs it will end up creating a misfire. The transaxle consists of a planetary set which is the power split device, and two heavy electric motors. The sun gear goes to MG1, (Motor Generator) the ring gear goes to MG2 and the planet carrier to the ICE (internal combustion engine).

    The engineers take into account the normal variations in crankshaft speeds and dampen the assembly sufficiently for them. That in fact is part of the reasoning (there are more reasons) for using the Atkinson cycle engine where the intake valve stays open well into the compression stroke ( almost 100 degrees crank after BDC). A misfire causes the crankshaft speed variations to be excessive and that causes thrusting of MG1 through the planet assembly and can destroy it. A misfire on one of these can make the planetary gear set rattle so loud that you will think the transaxle has already failed. Leave it like that long enough and it will fail and destroy the transaxle.
  • thecardoc3thecardoc3 Posts: 1,521
    I take it to Prius dealers. One has said NOT to drive it with too much and another says it won't hurt anything. Who do I listen to?

    Almost forgot this line. Advice is given by the experiences that a particular shop (or individual) has had. The dealer saying don't drive it is closer to being correct for the reasons that I have stated. The one saying that it doesn't matter has obviously not experienced the failure first hand and that could be the result of the techs always doing the oil service correctly.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,664
    I must respectfully disagree on one point of your otherwise excellent post--if you jam too much oil in a crankcase, it can cause seal leaks, and can also destroy a catalytic converter....perhaps, as you say, we have to indicate WHICH type of cars we are talking about when we discuss these symptoms.

    So in the case of a Prius, you might be right, but in the case of a Porsche, I might be right, regarding the effects of overfill.

    But I think we agree that overfill is not to be treated lightly.

    In my own cars, any overfill is dealt with immediately--no exceptions.
  • thecardoc3thecardoc3 Posts: 1,521
    I must respectfully disagree on one point of your otherwise excellent post--if you jam too much oil in a crankcase, it can cause seal leaks, and can also destroy a catalytic converter

    Define "too much".. ;)

    It does not create excessive pressure in the crankcase, between the fresh air breather inlet and the PCV system there is plenty of flow capability to prevent pressurization. Now shock loading if you literally have the oil being propelled at a seal, that's a different situation.

    So in the case of a Prius, you might be right

    Hmmm "might be".... There are two ways that a tech would know this happens, either experienced it personally or found out about it first hand through training. Fortunately for me it is the latter, I got and subsequently pass on the training first and then I started servicing these cars being well informed of the traps. BTW, the early Prius (2001-2004) if you used the wrong oil, and or over filled one could result in a no-start, won't crank condition.
  • mako1amako1a VirginiaPosts: 1,596
    I'm from another Edmunds site and I have a question on Ford engines.

    When looking at F-150s, a lot of the King Ranch and Platinum trucks have the 3.6 Turbo engines. They came out in 2011 so they're still new by my thinking.
    Are they any good? Would a 5.0 be a better choice for a long term keeper of a truck. I don't have any big towing needs, just wondering if 5.0 or 3.6 Turbo would last longer (years). Thanks, Dave

    2013 Mustang GT, 2006 Silverado 2500 LT HD, 2001 GMC Yukon Denali

  • MrShift@EdmundsMrShift@Edmunds Posts: 43,664
    "the early Prius (2001-2004) if you used the wrong oil, and or over filled one could result in a no-start, won't crank condition."

    On some Audis, they won't run right if the wrong oil filter is used!

    But yes, defining the term "too much" is very important. That's why the questioner who mentioned "1/2 inch over on the dipstick" left me with an unquantifiable term.
  • thecardoc3thecardoc3 Posts: 1,521
    But yes, defining the term "too much" is very important. That's why the questioner who mentioned "1/2 inch over on the dipstick" left me with an unquantifiable term.

    That's about a full quart over.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,664
    That's too much. If it were a '65 Chevy, I wouldn't be so worried--it would probably just vent through the open-air breather pipe.
  • thecardoc3thecardoc3 Posts: 1,521
    Similar to RB's question about the Focus ST, I really don't have much to go with to try and form much of an opinion about them. I like Fords approach to the technology and something interesting that they do is they have gone back to a speed density system instead of using a MAF (Mass Air Flow) sensor. It is really important to use an oil that truly meets all the specs if you do decide to get one.
  • roadburnerroadburner Posts: 6,020
    I like Fords approach to the technology and something interesting that they do is they have gone back to a speed density system instead of using a MAF (Mass Air Flow) sensor.

    I had a German Ford(AKA Merkur) Scorpio with the Cologne V6. Most of the European models used Bosch L-Jetronic fuel injection, but US cars got a speed density system.

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

  • jayriderjayrider Posts: 3,198
    All this chat of oil overfill got me out of the Lazy-Boy and into the garage to check the level of my 2010 Prius. Checked out fine -- so I made a pot of coffee and split a donut with my wife. By the time you read this I'll be back to relax-o-sizing in front of the old flatscreen.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,664
    your work is done..go in peace my son :P
  • driver100driver100 Burlington, ON 7 mo/Tampa FL 5 moPosts: 11,327
    Checked out fine -- so I made a pot of coffee and split a donut with my wife.

    Too bad humans don't have a built in dip stick to check their sugar levels so you know how much donut you can eat.

    2012 535ix 2013 Audi A4 2013 Passat

  • jayriderjayrider Posts: 3,198
    We do have a sugar dip stick of sorts. It's called a glucose monitor but "sticking" to half a donut instead of half a dozen donuts should keep things in balance.
  • thecardoc3thecardoc3 Posts: 1,521
    This car was sent to me by another shop. When they saw all of the codes that were set when the car failed its emissions test they felt uncomfortable trying to diagnose the car. The first check was to pull codes and I found P2106, P1295, P0171, P2187, P0174, P2189, P0101 and a P0504.

    Your challenge here is to use what ever resources you have available to you to try to diagnose the car in one visit, and fix the car right the first time.

    Any data that you would retrieve, or component that you would inspect ask about it and I'll answer what you would have found. Be specific on what you want to "inspect".

    An example would be if a tire was going flat, you have to ask "If I inspected the tread of the tire, to try and locate a leak, would I find a screw, nail or other object in the tire". My answer would then be, yes or no and you'll have to decide what you would look at next based on that answer.

    Going into this I expect to be able to demonstrate a number of different points. Keep track of your research time and how much time you think you would have to spend doing actual testing and inspections. Explain what your next step in the diagnostics would be and what you think you would find. When you think you have the final answer(s), post it(them).
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,664
    my first response would be to say that with that many codes thrown, one should test the ECM and its circuits right off.

    However, looking up the codes, they are not randomly thrown---there's a pattern here---fuel mixture is screwed up.

    I guess the first thing I'd do is start simple--- check for vacuum leaks, bad gas cap seal, loose oil filler cap, intake manifold leak, EVAP leaks.
  • roadburnerroadburner Posts: 6,020
    edited June 2013
    I started up the '99 Wrangler and found that none of the gauges are working. TJs in particular are notorious for this problem; the culprit is almost always the sockets that the gauge cluster plugs into. I've had this issue rear its head more than once, but the failure mode has usually just involved the speedo and tach. I also noticed that the 12V dash outlet doesn't work. So, armed with my trusty DVOM, fuse tester, and test light it's once more into the breach. In a perfect world, treating the plugs/sockets and sockets with DeoxIT would buy me another 3-4 years of problem free cluster operation- but I have learned that when it comes to electronics nothing is ever as simple as it appears...

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

  • thecardoc3thecardoc3 Posts: 1,521
    However, looking up the codes, they are not randomly thrown---there's a pattern here---fuel mixture is screwed up.

    OK.
    P0171, P2187, P0174, P2189

    But what about P2106, P1295 and P0101 and the P0504.?

    I guess the first thing I'd do is start simple--- check for vacuum leaks, bad gas cap seal, loose oil filler cap, intake manifold leak, EVAP leaks.

    How would you do that?
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