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Timing chain - slight slack between intake and exhaust sprockets

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by david173, May 3, 2022.

  1. david173

    david173 New Member

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    Just changed the valve cover gasket on my 2009 with 165k miles. I noticed that I could press the timing chain down slightly between the intake and exhaust sprockets (I know that's not the best description - I should have taken better pictures or measurements before reassembly). A friend got me a bit concerned that the timing chain was worn and needed to be replaced very soon. It seems this usually doesn't occur on these cars until well north of 200k miles unless there were oil issues. I've changed the oil every 5k since new and used synthetic only since ~50k.

    No codes or real issues. The engine is not abnormally noisy that I can hear. Seems this usually throws a P0016 when the chain stretches/skips a tooth (I assume when the tensioner is at the end of travel). Not sure how long you have after that to get it fixed though...

    I don't see an easy way to check the tensioner or chain wear without excessive teardown, at which point you might as well replace it anyway. Anything else I should check/watch for, or should I just keep going?

    Image below, but it's not a great shot of the area in question.
    IMG_3047.jpg
     
    #1 david173, May 3, 2022
  2. SFO

    SFO Senior Member

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    Welcome to PriusChat!!
    Nice patina. Best not to stress on it. Does it eat much oil between changes?

    FYI : you're moderated until you've posted 5 times.
     
    #2 SFO, May 4, 2022
  3. david173

    david173 New Member

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    Thanks. Burns maybe .5-1qt/5k miles. I wasn't monitoring how much I added too closely. Attempted to clean the rings (seafoam soak) to see if that helps. That's when I noticed oil in one spark plug tube, so changed the valve cover gasket (and plugs + PCV valve) and will continue to monitor.

    FWIW, oil analysis a couple oil changes ago was great, but slightly elevated fuel in the oil (1.5%). Can share if relevant/interested.
     
    #3 david173, May 4, 2022
  4. edthefox5

    edthefox5 Senior Member

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    Life of dino oil.

    That same burnt on brown patina is in the cat too and tough on the cat many clogged cats on this site performance will greatly suffer. Even though my engine is very clean I noticed when I replaced the cat on my car with an Amazon $125 cat the engine performance was improved. So easy to clog or reduce performance in this cars oem cat.

    Chain Slack not that bad but tension'er guides probably worn pretty good.

    Here's pics of my chain at 150,000+ miles. Did not eat any oil. Notice zero wear on the cam lobes.

    Lifetime of Redline Motor oil 10-30 and Redline D6 trans fluid. It is the worlds best engine & trans lubricant.
    You get what you pay for.
     

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    #4 edthefox5, May 4, 2022
    Last edited: May 4, 2022
  5. david173

    david173 New Member

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    Good comparison, thanks. I think the patina is probably from the first ~50k of dino oil. I've run Mobil1 5W-30 since ~80k or so, between 50k-80k a range of cheap synthetic oils. Didn't keep as many records as I should have but did trans fluid changes with factory ATF-WS every 30-50k. I'm hoping between my attempt at cleaning the piston rings and the valve cover gasket I've improved the oil burn at least slightly. Gas mileage might be down slightly but only time will tell if that's a trend.

    Here are some more images of mine at 165k (and I guess one does have a slightly better shot of the timing chain).

    Would anything be relevant from an oil analysis (I did one at 150k)?
     

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    #5 david173, May 4, 2022
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  6. mr_guy_mann

    mr_guy_mann Senior Member

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    I've seen much uglier engines that still ran fine. Slight "slop" in the chain right there is to be expected. The tensioner usually has the coarse mechanical adjustment (the ratchet mechanism) and then a hydraulic adjustment while the engine is running. Valve spring pressure against the cam lobes often makes the slack between the two sprockets.

    IF - it really bothered you then you could try to get eyes (or a videoscope) on the chain tensioner plunger to see how far that's extended (and try to find a pic of a "known good" unit for comparison). More chain wear equals more tensioner extension.

    Or, get a 2 channel scope and capture the cam and crank sensor signals. If the chain is way stretched it will affect the relationship between the two signals.

    Me, I would not worry- maybe I would look at fuel trims during a test drive (just because).

    Posted via the PriusChat mobile app.
     
    #6 mr_guy_mann, May 4, 2022
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  7. david173

    david173 New Member

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    Great ideas. Scope on the cam and crank signals sounds like something I will look at - what should I be looking for (have a scope and know how to use it, but not what good vs bad would look like there)? Wish I'd thought to try to inspect the tensioner with a borescope when I had the valve cover off.

    I assumed there was some mechanical play in the system that would make a valid measurement of slack at that location difficult. I didn't know there were multiple components of the tensioner but that makes sense as well.

    Long-term fuel trim is somewhere around -3% to -4%. I think +/-5% or less is considered good, and maybe ok up to +/-10%? Not sure how to interpret that as it relates to this topic.

    And I was over here thinking my engine looked pretty good overall given the age - if only I'd been running synthetic since new...
     
    #7 david173, May 4, 2022
  8. edthefox5

    edthefox5 Senior Member

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    Yeah chains not that bad top ends not that bad. This is not a sludgy motor at all you really have to go out of your way to make sludge in this motor.

    Mobil 1 is good oil. if I dont run Redline I run M1.

    Still the toughest little motor ever. Don't laugh but when my engine started eating a tiny bit of oil I tried running more oil in it. It really helped and the motor did not mind. It was 1/4 of an inch over the top line. Ran it like that for years.

    I would run 10-40 Mobil 1 also. This engine does not mind that 40 weight it will really help that oil eating.

    Try running 4 quarts of Redline 10-30 its actually a 40 weight oil at op temp. You will notice the motor will run much smoother. It will really quiet down the solid lifter racket.

    Its not a cheap oil @$10 a quart. But try it just once. Its noticeable how much better the motor will run.
     
    #8 edthefox5, May 4, 2022
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  9. Tombukt2

    Tombukt2 Senior Member

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    Taker 9n to 666K bud . Spend time on your hobbies this year model Prius warrants no mental anguish ever. Now a gen 3 that's another whole can of worms
     
    #9 Tombukt2, May 7, 2022
  10. mr_guy_mann

    mr_guy_mann Senior Member

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    Fuel trims are fine. Here are some "known good" captures. Two are 150-180+k, and the 08 at 137k (this has a little less chain stretch?). All drive fine, no codes even with 5+ degrees of variation between different cars.. 06 Gen2 sync.jpg 05 gen2 sync.jpg 08 sync.jpg

    I just backprobe the two red wires at the top left of the top connector on the ECM behind the glovebox, & grab the metal dash brace for ground. I have to "filter" the signals with the scope's software or turn sample rate down as there is quite a bit of EMF noise from the hybrid system.
     
    #10 mr_guy_mann, May 9, 2022
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