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  1. #1
    Bald Tire
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    Engine compression test and leak down test results?

    Hi everyone...need some help understanding what is going on with my '06 H3. Purchased this car new in '06 and have loved it. Put 137,500 miles on it. I drive 5 days a week 60 miles round trip...up two grades..both ways..yikes. It started with trying to find out what that engine "shudder" is when you are almost to a complete stop when the RPM'S drop. One time it felt like it was gonna die on me. So I decided to have a compression/leak down test done. These are the results.
    Compression: #1 120LBS. #2 120LBS. #3 120LBS. #4 112LBS. #5 120LBS.
    Leak Down: #1 30%- #2 45%- #3 65%- #4 72%- #5 60%-
    What does this mean? Is a rebuild in my near future? Can this engine go another 75,000 miles or more? Is there something I can do to help her (sorry my car is a "her"). Also I am religious on oil changes...I have always run Mobil One in it - since new.

    Second question....I increased my tire size to 17...rather than the 16's. I have BF Goodrich TKO's. Will this put added stress on the engine and worse
    gas mileage?

    I have a Volant air intake on it and K&N filter...poor girl she needs all the help she can get....
    Anyone out there that can help with either question?
    Carrie SOS - HELP!!!

  2. #2
    Super Swamper
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    Technically you did add stress on the car, but it should be a very small increase that you shouldn't worry about. Its more if you increased the entire size of the tire as well as the size of the wheel. As for power gains get a pcm tune. Should get a noticeable increase in power.

    As to the compression test, I'll let someone else answer that questions.
    06 H3, Birch White, Lux , Cooper AT3 35s, Borla Performance Cat-back, Bilsteins front w/ 1/2" extended stops, Hunner sleeve, Air Doc w/ K&N filter, Oem Roof lights, 55W HID Headlights and 35W Fog lights.

    09 H3 V8, Arctic Silver, LS376/480 Conversion, 3000 stall, Custom E-fans, 37" KM3 tires, XD Rockstar Wheels 17x9, OEM Sliders, 40K External Trans Cooler, Bilstein 5160s front 5100 rear, O.D. Steering Bracket, 2" Body Lift, Custom Exhaust, Custom intake pipe & K&N filter, Custom PCM tune, Pioneer DVD unit, Aurora 40" LED Light Bar, 50 W HID Headlights

  3. #3
    Mud Terrain
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    Was the motor warm during the compression and leak down test? Did you or the person doing it add a little oil turn it over and try again? To many variables really.
    2007 Hummer H3, 3.7L, auto trans, adventure transfer case. Rear locker.
    315/75R16 Nitto trail grappers, Thor parts frt/rr bumpers, 10,500lb winch, OEM rock rails, ucp, rear disconnects, blah, blah, ect.

  4. #4
    a.k.a. "The Jackal"

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    I dont think rim size will affect it as much as tire size. Whats the tire size?
    Squeaky3: 06 H3 ALPHA D70 front/Eaton HO72 rear 5.13 gears, custom crossmember for long arms, lockers, 4:1 T-case, v8 swap, hybrid cage, Warn 12k Custom bumpers....do it all vehicle

    "H3 front axles are like drunk cheerleaders....just use em until they get mouthy...then toss em and get another." -anonymous


  5. #5
    Mr. Beretta
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    Normal compression for a new engine should be around 215 psi. The lowest reading should not be less than 70 percent of the highest reading. • When the compression measurement is normal, the compression builds up quickly and evenly to the specified compression on each cylinder.


    • When the compression is low on the first stroke and tends to build up on the following strokes, but does not reach the normal compression, or if the compression improves considerably with the addition of three squirts of oil, the piston rings may be the cause.


    • When the compression is low on the first stroke and does not build up in the following strokes, or the addition of oil does not affect the compression, the valves may be the cause.


    • When the compression is low on two adjacent cylinders, or coolant is present in the crankcase, the head gasket may be the cause.



    Your leakdown test are very high. Normal cylinder leakage is from 12-18 percent.

    • Make a note of any cylinder with more leakage than the other cylinders.


    • Any cylinder with 25 percent leakage or more requires service.




    •Record the cylinder leakage readings for each cylinder. In excessive leakage situations, inspect for the following conditions:
    • Air leakage sounds at the throttle control module or air inlet hose may indicate a worn or burnt intake valve or a broken valve spring.


    • Air leakage sounds at the exhaust system tailpipe may indicate a worn or burnt exhaust valve or a broken valve spring.


    • Air leakage sounds from the crankcase, oil level indicator tube, or oil fill tube may indicate worn piston rings, a damaged piston, a worn or scored cylinder bore, a damaged engine block or a damaged cylinder head.


    • Air bubbles in the cooling system may indicate a damaged cylinder head or a damaged cylinder head gasket.


    Will it last another 75K? Could, and could also start burning oil at any time. Need some more testing to determine if it is just problems with the cylinder head.

    Don't know anything about Hummers, but I do speak Malamute.

  6. The Following User Says Thank You to f5moab For This Useful Post:

    LagunaH1 (02-05-2013)

  7. #6
    Bald Tire
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    Hi amrg! thanks so much for the reply. I just increased the tire size and not rim so guess I am good on that one right... What is a PCM tune? Can you got to any mechanic and get that done?

  8. #7
    Bald Tire
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    Hi jakesz28....well...I had my mechanics run the test. I can't answer those questions. They seemed to know what they were doing and talking about. Is it worth having the test run again but by someone else?...if so..who in particular...someone who specializes in????

  9. #8
    Bald Tire
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    Hi 06 H3...well I believe I have 275/75R/16...I didn't change rim size...but a bit bigger tire. BF Goodrich T/A KO's. Although I don't have the stock rims on there either.

  10. #9
    Bald Tire
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    Hi f5moab! thank you so much for such great and indepth info. I think I am burning some oil. My mechanics noticed I was due for an oil change soon..when then
    checked it....the oil didn't register on the stick! I have never had that problem ever before. I always have plenty of oil and change it regularly.Could that be a tell tale sign that it is pistons?????? Forgive me...I am girl and know somethings about engines but not a whole lot. I am just concerned since this is my only vehicle and need to be smart how I spend the money on my credit card to keep my vehicle running. In order to narrow in on the problem who and where do I take it to so they can perform the tests the way you have described to me and can accurately diagnose this. I live in Southern California...know of any place I can take it to here?

  11. #10
    Mr. Beretta
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    Unfamiliar with So CA, but there are plenty of people on this board who hopefully will chime in. I hear that Tustin Hummer is a great place, but not sure exactly where it is located.

    Don't know anything about Hummers, but I do speak Malamute.

  12. #11
    Bald Tire
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    Thanks...I will check Tustin Hummer.....I am about 40 miles away from there. Yes..if anyone else has info on a good Hummer dealer or GM...anywhere in So Cal that would be great! Preferably 20 mile radius around San Dimas.

  13. #12
    Bald Tire
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    If your burning oil your spark plugs should be brownish black and guuee a little, also check the PCV valve see if it is clogged, and yes with that high % of leak down you have engine issues, is there excessive knocking on the top of the engine or side, or is it a tapping sound on the top of the engine, does the oil dipstick milky brown in color, check the radiator fluid. If you take it to a dealer ask allot of questions like your from the SHOW ME State and if they repair anything demand you want to see the bad parts and the new replacement parts side by side before install if you have to wait around. A good service dept will be helpful a bad one will try to ask why you want that. even I do it and tell my wife too all the time if you have to use a dealer. FYI
    There is a Timing chain so I don't think that is stretched, did you have any GM Recalls done i.e the head gasket?
    Last edited by TheGunnyRet; 02-05-2013 at 09:33 PM.

    2007 H3 Blk
    3.7 ORLP

  14. #13
    Super Swamper
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    If you end up taking it to Tustin, make sure to ask for Dave Jones, he's the foreman in the shop. Also, can't hurt to drop hummech (whos real name is Mike) a PM here, he runs the service department at Tustin Hummer. Both Mike and Dave are really great guys.
    2016 RAM 2500 Power Wagon
    1995 Jeep ZJ V8


    NR6E

  15. #14
    Mr. Beretta
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    What GM recall on the head gasket? No PCV valve.

    Don't know anything about Hummers, but I do speak Malamute.

  16. #15
    Mall Crawler

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    Engine compression test and leak down test results?

    I don't think there was ever a recall on the head gasket
    2005 H2 Adventure


 

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