Did a Compression test today.
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500, 472, 425, 368 Discussion, Did a Compression test today. in Cadillac Engine Technical Discussion; Did a compression test today, came up with some interesting numbers: Spec: 165-185 (in reference to the second set of ...
  1. #1
    DaveSmed's Avatar
    DaveSmed is offline Cadillac Owners Connoisseur
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    Did a Compression test today.

    Did a compression test today, came up with some interesting numbers:

    Spec: 165-185 (in reference to the second set of numbers listed below)

    Odds: (First number-first puff, second number-about five puffs)
    #1- 145/180
    #3- 125/165
    #5- 125/175
    #7- 125/160

    Evens:
    #2- 90/125
    #4- 90/120
    #6- 70/85
    #8- 110/175

    Been getting a large amount of blowby lately too, as well as increased fuel comsumption. Put a leakdown tester on #6 and heard hissing in the crankcase as well. So, given that the engine has less than 80k on it, i'm really reluctant to think I have a worn bore or bad rings. With the blowby, don't think its the headgasket, so what does everyone think of the thought of the rings being stuck in the piston? Sound pretty plausable? I'm thinking of trying pulling the three plugs (2 4 and 6) and filling the combustion chambers with something like seafoam or B12 Chemtool, then letting it sit for about a day. Any thoughts on that, or am I pulling pistons in the near future?

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  3. #2
    zonie77 is offline Cadillac Owners Connoisseur
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    Re: Did a Compression test today.

    Good testing procedure!

    If you aren't losing coolant I'd agree with you on rings stuck.

    Given it's age/mileage it must have sat for long periods. That's consistent with rings sticking.

    The N* has a factory procedure to loosen stuck rings. Similar to what you suggest. There is a recommended solvent for that from GM.

    After the procedure I'd consider running about half a quart of ATF in the oil. It's very high detergent would help clean the rings too. This is just my opinion but I have done it on sludged vehicles before and I think it would free up sticking rings. If you think the engine has sludge built up you 'll have to change the oil and filter quickly to keep it from plugging the filter. A couple of oil changes is much easier than tearing an engine down.

    Have you taken it in any highway trips lately? WOT helps the N*'s free up sticky rings too.

  4. #3
    DaveSmed's Avatar
    DaveSmed is offline Cadillac Owners Connoisseur
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    Re: Did a Compression test today.

    Thanks for the advice, I might look for that GM solvent. The engine could use a crankcase flush as well, ever since I got the car it's recieved Delvac 15w40, so I should be good there, but it does get dirty quick. I'll give the ATF a try!

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