Cylinder leak-down test procedure (with percentage gauge)
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 15 of 25
Northstar Engines and System Technical Discussion Discussion, Cylinder leak-down test procedure (with percentage gauge) in Cadillac Engine Technical Discussion; I've got a little smoke on start-up and before doing the anticipated valve stem seals, I wanted to be sure ...
  1. #1
    km7648 is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Cylinder leak-down test procedure (with percentage gauge)

    I've got a little smoke on start-up and before doing the anticipated valve stem seals, I wanted to be sure I didn't have any other problems.

    Well I bought an engine leak-down test kit (with poorly translated instructions) but haven't been successful using it.

    Do any of you know how to test using a setup like the one in the picture?

    The left gauge show PSI and the right shows percentage loss. While it sounds easy enough, I'll be darned if I can find the right procedure anywhere (and I've looked).

    So far, my engine is either perfect or totally pooched <grin>
    Attached Images

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    70,377

    Re: Cylinder leak-down test procedure (with percentage gauge)

    What are you testing for? Head gaskets or burnt valves? What engine?

  4. #3
    km7648 is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: Cylinder leak-down test procedure (with percentage gauge)

    It's in a sand rail but from a 1996 Seville - a Northstar.

    While I think the motor is OK, I wanted to be sure the smoke is the valve stem seals that I expect.

  5. #4
    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    70,377

    Re: Cylinder leak-down test procedure (with percentage gauge)

    I don't see how that is going to tell you anything about valve stem seals. That is more for testing compression, rings & valve seats. You could also use the separate hose for a cylinder pressure test to check for bad head gaskets.

  6. #5
    km7648 is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: Cylinder leak-down test procedure (with percentage gauge)

    I "know" that I need valve stem seals and I don't need the leak down test to tell me that.

    I just want to be sure that I don't need anything else.

    I could still use help re. the proper usage of the leak down tool with a 2nd percentage gauge.

  7. #6
    zonie77 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 ETC,97 STS
    Join Date
    Sep 2003
    Location
    Arizona
    Posts
    3,531

  8. #7
    clarkz71's Avatar
    clarkz71 is offline Cadillac Owners Connoisseur
    Automobile(s): 1993 Mercedes 400E / 1995 Eldorado/ 2006 Yamaha R1 LE
    Join Date
    Mar 2006
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    1,272

    Re: Cylinder leak-down test procedure (with percentage gauge)

    To be accurate, you need to regulate the supply air to 100 psi, then a 10% reading on the leak-down tester is actually 10 %. A leak-down tester will help determine if an oil consumption/smoking problem is valve guides/seals or rings. If you hear air coming from the oil fill hole in the valve cover, and the percentage of leakage is high, you have a ring problem. Likewise, if air is heard from the throttle body, intake valve, exhaust pipes, exhaust valve. You want to see all 8 cylinders within 10% of each other. To use this tester, you need to have the piston at TDC on the compression stroke.

  9. #8
    km7648 is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: Cylinder leak-down test procedure (with percentage gauge)

    Thanks Zonie77

    My problem is with the style of gauges that I've got. The left one is a standard PSI gauge but the right one shows percentage of leak.

    I'm just trying to figure out how to calibrate and use it.

    The only links that I've found (and those you sent) show a PSI gauge on the left and right. Kinda' thinking I should buy one of those anyway...

  10. #9
    clarkz71's Avatar
    clarkz71 is offline Cadillac Owners Connoisseur
    Automobile(s): 1993 Mercedes 400E / 1995 Eldorado/ 2006 Yamaha R1 LE
    Join Date
    Mar 2006
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    1,272

    Re: Cylinder leak-down test procedure (with percentage gauge)

    The left gauge is the supply air, set the regulator to 100 psi. The right gauge is the percentage of leakage. IE: 50 on the gauge would be 50% leakage. (bad) You want to see no more then 20 or 30%.

  11. #10
    clarkz71's Avatar
    clarkz71 is offline Cadillac Owners Connoisseur
    Automobile(s): 1993 Mercedes 400E / 1995 Eldorado/ 2006 Yamaha R1 LE
    Join Date
    Mar 2006
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    1,272

    Re: Cylinder leak-down test procedure (with percentage gauge)

    Quote Originally Posted by Ranger View Post
    I don't see how that is going to tell you anything about valve stem seals. That is more for testing compression, rings & valve seats. You could also use the separate hose for a cylinder pressure test to check for bad head gaskets.
    Larry, a leak-down tester puts air in the cylinder at a lower psi then direct shop air (120 psi or more). You can hold your finger over the fitting. It measures the percentage of air leaking past the rings & or valves. If the leakage is 20% or less and you have an oil consumption problem, you know it's the guides/seals. If it's high, 40% or higher, the rings are suspect. You'll also hear the air coming from the crankcase.

  12. #11
    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    70,377

    Re: Cylinder leak-down test procedure (with percentage gauge)

    Understand that Clark. Just don't understand how it relates to valve stem seals. Shouldn't be any pressure there, right?

  13. #12
    clarkz71's Avatar
    clarkz71 is offline Cadillac Owners Connoisseur
    Automobile(s): 1993 Mercedes 400E / 1995 Eldorado/ 2006 Yamaha R1 LE
    Join Date
    Mar 2006
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    1,272

    Re: Cylinder leak-down test procedure (with percentage gauge)

    Right, if you don't hear air from the crankcase. If leakage is in specification (20-30%), and you have an oil consumption problem, it's the seals & or guides.

  14. #13
    km7648 is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: Cylinder leak-down test procedure (with percentage gauge)

    OK, I contacted the manufacturer and indeed, the instructions are in fact incorrect.

    For those following this thread, the correct procedure is:

    1) Bring the cylinder to be tested to top dead center, valves closed.
    2) Thread the hose into the the spark plug hole.
    3) Set the incoming air pressure to the tester at pressure 30-100 psi
    4) Slowly turn the regulator on the tester until the percentage gauge reads "0". This calibrates the gauge.
    5) Connect the hose from the cylinder to the tester.
    6) Read the percentage of leakage on the gauge that previously read "0" when calibrated. This will be the percentage of leakage.

    The instructions had step #5 before #4 and it made no sense to me.

    *Thanks to those that offerered assistance.

  15. #14
    clarkz71's Avatar
    clarkz71 is offline Cadillac Owners Connoisseur
    Automobile(s): 1993 Mercedes 400E / 1995 Eldorado/ 2006 Yamaha R1 LE
    Join Date
    Mar 2006
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    1,272

    Re: Cylinder leak-down test procedure (with percentage gauge)

    Your gauge must be set up different then mine. Let us know what readings you get.

  16. #15
    km7648 is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: Cylinder leak-down test procedure (with percentage gauge)

    First, I did a compression test and for all cylinders got reading of 195-200.

    Then I did the leak-down test and per the gauge, got readings right in the center of "low" leakage for all cylinders. The gauge indicates that the middle of "low" is about 30% OK for their gauge but lousy by other 100psi gauge tests.

    I did each of these tests while the engine was at about 60 degrees so I understand these readings would be even higher/better if the motor was warm.

    The attached photo shows the gauge dial face. You can read the numbers if you squint just right <grin>

    Then to be paranoid, I cranked up each cylinder to ~80psi and listened for any leaks, hisses, gurgles in the coolant etc. and - nada.

    Sounds like the motor is A-OK and I should go ahead with my valve seals and not tear down the motor?
    Attached Images

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting