Page 1 of 2 12 LastLast
Results 1 to 10 of 13

Thread: Interpreting compression & leak down numbers

  1. #1
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,184

    Default Interpreting compression & leak down numbers

    I could use some help interpreting compression and leak down tests on my 2.0L Duratec. Compression remains high and within 10psi across the board, but #1 now has very high leak down. No audible noise from the exhaust, and the sound from the intake didn't seem louder than the other cylinders, however, the whooshing sound from the oil filler was much louder. To me that means rings, but if it's rings, then why is the dry compression fine in that cylinder?

    Below are the results of tests taken about every 6k miles. As you can see compression numbers have remained pretty consistent, but #1 has always been the leak down outlier and has gotten much worse over the past 6k miles. Any ideas? I need to pull the engine to deal with a faulty oil pressure relief valve, and am contemplating a refresh and possibly upgrades as long as I'm in there, so donít want to miss addressing an issue while itís easier to tackle.

    Date 4/28/12 10/19/14 8/27/19
    Miles 22,146 27,894 32,853
    1 205 psi 190 210 Compression
    2 205 psi 198 210
    3 215 psi 195 200
    4 215 psi 201 210
    1 10% 13% 23% Leak Down
    2 7% 8% 10%
    3 7% 11% 10%
    4 7% 9% 9%


    Thanks,
    John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  2. #2
    Join Date
    Feb 2009
    Location
    NYC
    Posts
    4,520

    Default

    4000 miles in 5 years? Pathetic!


    Forgetting whooshy noises for a moment, a quick leak down on one cylinder is either:
    - stuck or open valves
    - worn rings
    - leaking head gasket

    I assume you have no symptoms of head gasket - leaks, mayonnaise in tank, overheating, swear words, etc so we should be able to discard this.

    How did you make sure the valves were closed prior testing? I know you probably set at TDC but did the test air pressure inadvertantly turn the engine over slightly and open a valve for number one cylinder test?

    I have found diagnosis from listening to air escaping to be inconclusive in the past - you never know where it is coming from. Engines are not like humans in that they fart and leak from many orifices. Humans only have 2...anyway... Is this the oil filler in the cam cover? Isnt it right over the top of cylinder 1 on a 2L Duratec? What if you keep that sealed and remove dipstick to see what air escapes from there or via the valve cover breather holes? I have never done it on a 4 cylinder but for V8s (notoriously leaky things) I just rely on dipstick hole and valve cover breather holes since they slow the process down enough to allow me to check thoroughly for where the worst air noises are coming from.

    Old hands always told me that you can have 20% leakdown with no appreciable loss of hp, its only if you are well past the 20% that you might consider a rebuild. You are only at 23% so you can punt the problem longer
    Last edited by Croc; 08-28-2019 at 04:50 PM.
    Mike
    2010 Caterham CSR with Cosworth 2.3 Duratec
    2018 Caterham 420R with 2L Duratec 210hp at Donington UK
    1975 BMW CSL Group 4 (restoration - engine and dry sump install time)
    1977 Holden Torana "A9X" (awaiting restoration)
    1985 Holden Commodore Group A (restoration - engine rebuild)
    1982 Ferrari 400i (will repaint to original color in 2020)
    1965 Ford Mustang Fastback "Holman Moody"
    1992 Ford Escort RS Cosworth WRC (fettling after long period of storage)
    1990 Range Rover 2 door Classic

  3. #3
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,184

    Default

    Yeah, I know. Life has gotten in the way of long tours to nowhere over the last few years

    No signs of head gasket or other issues. I went with TDC and did that test twice on a couple of cylinders including #1. That involved rotating the engine a full revolution between tests to reset the TDC point. I can't confirm that it was perfect, but I doubt I got it wrong in just the same way twice on that one cylinder. The difference between those tests was less than 1%. Someone else suggested repeating at BDC to see if it's an issue at the top of the bore. I'll try that when I re-run the test over the next couple of days before draining engine and trans oil in prep for the engine removal.

    If I do the upgrades I'm contemplating this is all moot as the pistons, head, and head gasket will all change, thereby renewing/replacing all the failure points. But I'm still riding that fence.

    Thanks,
    John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  4. #4
    Join Date
    Feb 2009
    Location
    NYC
    Posts
    4,520

    Default

    Quote Originally Posted by JohnCh View Post
    If I do the upgrades I'm contemplating this is all moot as the pistons, head, and head gasket will all change, thereby renewing/replacing all the failure points. But I'm still riding that fence.
    Can you handle all that horsepower? It may be too much for little ol' you? You are used to VW 911s and non-running Loti's
    Mike
    2010 Caterham CSR with Cosworth 2.3 Duratec
    2018 Caterham 420R with 2L Duratec 210hp at Donington UK
    1975 BMW CSL Group 4 (restoration - engine and dry sump install time)
    1977 Holden Torana "A9X" (awaiting restoration)
    1985 Holden Commodore Group A (restoration - engine rebuild)
    1982 Ferrari 400i (will repaint to original color in 2020)
    1965 Ford Mustang Fastback "Holman Moody"
    1992 Ford Escort RS Cosworth WRC (fettling after long period of storage)
    1990 Range Rover 2 door Classic

  5. #5
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,184

    Default

    Of course I can't handle all that horsepower. That's part of what makes it fun. As for the Elan, it runs just fine, thank you. Unlike your 400i....

    BTW I forgot to address your comments regarding oil filler proximity to #1. I was too distracted trying to figure out how a corporate finance guy could subtract 27,894 from 32,853 and come up with just 4,000. But I digress. It's a fair point and the breather is back by #4. I'll take a closer listen to the various leak points when I redo the test later this week.

    Thanks,
    John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  6. #6
    Join Date
    Feb 2009
    Location
    NYC
    Posts
    4,520

    Default

    Quote Originally Posted by JohnCh View Post
    I was too distracted trying to figure out how a corporate finance guy could subtract 27,894 from 32,853 and come up with just 4,000.
    Odometers on sevens are notoriously inaccurate (bodged connections, male builders, Westfield kits, bodged parts, wrong tire/wheel size for adapted part, etc.) so I took 20% off to allow for this knowing you built your Westfield. Its like the inaccuracy of a leak down test with a 2 inch open hole directly above number 1 cylinder...



    Quote Originally Posted by JohnCh View Post
    Unlike your 400i....
    Oooh...no chance of missing on that target. I suppose we did drive it onto the trailer to get it to the friendly mechanic....
    Mike
    2010 Caterham CSR with Cosworth 2.3 Duratec
    2018 Caterham 420R with 2L Duratec 210hp at Donington UK
    1975 BMW CSL Group 4 (restoration - engine and dry sump install time)
    1977 Holden Torana "A9X" (awaiting restoration)
    1985 Holden Commodore Group A (restoration - engine rebuild)
    1982 Ferrari 400i (will repaint to original color in 2020)
    1965 Ford Mustang Fastback "Holman Moody"
    1992 Ford Escort RS Cosworth WRC (fettling after long period of storage)
    1990 Range Rover 2 door Classic

  7. #7
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,184

    Default

    The plot thickens. Yesterday afternoon I warmed up the car and redid the test. I set #1 to TDC then confirmed it was correct with a dial indicator. Leak down was 10%. Hmm... Did again, with the same result, then checked the other cylinders using the dial indicator to confirm TDC. Those numbers were all the same as the last test. I suppose something was stopping a valve in #1 from fully seating and a short drive knocked it out.

    With that done, I started prepping the engine for removal, ending up with this Saturday morning. And then I found another head scratcher.



    Removing the Raceline/Jenvey DTHTBs revealed another "what the?" moment. The rear set looked fine, with a bronze cast of dried fuel running from the back of the throttle plates to rear of the tract. The front TB, however, was filled with shiny black crud that looks like a combination of fuel and carbon. #1 is the worst, yet the ports and back of the valves are very clean. Any idea what would cause this? I'm not running breathers into the filtration system so it's not oil. Pics below show #1 and #4 TBs for comparison purposes, and #1 intake ports. Tough to photograph, but outside of the very front, the intake ports and back of the valves look very, very clean.








    Thanks,
    John
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	engine out.jpg 
Views:	82 
Size:	73.8 KB 
ID:	15857   Click image for larger version. 

Name:	IMG_1236.jpg 
Views:	83 
Size:	67.4 KB 
ID:	15858   Click image for larger version. 

Name:	IMG_1232.jpg 
Views:	83 
Size:	51.9 KB 
ID:	15859   Click image for larger version. 

Name:	MG_1255.jpg 
Views:	83 
Size:	77.7 KB 
ID:	15860  
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  8. #8
    Join Date
    Nov 2010
    Location
    NC
    Posts
    159

    Default

    Do you have anything hooked to that runner from the Valve cover or PCV ?

    Your going back with a 2.5 right ? lol

    Tom

  9. #9
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,184

    Default

    Nope. I'm wondering if I'm getting some wear in the spindle assemble for that TB? I need to call Raceline next week about some related items, so I'll ask them if they've seen this before.

    As for the 2.5L, you have a PM and you now have me rethinking the head decision

    Thanks,
    John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  10. #10
    Join Date
    Nov 2010
    Location
    NC
    Posts
    159

    Default

    Your getting a lot of oil into that runner on the intake , the head runner looks clean but not sure if thats the same runner in the head as the black looking ITB runner ? Its oil you can see a good bit of wet oil where the intake seals , where is all the oil coming from ?

    Why not do a complete 2.5 ?

    Tom

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •