Interpreting compression & leak down numbers

[JohnCh]

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 don’t want to miss addressing an issue while it’s easier to tackle.

 

[TABLE]

[TR]

[TD] Date[/TD]

[TD]4/28/12[/TD]

[TD]10/19/14[/TD]

[TD]8/27/19[/TD]

[TD][/TD]

[/TR]

[TR]

[TD] Miles[/TD]

[TD]22,146[/TD]

[TD]27,894[/TD]

[TD]32,853[/TD]

[TD][/TD]

[/TR]

[TR]

[TD]1[/TD]

[TD]205 psi[/TD]

[TD]190[/TD]

[TD]210[/TD]

[TD]Compression[/TD]

[/TR]

[TR]

[TD]2[/TD]

[TD]205 psi[/TD]

[TD]198[/TD]

[TD]210[/TD]

[/TR]

[TR]

[TD]3[/TD]

[TD]215 psi[/TD]

[TD]195[/TD]

[TD]200[/TD]

[/TR]

[TR]

[TD]4[/TD]

[TD]215 psi[/TD]

[TD]201[/TD]

[TD]210[/TD]

[/TR]

[TR]

[TD][/TD]

[TD][/TD]

[TD][/TD]

[TD][/TD]

[TD][/TD]

[/TR]

[TR]

[TD]1[/TD]

[TD]10%[/TD]

[TD]13%[/TD]

[TD]23%[/TD]

[TD]Leak Down[/TD]

[/TR]

[TR]

[TD]2[/TD]

[TD]7%[/TD]

[TD]8%[/TD]

[TD]10%[/TD]

[/TR]

[TR]

[TD]3[/TD]

[TD]7%[/TD]

[TD]11%[/TD]

[TD]10%[/TD]

[/TR]

[TR]

[TD]4[/TD]

[TD]7%[/TD]

[TD]9%[/TD]

[TD]9%[/TD]

[/TR]

[/TABLE]

 

 

Thanks,

John

[Croc]

4000 miles in 5 years? Pathetic! :seeya:

 

 

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

Edited August 28, 2019 by Croc

[JohnCh]

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

[Croc]

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

[JohnCh]

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

[Croc]

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...

 

 

 

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....:blush:

[JohnCh]

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.

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15857&stc=1

 

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.

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15858&stc=1

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15859&stc=1

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15860&stc=1

 

 

Thanks,

John

[1turbofocus]

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

 

Your going back with a 2.5 right ? lol

 

Tom

[JohnCh]

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

[1turbofocus]

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

[JohnCh]

It's the same runner in the head and the TB. Here is better photo of that port and back of the valves. As you can see, it's very clean, just like the rest of the head. Although it looks like oil in the seal area, it's present to varying degrees on all of them, and it's a tacky consistency with a fuel odor. Given there is no way for oil to get there except through the valves or from a outside leak, my guess is it's a mixture of fuel and carbon giving it the color of oil. The Raceline/Jenvey DTHB are fed through a Pipercross sausage filter with nothing venting into that system.

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15884&stc=1

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15885&stc=1

 

Thanks,

John

[wemtd]

John.

any chance that can be oil fouling the intake from your filter. I previously noted increased oil in my ITB trumpet after cleaning and re-oiling my foam air filter. and that appears to be on cylinder #1?

[JohnCh]

Good idea, but everything is clean on the other side of the throttle plates. #2 also has the problem, but not to the same degree. I suspect that it's a combination of TB wear and dirty/failing injectors. Although the engine only has about 33k miles, it's been in the car for 15 years. I plan to speak with Pete at Raceline in the morning to discuss.

 

Thanks,

John