VERY Strange Leakdown/Compression numbers

[Xenocide]

Compression:

Cylinder 1: 200
Cylinder 2: 200
Cylinder 3: 200
Cylinder 4: 200

(this is a brand new compression test guage I just picked up today - I have no clue why it's so high and why it looks "better than good.") I just popped it in each cylinder and cranked the car over w/ the throttle open.

Leakdown:

Cylinder 1: 8% leakdown; Air leaks out valve cover when the oil cap is off

Cylinder 2: 100% leakdown; Air leaks out of the exhaust

Cylinder 3: 8% leakdown; Air leaks out valve cover when the oil cap is off and appears to leak into cylinder 4 a little bit as well.

Cylinder 4. 100% leakdown; Air leaks out cylinder 3 and intake. If I plug cylinder 3 it leaks out the intake even stronger.

Then engine that is in the car is a JDM "drop in" that was put in about 60,000 miles ago. It was an automatic (TD04 housing and 390cc injectors etc.) The car still runs and idles pretty good; I get about 25mpg average. It has a knock issue; it gets quite bad knock (10-20+) in any heavy boost situation or if I have to "lug" it at all (for example going up a hill at any RPM less than 3000 etc.)

I'm ready to boost the power a little but and have a budget of about $1500 (though it could be stretched a little.) I have a spare head w/ cams lifters etc. and a rusty shortblock that I can use as cores or replacements (the head appears good enough to bolt on if need be.) My goal for the car is to keep it as a daily driver but one with quite a bit more power. In a perfect world I'd like to build a stroker (2.3 or 2.4) but that likely wouldn't fit in the budget. I can buy JDM engines locally for about $1200 but if I knew my head or block were good I would rather throw a stage 1 or 2 head or block together with what I have. As for mods I have a big 16g and as soon as the engine is finished I have a 255 pump, 780 cc injectors, an Eprom with a dsmchips.com chip, cyclone intake, and an AFPR to install.

My question is; what the frick is up with that compression and the leakdown results; how can I have compression higher than stock that is even across the board and yet very bad leakdown? Is the headgasket blown between cylinders 3 and 4 to cause the air to leak between them? Is my knock likely from 2 good cylinders and 2 with major issues? And based on the results of these tests; would just go for a new block or head, or an entire "new" JDM engine?

 

[hostile]

Are you doing the leakdown with the motor in the right postion.

You need to do it with the engine right before top dead center or right after, you will also need somebody to hold the engine in place with the 1/2 inch wrench on the crank pulley.

You can also figure this out by holding your finger over the atachment while turning the crank. When your feel compression you know it is near tdc.

 

[Xenocide]

It should have been right at TDC (I lined up the dowels and marks on the cam etc. for cyclinders 1 and 4.) I also used a dowel to make sure the piston was at the top. I actually left the leakdown testor attatched to cylinder 4 and moved the crank slightly forward and backwards of TDC to see if anything changed as far as the amount of leakdown and it didn't. At the same time if I didn't move it when it was at TDC, cylinder 1 had 8% leakdown, but without doing anything but moving the gauge cyclinder 4 was loosing all air that was put into it.

 

[Xenocide]

Oh, and of course I moved cylinders 2 and 3 to TDC with by putting a dowel in the spark plug holes when I tested them as well.

 

[RedBird]

If the car is running fine and you don't hear anything obvious then your not at TDC on your leakdown tests, if you hear it leaking past the exhaust valves then you werent on the right stroke when turning the engine over, or it spun a little when you pressurized the cylinder also meaning you werent on the right stroke. so as mentioned have someone hold it in place when your sure your at TDC of the compression stroke. as for the compression numbers borrow a diff gauge and see what happens

 

[Xenocide]

I agree it doesn't seem like it's at TDC when one I hear exhaust leaking by the exhaust or intake valves, but each time that happened, if I moved the gauge to the other cylinder of the two that were at TDC; then that one was fine without moving the crank at all. So when 2 and 3 are at TDC and 2 has 100% leakdown and 3 had 8% and I know the valves are closed because it only leaks out past the rings on 3, but when I move the gauge to 2 it is going out out the exhaust valves.

The only thing I can come up with is maybe some very abnormal cam wear - would that make sense?

 

[Xenocide]

As far as the car running fine, I should clarify that it drives fine as a daily driver etc., but timing is pulled like crazy due to the knock whenever I drive it hard. My "fine" means it drives ok, idles a little rough (+ or - 25 or so RPM of 750) and gets normal gas mileage. I'm trying to narrow down what to order (block or head etc.) before I tear the car down and loose my daily driver and am forced to drive my TT Stealth every day.

 

[91 white tsi]

well if im not mistaken when you are switching betweeen the two that are on TDC one is on the compression and the other one is either one is on the exhaust stroke. i dont believe 2 cylinders are on the compression stroke at the same time. hints why one is 8% and one is 100% becuase the valves are open. so you need to rotate the engine for each cylinder and you cant use one posistion for 2 cylinders. I believe this is correct hopefully someone else will confirm it

 

[cbellsondsm]

retard the timing by turning the crank agle sensor

 

[Xenocide]

you need to rotate the engine for each cylinder and you cant use one posistion for 2 cylinders.

That would make sense - can anyone verify this? I'm at work otherwise I'd go try it right now. Thanks!

 

[thegreatms]

can anyone verify this?

I can.

You have to remember that you want TDC of the compression stroke. When piston #2 is on TDC of compresssion, piston #3 will be on TDC of exhaust stroke. That is what #3 was leaking. You must spin the engine 1 full rotation to put #3 into TDC of compression.

Same thing with #1/#4 when one is approaching TDC of compression the other is approaching TDC of exhaust.

 

[91 white tsi]

thats exactly what i thought but didnt wanna give false info untill someone else agreed with me. hopefully now you will see your engine is and its just something to do with tunning. best of luck with it and im supprised no one else caught that untill i said something

 

[Xenocide]

Great info - thanks guys! So now hopefully the only "real" problem I have is the leak between cylinders 3 and 4 which is likely just a crumby head gasket. Thanks again for the help!