Compression gauge shows nothing, but leak down test shows ~18% leakage?

So, I finally got an adapter for the compression tester (rather, a whole new one) that will seat properly on the Mariner/Escape's V6 engine so I could try and get an idea of the condition of the engine.

On all 6 cylinders I am not showing ANYTHING on the compression gauge. I know that it's moving air since I can hear it when I have the actual gauge disconnected and just the extender screwed into the head- but the gauge itself is just not showing a thing at all.

Since the new gauge is nice in that it has an air valve connection like my leak down tester does, I decided that I may as well give it a go- and it shows about 18% loss on all but one cylinder (#5) that has about 13%. The 5 lower cylinders are all clearly leaking past the intake valves, but the lower-loss one sounds to be like it's blowing past the rings. 

I should note that the engine is out of the car and thus cold (relatively speaking), and the engine hasn't been run for a while- so the rings aren't likely to be the best oiled at this point.

How am I to interpret these results? The compression test is worrying that I can't seem to show anything, but the leak down tester is showing more leakage than ideal, in most cases through the intake valves (interesting note- the leakage dropped if the crank and thus the camshaft was being turned), but still within what I've usually seen called as 'acceptable' for a normal (if not slighlty worn) engine.

Or rather, what it boils down to: for my wife's daily driver SUV that is likely going to get traded in later this year on something newer, are these results concerning enough to pull the heads and have them gone over (adding a week more that she won't have her vehicle) or should I call it good enough and finish putting it back together?

Thanks!

I bet the tester hose you’re using doesn’t have a check valve to hold the pressure for a compression tester. It’ll work for leakdown tests, but not for compression. 

In reply to Spoolpigeon :

Actually, it did- I had to remove the Schrader valve to do the leak down test...

How are you turning the engine over?

In reply to EvanB :

Breaker bar on the main pulley bolt. 

Ashyukun (Robert) said:

In reply to EvanB :

Breaker bar on the main pulley bolt. 

That's why you're getting no compression.  Not spinning anywhere near fast enough.  You won't be able to do a compression test unless you can crank it with the starter (preferably with the throttle held open and it would be more accurate warm, but that's not possible with the engine on a stand). 

Definitely need to use the starter ... remove the EFI fuse as well.

Well to crank it with the starter the engine would need to be in the car, which is what I’m trying to determine is worth the time at the moment. :p

Are the leak down results enough to assume with a decent amount of confidence that it will run decently if I put it in?

As others have explained you're not going to get anything reading on the compression gauge turning the engine over by hand.  Based on your comment about the leak down rate changing when you rotate the engine I'm wondering if you're performing that test correctly.  You should be checking each cylinder at TDC with the valves closed.

Maybe I'm a Luddite but what is 18% leakage? 

Doesn't there also need to be some sort of time frame measured?

Could have some build-up on the valves keeping them from closing all the way.  Is the oil filter still on the motor?  Cut it open and look for metal -- that'll give you a good clue on condition.

Can you easily pop the valve covers off to make sure the valves are seated when you pressurize the cylinder?  I suppose it could be out of time which is causing the valves to be open when you're at TDC.

Personally, if there's no metal in the filter, if the engine came out of a vehicle that was pretty banged up (ran when parked into a stationary object...), and it turns over by hand okay, I'd just drop it in and see what happens.  

Well, you put a regulated amount of air (like 100psi) into the cylinder and whatever pressure you can raise the cylinder to is a percentage less than that. So if you have 100psi going in and are only able to bring the cylinder up to 82psi (because of leakage) it is leaking 18%.

The test has to be done at TDC of the compression stroke because that's the only time that no valves are open and the pressure you're putting in won't push the piston to BDC (where the valves open again).

APEowner said:

As others have explained you're not going to get anything reading on the compression gauge turning the engine over by hand.  Based on your comment about the leak down rate changing when you rotate the engine I'm wondering if you're performing that test correctly.  You should be checking each cylinder at TDC with the valves closed.

I measured each valve at TDC for the individual cylinders- I have the valve covers off (and the timing cover too)), but since I was hearing the air coming from the intake wanted to check and make certain that I had the cylinder where it needed to be so was rotating the engine. 

I will have to try cutting open the filter and taking a look. It turns over easily and everything else has looked good so far... 

Does the starter mount on the engine or transmission side of things? If it’s engine mounted you can turn the engine over with it out of the car. I’ve done it before. Hook jumper cables from a battery to the starter positive and engine block for negative. Then wire a momentary switch to the starter solenoid or use a couple wires with bare ends as a makeshift switch.

I'm not looking at the block right now, but I'm 99% certain as I don't remember a boss on the engine for it to mount to and that like most modern FWD vehicles I've seen that the starter is mounted to the transmission.

It looks like the 3.0 is similar to my Mazda6 3.0 v6. The starter mounts to the engine on that car. I can't find a good guide on it, but watched a bit of this video: https://www.youtube.com/watch?v=TF99S2I2fVw and it looked like it was engine mounted. Maybe?

In reply to dculberson :

I'll take a look when I get home. Unfortunately skimming through that video it looks like getting the starter out of the vehicle to put onto the engine on the stand will not be as easy as it is on most vehicles.

Ashyukun (Robert) said:

APEowner said:

As others have explained you're not going to get anything reading on the compression gauge turning the engine over by hand.  Based on your comment about the leak down rate changing when you rotate the engine I'm wondering if you're performing that test correctly.  You should be checking each cylinder at TDC with the valves closed.

I measured each valve at TDC for the individual cylinders- I have the valve covers off (and the timing cover too)), but since I was hearing the air coming from the intake wanted to check and make certain that I had the cylinder where it needed to be so was rotating the engine. 

I will have to try cutting open the filter and taking a look. It turns over easily and everything else has looked good so far... 

That's how it's done.  For what you're trying to accomplish, I'd probably just stick the thing in the car and call it a day.  It should be fine.  Not great but fine.

^ I agree with this. 15-18% isn't great but it's a hell of a lot better than broken and probably wouldn't be noticeable without a dyno as long as it's fairly consistent across cylinders. 

Spent the last 3 days out in the hottest days of the year so far, but the new engine is in the Mariner and running like a top. Huge shout-out and massive thanks to eastsideTim for spending his day Saturday helping me with the pull and swap- I can't count the number of times he's saved the day helping out on things like this.

So far I'm not seeing anything remotely worrisome from the engine. It ran a bit hot the first run, but given the stupid cooling system setup where you can't really fill it remotely all the way up without a few hot/cold cycles that's not surprising. Hearing more noise, possibly from the valvetrain, than the old engine put out but I both dropped some Seafoam into the crankcase and am going to check that the exhaust manifold nuts are tight enough (didn't torque them to spec since it's a bitch to get a torque wrench on them. But, it's back drivable and if everything goes well today with the running around town I'm going to be doing with it I'll hand it back over to the Dancer tomorrow so she can have her own vehicle back.

Good job, man!! 

Honestly, these things are a bitch when they come up but for me personally, even being a 'professional mechanic' and objectively knowing i will get through it no matter what, i still find that after i've done some major disassembly/reassembly on one of my own vehicles i tend to like it more and worry about it less because there's a confidence that comes from laying eyes and hands on almost every square inch of it and knowing there's nothing in there that you can't (or havent already) beat. 

Ashyukun (Robert) said:

Spent the last 3 days out in the hottest days of the year so far, but the new engine is in the Mariner and running like a top. Huge shout-out and massive thanks to eastsideTim for spending his day Saturday helping me with the pull and swap- I can't count the number of times he's saved the day helping out on things like this.

So far I'm not seeing anything remotely worrisome from the engine. It ran a bit hot the first run, but given the stupid cooling system setup where you can't really fill it remotely all the way up without a few hot/cold cycles that's not surprising. Hearing more noise, possibly from the valvetrain, than the old engine put out but I both dropped some Seafoam into the crankcase and am going to check that the exhaust manifold nuts are tight enough (didn't torque them to spec since it's a bitch to get a torque wrench on them. But, it's back drivable and if everything goes well today with the running around town I'm going to be doing with it I'll hand it back over to the Dancer tomorrow so she can have her own vehicle back.

NIce!  Good job.  It's got to feel good to cross that one off your list.

Going to do another oil change before handing it over?  I can’t remember for sure, but I thought Seafoam isn’t supposed to be left in the oil for too long.  I could be thinking of ATF or kerosene or something else used to de-gunk an engine, though.

Awesome, good job getting it back up and running. And great job helping, Tim!

It is nice having it largely done and drivable, and obviously the Dancer will be happy to have her own vehicle back.

I'm not planning on changing the oil before handing it back over, but I will likely change the oil in a week or two as well as possibly getting as close to flushing the coolant as I can since I figure there's going to be a good bit of gunk flushed out- will also give me an excuse to get back under it and check things out (there's still some clunks that were there before that I have yet to hammer out, likely with the suspension/mounts- and hopefully not anything in the transmission). I'll probably have her drive the Infiniti to rehearsal Saturday and change the oil and look it over again then.