Cylinder leak down pressure test questions

I have a friend and I'm convinced his HG is blown but the dealer keeps giving it back without this diagnosis. A leakdown test would confirm it (though could be a valve as well on this test) and have never done one. What's involved? I have a compression tester - is this the tool that is used and you simply hand rotate the engine until that cylinder is in compression and watch if the gauge drops faster on a cylinder or two? I think my guage kinda ''holds" the pressure it gets to, so I'd have to hold the bleeder valve open so the needle could drop. So, wondering if there's a different tool for this as it seems kinda awkward with my compression tester.

FYI a simple compression test won't reveal a blown gasket in case you're reading this and wondering. Unless it's blown so bad the air has a sizeable hole to escape in the moment of compression.

Anyhow - anyone have a comment on this?

DougM

I have a leak-down tester, I've used it several times, it's VERY handy. No, it's not the same as a compression tester. This is the one I have, I got it at Summit:



There's several pages on the 'net where you can read how to use one, but basically you warm up the engine, then as fas as possible remove the plugs, take off the intake hose, oil fill cap, and radiator cap. You screw the hose into the spark plug hole, put that piston at TDC, then apply compressed air (at least 100 psi) to the tester. You set the inlet pressure to 100 psi with the yellow regulator knob, then read the second gauge. Even a brand new engine will have leakage, but this tester will let you figure out WHERE it's leaking to. More than 25% pressure drop is bad, but less than 20% is fine. Bt, it's very important that the engine be as close to operating temp as possible, so you have to work fast.

After you get it all hooked up, you listen. If you hear air leaking out the intake, then the intake valve is leaking thru the seat. If it's leaking out the exhaust (listen at the tail pipe), then the exhaust valve is leaking. If it's leaking out the oil fill cap on the valve cover, then your rings are leaking. And, if coolant geysers out the radiator, then the HG is gone on that cylinder.

I'm convinced that no other test will confirm a leaking HG as quickly and easily as this one will.

KLF said:

More than 25% pressure drop is bad, but less than 20% is fine. Bt, it's very important that the engine be as close to operating temp as possible, so you have to work fast.

Click to expand...

KLF,
How long do you wait to see if there is a 25% pressure drop? 1 minute or 5 minutes or 1 hour or ? ? ?

-B-

No waiting required... the gauge will indicate the reading immediately........

Does this imply that you keep the cylinder pressurized with 100PSI for the duration of the test on each cylinder?

-B-

Ah, bummer - requires a compressor I don't have. Also, it's a boat engine so no radiator. Also, how the heck do you find TDC for each cylinder? You've got to find a way to do each cylinder in firing order by turning the engine exactly the right number of degrees since the timing marks only give you cylinder #1.

DougM

Remove the valve cover and observe the rockers.... when both valves are in the closed position and the piston is at the top, thats tdc on that cyl.....

IdahoDoug said:

Ah, bummer - requires a compressor I don't have. Also, it's a boat engine so no radiator. Also, how the heck do you find TDC for each cylinder? You've got to find a way to do each cylinder in firing order by turning the engine exactly the right number of degrees since the timing marks only give you cylinder #1.

DougM

Click to expand...

Are you able to stick a long screwdriver or ratchet extension down the spark plug hole and watch where it hits TDC on this engine, or is there no room?

KLF said:

I'm convinced that no other test will confirm a leaking HG as quickly and easily as this one will.

Click to expand...

IdahoDoug said:

Ah, bummer - requires a compressor I don't have. Also, it's a boat engine so no radiator. Also, how the heck do you find TDC for each cylinder? You've got to find a way to do each cylinder in firing order by turning the engine exactly the right number of degrees since the timing marks only give you cylinder #1.

DougM

Click to expand...

So you sell the HG repair DVD? I think some forks that replied here are being played for a fool

Fuzzy Logic said:

So you sell the HG repair DVD? I think some forks that replied here are being played for a fool

Click to expand...

People often sell products they know nothing about... A Jasper rep. came by my shop to inspect a problem on one of their 1FZ long blocks, and that was the first time he had seen the inside of a motor of any kind.. so go figure! As far as the fool? I'm not the one asking the stupid fxxxing questions and turned this into a boat motor scenario.....

IdahoDoug said:

Ah, bummer - requires a compressor I don't have. Also, it's a boat engine so no radiator. Also, how the heck do you find TDC for each cylinder? You've got to find a way to do each cylinder in firing order by turning the engine exactly the right number of degrees since the timing marks only give you cylinder #1.

DougM

Click to expand...

1. Did you try activate CrystalBallBoatVision Version 5.63?

2. Wrong forum!

Sorry for the bandwidth, guys. I'm trying to help a buddy out before the boat dealer destroys the engine and then hands him a $5000 repair bill vs perhaps $600 for a head gasket replacement. It's hydrolocked once on me and the dealer replaced a part in the water impeller (which I replaced and serviced, so that was BS) in response as though that would fix a water-in-the-cylinder scenario. Nutcases all. So, I was thinking of helping him out and getting the tool for doing a leakdown to confirm MY diagnosis since we can't get them to do it. Frustrating all around and now I think I've spread some frustration here inadvertently. So, pardon one and all.

DougM

Doug,
Let's see if I can for once try to reverse the positive flow of info form you to me - I know a smidge about floaty things, mostly outboards but some sterndrive experience.

Assuming this is Chevy motor (nobody in their wrong mind puts a Ford in a boat):
TDC is when the timing mark is at zero & both valves on #1 cylinder are closed. Test . Rotate the engine by hand 90 degrees. Then test the next cylinder in the firing order. (GM V-8's: 1-8-4-3-6-5-7-2; left bank from front -1,3,5,7; right bank-2,4,6,8). It will take two revolutions to test all the cylinders, rotating 90 degrees per cylinder. To double check proper rotation, the timing mark should be at zero when doing # 6. I find it helps to put marks at 90 degrees on the balancer.

If it is a Ford, I don't know and don't want to, either, but one should be able to figger it out purty quick like.

What is the symptom that makes you think it's hydrolocked?

Bear,

Thanks for the input, but at this point I'm letting my buddy handle it with the dealer as I think it's going to get messy. The dealer's telling him it's fine - just a pump issue around the impeller. Uh, no.

After a whole bunch of stuff I won't waste time on, I got fed up and we went to the boat shop with my toolbox and found water in 3-4 cylinders by removing the plugs and cranking it over. Slapped the plugs back in and took the boat to the boat ramp. Started/ran fine but began to overheat. I put it in neutral/idle for a couple minutes feeling various components to establish what is getting hottest before turning off the key. Ominous bubbling in the block for 15 seconds or so. Spent 10 minutes pulling hoses off and checking for blockages with none found. Tried to restart and the engine rotated briefly and then the sickening sound of hydrolocking - bang and stopped turning. Confirmed by bumping the starter again. Got towed in.

Since the engine had water in it when I got to it and then it hydrolocked on me I am absolutely convinced someone overheated the engine and either blew the head gaskets or cracked both heads or cracked the block. Cylinders on both sides of this V8 had water, so not looking good.

So now it remains to be seen if my buddy will pick Door #1 where he goes ape**** on the dealer to listen to him (me) that there's an internal water leak in the engine and gets a test done to confirm which part's affected. Or Door #2 where he accepts the dealer has some mystical inside knowledge that the engine's fine with a new impeller plate. In #2 it will probably be a nice summer evening here in N. Idaho over at the popular Joe's for food overlookng the lake that will be when things go horribly wrong. Sated, the passengers in expensive clothing lounge in their seats as he turns the key. Sadly, the engine does not start. As evening on the water slips into night the engine merely runs halfjway until the locked cylinder acts like a water hammer and bends a crank arm or flattens a valve. Bingo, the night's over, you need a tow home and the cranky guy who runs the marina's shop in the morning will hand you a$ 3400 estimat to pull the heads and pressure test both. Then pull the block and pressure test its integrity as well Ugly, eh? All a boat wants to do is go out floating aroud and imagine a long journey but some bonehead had to run it with an old impeller and overheat the engine badly.


There-enough of the sob story, eh? She's hydrolocke.

Doug

Si, comprende, senor. Sometimes it's best to step out of the way.

That much water inside the cylinder on a domestic V8 probably isn't the head gasket. Your prognosis of cylinder head cracking is most likely spot on. Tell your buddy to find a local auto shop that works on hot rods, etc. If it's a small block chevy, parts are cheap, unless you get the ones that say "Mercruiser" on them, and you won't have an outboard monkey wrenching on it at $90 per hour

IdahoDoug said:

Ah, bummer - requires a compressor I don't have.
DougM

Click to expand...

Maybe too late, but you could use a CO2 tank to run the leak down tester gauge thing.

Very nice leak down gauge!

Either way the engine will need to be pulled. If you saw water in 3-4 the bottom end should be checked too. I love to ride in boats, just way too expensive for the amount of enjoyment/time of use.