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Testing rings question

Number4

"I'm counting to 3, then I'm getting your dad."
Elite Explorer
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City, State
Woodstock, GA
Year, Model & Trim Level
04 Ford Explorer 4.6l
I bought this '03 Mounty knowing it had issues. However, I believed the issues to be blown head gaskets. I didn't do a wet test on the pistons with the heads on because it was clearly burning antifreeze.

See attached image for shops diagnostic results. They didn't do a wet test either.

Now with the heads off, I rigged up a device to test the rings. Only issue, is that the engine is going to be cold.

After wasting time with a Harbor Freight leak down tool, I made my own. The leak results are horrible, even in cylinders the shop said had good compression.

Here's the shops compression results and my leak down results.
#1 175 80%
#3 160 70%
#4 110 60%
#6 115 80%

I can test the rest of the cylinders, but I'm thinking that the cold engine is ruining the test. Mixed reviews on this doing a Google search.

How would rings with good compression have the same leak down as those with supposed bad rings? The shop thought the rings were the issue, I was gambling on head gaskets.

Should I clean up the heads and engine, slap new head gaskets on it?

Also, timing stuff all looks good, seeing as how the head gaskets may be a gamble, should I reuse the timing components, at least the tensioners, chains and gears? (They are the metal ones.) After sitting for a few months, chains were still taught.

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@Number4
Like your ingenuity! Had you not shown the pressurization rig, I might have doubted the post a bit. So, you applied pressure, shut off supply, then measured leak-down time? Like time to reach zero? How did you convert that to a percentage? One point: (or two), is this a 4.6L? Leak-down ought to be done with each piston at TDC, where cylinder wear is greatest, (and consequently, ring gap at it's max.). Most usually, I have been able to shine a very bright light down atop the piston, and piston clearance is sufficient to see the top ring's gap. An eyeball can tell the difference between 0.005" and 0.030". BTW, scratch the 4.6L question; assholish of me to not see 8 cyls. listed!

If it twere mine, I'd get an inside "Mike", better yet, a dial bore-gauge, and check the cylinders for wear: how much over nominal allowed, and how much taper: 4 measurements each hole, taken in line with crank and at right angles to it. IF the cyls. have not been bored oversize, specifications should tell whether yer wasting effort not replacing the rings. However, I am not familiar enough with this engine to know whether it is possible to re-sleeve the cyls. Incidentally, allowable ring gap is called out as 0.010" - 0.020", both top and bottom rings. imp
 






I made the device to cover the cylinder and then made a leak down tester (as the Harbor Freight one was junk.) Set the air compressor to 110, the tester regulator to 100 and attached it to the jig. Gauges on the tester were pressurized to 100, so second gauge reading 20 psi = 80% leakage.

I ended up getting way too much leakage. So basically, you can't do a leak down rest on a cold engine?

I was thinking about getting a dial bore gauge, but haven't found one to rent. Would like to know if the 110/115 psi was due to the head gaskets or the rings. If it's rings and cylinders aren't warped I may put new rings in. If cylinder and rings are okay, just do new head gaskets (preferred.)

Next step needs to be bore gauge. If the engine comes out now, it's not getting put back together, let alone going back in.

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I made the device to cover the cylinder and then made a leak down tester (as the Harbor Freight one was junk.) Set the air compressor to 110, the tester regulator to 100 and attached it to the jig. Gauges on the tester were pressurized to 100, so second gauge reading 20 psi = 80% leakage.

I ended up getting way too much leakage. So basically, you can't do a leak down rest on a cold engine?

I was thinking about getting a dial bore gauge, but haven't found one to rent. Would like to know if the 110/115 psi was due to the head gaskets or the rings. If it's rings and cylinders aren't warped I may put new rings in. If cylinder and rings are okay, just do new head gaskets (preferred.)

Next step needs to be bore gauge. If the engine comes out now, it's not getting put back together, let alone going back in.
@Number4
Clever set-up! I've replaced rings in engines with them in the chassis. Before I got a bit smarter. Examine the head gaskets very closely. Cylinder-to-cylinder leakage often shows as a darkened area on the cyl. opening flanges. Such leakage of course does not pressurize the cooling system, nor will exhaust products show up in the coolant if tested for them. I've seen head gaskets where the entire gasket material was eaten and burned away between two adjacent cylinders. Such huge leakage would hardly pump up a compression gauge to 50 psi, and immediately drop off to zero. imp
 






How much sludge was in the engine? Usually when I have low compression and the heads check out good, I get a new bottom end or whole motor. Usually bad rings will be the cause smoking, fouled plugs and compression loss is minimal unless cylinder walls are obviously damaged.

Any chance it had water ingestion and bent a few rods? All valves look good and valve guides all in place? (They like to crack)
 






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