It’s a 07 hummer h3 with the 3.7l it has about 240,000 miles on it.
Okay so this is my girlfriends car, she has owned it for about 4 years now and more recently it has had a cylinder 3 misfire, followed by a cylinder 3 coil continuously going bad, this was before she got me involved. Went through different spark plugs and about 6 coils until it was running okay for the last week. It would seem to fire up cold and then miss after a few seconds and sometimes just misfire all the time. It was running good so she said for about a week then she said her cv axle fell out ( the boot was gone and dirt was in there) she also told me at that time when she got it towed home that her radiator was leaking, well I got to it, it wouldn’t fire up, just cranked slow and seemed to lack the umph. I looked up specs on coolant capacity and as I filled it (it was empty) I could hear it bubbling the coolant traveling somewhere, I listened and thought it was passing though the thermostat. Kept filling and the bubbling didn’t go away, after about 9-10 liters and still wansnt filling and I could constantly trickle the coolant in I thought something else was wrong, at that point I drained the oil and all of the coolant I put in the car had went into the oil pan. At that point I told her I was towing it to my house.
I pulled the plugs first and the two outside cylinders were normal the two inner ones has water residue on them like I could wipe a tiny bit of water off them, the center cylinder her coolant showing in it and the spark plug was obviously wet. Pain taking it apart I found the throttle body electrical connector was broke so it could pull off at anytime, and the two back bolts closest to the firewall on the intake was not as tight as all the rest of the intake bolts.i shocked the head bolts removed the cam gears, didn’t break any of the head bolts but they were surly sketchy thought some were gonna break. Removed the head and located a hole in the piston in cylinder #3. I’m just wondering if that could be from coolant slipping past the head gasket for a while now and ate the piston? I checked the head for cracks and filled it with water for cracks, also checked the block for cracks or loss of coolant into the oil pan. The head gasket is a multi layered steel gasket it had no visible defects to suggest a leak. I’m not very familiar with hummers this is my first time going to be removing the engine. I also noticed the exhaust manifold is cracked and the rear main seal is leaking. I did notice some unusual “gunk” or maybe even cavitation, it’s just cylinder #3 that looks that way and only on that one side. Thank you in advance everyone!! The

This photo shows the extent of the piston damage

Two rear cylinders got wet after removing the head.

This is the scuffing on the sidewall of the cylinder #3.

This is the same angle of the sidewall of cylinder #4

This is the same angle of the sidewall of cylinder #2.

 

I doubt I would spend the time to replace the pistons and lower end to bolt it back together. Better to look for a used motor or re-manufactured motor.

Coolant does not eat or blow a hole in a piston. The radiator leaked or burned out coolant, got way too hot, had a blow by situation going on that side of #3, the hot gases kept blowing by in/through that leak and finally got the piston metal hot enough to burn it. Like as in bye bye its gone and in the oil. That more than likely has #3 cylinder out of round, not to mention what is going on in the bottom.

 

Doc Olds is giving you great advice... Look for a used motor or re-manufactured motor.

Ebay has 2007 -3.7 Hummer motors

 

Agree with Doc diagnosis. With that kind of mileage. And your report.

Time for a change out.

 

Advise your girlfriend to get a bus pass.

 

Thank you doc olds, I was afraid of hearing that.. I still have to explain it to her, so I’ll have a little chat with her and explain the engine with that mileage and had that problem for some time it’s time to get a new engine, unfortunately she is still paying on the it! I was just wondering though you said the it got hot and the blow by has caused the hole to arise but where would all the coolant leak from?? To move that quickly from the radiator to the oil pan. Thanks again!

 

the head gasket should reveal the issue. probably blew a hole in it.

 

Lol! I'm one of those optimistic people who sees potential in things.
I'd take the time to pull the engine and pull the bottom end.
Pistons can be replaced. Cylinders cut, honed or resleved. Heads and gaskets replaced.
But as always bottom line is green back's. If it's cheaper to rebuild or replace. In this case don't know.

 

Thank you happy hummer. I couldn’t find the obvious head gasket leak but I was throughly looking at the coolant jacket to the cylinder walls. Maybe the leak was from the head gasket between the oil cavity and the coolant jacket. As for the hummer I don’t know the fate yet. Definitely going to examine the bottom end better. Thanks again for everyone’s input!

 

looking a bit better at your picture it looks like it had a really bad exhaust gasket leak at that cylinder.
the rest of the exhaust manifold ports are normal rust colored but that one is carbon black all around even the mating surface. a bad exhaust gasket can damage a piston like that.