Possible cracked cylinder head?

[AKexplorer21]

I have a 1996 manual transmission Explorer, 4.0 L with almost 150,000 miles. I love having a stick shift explorer, but I've been experiencing engine problems since almost the time I bought it a year ago.

I thought I resolved this issue a while ago, after I took my car for a rough idle. I had all the upper intake manifold gaskets and valve covers replaced, as well as swapping out a cracked head gasket for a new one. All plugs and wires were replaced too, as well as the fuel filter.

This repair held up for a while, but a couple weeks ago I noticed that my explorer was idling rough again. The rpm's were stable at just about 1K unlike last time, but the engine shakes hard enough to rock the whole car. Shortly after that, my check engine light started blinking under hard acceleration. I've also heard the infamous "tic tic tic" of a noisy lifter, but this has happened sporadically over the past few months and may be unrelated.

I didn't have a code scanner, but I was positive that one or more of the cylinders must be misfiring. I was worried that the head gasket had cracked again. I took it into my mechanic to find out that the catalytic converters were incredibly clogged, and one of them was over 800 degrees when I pulled it in. Hoping this was a result of my previous problem finally manifesting, I had my cats removed, scraped, and replaced. (No emissions testing here)

The engine ran better, but still not near 100%. My mechanic told me that it was hard to tell without pulling the heads, but he thought it was likely a crack in my cylinder head itself. After putting about 1500 into this vehicle already, this was the last thing I wanted to hear.

I'm wondering where my next step from here is. I could buy a new or refurbished cylinder head, but that seems risky without knowing that it's the problem for sure. Would it be more economical if I simply found another motor out of a salvage explorer or ranger and swapped it out? If there's a good oil additive that would work well as a stopgap for now it would be nice to know. I love this explorer, but I'm starting to think about cutting my losses and selling it.

 

[AKexplorer21]

Update: A few days after taking it into the shop, getting the cats cleaned out has made a bit of a difference. I'm not getting a blinking check engine light as often, but it still happens. After checking the exhaust, the odor of burning oil is a lot more evident now. No moisture though, so I don't think it's burning coolant. You can hear the engine making a chugging noise through the exhaust pipe.

I got a new code scanner as well, the only codes I was getting were p0301 and p0306, for cylinder misfire in 1 and 6.

 

[imp]

If your exhaust system is reasonably sound, no big leaks, holding a paper matchbook which is open, up against the end of the tailpipe, like a little "flapper", a sucking of the paper up against the opening of the pipe is nearly a certain indication of a burnt exhaust valve (or valves). Try it! imp

 

[Fordian]

Hows ur oil pressure? Sounds to me like ur oil pump could be bad causing ur problem to begin with. If the oil pump isnt pumping oil then your lifters and valves will make noise and your engine will overheat. When ur engine overheats, your heads can warp and crack. A warped head will cause a space between your engine and the head and allow pressure to escape the cylinder. So check for compression and possibly a loss of coolant depending on where the crack or warping are. Also, lack of oil to your valves will make them hot and cause any oil that does make it there, burn and cause you valves to stick. It could also just be varnish buildup, in which case id recommend running seafoam in the oil to free them up. That was the case with an explorer i had and that fixed the problem. I hope thats ur case.

 

[AKexplorer21]

If your exhaust system is reasonably sound, no big leaks, holding a paper matchbook which is open, up against the end of the tailpipe, like a little "flapper", a sucking of the paper up against the opening of the pipe is nearly a certain indication of a burnt exhaust valve (or valves). Try it! imp

I didn't have a matchbook, but I help a paper receipt up against the exhaust pipe. It definitely did appear like it was getting sucked up against the opening, along with a paper rattling sound, once every engine cycle. Could the burnt exhaust valve be indicative of some other problem, maybe damage from my earlier cracked head gasket or a warped or cracked head burning fluids?

 

[AKexplorer21]

Hows ur oil pressure? Sounds to me like ur oil pump could be bad causing ur problem to begin with. If the oil pump isnt pumping oil then your lifters and valves will make noise and your engine will overheat. When ur engine overheats, your heads can warp and crack. A warped head will cause a space between your engine and the head and allow pressure to escape the cylinder. So check for compression and possibly a loss of coolant depending on where the crack or warping are. Also, lack of oil to your valves will make them hot and cause any oil that does make it there, burn and cause you valves to stick. It could also just be varnish buildup, in which case id recommend running seafoam in the oil to free them up. That was the case with an explorer i had and that fixed the problem. I hope thats ur case.

My oil pressure seems fine from the gauge, a little under halfway between high and low. Sometimes I've seen it drop to almost touching low, but I figured this was a loose electrical connection to the sensor. I'll try putting some Seafoam in the oil too. How much will a compression tester run me, I've been thinking about picking one up.

I think I might have a coolant leak as well, the overflow tank seems to be dropping a bit and there's signs of vaporized coolant on the bottom underside of the engine. Not sure if it's coming from the engine itself, I haven't noticed anything dripping lately before I had a look. Also there's a light hissing noise if I check the engine immediately after turning it off sometimes.

On the bright side I checked the oil again, and saw no signs of any coolant entering my oil system like it did when my head gasket went bad. I'm also starting to think my exhaust smells more like unburnt fuel than burning oil, like a lawnmower is the best way I'd describe it. The exhaust looks more white than blue in tint too.