New member + old truck + dead cylinder

Hey hey all, first post. Started out with a 2nd gen Tacoma a few months ago, but I've been itching for something with an extended cab. (tough to fit the GF and dog into a regular cab Taco) And last night I happened to stumble across a Tundra I couldn't pass up.

2001, double cab, 4x2, 203k miles, 4.7l V8. Looks rough, front and rear bumpers are banged up, tailgate's trashed, and needs paint.
But on the bright side, the frame is absolutely spotless, and there's no real body rust to be found.

Bought it with a miss fire in cylinder 4. The PO threw new coil packs and plugs at it, and gave up.
So, I drove it home on all 7 cylinders, knowing it was cheap enough to be worth an engine swap if it came down to that.

Checked the compression on the dead cylinder. Absolutely 0.
Poured some of the thickest oil I could find into the cylinder, checked it again.
Got, basically one good shot of compression (60psi) before it presumably all blew past the rings.

So I'm guessing either totally stuck, seized rings, or maybe more likely, cracked rings.

Am I missing any other ideas? I've never worked on a DOHC motor before, so I definitely have some figuring out to do.

Gut reactions.... Pull the head, try and re-ring one cylinder and call it a day?
Better just to find a cheap ebay motor and swap it in?

 

Turn the engine so the dead cylinder is tdc of the compression stroke. Then, Blow air into the dead cylinder thru the spark plug hole, and see if it comes out of the crankcase or intake/exhaust ports.

or water jackets?

 

Wow, you bought yourself a project! Welcome from LA (Lower Alabama)!

 

Welcome

 

long shot, but maybe timing? if the timing belt is off or overstretched than a valve is not closed completely and it won't hold any compression

 

Welcome from OKC! Congratulations on your project purchase!

 

Welcome from NC! If you are going to go through all the trouble and tear the motor apart for one cylinder just redo them all while you are in there….with no rust and a good frame I wouldn’t think twice on rebuilding the stock motor.

 

You could scope the cylinder to check for cylinder wall wear. Agree that valves could also be the issue. 0 is pretty low.......

 

Welcome from Nevada

 

Welcome.

 

Just a quick update. Happened to get the day off, and decided to start out by pressure washing the daylights out of the truck, and getting a good look at what I'm working with. Pulled out the bed liner to clean out under there too. Still not decided if I'll end up putting it back in or not.

For being an obviously used and abused work truck, I still can't get over there being NO real rust. Little surface rust here and there, but no cancer whatsoever.

Now to dig back into figuring out why it's only a v7...

 

So. Dead cylinder. Get the piston to TDC and do a leak down. My bet is valve related, not ring related. If it’s valve related a new head would be far easier than re ringing.

if it is the rings, just find a used motor.

 

Welcome from NY.

 

Well, just got back from a few little experiments...
I don't have a leakdown tester, but I screwed the compression tester back in, and shot my air compressor it in, at TDC.
Could hear the air rushing through as fast as my compressor could give it up, but was having a really hard time telling where it was going.

So I had kind of an off the wall idea.... I poured some motor oil through the spark plug hole to see if it would hold it and pool up or not.
Took a full quart as fast as I could pour it through the funnel. In my head, the only place that could be going, is past the rings, or even though a hole in the piston?

 

Potentially.

 

I'd say get your hands on a borescope and have a peek. That will give you a definitive answer and take any guesswork out of the issue.

 

I think my brother has a borescope. I'll see about borrowing it and checking things out.
Pending that, I might just go ahead and pull the head off. Won't cost me anything, and it'll be a learning experience even if I end up going with an engine swap.

Spent the rest of today just cleaning things up. Pulled off the broken fender flares and the side steps, pulled out the seats and carpet and pressure washed everything. Found a lot of mouse turds, so it definitely needed a good going through.
Gonna be a couple weeks before I can start pouring money in it, so I just went for some easy, free, instant gratification stuff today....

 

Bonus 2nd gen Taco pic

 

Pulling the head is quite the adventure in an OHC motor. Although likely inevitable with your symptoms. Surprised your truck runs at all with that much blowby into the crank. Gotta be pressurizing the crankcase and pushing oil out into other places.

 

Blowby into the crank..... Just scratching my head for a moment. Would that help narrow down where my compression is going?
Just like doing a leakdown test. Would running the engine and feeling for blow by from the oil fill narrow down rings vs valves?

 

Just tried it out real quick. I can actually feel a little vacuum on the oil filler.
Just basing it on what I remember from my old jeep that had SUPER low compression and tons of blow by...

That would have to be a pretty good sign for it being valves, right?

 

But where is all the oil going?

 

That's an awfully good question...

 

Does not really matter, the head has to come off to confirm thoughts of broken piston crown or stuck valves. Because of comment about 0 compression would tend to believe hole in piston that is not pulling air into cylinder due to no vacuum, so when piston goes up nothing to compress. You could pull cover over valves to determine if they are working properly but you know if not you will still need to pull head. Just go for it.

 

I actually forgot to mention I pulled the valve cover last night. It all looks foreign to me, (only other motor I've seen the guts of was an old AMC 360, pushrod engine...)
But as far as I could tell, everything was opening and closing, and doing what it should. Cam didn't look wiped or anything

 

Cam(s). DOHC engine with timing belt. Pulling the head will require removal of the timing belt. If oil readily drains down through the cylinder, the valves are not the issue. A hole in the piston or missing rings would do that. Worn rings shouldn't drink a quart of oil all at once or have zero compression. Gotta pull that head. Or ditch the motor and swap for a replacement. I couldn't resist the teardown either way. The borescope will give you a clue as to which way to go I would think.

 

Did you verify cyl#4 was on the compression stroke? With all the valves closed? Otherwise its gotta be ring or a holy piston. Since its 2wd, drop the oil pan and have a look-see.

anyone know if factory 2uz’s have gas ports in the oil ringland? Or whatever they’re called? The lower larger holes, not the tiny holes on top.

Having a hard time finding pics of factory 2uz pistons without rings.

 

I was working by myself, so it was a little hard to tell which stroke it was on. (last time I did this, I just held a thumb over the plug hole to feel for compression when somebody else turned it over)
But I checked it twice, compression and intake stroke, and it was blasting air either way...

 

Dropping the pan is a nice simple idea I don't have to borrow any tools for... If I get done work at a decent time tomorrow, I'll try and get that done

 

If it was me and I had the money to spend, I'd get a new engine, they're cheap and easy to find, just make sure the oil seals are done while its out. Also upgrade the valve body is you can, you might have a trans failure if it's high mileage and hasn't had its fluid changed routinely. Congrats on the new rig I am gonna keep an eye on the build