4.0L Crankshaft Removal

Looking for a little insight on removing the rotating assembly from a 4.0L SOHC motor in a 2005 Ranger FX4 II. I'm having to do a timing chain job on this unit (184k mi), and would like to remove the crank, etc. so that I can clean all of the oil passages to remove tensioner debris and such. At the moment, I would prefer to leave the heads intact with the block. However, according to the 303-01 disassembly instructions, it warns you to NOT remove the crankshaft until you have first removed the heads. 'Serious engine damage may be the result'.
My question is: what are the effects of removing the crank before the heads? Block flexing / torsion?
I have looked in the cylinders with a camera, and all looks well enough. If I did pull the crank and found valve damage, I would do the heads as well.
Any information on this matter would be greatly appreciated.
Thanks in advance, Jim

JStiles said:

My question is: what are the effects of removing the crank before the heads? Block flexing / torsion?

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i'm thinking that the direct effects may be more along the lines of a piston sliding up the bore and dinging an open valve or scoring the top of a piston. the attached connecting rod scratching the cylinder walling during a slide. i don't know if a piston can move up a cylinder far enough to damage a ring on a ridge(if ridge has developed) with the head on, but something will hit something IF a piston moves that way uncontrolled. maybe six conrods falling as they clear their journals going dink, dink, dink, dink, ding, dink, dink as they contact the bottom of the cylinder wall might start some kind of injury.

i have a question, and please bear with me as i may be misunderstanding your intent. is it really necessary to remove the crank to clean out any debris from the chain guides? the only oil passages the crank blocks are the oil passages under pressure which means the oil just got screened at the oil pump pickup, pumped through the oil filter and should be (somewhat) clean. the t.c. tensioner and the guide are, as far as i know, in an area where oil that has left the lube system is dropping back to the oil pan(i'm not intimately familiar with this engine and am using knowledge gained from working on many other chain driven valve timing configurations, so if i am incorrect will someone please inform me). it may be necessary to just remove the oil pan to clean the screen and nail the inside of the pan with a can or two of brakecleen. that, and the new filter you'll install should get rid of most of the bits and pieces of concern.

also, if only the crank is removed the pistons would still block the view of the valves.

although not asked i'll make a suggestion regarding head removal from my lazy guy perspective: unless you insist on removing the crank, just change the chains, guides, and tensioners. remove the pan to clean the screen and make sure there aren't any big chunks in there that won't fit through the oil drain hole. install the engine and before you bolt on the exhaust manifolds slap a compression gauge on the cylinders to see if there may be some indication of valve problems.

you can check the exhaust valves for leakage before the engine is installed by rotating the engine on the stand so the exhaust ports are facing straight up and pouring some solvent in the port(s) that have a closed valve. any leakage would present itself rather quickly.

alright, i'll be honest with you, i'd just change the parts, change the rear main seal, clean the pan and screen and bolt everything back together. if the truck runs relatively smooth and strong the job is considered done and i'm down the road.

but you seem to be a bit more meticulous.

Thanks for your input 'huh?'. Just to be a little more clear, if I did remove the crank I would also pull the pistons. The cams have been removed, so all valves are closed. If the pistons were able to 'slide' through the cylinder, that would probably be an indication that the rings are shot (could be). I can't wrap my head around the crankshaft / head issue...
After reading other horror stories of debris in the lube circuit due to tensioner detonation, I guess I'm just a little leery of what's in the oil passages. The oil had a nice metallic sheen to it, as did both sides of the oil filter element when I cut it open.
You're probably right though. I should just bomb the bottom end with solvent, rinse and repeat and run it. Other than sounding like a chainsaw chewing through a box of nails, the motor ran great.
Thanks again

The pistons won't come out from underneath.

Been wondering about that...
If I had to leave the rods / pistons in the cylinders, I would still be able to clean the oil passages to the mains, if it didn't cause damage to the block by doing so.
The plot thickens...
Many thanks for your input.

fastpakr said:

The pistons won't come out from underneath.

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Oh they will come out the bottom. They won't go back in though.

Can you explain the damage incurred by removing the crank before the heads?

I can't. It probably has something to do with not letting the pistons drop onto the heads, although I have never had a piston that didn't need coaxed out of it's hole.

JStiles said:

Can you explain the damage incurred by removing the crank before the heads?

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It probably has something to do with having the timing chains off and rotating the crank to get to the nuts on the rod bolts, and positioning everything to pull the crank out. Rotating the crank with the chains off is a bad idea. Since you have the cams out this should not be an issue.

Thank you all for your input. I guess I had looked past the obvious. I figured that if anyone who had taken on the task of rebuilding a motor would know not to run the pistons into the valves. Kind of like holding a scalding hot cup of coffee in your crotch - some things you just don't do.
Any way, it makes perfect sense.
Thanks again for your time and effort. I do greatly appreciate it.