I have a friend who has a 1998 4.0 ranger that died while driving down the road-when they were troubleshooting they found that the lifters had pumped up and opened all of the valves thus no compression on any cylinders-they pulled the engine and replaced the oil pump and all 12 lifters and replaced the engine and started it up and as soon as the lifters pumped up again it died and has no compression-does any one have an idea on what would keep the lifters from bleeding off or what would cause them to pump up and hold the valves open? it acts like a solid lifter that is too tight

 

Welcome to the forum

No, never heard, or even read, about that in regards to the 4.0l OHV engine
And especially across all lifters, they don't share a common oil passage on both banks,I assume, but have yet to find an oil passage diagram for the 4.0l OHV Block

Would it be possible to put an oil pressure gauge on the block to see what the oil pressure is while cranking, 200rpm, should only be about 3-4psi

 

that was my question to him but he hasn't tried that yet-however when you loosen the rocker arms the compression returns

 

4.0l OHV has the 3 bolts that hold rocker assembly on each head, so not adjustable

When the valve is closed, Cam lobe opposite of high point, you should be able to twist push rod with your finger, hard to turn but should turn, wipe oil off first, lol

While is hard to do, if there is an engine problem usually overheating in cylinder(s) Intake Valves can "tulip"(gets a tulip flower shape) this would cause the valve stem to be higher and valve wouldn't close all the way
But easy to see with rocker assembly off, the valve stem(s) would be sitting Noticeably higher than the other valve stems
Generally from a Lean condition, not lean codes, an actual Lean condition, when you hear pinging/knocking when accelerating or at highway speeds

4.0l OHV uses solid push rods, not hollow, so lifters don't pump oil up to valve train, oil should just be pushed out on compression of the lifter and oil drips back to the oil pan thru the valley openings

Rocker assembly is oiled via its center post, there is a passage thru the head/head gasket to the block, I believe oil passage comes from one the the center cam bearings, other head gets oil from other center cam bearing

He could try an oil system flush, never a fan of that, but not sure there is much else he can do except pull the engine and have the block hot tanked then reassemble

 

he is going to pull the valve covers and remove rocker arms and place a straight edge on top of valve to see if the exhaust are higher-but why would all 6 beat out at the same time? It ran perfect and just died driving down the road-the oil pump was replaced with a new one but it is still doing the same thing-do the lifter bleed off inside the lifter bore or is there a seperate passage that could be plugged?

 

As far as I know the lifters are fed oil thru passages but when compressed that oil comes out into the valley, no return passage
And I doubt it could even be an oil pressure issue, as the lifters have enough side clearance to allow travel up and down so higher pressure would just squirt out around the lifter case

Are you sure its the valves that are staying open and not the crank/cam timing that is changing and causing loss of compression?
I have read of crank timing chain gears shearing off the woodruff key, on many engine models not just 4.0l
4.0l OHV is a non-interference engine so valves can't hit pistons, you just get a loss of compression

 

The first thing they did was remove the timing cover to see if it had jumped time-It is like the lifters are pumped up to full length- no one around here has any explanation for why the lifters are at full length-It seems odd to me that all the exhaust valves would sink at the same time-it is surely not the only 4.0 on here to suffer this malady

 

Lifters are always at full length, preload is only 0.05" to 0.1" when rocker assembly is tight, 1/10" so less than 1/8", not much preload, just enough to keep them from "ticking"

 

Thank you for your response-I will tell him to check the valve stem height today and see if the seats or valves are bad-update- I pulled the head off for him today and the exhaust valve seats were sunk about 1/16 of an inch or more-have heard 4.0's have that problem but I never thought nothing would show up until it just quit running driving down the highway