new 4.0 heads vs used motor

[frodo9415]

I recently bought a '93 4.0 auto ranger and it is definitely leaking coolant I can see it seeping out of the head might be coming out in between the valve cover and the head or a small crack in the head on the outside. just trying to figure out a route to go on it. I have thought of getting re-man heads and putting on there and going that route or finding a used motor to put in it I have also thought about swapping out a used motor

need some input please looking for the more reliable route to take making the truck into my hunting truck so it wont be a daily driver but I will be way back in the woods so it needs to be just as reliable

thanks in advance

 

[cp2295]

Far as im concerned slapping new heads on would be the better approach these motors are known to crack heads, and the bottom ends are tough as long as the bottom end is good and the motor isnt "tired" i would slap new heads on it. $400 on ebay and they are brand new not remans. New valves seals guides castings everything


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[RonD]

4.0l heads rarely crack on the outside, actually never even read about one that did that.

They do crack between valve seats when overheated, no external leak with that crack.

Common external coolant leak point on 4.0l is at the intake manifold where it meets the head, aluminum intake manifold and iron head with fluid passing between the two causes electrolysis and can eat away at the gasket and aluminum.
Passenger side front and drivers side rear are where this leak can show up.

Also core plugs(freeze plugs) can rust from the inside out this will cause external leaks.

And then there are pin holes..............I have run into hoses that get pin hole leaks that spray a fine stream, almost invisible, onto an engine area that should not even have coolant around it that could leak out, lol.
Very had to find because it doesn't leak at all cold, only warm and after cooling system has some pressure in it, then the spray starts.

You can rent a cooling system pressure tester, it installs on rad cap opening and has a gauge and hand pump.
You pump up the system to 20psi and then start looking for the leak point, and this is on a cold engine so you can feel around and get into place that you can't after engine is warmed up.
I would find the leak first before investing in heads.

 

[cp2295]

Yeah totally right ron i overlooked that part of the op!


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[trail B2]

Buying a used motor can be a bag of snakes believe me I know.If I had any doubt about the head condition I wouldn't hesitate on new heads.

Ron is giving you good advise us amateur mechanics have a tenancy to skip through the diagnosis.Diagnosis is what separates good and bad mechanics to me anyway.

 

[adsm08]

Another fun test I have picked up over the years is to pressurize the cooling system when cold with a pressure tester and then start the engine and let it warm up.

This can show some hard to find leaks. Ford had us using it to look for possible head issues on the new 1.6L.