4.0 major overheating.

[W.E. Racing]

first, ive been lost n gone for wahile. i sold my ranger last fall after i bought an f-150 and was happy until i felt compelled to build the sweet truck my dad never approved of. so my sis got a 4.0 ranger years ago one day blew the water pump and it overheated. overheated to where it was boiling out the overflow

new pump, new thermostar, new fan clutch. still overheated baddd. she drove it and i got it for a whopping $260

i though blown gasket or cracked head. got it all apart today and everything seems to be great. even the pistons and cylinders look good at 200k+.

problem, now what do i do???? i dont wanna put any money into what might fix it and i dont wanna reassemble for nothing. im lost and i need help.

sorry for the long post but had to be done. thanks

 

[RonD]

You are kinda stuck here, you probably should of tested for head gasket/head crack before disassembly.

Plastic bag test
Start cold engine, remove rad cap and overflow tube, place sandwich bag over rad cap opening, pinch it tight around opening, put finger over overflow outlet.
If bag starts to inflate you have a blown gasket or cracked head.
Cold cooling system has no pressure, only place pressure could come from is piston cylinder, water pump circulates it doesn't pressurize.

I guess you will need to get the heads surfaced and pressure tested.
The 4.0 heads crack between the valve seats, sometimes hard to see but that's the most common location.

Head gaskets don't always show where they were leaking into the cooling system, but if you focus on the metal cylinder rings, only 6 of them, you might see the failure point, feel them with your fingers, any deformation would be a possible leak point, look closely at that area.

You can pull the rad and test it for blocked tubes.
With rad out and cap off, put hand over lower hose opening
Fill rad with water
remove hand
water should gush out, not flow, gush, should empty rad in a second or two,
tip rad slightly to empty out the rest of the water.

Now quickly flip rad upside down
If any water comes out, it could only come from blocked tubes.
Old school test but still works

Hard to clear blocked tubes, you can try back flushing; with rad upside down put water hose in lower rad hose opening(now upper opening), use towel to hold pressure around hose, crank up hose pressure.

repeat "flip test"

 

[W.E. Racing]

thats a neat trick never though of that. i ordered a new radiator. i got gaskets, now i need manifolds or headers for it. and reassembly. the fun part

 

[2813josh]

Did you have the heads checked/machined? They are likely warped.