I recently bought a 1994 4.0 Ranger and replaced the head gaskets as well as fixing a cracked cylinder head. Everything was put back together and upon driving the temp gauge started moving around more than it should. (Fluctuating when being on and off throttle and having a hard time staying cool) We also discovered upon punching the throttle that it would shoot coolant out of the radiator. I've read everything I can on it and lowered it down to air being in the lines, the heater core being plugged, bad radiator, needing a lower degree or having a bad thermostat, or having a cracked block.

Please help.

 

How did you fix the Cracked Cylinder head???? Coolant shooting out of the rad when using the throttle is a sign of a bad head gasket.

 

+1 ^^^

First, you can refill cooling system by removing one heater hose at the firewall, then refill at rad cap opening, this will let ALL OF THE AIR out from the engine side of thermostat
When water/coolant comes out the heater port and heater hose air is gone, put hose back on

Cold engine
Remove radiator cap
Top up if low
Start engine
May see a "burp" of coolant come out rad cap opening
Let engine idle
If coolant starts to overflow within the first minute or so you have a bad head gasket or cracked head................period, no other reason for the continued overflow

Bad head gasket or cracked head allows the 900psi air pressure from a firing cylinder to be FORCED into the cooling system, this "air"(exhaust gases) displaces the coolant that is in the head, that's why radiator overflows almost as soon as you start the engine, the engine is pumping IN "air" to the cooling system
The "air" doesn't cool the heads very well, and the "air" can also form an "air" dam blocking coolant flow for a few moments, temp goes UP, then when some of the "air" is pushed out and replaced by coolant temp goes DOWN
But eventually there is just too much "air" in the heads and it Over heats


Let it idle for a few minutes and with no overflowing of coolant then head gaskets and heads are OK

Clogged heater core won't cause "OVER" heating but will cause gauge to go up above 1/2 and then back down below 1/2, for no good reason, just random up and down after warm up

 

i went a got a new cylinder head with no cracks and good pressure. like said the head gaskets are brand new and were fixed the same time as the cylinder head.

 

i will try this. ill update after trying