at wits end

[vtranger1]

let me bring you up to speed with me situation. i was having some overheating issues, so i replaced the temp probe, then the thermostat. after still having the same problem i replaced the water pump, went smoothly and got everything back together. me being dumb i forgot to put the drained coolant. long story short i blew the head gasket. after many hours and lots of curse words later i finally got the gasket changed and the engine put back together. everything ran good, until i noticed the fan was stuck on defroster, and wouldnt change. not a huge deal, i did notice my temp gauge bouncing around, so i attempted to bleed the system a few times. this last time i bled the system my heater went out and the temp gauge no longer bounces, it hits red and goes further. so my cooling system is not working, as well as my fan being stuck on defroster, from what i can gather there is no circulation of the coolant at all. im kinda on my wits end with this, considering my truck has only been driving less than 6 months this year. so any help is welcome,

 

[RonD]

Were the heads pressure tested when they were surface at machine shop?

4.0l heads are known for cracking between the valve seats when overheated, a weak spot on the casting.

If a head was cracked it would start to leak again and it pumps "air" into the system, displacing coolant and you get the start of overheating again.
This also cause temp gauge to go up and down as the "air" gets trapped in the head and then pushed out all at once, this would be gauge moving from 1/2 to 3/4 and back.


There are two hoses from the engine to the heat control/by-pass valve, these two hoses must have coolant flowing thru them all the time, or you will get temp gauge going up and down randomly.
So if this by-pass valve should start to fail or the heater core is starting to get plugged up you would see the temp gauge going up and down, but not overheating, just up a little above 1/2, and then down to 1/3, back and forth randomly.
This has nothing to do with defrost being stuck.

You can get correct size joiner and hose clamps, then remove the two engine hoses from by-pass valve and connect them together, this by-pass the "bypass", lol, no heater but this will test if that system is indeed the source of the temp gauge movement.
Mark the hoses so you know which goes where on the bypass valve

 

[vtranger1]

Where the heads pressure tested when they were surface at machine shop?

4.0l heads are known for cracking between the valve seats when overheated, a weak spot on the casting.

If a head was cracked it would start to leak again and it pumps "air" into the system, displacing coolant and you get the start of overheating again.
This also cause temp gauge to go up and down as the "air" gets trapped in the head and then pushed out all at once, this would be gauge moving from 1/2 to 3/4 and back.


There are two hoses from the engine to the heat control/by-pass valve, these two hoses must have coolant flowing thru them all the time, or you will get temp gauge going up and down randomly.
So if this by-pass valve should start to fail or the heater core is starting to get plugged up you would see the temp gauge going up and down, but not overheating, just up a little above 1/2, and then down to 1/3, back and forth randomly.
This has nothing to do with defrost being stuck.

You can get correct size joiner and hose clamps, then remove the two engine hoses from by-pass valve and connect them together, this by-pass the "bypass", lol, no heater but this will test if that system is indeed the source of the temp gauge movement.
Mark the hoses so you know which goes where on the bypass valve

i had to get a new head because as i was working on removing a stuck manifold bolt i dropped it. i got a new head from cylinder head international and they say it was pressure tested. unless the head i got is SNAFU, then its something else, could it be that my water pump is bad again? or could the thermostat be stuck closed? thanks for the reply, this is the most trouble ive had with my ranger,

 

[RonD]

Just to take head/gasket issue off the table do the Glove Test.

Get latex glove and rubber band or zip tie, or a balloon or even a condom will work, lol.

Cold engine
Remove rad cap
Drain some coolant out so it is down about 1/2"-1" below rad cap opening.
Pull off overflow hose and block that opening, vacuum cap from engine will work, putty, chewing gum..............just need to block it.
Put glove over rad cap opening, seal it with rubber band.
Cooling system is now sealed, cooling system has no internal pressure when cold, water pump isn't really a "pump", it circulates coolant so doesn't add pressure to the system.

Disconnect Coil Pack wire connector or pull off spark plug wires, you want a No Start.

Crank engine and watch the glove
It should just lay there, no movement

If it starts to bounce you have a leak from a cylinder into the cooling system.
You can ID which cylinder by removing 1 spark plug at a time and cranking the engine again.
When glove stops bouncing last spark plug removed is the effected cylinder, reinstall it to confirm.

Each cylinder will have 150+ psi of compression stroke pressure when engine is rotating, if some of that pressure is leaking into cooling system then head is cracked or gasket is blown on that cylinder.

This will tell you if you are chasing your tail with heater, water pump, thermostat issues when it is really a cylinder leak

 

[Josh P]

The van I bought had an overheating problem, po changed just about everything but the fan hub. Clutch was worn out so even though it was spinning it wasn't enough to keep it cool. If the fan blades are cracked either a super cooling fan or an 11 blade from an s10 works really well.