i was recently having problems with my engine running hot. so i replaced my thermostat and it helped for a couple weeks, then started having the same symptoms. so now it was time for a water pump replacment. i did it by the book, however while trying to be conciderate for the dogs that sometimes wander into my yard i put the bucket of coolant drained from the radiator into a back room in my basement. promptly forgetting it. fast forward to the next day i finished up the work and replaced the coolant that leaked out of the pump itself. i started the engine up and listened, couldnt hear any issues or out of the ordinary. so i decided to take it for a test so i drove into town to my local auto parts store. the engine over heated, so i quickly pulled in and let the engine cool down and put a jug of coolant in. again didnt fully fill it up, after about an hour i drove back home, total time running is no more than 20 minutes. when i got home i saw the bucket with the coolant i drained, started to verbally abuse myself for being such a moron. i filled the cooling system full. the next day i went to start the truck, and the first time it sputtered and died, then the second time it started fairly rough, but it stayed running. so now im trying to figure out what i need to look at or repair. or should i just bring it to my mechanic and let him deal with it.

 

4.0l OHV engine, 1990-2000, is notorious for a head cracking when it gets overheated, it cracks between valve seats.

There is a simple test to determine if you have a cracked head or head gasket issue.
The Glove test, or balloon test

Remove rad cap
Remove overflow hose and plug the hole in rad cap fitting
Disconnect coil's connector, 4 wire connector on the side of the coil, we want a no start

Place latex glove over rad cap opening and seal it in place with rubber band, or use a balloon on rad cap opening.

Cooling system is now sealed
Crank engine with start motor and watch the glove
If it bounces, inflates, then you have a leak from a cylinder into the cooling system, so a cracked head or bad gasket.

If glove doesn't move then you don't

If glove bounces then remove 1 spark plug at a time and crank engine, when bouncing stops the last spark plug removed was from the leaking cylinder.
Replace that spark plug to confirm

 

with only one plug removed at a time i assume correct?

 

i did what you said, and when i removed the plug from the number 1 cylinder there was a huge difference. so its on that side, but if its a header or gasket ill have to pull it apart correct?

 

Yes, you continue to remove one spark plug at a time and crank engine, you don't need to put the spark plug back in after it is removed.

If glove stopped bouncing, completely, after #1 spark plug was removed then yes that cylinder has a bad head gasket or crack.
If glove still bounces a little then continue on, but leave #1 plug out, you will find another one leaking.
0 bounce = 0 leaks

The leak pulls in coolant causing the rough running because if fouls the air:fuel mix resulting in a misfire until engine warms up.
But the big deal is that when the leaking cylinder is on it's compression stroke some of that "air" is pushed out the leak hole and into the cooling system, it is what makes the glove bounce, and when engine is running that "air" displaces coolant in the head, cause engine to start overheating because air doesn't pull out as much heat as coolant.


Yes, if results are bouncing glove then heads will need to come off and be pressure tested, or if crack is obvious replaced
IDing the leaking cylinders is not required but can help you find if it was a gasket or cracked head that was leaking.

 

the number 1 was the last cylinder i tested, the glove didnt bounce but had a slight inflating, i replaced the plug and coolant spat out into the glove like all the other cylinders.

 

so now the question is should i just replace all seals just to be safe or inspect and buy as needed, incase its a cracked cylinder head i found a place that has them as well as a gasket kit and head bolt set.

 

??? "and coolant spat out into the glove like all the other cylinders"

Drain out a little coolant from rad, it doesn't need to be full, or to even have coolant in the system.

Glove will bounce, no mistaking it, or it will just lay there if no cylinder leaks.

A cooling system has no internal pressure at all, the water pump is not really a "pump", it just circulates coolant.

 

Part 2 -How To Test for a Blown Head Gasket (Ford 4.0L)

this a similar test i found online, but either way the glove bounced with all the plugs removed except the number 1

 

Then you do have a cylinder leak, bummer.

Head bolts are TTY(torque to yield) so can't be reused, so you need a new set.
If you get the head gasket kit it will come with new valve guide seals, if you don't have a valve spring compressor and are sending the heads to machine shop then include the new seals they will change them for you