Over heating

[Bustedranger]

Ok, I have a 1994 ranger, 4.0. I have a problem with my engine getting hot. Recently I started doing small things to it, drained the radiator and added new coolant, changed the thermostate, and just replaced the fan control clutch, which actually made it run cooler that it has been. I'm able to drive it with my ac on, but my needle likes to hang around in between normal and hot but never gets all the way to red. When it gets that hot though from driving it for a while the coolant inside will boil after I shut the engine off but doesn't leak out. I do have to add coolant often though which tells me it's burning up somewhere. It's not leaking anywhere and there is no white smoke coming out of my exhaust pipe. I would like to note that I have no problems with my truck during the winter time, only when the weather starts to get hot like right now is when it starts to overheat. I don't get it, can someone help me.

 

[UrbanRedneckKid]

Go to your local auto parts store, and rent a block tester. It's a tube you install on your radiator, it uses a color changing fluid to detect CO2.

Also pull your dipstick out and post a picture of it.

 

[shane96ranger]

Off of your description, I'd say it could be a lower intake gasket. That is always a hard one to find. I had the exact same issues (missing coolant, weird gauge activity) on my 91 Explorer, and one day I heard it sucking air back in the leaky gasket after I shut it off.

 

[RonD]

Couple of things I had issues with on my '94 4.0l

The heater core on this model is the water pump by-pass, over time the core can get clogged tubes, restricting the flow, engine temp will run higher and sometimes spike randomly.
New core is less the $30, and literally 4 screws and 2 hose clamps are removed to replace it, 20 minute job the first time.

My old core was still blowing warm air, so was only partially blocked.

Second issue was a leaking/cracked overflow hose, it was where it ran across the top of the rad, it would leak coolant when engine got warm and rad was warm at that time so leaked coolant evaporated, but worse part was it would then allowing air to be sucked back into the engine as it cooled, so a couple of warm up and cool down cycles would give me an air lock and overheating until I purged the system, AGAIN.
I pressure tested the system and had no leak........yet coolant was leaking and air was coming in.
Pain in the butt finding that one, lol.

+1 on the intake manifold leak, I had that too but was in the front so I saw the residue from the coolant leak.
Pressure test would ID a hidden leak, you can rent pressure tester.


Head gasket leak would most likely cause the overflow tank to.....well, overflow, as the cylinder pressure is leaked into the cooling system it tends to push out the coolant into the overflow tank.
The max. cooling system internal pressure is 16psi(rad cap valves pressure)
If a head gasket is leaking compression(170psi) and firing pressure(500+psi) into the cooling system then that 16psi is exceeded within a minute or two even on a cold engine, this pushes out coolant to the overflow tank causing a high level and even overflowing from the overflow tank.
Pressure tester also works to ID head gasket leak, pressure goes UP when engine is running, then down when engine is off.

 

[Bustedranger]

Cool, thank you very much. Time to run some tests.

 

[Andy D]

The cheapest and easiest thing to replace in the entire cooling system is the radiator cap

 

[snake]

If this has been occurring slowly, like getting a little hotter every summer, your rad may be starting to clog as well.

 

[RonD]

+1 on the rad being partially clogged.

The water pump sucks coolant from the lower rad hose and pushes it thru the engine to the upper rad hose, where it cools as at travels thru the rad tubes to the lower hose.

So after engine is warmed up squeeze the upper hose and then the lower hose.
The lower hose should be slightly cooler, not a lot cooler, and should have slightly less pressure not a lot less.
If lower hose is easy to squeeze that means coolant is not flowing thru the rad fast enough for the water pump, it is sucking the coolant faster than it can be replaced and since it's a closed system this slows down the flow through out the system so temp rises.

Remove the fan shroud bolts and move shroud back out of the way.
Feel the rad, it should have even heat across and down, no cold spots, a cold spot is where it is blocked, lower rad is where clogging starts, gravity being what it is, lol.

While its popular to "flush" a rad while it's in the vehicle this really doesn't work once it is starting to get clogged up.

If you think rad is the problem just replace it, if money is tight then pull the rad and back flush it, run water backwards thru the rad, push out any debris the way it came in, this works on heater cores as well but you don't need to pull them out to do it.

With rad out you can also lay it flat and fill it with a warm CLR solution, let it sit for 20 min. then back flush again, repeat as you see fit.

To test a rad for blocked tubes:
Put rad cap on
Put rad on its side so tubes are running up and down
Put hand over lower hose outlet
Fill rad with water via upper outlet, stop filling when full
Remove hand from lower outlet
Water should rush out instantly
Listen at the upper outlet for gurgling noise of air trying to get thru blocked tubes
Now the test
Once all the water has drained out flip rad upside down
If ANY water comes out it could ONLY come from blocked tubes, a little or a lot of water isn't the point, if there are some completely blocked tubes then there is a lot of partially blocked tubes as well.