My 1998 Ranger, 4.0 L, 4-Door, 4x4 recently overheated - the Check Engine light came on, but the temperature warning did not. I was on the freeway, turned on the heater and slowed down. The temperature instantly went down (not quite to normal temp), but a few miles later the temperature went back up and cold air came out of the heating unit.

I managed to pull into a gas station just as smoke started coming out from under the hood.

The next morning, I rinsed off the engine, let that water dry and then tried adding water to the radiator - it's definitely leaking.

My plan - please let me know what you think:
1) Replace radiator, upper & lower hoses, thermostat, radiator cap
2) Remove and inspect water pump
***3) Inspect fan & fan clutch (not 100% sure what to look for with that)***
4) Get that all together, fill up with coolant/water and try to start the truck

My questions:
1) How do I know if my head gasket is torched (other than the fact that my truck won't start)?
2) Should I replace all the spark plugs? Is it common for them to foul when the engine gets hot? Is it possible to have a "false positive" for the head gasket if a plug is fouled?

I managed to get all the radiator & cooling parts cheap (minus the water pump at this point) but am very afraid if I need to replace the head gaskets - the truck has over 200K on it and I just rebuilt the tranny.

Anything else I am possibly missing?

Thanks for the input,

Spin the radiator fan. If you spin it and it's very easy to spin, almost no resistance, and when you do spin it, if it keeps spinning for a while on its own, the clutch is most likely out.

If the head-gasket is toast it'll blow white smoke while your engine is running and it'll be hard to start. Those are the usual symptoms.

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Don't panic yet. I will add to ^^^^^ his post. You need to find the leak. No need to throw anything at it yet. Does it crank? Maybe The Coil got wet?

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2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).

Thank you for the tips thus far.

I removed the belt and the fan does have a little resistance, so that is a piece of good news.

Regarding the water pump, I did not pull it off, but removed the bottom hose and looked inside with a flashlight - I could see the impeller moving. Based on that, is the water pump likely okay?

do you know where it is leaking from?

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2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).

The radiator itself was leaking - somewhere along the bottom/right side. I don't think any other part of the system was leaking, but I am not positive.

There was a lot of corrosion around the thermostat and in the housing, but the thermostat itself looks clean.

so you are saying that the radiator is definitely leaking? not a hose or something else? the radiator?

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just throw in a radiator, tstat and whatever hoses you have and see what happens. no need to do the waterpump unless you really want to.

create a signature up at quick links.

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2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).

Yes, definitely a leaky radiator. I just put it all together - new rad, hoses, hose clamps, thermostat, thermostat seal. The thermostat housing had quite a bit of corrosion, so I cleaned it up as best as I could.

I filled with it water only and the truck started right up. No obvious signs of water/smoke from the tailpipe and no leaks.

There was some residue (small, white chunks) present when I opened the radiator cap, but no oil.

At this point - should I drain and fill with 50/50 and test it around the neighborhood?

Thank you again for all the advice!

If the water looks clean then drain and fill with concentrated coolant and the remainder using distilled water. If the water is dirty drain and fill with water. Don't use 50/50. You never get all the coolant/water out when you do a flush like you're doing.

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2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).