Lean and overheating... help!

[freak]

2000 4.0 OHV. I get fairly bad ping when accelerating and especially when hot outside. The engine also overheats. The gauge goes up and OBDII says it's 230 degrees. I have to run the heater on max and I can get it down to around 212. I've changed the plenum orings. Checked for vacuum leaks with a home made smoke machine. I need to take this on a 10 hours drive on Tues in high heat and do not want the heater on the whole time. Timing is about 35 degrees at 65mph. Cleaned MAF sensor. Only code was lean. Cleared it and it hasn't came back again. Idle is high around 1200 then slowly drops to 800ish. Engine runs absolutely beautiful otherwise. I'm really desperate to get this fixed. Any tips appreciated!

 

[koda2000]

Cracked head? Typically between the valve seats. Pretty common on the 4.0L V6 OHV engine.

 

[freak]

That would cause ping right away even when cold?

 

[Mbrooks420]

You likely have a blown head gasket, warped heads, or a cracked head. Don’t take that thing on a 10 hour trip.

 

[freak]

I replaced the egr gasket last night. Went for a test drive this morning. Ping seems significantly better. Still overheated. Ran the heater for a while till it got down then turned the heater off. Seems to be ok then. That "overheat/run heater/then ok" cycle seems to be repeatable. Any more ideas?

 

[Turdle]

My list of possible issues

Low coolant level. Check radiator level, do not rely on the level in the reservoir. Park on an uphill incline to purge air out of coolant system.


clogged output from reservoir Gunk clogs the nipple, which allows fluid to go in to reservoir but not back out, pull reservoir hose from radiator, and make sure coolant fee flows out of reservoir, use a coffee can to catch and reuse coolant. The reservoir should empty rather quickly if the nipple and hose are not clogged


collapsing lower radiator hose. When hot the water pump sucks water through hose sucking it closed. squeeze hoses to see if they are soft.


bad radiator cap leaking pressure

Corroded water pump impeller.

Clogged radiator

 

[freak]

Anyone ever see a thermostat behave this way?

 

[freak]

I'll also add that the radiator is not low at the radiator. I never have to add coolant. Coolant is perfect color. No white smoke.

 

[Mbrooks420]

If that’s the case I’d say one of Turdles suggestions are the case. Clogged radiator, collapsing hose, crusty or worn water pump impeller. Bad cap.

I’d really try and find the cause, and not take it on a 10 hour torture test.

 

[974X4BLACKSPORT]

When the engine is warmed up, feel top hose, it should be hot, then feel bottom hose, it should be much cooler than the top, and it should not burn you when touched, if it does burn you when touched, then you have to verify that the water is flowing through the radiator, and that proper air if flowing across the fins.
If your top hose is cool when the engine is warm, your thermostat might be stuck.

 

[poker4me007]

Your Thermostat could be acting lazy, I'd change it out.
I've had good luck with the Stant #45369.

 

[freak]

Pulled the thermostat and tested it on the stove with an instant read thermometer. 220F and still closed. Dropped in a new one and no longer overheats! Glad I didn't start pulling the heads off. Lol. Thanks everyone!

 

[974X4BLACKSPORT]

WOW, good catch! Bad thermostats are supposed to default to the open position, that way when they malfunction the engine stays too cool, instead of overheating (lesser of two evils) .

 

[koda2000]

WOW, good catch! Bad thermostats are supposed to default to the open position, that way when they malfunction the engine stays too cool, instead of overheating (lesser of two evils) .

This is only true of "fail-safe" thermostats.

 

[RandomNerd2000]

Thermostats do NOT always stick open, when I started driving my 2000 V8, I had one stick CLOSED, the gauge was normal, don't remember how I found it but it was a major PITA to change, how it didn't overheat is beyond me, and if it did it was a minor overheat.

 

[JER-1]

Had an old man at shop with young boy helper put in new radiator, 1996 v8 Explorer.
Over heated from get go, was putting in new steering rack had bottom hose off, just happened to notice when putting all back together the plastic plug still in the new radiator, dam I was pissed.

 

[freak]

Well.. drove 900+ miles loaded with 7 bicycles, 3 people and luggage! Ran great. A little spark knock occasionally which I think may be a slight vacuum leak but I'll deal with that in a couple of weeks. Love that old explorer!