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Overheating Mystery


Tomm1468

Well-Known Member
V8 Engine Swap
Joined
Apr 22, 2021
Messages
110
City
Spokane, WA
Vehicle Year
2000
Engine
Transmission
Automatic
Total Lift
3"
Tire Size
245/75R16
I bought a 95 ranger 4.0L with 4x4. It ran fine but had some work that needed to be done, and I decided to just redo the whole engine. My Engine rebuild I replaced the following: New Heads, head gaskets, cam synchronizer, exhaust manifold (drivers side), erg valve, and tube. lower intake gasket, idle control, erg control, thermostat, thermostat housing, valve cover gaskets, upper intake gaskets, heater core, coolant tubing, upper and lower radiator tubes, clutch fan. Now my truck runs great but is overheating. I don't have my MAF sensor plugged in because it's gone bad. I figured at first it was just air in the system so I burped it several times, still overheats. got a new radiator cap, and both temp sender, and coolant temp sensors, and it still overheats.
So now I figured that was all the cheap easy fixes ill start doing some testing.
I let it warm up, and did the glove test, and the glove doesn't move at all.
then I took it out driving, and it didn't get cooler when I started driving, or when I got up past 35.
check engine light is on, so I read the codes, and it's only on because the MAF is unplugged.
after driving it a bit, I checked my oil dipstick and oil cap, no milky build-up, and no leak from the exhaust.
I checked my spark plugs, and they are a little bit chalky looking, it's hard to tell if that just normal use or not. (it was really hard to tell if one was even discolored.)
so I rented a pressure tester from Oreilly's and tested it, but it just kept leaking out at the lid spot of the radiator. (i could hear it)
It doesn't leak coolant anywhere. and I decided to go back in and make sure the gaskets I had were good and properly functioning. so I redid both the head gaskets again and the lower intake.
and another thermostat and radiator cap.
I burped it again, and it's still overheating. I can't think of what's wrong with it.
I redid all the parts that were cheap to buy, and I don't want to just throw parts at the problem, but I'm at a loss for what's wrong.
The truck runs smooth, and sounds great, when it gets all the way up to H on the temp, it's not steaming, but it is hot, so I'm wondering if the new temp sensor is faulty.
HELP.
 
Whats the DegF & PSI ratings of the ThermStat & Cap?
 
Do you have cab heat full on?
Are both HeaterHoses getting hot?
 
What exactly do you mean by "overheat"? Is it blowing out coolant or is the gauge reading high? Did it overheat before? Does it overheat at idle or only while driving? Does the gas gauge read high too?
 
Yes, how do you know it's overheating? I hope you have water spewing everywhere and are not relying on the factory gauge.
 
What exactly do you mean by "overheat"? Is it blowing out coolant or is the gauge reading high? Did it overheat before? Does it overheat at idle or only while driving? Does the gas gauge read high too?
I've never blown out coolant, or seen steam coming out of the engine, but my temp sensor is reading high. I have a Motorcraft temp sensor in the mail. because i thought about how it had never blown coolant even when it gets super high on the dash heat meter.
 
Yes, how do you know it's overheating? I hope you have water spewing everywhere and are not relying on the factory gauge.
overheating as in the gauge on the dash says its way too hot, ive never had coolant blow out. or steam come out. so i have a new sensor from motorcraft in the mail, cuz i was thinking it might just be a weird sensor thing.
 
How is the fan clutch? Does the fan spin really easy when cold?
 
Need to confirm your thermostat DegF rating?
 
If radiator inlet hose & side tank get hot after warmup;
I suspect it's a bad TempSensor or Wiring or Gauge.
 

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