Engine Temp Problem.

[1shot]

Hello folks - Im new to posting on this site - but since Ive got a problem with my old Exploder that I cant figure out, I thought I'd ask the experts. It's my daily driver, and as such I need to fix this irritating problem before it cause long term problems. I would like to know if anyone else has had similar experiences before, or suggestions.
:exp:
92 XLT 4.0L V6 auto, air, cruise, PW,PB etc.
Truck has 395,000 km on original motor, mostly highway. (aprox 250,000 miles)
Problem:
Temp of motor climbs to normal area on gauge (about the M in Normal) swings back down from the middle to almost the C (cold below the N of Normal) while driving, then back up to normal, doesnt matter if its city or highway, temperture still swings wildly. I can tell the actual coolant temp is swinging from the variance in engine performance (severe pinging etc.) and the temperature of the air coming off of the defroster vent. It continues to act as if there is no thermostat in it and over-cools the fluid.

Ive replaced the thermostat twice with new 195 F units. Same scenario. All hoses have been replaced recently. No fluid leaks. Water pump is good, no leaks in the system whatsover. New Antifreeze. No oil or other polutants in coolant. Fluid levels remain constant.

Any suggestions?

 

[1IronMike]

You might check out you fan clutch.

 

[Jason94sport]

Fan clutch, fan & coolant temp sensor, replace all those.

 

[ma96782]

My STOCK answers on over heating problems: (beside changing a radiator or water pump)

If you got the tools or access to the kit........pressure check the system.
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T-stats can be checked w/ a thermometer and a pot of hot water………or just replace them……….they aren’t that expensive.
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While running and with the engine off, make a visual check of the hoses for a hole, check for leaks at the connections. If it passed the pressure test, you should be OK. But, still check for a, "too soft" hose, which may collapse.
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Test the cap (pressure test). Or if you don‘t have the test equipment……..replace it, if you can't remember when it was last done........or if it's been more than a couple years since it was last changed.
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Perhaps, it’s time for new anti-freeze………don’t forget to mix it right.
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Fan Clutch...............when cold (engine off) try spinning the fan....it should spin freely or with very little resistance. If it won't spin.....replace.

When hot (engine off) try spinning the fan........in some cases it will feel like it's, "locked up," or it will be like there is syrup/glue holding it back. Tougher to spin, than when it was cold. If so, It's OK. If, it spins like a top.....replace.
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The below elec. tests are the, "cheap test methods"........there are more sophisticated tests with values, that can be run.

Test for the dash thermo gauge................disconnect the wire from the temp sender unit.........KOEO...........ground that wire.........it will peg the gauge on the hot side............disconnect from ground and it will return.

Sender unit.........if you suspect it..........replace, replacement is cheap.

Aloha, Mark

 

[1shot]

thanx fer your quick responses....but...

Thanks for the suggestions peeps but here is more detailed explain'n.

Coolant is new, use premixed Prestone...replaced 2 weeks ago along with new heater core, all hoses new and t-stat (twice) was replaced. All hoses seem to hold shape under pressure, niether bulging or colapsing. Radiator is new 1 year old and not scaly or sludgey. Rad cap is 1 year as well - and system holds pressure for hours...
Clutch fan is good, spins free when it should, no wobble or noise from bearing pack.
The old tstat felt like it had a weak spring, and in fact compared to both new ones it was noticably weaker and you could press it with 1 finger easily. New tstats both seem to operate okay. Tstat was correctly installed with bullet towards engine and air relase hole near top. The first t-stat I replaced I checked on the stove and it opened fine and closed again.
Waterpump apears okay, bearings are good , no leak and was replaced last year when I did the rad.
The system does not have an air pocket, is not leaking and does not lose fluid, as the level in overflow container is exactly the same after 2 weeks and 1200k of mixed city/hwy drivin'.

Still the truck engine temp wanders wildly, and the proof is in the cold air out of defrost vents, after miles of drivin on the highway, where I notice the temp dropping the most.

What confuses me most is all of the faults in cooling systems I have had in my 33 years of driving, made the engine overheat. Not over cool...

oh and also...temp range Im drivin in currently is +5 to +15 celsius, (aprox 40F to 60F) its not yet winter here...

Cheers...

 

[Jason94sport]

I didn't see you replaced the coolant temp sensor. Try that. It's a cheap part & easy to do.
Does your fan have cracks around the hub? It could be slipping & you don't know it.
I can tell you from my experience. My temp will rise up high, then fall back down in a minute. This is the t-stat opening.

 

[marragtop]

I agree that the temps can fluctuate to a certain extent, but if it gets to where the engine is pinging, you have a problem. Keep looking and let us know what you find out. I'm sure others will have advice. One thing that comes to mind is.... is the fan shroud intact?

 

[1shot]

more

Well today I put a new rad cap on it, factory unit, not a jobber unit, just in case the rubber seal had some badness to it and or the spring was weak. No change in temp behavior.

Well today it dropped down to -14 C ( +15F ) and with wind chill at hiway speed Im figurin the radiator is experiencing aprox -40 C temp which is also aproximate -40 F.

Truck works normal, nice hot air coming out of vents, so im startin to believe its more an erratic gauge and sending unit, and the pinging was in my imagination or something else unrelated...but then - why does air temp change noticably and guage change when i accelerate or drive on highway?

So after another highway run, I cardboarded up the grill.
ABBB-SOLE-YUTE-ly no imporovement. Gauge acts the same.

Im getting a new sending unit from Ford dealer tommorrow, will install it and see if any change, and if not - im going to try an aftermarket temp gauge/sending unit combo with actual temp on it.

 

[shamaal]

You've probably seen this before so ignore if no help....

There's two sending units, one for the gauge and one for the computer. I've also attached a resistance chart that should help determine what the sensors should be reading at the various temperatures.

Good luck

 

[1shot]

thanks but i have had many more probs since the last post...
ok so i now have discovered a big rip in the rad ... losing only a few ounces of coolant per day - new radiator ordered-will continue to investigate.

 

[1shot]

thanks for your help

Thanks to everyone that tried to help me out with this one, It has been solved, I don't know what was the cause of the problem initially, but all works fine now as far as heat/cool goes.

I replaced:
Radiator, Rad hoses, Heater Core, Heater Core feed hoses, Fan, Coolant, Sending Units, t-stats x2, some wires, etc, etc, etc, eventually one or a combination of these solved my over-cooling problem.