Fluctuating engine temperatures

[Brandon96]

For about the past month my Explorer's temp gauge has been fluctuating any where between 180 and 219 degrees while driving in outside temps ranging from 44 - 98 degrees (April has been crazy in VA). I can't pick up on any trends except it will soar from about 160 to 219 when I enter the highway in the mornings until I reach the top of that first hill, then it immediately drops.

I've been monitoring it with my ScanGuageII and have actually gotten nervous a couple times this week to the point where I've thrown it in neutral and shut it down. The incoming air temperature is always constant and is usually 1-3 degrees different than my overhead console. No coolant leaks and I'm not burning coolant anymore. I've began to put more water in the mix about 2 weeks ago and had a fair amount of rust water come out when I drained it. Since then the water has been clearer.

Could this be the thermostat, fan clutch, water pump... something else? I'd like to test some things to find out what the heck is going on, but have no clue where to start. I found one thread regarding a snow plow blocking incoming air to the radiator, my radiator looks to be in very good condition with minimal road debris dings. HELP!!

[lcplgolden]

After you run it, let it cool down and slowly take off radiator cap. Be careful of it spraying at you. Then run it with cap off. You could have air in your system. If not, try a thermostat cause it's cheap.

[ranger7ltr]

More than 50% will actually tend to slow thermal release...Is the coolant overflow bottle filled to the proper level?

It sounds like you either have too much antifreeze and not enough water and/or the system has air in it... If the system is sealed you can get the air out by heat cycling the system...

Heat the engine then with a full coolant recovery bottle let the engine cool off..This will displace air in the system with coolant from the recovery bottle and eventually remove all air from the system...

One other possibility is the fan clutch...does the fan clutch engage as the engine heats up or does it continue to free wheel as the engine heats up?

[Brandon96]

Originally Posted by lcplgolden

After you run it, let it cool down and slowly take off radiator cap. Be careful of it spraying at you. Then run it with cap off. You could have air in your system. If not, try a thermostat cause it's cheap.

I have burped and reburbed the system multiple times, to no avail

Originally Posted by ranger7ltr

More than 50% will actually tend to slow thermal release...Is the coolant overflow bottle filled to the proper level?

It sounds like you either have too much antifreeze and not enough water and/or the system has air in it... If the system is sealed you can get the air out by heat cycling the system...

Heal the engine then with a full coolant recovery bottle let the engine cool off..This will displace air in the system with coolant from the recovery bottle and eventually remove all air from the system...

One other possibility is the fan clutch...does the fan clutch engage as the engine heats up or does it continue to free wheel as the engine heats up?

What do you mean to heal the engine with a full coolant recovery bottle? Haven't checked the fan clutch yet, will I physically see an engagement while letting the engine heat up? My fan spins no matter what, though it does spin freely when the engine is off.

[ranger7ltr]

I meant "heat" the engine .....not heal....I'll correct that...

But if your coolant system is pressurizing correctly, when the engine cools off the vacuum from inside the block and radiator will pull coolant from the recovery bottle and displace any air that happens to be inside the engine..

And right the fan clutch will spin whenever the engine is running, but as the engine heats up, the fan clutch should freewheel less and you should notice a definite roar of air being pulled in by the fan when the engine is revved and hot that you didn't hear when the engine would be revved and cool or cold...

[bradweezy]

i think it would be temp sesor or the temp sender my 96 ex is showing simila issues. goes up to bout 3/4 then drops to bout 1/6,up and down, dont fan clutch thermo, everything but sender and sensor. think the parts are like 35 bucks for both

[Wrench]

You mention that you had previous coolant loss problem. Any reason found? Ford used a very poor quality thermostat and recommend a Stant brand replacement with new seal. Be sure to locate the vent hole properly. Make sure you are using good quality antifreeze with at least a 50/50 mixture.
The fan clutch will only come into play when you are not moving enough for air flow to cool the rad or the AC cuts in. Use a heat sensitive tool to qualify that the rad or the sender/guage is accurate.

[Brandon96]

Originally Posted by ranger7ltr

***

ohhh okay, I can confirm the radiator does not have air in it, and the system is holding water very well. I checked the fan/fan clutch, they're fine.. except my fan has about 3,000 wear cracks in it, and my finger feels like it may be broken.. ouch.

Originally Posted by Wrench

***

The coolant loss was a combo between a poor seal of the lower hose on the block, fixed, and the passenger bank head gasket was failing, fixed.

I did happen to take a look at the thermostat today, the one I found must be stock... when I removed the hose mount the thermostat literally fell out of the block, between the fan blades and came to rest inside the fan shroud up against the radiator. Total B**** to get to. The rubber gasket looked mashed and was obviously in the process of failing like you stated. When I put it back in I couldn't remember if the little valve for lack of better terms went up top or down bottom... hopefully it was the top, that's the way I positioned it. I will pursue the thermostat tomorrow. I'm going to suck it up and go to the new Motorcraft ones, I understand they run a little cooler?

[sport'96]

Originally Posted by Brandon96

hopefully it was the top, that's the way I positioned it.

yep, that's the way they go.
i have been working on this problem too.

[Brandon96]

Alright, replaced the Thermostat with a new one. Now it fluctuates between 179 and 199 degrees. I hope this is more normal? This is getting weird, but it's cooler, so I'm fine with it.

[DLinkOZ]

Isn't the stock tstat 190 degrees? So you're roughly 10 over/under. Never paid attention, but that doesn't seem too far away from reasonable.