94 Rangers temp doesnt hold steady

So lets just go through the average day of my temperature gauge on my 94 3.0. Start the truck in the morning, temp get up to the N in NORMAL, drive off the mountain, get into town, its stays at N. Sitting at a red light, it climbs up to R, and if I'm sitting too long, it will climb to the L. start driving again, and when I hit 30+, the gauge goes back down to N. If i go up too steep of a hill for too long, the needle will go between L and H, but it has never hit the H (I wont let it, if i got too hot i would turn the truck off), and when it gets that high, it starts peeing coolant. and going down hill the temp will go down to N, and the heater will take the heat off it pretty quick. I looked at my overfill the other day and the coolant in there was Grey and had chunks of dirt or something floating in it, and that has been pulled back into the radiator. it was pretty low one morning so i put fresh coolant in it and in the over fill, and that helped a little bit, but the issue is back.

The truck is sitting on 32x10.50 TSL swampers as well
It has also been 85+ the passed couple days.

Please help me resolve the issue. The truck is my DD and i give her breaks where i can, but its hard since the truck is so much fun to drive.

Could be a couple of things.

Fan Clutch is not engaging all the way, the clutch on the fan grips the fan blades tighter as radiator heats up, if this doesn't happen then air flow through the rad is less at stop light or when engine is under heavier loads, i.e. going up hills.
With engine cold and OFF, spin fan, should spin a full turn or so, free spin
With engine warm and OFF, spin fan again, should be tight, no free spin at all.
With engine warm and running you can also use a rolled up newspaper to see if you can stop the fan, if so clutch is bad.

Radiator is not passing enough coolant because some tubes are getting blocked.
At higher rpms coolant is being forced through rad, so all is good, at idle coolant is not flowing as well so engine starts to heat up, going up hill engine heats up more so even with forced flow of rpm it will still start to heat up.

With engine warmed up and running squeeze upper and lower rad hoses, both should be about the same pressure, upper is IN to rad, lower is OUT of rad into water pump.
Now raise RPM and squeeze hoses again, if upper gets harder and lower gets softer then rad is getting clogged up.
Another test is to warm up engine/rad, turn engine off, remove the two shroud bolts at the top of the fan shroud, move it back towards the engine.
Feel the rad surface for colder spots, rad should have nice even heat across and down, any cooler spots are blocked tubes.

You can remove a rad and back flush it, straight flush with rad in truck won't help.
Back flushing might get you a few more months of use but that's about all, replacing a clogged up rad is the best bet.


I wouldn't think the thermostat would cause those symptoms, they usually fail open so engine doesn't heat up quickly.

Just FYI, My '94 4.0l had random over heating, not related to sitting in traffic or up and down hills, would just start to heat up and then go back down.
Turned out to be the heater core, on my model the heater core is the by-pass for the cooling system, no heat control valve, heater core always has coolant flowing through it.
So it got blocked up and was causing the random heat up.

Good info man!

One other thing after testing by all of Ron's mentioned practices, I have seen these 3.0's rust the impeller on the water pump, to the point of not having any blades left on them to move the antifreeze throughout the system.

JP02XLT

Thanks Ron. The truck actually doesnt have a fan shroud on it, and my local auto parts store said that could be a major factor. also the water pump could be going out. I just spun the fan with the truck warm, and it free spins with resistance. i was just in rush hour traffic so i dont want it to idle right now, so ill check the fan while truck is on, and the hoses.

Yes, I would hit a wrecking yard and find a shroud, fan really doesn't do much pulling of air through the rad without it, and if weather is warmer than normal that could be what is wrong.

The shroud does two things, it makes the fan pull air through the rad, and it also causes the fan clutch to heat up from rad heat, which makes it engage more.
So you end up with a double whammy for extra heating.

On the front of the fan clutch is a bi-metal spring, as that heats up it engages the fan blades more.
Without the shroud that spring is getting cooler air from the sides so not getting as hot as it should.
So it probably won't test well since spring is not getting as hot as it should.

It could still be a failing fan clutch or blocked up rad, but for $20 on ebay or similar at a wrecking yard I would get the shroud first.

You do need to pull the rad or the fan clutch to get the shroud in,


There is an old timer trick to test a rad if you do pull it.
The tubes in a rad will run side to side or up and down
Place rad so that the tubes are up and down.
Put rad cap on
Put hand over lower hose outlet
Use hose to fill rad with water through upper hose outlet
When it is full, remove hose

Remove hand from lower outlet, water should drain out instantly like dumping out a bucket, the hole at the top and hole at the bottom are the same size so there is no "air lock", gravity should dump water out fast.
lead rad forward a bit to get all the water out

Now the TEST
Flip rad upside down
If ANY water comes out it could only come from blocked tubes.

You can lay the rad flat and fill it with a vinegar warm/hot water solution, let it sit 20 min. then flush, repeat as much as you want but no more than 20 min. sitting, after that the gunk will start to harden up again.
CLR works as well but harder on aluminum parts.


EDIT:

I forgot to mention your overflow tank.
You should clean it out.
It is normal for the cooling system to push some coolant into the overflow tank when it warms up.
If there are chucks in the overflow tank then when engine cools off they are sucked into the overflow tube and block it.
This can cause the cooling system to suck in air instead, as the cooling system cools down it can create quite a low pressure inside if overflow tube is blocked.
You will often see collapsed upper rad hoses from this, but usually they suck in air from around the overflow hose clamp or any hoses that might have small openings.
So you now have air in the system.

So, the fan free spins when warm, and I stopped the fan with a rolled up newspaper, and the bottom hose is stiff and the top is soft at idle. I'm too much of a scaredy cat to do it with the truck revving. The radiator seems to have even heat all across the fins. An there is no shroud on the fan at all.

It has sucked the coolant from the over fill back into the radiator. I bought clean coolant and a flushing kit and plan to do that tomorrow. I will also test the radiator with that tip above. As for the shroud, I'm not sure where to get that, and the clip you were talking about is about half on half off.

Just call some local auto recyclers(wrecking yards) that have Ford truck parts, there are a few model years that use the same shroud as your truck/engine.
Or check with local Parts store, they don't look that expensive.

I would get and install the shroud first then test fan clutch again, as said above the fan clutch works by the radiator heating up the spring on the front of the clutch, with no shroud this doesn't happen, cooler air is keeping the spring cooler than it should be.

If you want to replace the fan clutch, that's fine, but get the shroud no matter what.

Ok will do. I blew the last of my available money on oil, Coolant and gas so I have to wait till I get paid for the fan shroud.

I flushed out the cooling system today, and was much needed. the coolant coming out was a cloudy green so i am glad i did that. Truck is already running much much better.

That's great

Good maintenance will always pay off in the long run.

It is indeed. I've only seen the temp as high as R, and not a single check engine light since. I'm picking up a shroud next week I'm hoping.

Got the shroud, didnt really realise its a one piece, how do i put it on? might sound silly, but i havent picked up a service manual yet and I haven't bothered to look at it yet. Also, do I NEED bolts or can I zip tie it on?

So the fan shroud is on already runs tons better. I think I have too much coolant (4 quarts coolant, 2 ish quarts of water and whatever residual there was in the block) since the temp goes higher than it did even with straight water, and before the fan shroud. I may bed to add more, but the truck is hot as we speak so I can't check. It also boiled over last night coming home. And was hotter than I've seen coming up the hill.