Water Temp needle jumping around (thermostat issue?)

[ext94cab]

Hey guys, new to forums. Just picked up a 94 Ranger 3.0L a couple weeks ago. Something I've noticed is the water temp needle won't stay in one spot once I've reached operating temperature. I took a pic to help show what I'm dealing with.

This pic was taken before I reached operating temp. What happens is the needle will rise up to the red line then fall back to the green line. It will then rise up to the red and fall back to the green. One cycle of rising and falling will probably take about a minute.

I'm really low on antifreeze (expansion tank almost empty) and I noticed some sediment at the bottom of the tank so I was planning flushing the system and filling up with some new stuff. Anyone have any idea what could be casuing the problem with the water temp? I was thinking possibly the thermostat. If so it would make sense to replace that when I flushing the antifreeze. Thanks for any help

 

[adsm08]

Low coolant will cause this.

 

[wildbill23c]

Thermostat, the gauge itself, the temperature sensor, or a wiring problem. Another thing that could cause it too is an air pocket in the cooling system. I'd flush the system out and get some new coolant in there 50/50 mix and get the air worked out of it then go from there. I don't know much as far as testing the gauges sensors etc. But I'd check all the above while you are changing the coolant. And yeah umm low coolant will definitely cause the gauge fluctuation like that.

 

[2813josh]

^ Yep,my exploder does this to let me know when I really need to top off the coolant...one of these days I'll replace that leaking water pump...

 

[ext94cab]

What kind of coolant would you guys recommend? I'm coming from a 98 Audi A4 which needed special coolant from the dealer but after a quick search it looks like I can just use some off the shelf stuff like Prestone?

 

[adsm08]

Green.

 

[ext94cab]

Its got some really crappy looking red stuff in there now. Looking forward to getting some fresh coolant in there. Thanks for the quick responses

 

[FritzTKatt]

Flush and fill, while you're under there run a test of the coolant temp sensor. Mine was bad and caused those symptoms. Not sure about the 3.0 but I had to take the throttle body off and IIRC it's a 15/16 wrench (don't think sockets fit over it).

 

[RangerSVT]

I agree with adsm, you are just low on coolant. I've seen this many times before. If your coolant looks red, odds are its rust and you don't have the correct ratio of coolant-to-water. It's also a good chance it has or is affecting the t-stat. Pull the t-stat, do a complete flush and clean, install a new t-stat and fill with a correct ratio of green coolant...

SVT

 

[Tedybear]

As a sidebar note to any new 'backyard' mechanics.

I've noted the huge push for the selling of the pre-mixed 50/50. And it sells for about the same as a gallon of the "DYI" 100% proof antifreeze/coolant. Are we that lazy of a society we can't measure or mix this ourselves? Save the money and do the mix thang.....

(Yeah I know...I'm not very 'hip') LOL.

and now..back to our normal post, already in progress.

S-

 

[RonD]

Something I just learned about my '94 Ranger with 4.0l.

The heater core on these are part of the coolant bypass system for the water pump!
There is no heat control valve or diverter.
What this means is that if the heater core starts to limit coolant flow, some tubes getting blocked, the coolant circulation will be limited.
The symptom of this is the t-stat opening and closing, so temp gauge going up and down.
You will also notice slightly less HOT heat inside, it is still warm just not 200deg HOT air coming out.

Heater cores for these are $30, or less, and take 15-20min. to swap out.
At 18 years old it might be worth it to just swap it out, but you can check if this is the problem by removing the heater hoses from the core/firewall and either connecting them together with a coupler and 2 hose clamps or using one the heater hoses as the bypass.

After doing this if your up and down gauge goes away then replace the heater core.

You can also try back flushing the core, to find out which is the IN and which is the OUT just feel the two hoses, the hotter one is the IN.
Connect garden hose to OUT and try to flush out any debris.
I would have a hose connected to the IN and pointed down at the ground.


Replacing heater core:
Phillips screwdriver, remove 4 or 5 plastic "pop-outs" under glovebox to remove fiberboard covering, just so it can be layed on the floor to the center hump, you don't have to remove the whole cover.
5/16 socket, remove 4 screws that hold the plastic heater core cover, these all face down .
Remove cover
Remove heater core, have a towel under it as some coolant will come out when you angle it.

If you have some 1/2" peel 'n stick weather stripping to replace the stock stuff on the old core, great, if not the old stuff can be reused if you are careful, or don't use any, up to you really.


The 50/50 pre-mix is sold because you should use deionized or distilled water to mix with concentrate, not unknown PH tap water.
So this is sold as a preventative measure for those that forget to get distilled water, which is sold at pretty much everywhere concentrate is sold, lol.

 

[kryptonitecb]

Didn't know about using distilled water but it can be found a grocery store for $1 a gallon.

And yes people are that lazy and or stupid.

Sent from the road while ignoring traffic

 

[ext94cab]

I actually hard a hard time finding distilled water over the summer when I was doing this for my old Audi. Ended up finding it at CVS after looking in a few grocery stores.

Can someone tell me what temperature thermostat I should look for? Looks like most parts sites have a 195 degree part listed as the replacement I saw a couple other listed too.

 

[Tedybear]

Distilled water is usually used for Ironing cloths. Putting tap water into an iron can bung it up with mineral deposits. I do have an issue with places that sell 50/50 for the same price. Also I've never had an issue with using tap water mixed with coolant. Is it better for the engine? Probably. It would create less scale and slime build up. But as I've said. If we are that lazy as a society we can't mix our own coolant? So carry a $1.00 jug of distil water...and a $8.00 jug of pure coolant for $9.00 you get two gallons. Or for $8-$9 you can get premixed...And that's only one gallon.

Stock thermostats should be fine for the temp. Most places will list alternate temps that can be used depending on your area. For what it's worth? The 89 2.9 v6 uses a stock of 195. We've run it about 10 degrees lower using the alternate temp thermostat and have had NO ill side effects---and that includes no ill effects on the engines mile per gallon. Others here will disagree I'm sure. But that's just my opinion and driving this little truck for 2 years + (Now if you go tooooo far to one extreme? Yeah, that will cause problems)

S-

 

[RonD]

Most Fords now use a 192-195 thermostat.
A t-stat sets the minimum operating temp for an engine.
And in most cases the higher the better, oil is rated at 212deg, so 30w oil is 30w at 212deg.
Gas mileage is also better at higher temps.
Best economy and lubrication is at 200-220deg operating temp.
The t-stat helps to get engine to operating temp faster and prevents the engine from running too cold in cold weather, but won't cause overheating in warm weather.

Some run a colder t-stat, i.e. 160 or 180, in an attempt to get more power from an engine, and this can work, the reason it works is because of intake air temperature.
Cooler air is denser so more fuel can be mixed with the air, more fuel = more power.
If engine operating temp can be lowered 10-20deg then intake temp is lowered 10-20deg, so intake air temp is lowered 10-20deg.
You do need to adjust air/fuel mix for this to gain the extra power, some fuel injection systems will do this others have to be programmed to do this.
But if you're after economy and longevity then run the recommended t-stat temp.



Most auto parts stores sell distilled or deionized water, deionized is cheaper.
The point of using distilled or deionized water is the PH of it, it is PH 7 so neutral on the 0-14 PH scale.
Tap water can be acidic, less than PH 7(soft water) or alkaline, greater than PH 7(hard water)
Because there can be no way to know what local water PH will be, distilled or deionized water is recommended over tap water, but if your tap water is PH 7 then it is fine to use.

Coolant uses chemicals to neutralize acids that build up in the system normally, so a coolant is usually PH 8-10, this prevents corrosion but can promote scaling if alkaline water is added and raises PH above 10.
The chemicals used to neutralize the acids can be used up faster if you add acidic water.
The reason you change coolant every 2 to 5 years is to replace the chemicals that neutralize the acidic build up.
Once these chemicals are used up corrosion starts to eat away at the metals in the cooling system, aluminum is especially vulnerable to this corrosion.

So using tap water is not the end of the world.
Bottled drinking water is not the same as distilled water, it is usually acidic, not neutral.


The anti-freeze properties of coolant never wear out.