I have a '98 2.5 litre Ranger with 177,000 mi. Recently, it APPEARS to be overcooling.Here are the particulars.( I'm a toolmaker,not a mechanic, so bear with me, I may not get my terminology and such just right but I'll be as clear as possible.)

1) Temp. guage was fluctuating from "C" to about 1/3 up(it usually ran right between "C" and "H") but heater seemed to work @ outside temp. in the 50's.
2) Replaced t-stat(192 deg.) , replaced old coolant and purged air from system.
While purging I had a very hard time ever getting engine hot enough to open t-stat. Finally confirmed coolant flow by looking into radiator.
3) Guage still fluctuating, but indicating even cooler temp.,seldom getting more than 1/4 up the scale and quiclkly dropping back to "C" or BELOW. Heater still seemed to be about right. Outside temp. still around 40-50 deg.
4) Two days ago(outside temp. cooler, around 33- 40 deg.) needle dropped to or almost to start-up position, well below "C", and heater barely puts out any heat even with control on full hot and fan wide open. After prolonged idle, needle finally came up to "C" and a little heat came out.
5) Several knowledgeable guys have said my t-stat is stuck open but I just pulled it and it was closed and installed correctly.
6) Fan is viscous clutch and not locked up or loose, no noticeable coolant loss anywhere.
7) Upper radiator hose didn't seem to be as hot as I thought it should be, but that's subjective.

What are the chances that I've had a coincidental guage/sending unit failure and blocked heater core at the same time. Keep in mind that when the engine temp did rise a little I got a little heat, about as much as I'd expect with the needle where it was. I've got another t-stat and will install it tomorrow but I'm pessimistic. Has anybody else seen similar stuff and/or have an idea what I should do next.

 

thats what my 89 does.put cardboard in front of the radiator.And it helped a little.But don't know anything else.would like to find out also.

 

I can't see how a truck that has always had particularly good heat and steady eng. temp. could develope the problem in 2-3 weeks. Baffling...and extremely irritating. Everyone says it has to be tht t-stat.,but it seems to be working perfectly.Good luck, I'm going to keep looking for some reasonable explanation. Thanks for the input.

 

You thermostat is not stuck open, but it is opening way before 192. What brand thermostat did you use? I have had overcooling problems with one of my truck and used 3 different brands and all three brands overcooled. I finally bought a dealer part and it has worked ever since.

 

Seeng as how you seem to want to do some testing, before replacing the thermostat again, you might consider trying the following.

Ground the under hood single wire connector to the temp gauge sending unit, the temp gauge should then read Full Scale Hot, if the wiring & gauge are ok.

You can check the temp sending units resistance, with a ohmmeter, to see if it's within spec.

If all that checks out ok, with the engine running long enough to have fully warmed up, the upper radiator & heater hoses should be hot enough that it's uncomfortable to hold.

If the new thermostat is faulty & the engine isn't fully warming up, the computer won't be happy & will store a cold temp trouble code, so you might run this puppy by your favorite autoparts store for a computer trouble code scan.

The computer can store CM, or sometimes called Pending codes, that won't set a CEL (Check Engine Light), so even if you don't have a CEL lit, there may be CM codes stored.

If the store uses a ScanTool, that'll read PID's, it can also likely read the computers engine temp sending units feed to the computer, so you can thus get a second separate reading of engine temp, as the temp gauge & computer temp sending units are separate parts & not interconnected.

On the heater core being clogged, you didn't say what kind of condition the coolant was in, nor if you've been changing the coolant on time, but seeing as how the heater had been putting out heat ok in the past, I doubt it's clogged up, unless the coolant was in bad shape & full of debris.

If you do suspect the core may be clogged up, remove the heater hoses & try a reverse flush of the core, sometimes a reverse flow can unclog one.

All that said, in general I agree with it likely being a bad new thermostat, as I too have seen bad ones right out of the box.
Test a new thermostat with a thermometer in hot water, before installing it, make it prove itself. It should begin to open at about 150-160F & be fully open at 195F.

Dont buy the same brand, from the same store, as they may be into a bad producton lot.

I've opted for OEM Motorcraft thermostats, with the air bleed valve, as it makes burping the system, to get entrapped air out, much easier.

Just a bunch more test thoughts for pondering.
Let us know how it goes.

 

Previous coolant was in poor condition,rusty but not much particulate. I did see some small particles in the heater line. New coolant has remained green and pretty clear, I did notice that the coolant that drained out of the heater line looked more like the old coolant than the new. CEL has been on for a while, but that has been an intermittant thing for several years. Checked both suspect t-stat and brand new one(both Duralast from AutoZone). Using both digital and regular thermometers and allowing time for thermal transfer from water to bulb, both started to open at 194-196, were pretty much full open at 198-200 and returned to closed at 186. I cant even see the sending unit when I look on driver's side, rear of engine, just below the head as the Haynes book said. The intake and other stuff almost totaly block my view, so checking that doesn't look likely. I'm starting to think that I really do have a faulty guage or sending unit and clogged heater core. Thanks for the help and if you guys or anyone else has any ideas, please keep 'em coming.

 

Voyager, i have the same problem i just asked about in another post(heating/cooling prob) ive changed the thermastat twice and still have the same problem, i also have antifreeze backing up through the overflow resevoir, is this happing with yours also??

 

I thought my heater core might be clogged also but would that really cause the guage to move around so much??

 

Bruceknee,
I don't have coolant backing up into overflow but the guage thing sounds like mine. I can't see any way that the heater would affect it, but then I can't even FIND my sending unit. Speaking of sending units... can anyone tell me what the two sensors on my t-stat housing are, both are on the molded in heater line.

 

Well I'm not a 4 banger guy, but I may be able to get you close to your 4 bangers temp gauge, temp sending unit.

On the 4 cylinder engine, look on the rear drivers side BLOCK, just below the head.

DON'T confuse the oil pressure sending unit, which is in the HEAD, just above the temp sending unit, which is in the BLOCK.

Just a thought, but if you can get a probe in there, to touch the temp senders wire connection & then ground the probe, while someone watches the gauge, to see if it pegs full scale hot, you could get a gauge & circuit test that way.

Not sure yet what the other two reference items are.

 

pawpaw,
Thanks but that's the same thing the Haynes manual said. Problem is that entire drivers's side of block is obscured by the throttle body, intake manifold and misc. hoses and wires. Actually, even seeing ANY portion of the block is nearly impossible without removing the whole throttle body/ intake assembly.

By the way...does anyone out ther have a set of **** to fit a 52 gal. wooden rain barrel? If you do, I have a nearly new Haynes '93-05 manual that I will trade.

 

A set of ****??????????

 

That's about how useful the Haynes manual has been on both my Grand Am and the Ranger. *"About as usless as a set of **** on a rain barrel."

* It's an old saying, like...useless as **** on a boar hog. Neither rain barrels nor boar hogs nurse, therefore ****(more correctly,teats) are a useless appendage. Probably not a widely known saying among a younger or more urban crowd.I'm in my 50's and live in a somewhat rural area(middle Tenn.) so it's not an uncommon saying here.

 

Yup the saying is common around here in SW Va, for useless things.

But you know, nothing turns my stomach quicker, than a warm pair of those in my back!!!! lol

 

Yoyager, your problem is the water pump. Sending units have nothing to do with the cold air coming out of your heater vents. At 177K and with your described problem, I'd bet big bucks on it. Replace it and you'll get your heat back. But before doing so check one last thing, check the inlet and outlet hoses to the heater core, if one is cold or noticeably colder than the other, you have a blocked heater core. If so, flush it out with a garden hose (just remove both hoses and flush it till clear water comes out). But I'm banking on the water pump.