My '03 Ranger, 2.3L temp guage has started to peg out unexpectedly. I will be riding along with the gauge in the normal range and then all of a sudden it will peg Hot and the Check Gauges light comes on. The engine then starts running real rough like it is firing on only 3 cylinders.

Coolant level is good and no signs of leakage around the water pump. The upper hose gets hot as the engine does, but the lower hose does not. My thoughts are either the gauge, the thermostat or the water pump.

Any suggestions and/or ways to narrow down where the problem is?

Thanks

 

My guess would be thermostat. When you replace stat on this Duratech 2.3 it is only sold as an assembly with sensor installed. It is a bit pricey. Should also flush radiator and replace antifreeze. Also verify that the fan clutch is working properly. At slower speeds the fan should operate but it should freewheel at higher speeds.

 

I would think that it's not the guage because there wouldn't be the associated rough running if it was just the guage.

It could be the thermostat that would be the first thing to check. Don't let the engine overheat that could lead to a bad head gasket.

 

Thanks. I will start with the thermostat. The thermostat is where the lower hose connects to the block on this engine, correct? I am used to it being where the upper hose connects on other models.... I have a Hayes manual, but it doesn't have a whole lot of details in it...

 

Welcome to FTE.

I'm not clear on all of your descriptions, so maybe you could have more than one problem, depending on what you mean by, "the temp gauge will suddeny peg hot", but the radiator hoses seem to feel normal.

If suddenly means instantly, you could have a short to ground in the gauge temp sensor wire, from damaged insulation.

If suddenly means a minute or so & the engine then running rough, like the computers temp sensor is detecting an overheat condition & cutting the fuel injectors back to lower engine load, as in the limp home mode, then I agree it sounds more ominus, like overheating from restricted coolant flow, like an acting out thermostat as has been suggested.

OR maybe a slipping serpentine belt from it being worn or having oil or coolant on it, or maybe a bad belt tensioner, all of which would not be properly driving the fan & waterpump, or the fan clutch acting out as has been suggested, or a collasped lower radiator hose, faulty radiator cap thats not properly holding coolant system pressure, clogged radiator, or even a plastic bag or varment nest in front of the radiator thats restricting air flow, are some more possibilities that come to mind, so maybe consider doing some more trouble shooting before replacing that expensive thermostat assy.

More thoughts for pondering, let us know what you find.

 

I don't own one of these engines so maybe I am missing something. I am with pawpaw I am not clear on what is happening. doesn't the tstat open thus letting hot coolant go thru the upper hose then thru the radiator cooling off and coming out cool thru the lower hose..........Could the t-stat be opening late and thus causing the issue...........could the radiator be a little clogged?...........just my 2 cents

*you got to love ford a motorcraft tstat on rockauto is $122.....yikes

 

I knew that stat was pricey but didn't have an exact price. The housing comes with the stat,heat element and sensor. I can think of no good reason other than making a quick buck for not making it so thermostat could be replaced as a separate unit.

 

If the thermostat is that much I would consider that maybe the radiator is clogged. Have it checked and cleaned out at the radiator shop. That should cost alot less than a thermostat.

 

PawPaw and all - thanks for the great suggestions. To clarify, I can be driving the truck for 10-15 minutes at highway speeds with the temp in the normal range, when the gauge immediately jumps to hot, the check gauge light comes on and the engine starts running rough. It sound like the "limp home mode" that you mention.

I am going to start by checking the belts, water pump and fan to see if anything seems out of wack. I am doubtful there because there is no squeeking that I have heard waterpumps on my others have gone out in the past, but I will start there. I will then attempt to remove the thermostat and see if I can see any issues before I plunk down $120+ for a new one.

Any other suggestions?

 

Ok, so after your on the road for 10-15 min, the gauge immediately jumps to Hot.

So how fast is "immediately"???? Is it instantaneously, or does it take 10-15-20-30 seconds to move up to Hot???? We need a calibration on "immediately"!!!!

Did this problem come about after some event, like having the cooling system opened, or serviced lately????

If so, maybe it wasn't burped completely & you have an air bubble trapped in the block.

Hear any noises under hood, or in the heater prior to, or when this temp spike happens????

Edit: Do you have a CEL lit???? If so have the computer scanned for trouble codes & post ALL of the trouble code Numbers.

Most autoparts stores will scan the computer at no cost if your having problems, even if the CEL isn't lit

Seems to me you should have at least an over temp code stored, or set & if so that would confirm a true over heat condition & not a short in the gauge, or gage temp sensor wiring.

 

Check for combustion gas in the coolant system, worse case scenario is a blown head gasket. This is what happens: The engine warms up and the parts expand. A good head gasket maintains contact with the moving (expanded) parts, a bad gasket lets high pressure combustion gases migrate into the cooling system which is the nearest low pressure area to the cylinder. The combustion gas causes a bubble in the cooling system that registers as a spike in the temp when the bubble gets to the temp sender.

Try running without the pressure in the cooling system, i.e., no radiator cap.

 

have you gotten any codes? Any chance the ECT sensor is fubared and after 10 minutes sets the limp mode?.........Did I read in the thread that the truck is actually starting to overheat or is it just the gauges going whacky......

 

Folks, Thanks for all the comments. Turns out it was the thermostat. I took it off, flushed the system, plunked down my $152 for a new one and now am back on the road. Still can't believe it cost me $152 for a thermostat, but it is working well now.

I appreciate all the suggestions and coaching. Till next time....

 

I replaced the thermostat and everything worked fine for the last two weeks, but yesterday the truck stated during the same thing:

- Gauge starts in the normal range and within 60-90 seconds moves to pegged out on H.
- Check gauges light comes on
- The limp home mode is activated, i.e. engine starts running rough, almost like it is only running on 3 cylinders.

As I said, I replaced the thermostat (with the combined electronic sensor), flushed the system and replaced with new coolant. The radiator seems fine and there is no noise coming from the water pump area.

I also stopped by the autoparts store and asked them is there was any electronic code/error message that may be causing this problem, and the guy said he wasn't aware of anything that could cause this issue.

Before I have to say 'uncle' and bring it into the shop, does anyone have any suggestions?

 

Try running with no pressure on cooling system, check for combustion gases.