I have a 1994 Ford Taurus 3.8L. The temp if fluctuating wildly, from about 1/3 to below Normal. My suspicion is that there is either a problem with the thermostat or there is air in the cooling system, but I’d like to know what others think.
If anyone has any ideas of simple things I could check, I’d be most appreciative! I can do simple things, but beyond changing a thermostat I can’t do much.
Thanks!
Assuming you don’t have any flud leaking, or any noises from the water pump, the thermostat or the temperature sensor are the best bet, with the thermostat as the most likely one.
It’s easy to change, and it’s cheap (less than $10 for the part), so try that first. Of course if I was changing the thermostat I would take the opportunity to replace the radiator hoses, and flush/refill the cooling system.
Thanks for the tip. I’m working on the thermostat even as we speak, which will mean a flush/refill of the radiator. I’ll check out the temp sensor if this doesn’t work. I’ll need to find out how to do that, though! Any advice where to find out?
It’ll be somewhere on the engine block, sorry, can’t do better than that. But I’d strongly recommend a Haynes manual for your make/model car. IMO they’re much better than Chilton, and will walk you through most tasks (with pictures!), from checking the oil to replacing a transmission.
The temp is going from 1/3 to below normal? I wouldn’t think the thermostat would cause that, since once the engine gets to operating temp, it shouldn’t go below normal for any reason, unless you drive it into a freezing lake. I’m guessing it’s either the temp sensor, or some other electrical glitch.
The temp if fluctuating wildly, from about 1/3 to below Normal.
I’m afraid I don’t find this clear. From 1/3 of what (the whole range? the “Normal” part of the range?) to how far below Normal? (Kind of an academic question, the fact that’s it’s fluctuating is probably all that matters.)
With significant temperature fluctuation, the logical first step is to check the coolant level (cold engine only). If it’s low, top it up and see if the symptom is gone. Next, find and fix the leak.
Check the drive belt and make sure it’s driving the water pump properly (no slippage).
Fluctuation is not a common symptom of a faulty thermostat, however it’s often cheaper and easier to replace a thermostat than to test it.
I’ll check out the temp sensor if this doesn’t work.
A bit of terminology clarification: sensor is properly used to refer to devices that send signals to the electronic control system (computer); sending unit or sender is properly used to refer to devices that send signals to gauges or warning lights. (Some late model cars do not have temperature sending units, using the coolant temperature sensor to inform the computer, and the computer to operate the gauge, but the 94 Taurus does have a temp sending unit.) Unfortunately, many parts countermen do not seem to know this, so to avoid confusion say “sending unit for the gauge” or “sensor for the computer.”
To test the sending unit, you need an ohmmeter, resistance specifications, and some way to measure or at least approximate the actual temperature at the sending unit. Again, it’s probably easier and cheaper to replace it than to test it. However, if you want to test it, first find a repair manual with the resistance specs (I question whether the non-factory manuals readily available have this degree of detail). Also be aware that if there is a problem with the gauge system, it could be the sending unit, the gauge itself, or any of the wiring or connections to those two items. Testing the sending unit won’t necessarily be sufficient to evaluate what’s happening.
Take care to make sure that the system is full of fluid, without air pockets. Thermostat replacement often results in getting a fair amount of air in the system, which will be a problem.
If you regularly perform your own maintenance, or plan to do so, I would go buy a Haynes manual for your car - they’re only about $15 and they explain most of the basic and intermediate repairs you’d need to make in step-by-step detail. (There are other publishers of manuals, but in my experience Haynes contains more model-specific information and doesn’t make as many assumptions that you already know what you’re doing, both of which are good things IMHO.) The information you’ll find in there is probably more complete and reliable than anything you’ll get from the Internet.
First, I’d like to say thanks again to all the advice and information everyone is providing. This place is amazing and I’m truly grateful for all the help everyone seems so willing to offer.
I honestly didn’t think the thermostat was to blame, but I did see quite a bit of coolant crud around where the thermostat sits, which made me believe I needed to change the gasket for the thermostat which made me just change the thermostat as well. As others have said, changing cheap parts is a heck of a lot easier than trying to diagnose them or even worrying about them. I’m there, just do it.
What is the best way to get the air out of the coolant system? Someone recommended squeezing the coolant hose, but I was wonding how else to do this. Anyone have a suggestion?
Also, does anyone have any suggestions on how to get the %^&%$ thermostat assembly re-assembled without having the thermostate slip out of place?
I know, Haynes manual. On my way for one this afternoon!
How hard would it be to track down a short in the steering column where turning on the right hand signal turns off the wipers? Mind you, turning on the left signal doesn’t turn them off, but the right signal does.
Gary T - For my car, 1/3 of the normal range is identical to 1/3 of the entire range (the normal range is centered). I’ll try to quantify it a little more like this:
The gauge has the word “Normal” centered on it. To the left of the “N” is a line, then a little to the left of that is a C with a blue square. When this problem was not occurring, the gauge would normally be around the “o” or maybe the “r” of “normal”. This would be approximately 1/3 of the range (both the operating range and the entire range); at least to me. Now, the gauge will run up to about the “o”, then drop below the line that indicats the lower start of the normal operating range. It has been my observation, although I haven’t observed this enough, is that it operates fine while idling like at a light, then drops when being driven through moderate speeds. This told me the engine was being air cooled as it was moving. I’m not sure if air pockets in the cooling system would do this or not.
Weird. My 1994 Mustang GT does the same thing only it’s the left signal instead of the right.
So what you’re saying is that the temp needle drops from where it normally sits? An air pocket would cause the opposite effect. It sounds like the needle goes to an “off” position which would be a faulty guage or an electrical problem.
I have a Supra with a temperature gauge that will fluctuate occasionally. As with your car, the temp would decrease as I picked up speed. Every time my gauge has done that, there was a leak somewhere - a hose, the radiator, the water pump gasket…it never ends with this car. Are you having to add coolant? Have you driven the car, shut it off, popped the hood, and checked for leaks / steam / the smell of coolant? I’d guess you did, but I’m just throwing it out there.
My temp gauge started fluctuating again last week. When I first start the car, I hear the coolant gurgling within the hoses someplace around the firewall. I shut the engine off and noticed a small wisp of steam from, of all the damn places, the area where the head gasket would be. Great.
I also suspect there may be an electronic problem with the gauge, but I’m still losing coolant.
Anyway, my point is that you may have a leak someplace, and that it’s not the thermostat. Just a guess.
With car and engine cold, take off radiator cap. Fill radiator, if needed, to just below the neck.
Squeeze the upper radiator hose a few times, re-fill with fluid if needed.
Start engine. Run engine until water starts circulating, and leave running for 10-15 mins. Turn off engine. Leave cap off, and wait until car cools down again.
Add any fluid as needed, to radiator and to fluid reservoir.
Btw, a malfunctioning thermostat can cause your engine to run cooler, or hotter, or alternate, depending on how it’s malfuntioning. If the thermostat is stuck open the fluid will flow through the radiator continuously, causing the engine temperature to be below normal. Conversely if the thermostat is stuck closed, the fluid will never flow through the radiator and your engine will overheat. A cranky thermostat will be slow to open or close causing either or both symptoms, seemingly at random.
Probably not a short circuit. I suspect that the right turn signal and the wipers share some type of ground (motor, or more likely a relay) When the power from the turn signal is present on the ground wire, and the ground is not perfect, the relay using a very small current loses it ground to the large current of power from the turn signal.
To fix this you will need an accuate wiring diagram, an understanding of how to read the same, and the ability to use test equipment. Probably beyond the scope of a post on a message board.
cmosdes, you are running into one of Fords better ideas, mounting the thermostats vertically instead of horizontally. To install the new thermostat, remove the thermostat housing from the upper radiator hose. Use a piece of coat hanger or piece of stiff wire, make a hook and stick the hook end of the wire through the hose part of the thermostat housing and hook the top of the thermostat. Pull on the wire to hold the thermostat tight to the housing and install the gasket and bolts. I use a very thin coat of silicone on both sides of the gasket as a leak preventative. Plus it holds the gasket in place. Remove the wire and reinstall the radiator hose.
Your temperature sensor should be on the intake maniford near the thermostat housing. Temp sensors work like a variable resistor, when cold they have lots of resistance. As the coolant warms, the resistance decreases and the temp gauge, which is just a form of an ohmeter, moves along it’s scale. I doubt it is anything to do with the thermostat, water pump, or amount of coolant that is causing the problem. The problem could be a loose connection at the temp sensor. My daughter had a 97 Taurus and her temperature gauge did not work when she bought the car. Turns out someone unplugged the sensor and did not plug it back in. Yours looks just like this. I would check the connection and it will cost you about $25 to replace the sensor.
bayonet1976 - Are you saying to leave the radiator cap off the entire 10-15 mins I’m running the engine? I can do that, but I would think radiator fluid would squirt out as engine comes up to temp???
Rick - I can read schematics and I can do some probing. I’m actually an electical engineer by trade, so that wouldn’t be the problem. Finding where to probe and knowing what to probe would have been. Thanks for the suggestion on what to look for.
Skelji - There is a leak, as I have had to add coolant recently. And there has been a coolant smell, as well. It looks like this was from around the thermostat, as I mentioned earlier. I’ve not popped the hood since doing the switch out today. I’ve had other things I’ve had to get done, but I’ll get working on the car again tomorrow, so I’ll be able to check it out more thoroughly then. Thanks for the tips!
I hope the person before didn’t put the thermostat in backwards…
Here is an website that tells you how to put in a new one & test it:
"There are two types of thermostats, one with a bellows and the other with a wax element.
The bellows type includes a metal container of fluid that expands the bellows when heated, making the thermostat valve open.
The wax type has a rubber diaphragm surrounded by wax and with a rod. The wax is sealed in a brass container that is in contact with the coolant. The valve is closed when the wax is cold and water cannot flow between the radiator and engine. When the wax is hot it melts and opens the valve, allowing full flow."
http://vtvt.essortment.com/replacingcarth_rhis.htm
That’s exactly right. What your’re trying to do is let any air that might in the system vent out of the radiator, the fluid should not squirt out as the system will not build any pressure with the cap off. It will still get hot, so be careful though.
bayonet1976 - I did leave the cap off for a while, but the coolant was just pouring out of the radiator. Is that supposed to happen? What did I screw up?
racer72 - Strange enough, I hadn’t seen your post until just now, but I actually did just what you had said. I bought a Haynes manual but they didn’t have a very good description on how to keep it installed. Instead, they simply said something to the effect of “just install it”. It was a bit of a pain in the butt, but I got it done.
The temp seemed more stabilized to me after having done all this, so maybe it was just an air pocket in the system. The temp is still lower than what I’ve seen in the past, but still in the “normal” range, so I’m happy.
Now to go to work on that stupid windshield wiper/turn signal problem. I’m not looking forward to taking apart that steering column, although the Haynes manual makes it look incredibly easy.
Does anyone know if it is as easy as it looks? Can a novice do it?
Your only screw up might have been filling up the radiator too much.
Thanks… I’ll see about running all the way up to temp with the cap off, then, and let the fluid run out as it will.
I really do appreciate all the help.
Warming a car up with the radiator cap off was a fairly routine procedure decades ago, but I don’t recommend it on modern cars. In my experience, it makes a huge mess, and it’s often difficult to add enough coolant between the time the thermostat opens and then closes again.
The pros now have tools that evacuate the air from the cooling system, then fill it with liquid. Works great, but not a cost-effective investment for the typical do-it-yourselfer.
The problem is, when a thermostat gets replaced, there’s air behind it that you can’t get out by manipulating the radiator hoses. Sometimes it will even keep the thermostat from opening. You need to get as much air as possible out of there before running the engine.
So, my suggestion–find a high point on the system that’s on the “back side” of the thermostat. On some cars, there is an actual air bleed plug you can loosen. Otherwise, I’d disconnect a heater hose or throttle body warmer hose. Watch the open area as the radiator is being filled. You should be able to hear the air coming out, and eventually liquid will come out, at which point you reconnect the hose or tighten/reinstall the bleeder screw.
Start the engine and run it until the thermostat opens. Watch the temp gauge, this will be when the needle goes up to or beyond its normal point, then comes down a noticeable, if small, amount. If the needle gets close to hot, shut the engine off. This could happen if the stat sensing bulb is surrounded by air, but often the stat will open shortly after that, allowing liquid to surround it.
Let the engine cool. It should suck coolant in from the overflow jar, so make sure the jar is at least half full beforehand. When it’s cool enough to open the cap, make sure the radiator is full to the brim and fill the overflow jar to the “cold” mark, or a little over. Keep an eye on the coolant level in the radiator (cold engine only) and overflow jar for another couple of heat up/cool down cycles, and you should be fine.
