Bad Thermostat = Poor Gas Mileage?

[goheels681]

2000 Explorer, OHV

I bought my Ex back in June and always noticed that it seemed to take a very long time for the temperature gauge to reach the "normal" area- roughly 20 miles into a drive it would come up. Recently, since the weather has gotten much colder, I notice that the gauge does not move at all. Today, I drove 110 miles from home to school and the temp. gauge did not move AT ALL.

I have also noticed that either I'm getting horrendous gas mileage, or my gas gauge is hilariously inaccurate (I left home with the gauge just under 3/4, and now it's sitting on 1/4).

Would a bad thermostat cause both of these issues? The heat does work very well in the truck as is, and there don't seem to be any engine abnormalities that I can tell.

 

[stocked]

Does the heat take forever to warm up? If so then i'd say its a bad t-stat. If it gets warm at a good rate then i'd venture to guess that the sensor might be bad. I'm not 100% but i know that on my old tempo there was only one coolant temp sensor and it fed the gauge and the computer, so when it went out and read low like yours... The computer thought that the motor was constantly cold and dumped more fuel thus running it rich. Either way its a good idea to replace your t-stat if your not sure of its condition, they are cheap and a good piece of mind to have it replaced. Just dont be cheap and get the junk ones.. I always recommend FailSafe stats.

 

[goheels681]

I suppose the heat could be a little faster to warm up, but it does eventually get quite warm. If I replace the thermostat and it's not the culprit, what other parts of the cooling system would be left to blame? Is this a job that can be done with basic tools in the middle of a snowy parking lot?

 

[Car-Dog]

hmm I mine does something similar. I can drive about 40 miles before it gets completely up to operating temp, and i live in cali so its not that cold either

 

[Stinger357]

Same here also. It takes over 10 min of driving before my temp gauge goes to normal.

 

[joachimf]

I have driven some Explorers over the last 20 years, 4.0 OHV, 5.0 OHV and 4.0 SOHC. All of 'em have had a short warm up phase even with temperatures below 0°F.

When the thermostat failes open you will need some extra time to heat complete coolant. CTS will tell your EEC IV or EEC V your vehicle is not warmed up and will limit your power train, read no overdrive. With the richer mixture in the now very long warm-up-phase and the missing overdrive ratio your gas millage will become at least 'poor'.

So exchange your thermostat and that's it.

 

[2000StreetRod]

sludge

A stuck open thermostat will result in excessive sludge in the engine as well as poor fuel economy, performance and personal comfort. Lubrication of the engine will also be less effective unless using synthetic oil.

 

[CDW6212R]

Buy a Fail Safe thermostat if you buy one, they are not supposed to be able to fail closed, which will kill the engine. O'Reilly's has them under the Murray's brand, Motorad was the original maker. They cost about the same as stock.

T-stats can stick and likely that's what is happening if the engine isn't warming up quickly enough.

 

[Car-Dog]

Mine drives like its warm. its just that the gauge dosent seem to register it quickly. As far as mileage is concerned i get about 15 everywhere. Just kind of resigned myself to the fact that I have to fill up everyday.

 

[wow97]

i have 1997 ford explorer with 4.0 ohv v-6 it about 20min to warm up last year i put a new radiator because big ass crack so i said #### change the thermostat after that it take long time warm up

 

[budwich]

my guess would be bad fuel pump which is under pressuring your fuel system which then doesn't "spray" efficiently for burn, which then cause the comp system to run a rich trim to make up for the poor efficiency. a data logger / odb live stuff might help you out if you see a couple of things.

 

[CDW6212R]

The fuel pressure for 99+ Ford's is more critical than prior models. Even 5psi loss is noticeable and generates a lean condition CEL. I had that happen with my 99 just after running it. The idle was about 50psi and similar with throttle. The pressure needs to be 55-62psi at all times. I had only high speed issues with it like that, it drove fine and the mileage was good. That turned out to be a dry rotted hose in the tank, at the pump and regulator. The tiniest leak will be noticed in 99+ models. Regards,

 

[wow97]

i check my fuel pressure only get 30 p.s.i only for 4.0 ohv 1997 ford explorer

 

[CDW6212R]

That's about right for pre 99 Fords, 30-32psi is good, with close to 40psi with the vacuum off of the regulator.

 

[wow97]

i love my ohv 4.0 v-6 i think it is the best motor in the world i race 1997 toyoa 4runner with 3.4dohc v-6 i be them all the time toyota 4runner owner get mad i put a k&n cold air intake way more horsepower and torque way better gas mileage

 

[Havalilsi]

To the OP what did you ever figure out with your ride? I have the opposite problem from you. My truck over heated. The needle went to the very top of the gauge a couple nights back. The thermostat failed closed. The heater even stopped blowing got air. My thermosta failed shut. I nearly crapped my pants because I figured that was it for my motor. Anyways I took out my thermostat and now the truck takes forever to warm up to temperature if it ever does. Sounds similar to what you're experiencing. Now I'mooking for a failsafe but it seems kinds tough to find in my area.
Compared to all the other possibilities listed for your problem the thermostat is the least expensive sounding. Good luck.

 

[CDW6212R]

To the OP what did you ever figure out with your ride? I have the opposite problem from you. My truck over heated. The needle went to the very top of the gauge a couple nights back. The thermostat failed closed. The heater even stopped blowing got air. My thermosta failed shut. I nearly crapped my pants because I figured that was it for my motor. Anyways I took out my thermostat and now the truck takes forever to warm up to temperature if it ever does. Sounds similar to what you're experiencing. Now I'mooking for a failsafe but it seems kinds tough to find in my area.
Compared to all the other possibilities listed for your problem the thermostat is the least expensive sounding. Good luck.

They can take a high heat level for a short time. You were fortunate, I had that happen two years ago due to a frozen radiator. My antifreeze wasn't as good as I thought, and the 3 degrees outside was too cold.

My Failsafe T-stat stuck open as it's designed to. So when the radiator thawed out, I added about two quarts of water and delivered mail with it and drove it home. I waited about a week to replace the T-stat.

Your truck will run very cold without a good T-stat, or none. I didn't see temps above 105 normally going home. On my route it would usually stay above 165 or so, but that was from averaging less than 10mph for three hours.

Get a new T-stat, order it online if needed. The SOHC part is like the OEM part in price, around $28. The other two engines don't cost that much.

 

[goheels681]

To the OP what did you ever figure out with your ride? I have the opposite problem from you. My truck over heated. The needle went to the very top of the gauge a couple nights back. The thermostat failed closed. The heater even stopped blowing got air. My thermosta failed shut. I nearly crapped my pants because I figured that was it for my motor. Anyways I took out my thermostat and now the truck takes forever to warm up to temperature if it ever does. Sounds similar to what you're experiencing. Now I'mooking for a failsafe but it seems kinds tough to find in my area.
Compared to all the other possibilities listed for your problem the thermostat is the least expensive sounding. Good luck.

No I haven't been able to figure out exactly what the problem is. I bought a new thermostat from NAPA and I'm waiting for this blizzard to stop so that I can try to put it on! For someone that has a Haynes manual and has never done it before, can anyone give a rough time/difficulty estimate for doing this?

 

[Car-Dog]

I replaced the t stat in mine and it fixed my problems. Took me about an hour. Probably could have done it in 20 min but I stopped and boiled my old stat just to make sure it was bad. sure enough it was stuck.

 

[Steeda90GT]

I replaced the t stat in mine and it fixed my problems. Took me about an hour. Probably could have done it in 20 min but I stopped and boiled my old stat just to make sure it was bad. sure enough it was stuck.

Is the fuel mileage better now?