Thermostat Reads hot After Coolant/Rad Flush

[ds08tf]

Hey. Just posting cause I'm a bit nervous. I did a coolant/rad flush today and a power steering flush (first time doing it in my driveway), and when I was driving around after (hours later) I noticed the thermostat was reading really hot (near the H). I was almost home so I waited got home and popped the hood. No excessive noise/smell/heat. Coolant level while engine is idle is within the acceptable range and raises a bit to max when engine is stopped.

I waited a couple minutes and just turned the key to on without starting the car and the temp reads normal right in the middle.
Also I checked the fans (they blow hot or cold fine). Am I overthinking it ? Or is this something I should be worried about?
-D

[Lumberjack]

Judging by your lack of experience and the apparent problem is it safe to assume you did not purge the system of air? I am putting the coolant change and the temp rise together and going out on a limb and saying they have something in common. I am not going to go over the entire check list but purge the system of air and recheck level. I would then check the system to see if it is running at proper temp and if not there is a bunch of things to go through. That being said if you can't figure it out on Youtube perhaps you should get someone who knows to help you?

If the temp gauge is too hot do not drive home and please pull over - it is telling you it's not happy. No offence but YOU probably can't smell, see, or feel what is wrong as you are inexperienced and don't know what to look for. That being said if you do find something it is probably right in front of your eyes and have done damage by this point.

[ds08tf]

Judging by your lack of experience and the apparent problem is it safe to assume you did not purge the system of air? I am putting the coolant change and the temp rise together and going out on a limb and saying they have something in common. I am not going to go over the entire check list but purge the system of air and recheck level. I would then check the system to see if it is running at proper temp and if not there is a bunch of things to go through. That being said if you can't figure it out on Youtube perhaps you should get someone who knows to help you?

If the temp gauge is too hot do not drive home and please pull over - it is telling you it's not happy. No offence but YOU probably can't smell, see, or feel what is wrong as you are inexperienced and don't know what to look for. That being said if you do find something it is probably right in front of your eyes and have done damage by this point.

I am fairly ignorant, but I am trying to learn hence the doing the coolant flush and all that by myself. I did my best to burp the lines and what not when I was filling and did it nice and slow but I probably still messed up and got some air trapped. Hot air bubbles would explain the fluctuating thermo. Also, I was literally 30 seconds from my house. It wasn't in the danger level of heat anyway and just by hitting cruise control the temp gauge lowered. When I engine braked it shot back up. In the future though I will pull over asap I guess. Thought I could make it the km to my house safely. Thanks for the tip.

I will purge the lines of air tomorrow and see if the problem remains. Any advice on how to best purge the lines of air? I've heard taking the radiator cap off and letting the engine idle for ten minutes while burping the lines is supposed to work... but like I said I'm not very experienced so any insight would be greatly appreciated.

Thanks, Cheers

[Lux]

To be clear, a thermostat is a temperature-sensitive valve in the engine that moderates water temperature.
The gauge on the instrument cluster is the water temperature gauge.
It is fed a rheostatic electrical current from the water temperature sender in the cooling system.

The first step is to verify that the gauge is accurate.
This is the professional method.
Use a decent diagnostic scan tool with live data capabilities.
It can give you real-time water temperature from the water temperature SENSOR.
Compare that value with what gauge gets from the water temperature SENDER.
(Some cars have only the sensor and no sender)
Alternatively, use an infrared pyrometer and take a temperature reading from the thermostat housing to compare with the gauge.
Another alternative is to backprobe the water temperature sender and check its output resistance and voltage.
The higher the resistance and lower voltage, the hotter it is.
Compare your overheat reading with what Ford specifies for a specific temperature.
If after all the above the sender output is fine, then the cluster is fuct.
Only after all of that to verify the integrity of the gauge can you proceed with the bleed...
It might seem complicated, but it is the professional method for automotive service technicians.
Absolutely no tolerance for error by eliminating the unknown factors first.

I don't know what you mean when you say burp, but the correct method for filling and bleeding the cooling system involves the use of this tool:


Rev the engine until the thermostat opens.
Then idle until all the air purges itself through the filler.
You can buy it at Princess Auto for $30.

If you lived close enough, I would just get my vacuum tool to duck all of the air pockets out of the cooling system for free.
Takes 60 seconds and there's no need to idle the car afterwards.

[slam525i]

Lux is perfectly correct...

But the cheap and easy way is to open the radiator cap and let the engine idle for a while after the temperature has reached normal operating. Hopefully that'll get the air out of the system. Make sure it doesn't overheat while you're doing that.

[ds08tf]

Wicked. Will do. Thanks for the help. Will an OBDII reader have the ability to display data from the water temperature sensor? Regardless I will attempt a ten minute idle as slam525i suggested... by burping I meant the method where you squeeze the tubes to push liquid(and air) through... clearly it didn't work very well. I will see how this all goes tomorrow. Learning experience hah.

[gabbygenier]

it may be different on the second gens, not sure. but on the first gens. there is no radiator caps on the 3, you fill it up with the reservoir. so taking it off wont work. unless you guys are talking about the reservoir car. but the pic that Lux showed wont work

when i changed my thermostat, the way we took the air out was with 2 ppl, one reving the car at around 1500 rpm, and the other was squeezing the coolant lines that were going to the rad. I never had issues with anything by doing it this way.

[ds08tf]

So i purged the lines of air and added more coolant and everything seems to be dandy now. I will keep checking fluid levels and monitoring my water temperature gauge. Thanks for the help peeps.

[slam525i]

Good to hear. I've actually never had to mess with the cooling system in my car, so I completely forgot these cars don't have a rad cap. It's been almost a decade since I've had to mess with one.

As to whether OBDII will give water temp, yes it will, and it's a lot more accurate than the gauge in the car that sits at the middle. I monitor the OBDII via a transmitter that talks to my Garmin GPS. Other guys on here like to use Scan Gauge. I find the OBDII transmitter to give interesting info, but it's probably not useful for day to day driving.

[Gizzmo_jr]

I had to burp mine by squeezing the lines in and out to the heater core (Gen1). Once I did that the reservoir was full of bubbles, waited and then I topped it off.

[DLYDRVN]

For the love of God don't ignore the gauge. Everything above is great, but take it from someone who has lost an $8k engine to coolant issues... Don't ignore coolant issues. Use the above info and get it right.

[ds08tf]

I won't ignore it anymore I promise! haha
I've been keeping a close eye on it and will continue to.
Thanks again
-D

[Lumberjack]

The fact that you had to add coolant proves there was air in the system (assuming it was topped previously). Glad it worked out for you!