Resolved Grand daughters 2003 3.8 v6 overheating

def_68 · Oct 5, 2023

Not sure if you mentioned that you change the coolant temperature sensor. Are you relying on just the gauge telling you that it’s overheating?

Rck · Oct 5, 2023

Funny you mentioned that. Yes I am only using gauge. I am picking up a lazer temp gun from a friend Friday. We arrived at that also.
Thank you and Ill let you know.

def_68 · Oct 5, 2023

Thumb up.

Rck · Oct 5, 2023

Not sure my reply went thru.
Yes gauge only. Getting a laser temp gun from friend Friday.
Thank you and I will let you know.

Mustang5L5 · Oct 5, 2023

Sounds good then. Test the cap as well if that’s part of the kit you have

Rck · Oct 11, 2023

Ok gang. Bought an infrared thermometer to check engine heat. Gauge shows overheating yet all points I check show nowhere near 200° including radiator and thermo housing.
Electric fan comes on just over 90° which is wrong.
Does the temp sensor on the driverside head dictate fan also? I believe that to be problem but hate just changing parts.
This car did have blown head gasket. Had heads planed, new water pump and thermostat installed.
2003 mustang 3.8 v6

def_68 · Oct 11, 2023

90° is obviously too cool I believe the temperature sensor in the cylinder head controls the fan unless it has a separate radiator fan switch which also measures temperature also what are the temperatures when it’s overheating

Rck · Oct 11, 2023

Highest temp on engine is 180's.

Rck · Oct 11, 2023

Reading at sensor when gauge in car shows normal is 165°

def_68 · Oct 11, 2023

I have access to an online service manual. I’ll look up the radiator fan switch and system to tell u real quick where it is located.

Rck · Oct 11, 2023

Antifreeze is at 77°

Rck · Oct 16, 2023

I am back. Changed temp sensor and things are a bit better. Gauge shows last mark prior to red. All readings are with a infrared gun
Thermo housing is 195
Temp sensor is at 218
Freeze out plug at 180
No air in system. If I loosen rad cap I get antifreeze at pressure and temp shows normal on gauge. Temp at temp sensor 198. No antifreeze missing.

def_68 · Oct 16, 2023

Looks good per those readings. Gauges are finicky especially with mild corrosion and older wiring temps outside etc.

Rck · Oct 16, 2023

Has anyone installed an aux temp gauge on the engine. 3.8 V6?

def_68 · Oct 16, 2023

Auto meter sells great gauges but you’ll have to mount it somewhere or someway. Find out if there is a port anywhere on the engine near the thermostat and install one.

def_68 · Oct 16, 2023

They also have a probe type that goes on the radiator

Mustang5L5 · Oct 16, 2023

Do you have a half-decent OBD2 reader? You can plug that into the port, and pull up the coolant temp PID and see directly what temp it's reading live, as it happens.

TIGGER · Oct 16, 2023

Mustang5L5 said:
Do you have a half-decent OBD2 reader? You can plug that into the port, and pull up the coolant temp PID and see directly what temp it's reading live, as it happens.

That is a good idea.

def_68 · Oct 16, 2023

Even then the 5 volt reference could be skewed causing false info

Rck · Oct 17, 2023

Thanks folks.
Going to investigate scanner idea. Radiator cap stays 80 - 90

Resolved Grand daughters 2003 3.8 v6 overheating

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