Engine Themostat

Mindseye007 · Jan 30, 2026

What thermostat are you running ?
I have a 180 degree that was installed 2 years ago with a brand new water pump, my radiator is a Fluidyne 3 Row Aluminum with SVE Silicone Radiator hoses Matte Black. I also run march underdrive pulleys the stock temp gauge is just under half and goes higher it hit the 3/4 mark while cruising with the A/C blasting ice cold on a HOT humid july day last summer , thinking of going with 160 degree suposed to be better if you have an electric fan set up? What do you think ? Or maybe just put the stock water pump pulley back on?
I run the flex a lite electric fan that is one sweet powerful fan.

86HO5.0 · Jan 30, 2026

IMO--Get a real temp gauge before making any more changes, it's an understatement to say the stock gauge is vague.

I like my cars to run in the 175-185 range so 180 T-stats are my weapon of choice.

AeroCoupe · Jan 30, 2026

So the OEM thermostat is 192 deg and that is what the ECU is basing its programming (read tables) off of. You put a colder thermostat in it and it will not reach ideal operating temperatures.

Do you have the side and lower deflectors installed? This one goes under and attaches to the core support:

Mustang Radiator Air Deflector Kit (87-93) E7ZZ-8349

Replace that broken, or missing 1987-1993 Mustang radiator air deflector with this direct replacement from DCR!

lmr.com

These go on either side of the radiator:

Mustang Radiator Side Air Deflector Pair (79-93) E4ZZ-8310

Replace those rotted out radiator side air deflectors on your 1979-1993 Mustang with these direct replacements from 5.0 Resto!

lmr.com

All of these force the air to go through the radiator rather than around it. If you are running AC are you 100% sure the condenser (mounted in front of the radiator) is free of debris and the cooling fins are not plugged? This happened to a buddy of mine and all we did was power wash the condenser and the amount of small rocks, dirt, and grass that came out of the fins was insane. Car ran way cooler and the AC worked like new.

Mindseye007 · Jan 30, 2026

AeroCoupe said:
So the OEM thermostat is 192 deg and that is what the ECU is basing its programming (read tables) off of. You put a colder thermostat in it and it will not reach ideal operating temperatures.

Do you have the side and lower deflectors installed? This one goes under and attaches to the core support:

Mustang Radiator Air Deflector Kit (87-93) E7ZZ-8349

Replace that broken, or missing 1987-1993 Mustang radiator air deflector with this direct replacement from DCR!

lmr.com

These go on either side of the radiator:

Mustang Radiator Side Air Deflector Pair (79-93) E4ZZ-8310

Replace those rotted out radiator side air deflectors on your 1979-1993 Mustang with these direct replacements from 5.0 Resto!

lmr.com

All of these force the air to go through the radiator rather than around it. If you are running AC are you 100% sure the condenser (mounted in front of the radiator) is free of debris and the cooling fins are not plugged? This happened to a buddy of mine and all we did was power wash the condenser and the amount of small rocks, dirt, and grass that came out of the fins was insane. Car ran way cooler and the AC worked like new.

Yes I have those side and lower deflectors installed bought brand new off LMR . And the condenser was changed afew years ago looks like new still. What if I put a 192 degree back in instead of the 180 degree?

86HO5.0 · Jan 30, 2026

180 degree thermostat will be fine, it's warm enough that the engine will no longer be in WUE and it will be in closed loop.

160 degree T-stat starts teetering on the edge of what's acceptable, 180 is fine.

Mustang5L5 · Jan 30, 2026

My car with a 180* stat, and a 192* stat always ran at the same time. 195 degrees

However, the motorcraft 192 I had never really opened consistently. It was always a delayed opening where the temp would hit 205 degrees and then it would open and run at 195-200. The stant 180 I used had a more gradual opening. Temp would stablize around 185 degrees and slowly rise to 195 after that and then hover in the 192-195 range. Since i liked that stable pattern more, i run the 180. But the car does run warmer than 180.

Mindseye007 · Jan 30, 2026

Mustang5L5 said:
My car with a 180* stat, and a 192* stat always ran at the same time. 195 degrees

However, the motorcraft 192 I had never really opened consistently. It was always a delayed opening where the temp would hit 205 degrees and then it would open and run at 195-200. The stant 180 I used had a more gradual opening. Temp would stablize around 185 degrees and slowly rise to 195 after that and then hover in the 192-195 range. Since i liked that stable pattern more, i run the 180. But the car does run warmer than 180.

What is the best thermostat? Motorcraft 180 degree or how about the Edelbrock 8604 High Flow 180 degree Thermostat?

AeroCoupe · Jan 30, 2026

I’m with Mustang5L5 and use Stant thermostats.

General karthief · Jan 31, 2026

Most T stats are a crap shoot as to opening temp, do the pot of water on the stove trick to test.

Mustang5L5 · Jan 31, 2026

Mindseye007 said:
What is the best thermostat? Motorcraft 180 degree or how about the Edelbrock 8604 High Flow 180 degree Thermostat?

I can’t really answer that. I don’t know.

My stant T-stat is over 20 years old.

I bought a few, stuck them in boiling water with a thermometer and observed when they started opening and when fully opened. It was all over the place.

Monkeybutt2000 · Jan 31, 2026

Put a Cobra water pump pulley on,made a HUGE difference on my car.

Mindseye007 · Jan 31, 2026

Mustang5L5 said:
I can’t really answer that. I don’t know.

My stant T-stat is over 20 years old.

I bought a few, stuck them in boiling water with a thermometer and observed when they started opening and when fully opened. It was all over the place.

that what I was thinking of doing buying a few and observe them opening and closing in boiling water.

KRUISR · Jan 31, 2026

I have a 180 t-stat (no idea the brand) and Contour fans on a copper/brass 3 core rad. In the summer it will run 190-205 all day long. In early spring/late fall when temps are low 40s and lower, it will peg at 180 when driving the highways.

Mindseye007 · Jan 31, 2026

KRUISR said:
I have a 180 t-stat (no idea the brand) and Contour fans on a copper/brass 3 core rad. In the summer it will run 190-205 all day long. In early spring/late fall when temps are low 40s and lower, it will peg at 180 when driving the highways.

where should the stock temp needle be at with the temps at 190-205? and 180?

Shakerhood · Jan 31, 2026

I put a 180-degree Stat and an Edelbrock Water Pump on my car in 1999, still functions great today.

AeroCoupe · Jan 31, 2026

Mindseye007 said:
where should the stock temp needle be at with the temps at 190-205? and 180?

Wherever that inconsistent mofo reads. You need a known gauge to compare it to to know if what it is reading is good to go or not.

86HO5.0 · Feb 1, 2026

2 Critical gauges these cars lack from the factory--oil pressure and coolant temp. Stock gauges are marginally better than an idiot light.

General karthief · Feb 1, 2026

Mindseye007 said:
where should the stock temp needle be at with the temps at 190-205? and 180?

It will be wherever it feels like the temperature is, mine read different when I changed the sender and again with the t stat so I figure ford got the gauges from a company in California, whatever it 'feels like' reading.

KRUISR · Feb 1, 2026

Mindseye007 said:
where should the stock temp needle be at with the temps at 190-205? and 180?

When I built my car 200-ish was one line above half. A few years later I had to replace my sensor and now it is at half (horizontal needle). As mentioned above, it can vary car to car (and that's normal and okay).

If you have a 180 t-stat, start your car from cold with the rad cap off. Let the car idle and warm up watching the inside of the rad. Coolant will really drop in the tank and will start to flow out of the tubes back into the tank when the t-stat opens. Check your gauge, that is 180. Probably one line higher will be 200.

Mindseye007 · Feb 1, 2026

KRUISR said:
When I built my car 200-ish was one line above half. A few years later I had to replace my sensor and now it is at half (horizontal needle). As mentioned above, it can vary car to car (and that's normal and okay).

If you have a 180 t-stat, start your car from cold with the rad cap off. Let the car idle and warm up watching the inside of the rad. Coolant will really drop in the tank and will start to flow out of the tubes back into the tank when the t-stat opens. Check your gauge, that is 180. Probably one line higher will be 200.

Or maybe I will just put the stock water pump pulley back on ?

Engine Themostat

Mindseye007

86HO5.0

Active Member

AeroCoupe

lube between the nut and the face. I know my lubes

Mustang Radiator Air Deflector Kit (87-93) E7ZZ-8349

Mustang Radiator Side Air Deflector Pair (79-93) E4ZZ-8310

Mindseye007

Mustang Radiator Air Deflector Kit (87-93) E7ZZ-8349

Mustang Radiator Side Air Deflector Pair (79-93) E4ZZ-8310

86HO5.0

Active Member

Mustang5L5

That is…until I whipped out my Bissell

Mindseye007

AeroCoupe

lube between the nut and the face. I know my lubes

General karthief

wonder how much it would cost to ship you a pair

Mustang5L5

That is…until I whipped out my Bissell

Monkeybutt2000

Mustang Master

Mindseye007

KRUISR

Mindseye007

Shakerhood

AeroCoupe

lube between the nut and the face. I know my lubes

86HO5.0

Active Member

General karthief

wonder how much it would cost to ship you a pair

KRUISR

Mindseye007

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Active Member

lube between the nut and the face. I know my lubes

Active Member

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

Mustang Master

lube between the nut and the face. I know my lubes

Active Member

wonder how much it would cost to ship you a pair

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