Running Hot

[Moondog2178]

Hi all, I have an ‘89 LX 5.0 vert. Car has 39k miles. I’ve noticed that the car runs hot. Temp gauge reaches 3/4 at normal driving. I understand that is still considered “normal” according to the gauge but that seems hot. It does go down to slightly above half but still seems hot. This is my first fox body so not sure if it’s normal for them to run hot. Thanks

 

[Bullitt347]

It is Normal.
Put a mechanical gauge on it if you don't believe the factory gauge.
195-210*F is considered normal.
195-210*F is not hot.
Over 220*F would start approaching hot.
As you have already noted, if it is in the normal range, then it is normal, not hot.

 

[Moondog2178]

It is Normal.
Put a mechanical gauge on it if you don't believe the factory gauge.
195-210*F is considered normal.
195-210*F is not hot.
Over 220*F would start approaching hot.
As you have already noted, if it is in the normal range, then it is normal, not hot.

Ok good to know. Thanks for your input

 

[TIGGER]

When was the last time you serviced your cooling system?

My 89 does not go past the half way mark anymore that I have noticed. When I first picked up my 89, it would get warm in stop and go traffic. It would go to the 3/4 mark or a little past. After it you got moving again, it would go down to the half mark or maybe a little above. Originally, I attributed it to the underdrive pullies that the car has. Shortly after the radiator started leaking. I had a used one so I put that in to get me by. When I tore the old one down for scrap, I noticed it was full of rust flakes at the bottom. Made it thru that summer with the used rad and then the original heater core let go. At that point, in addition to the heater core, I replaced the water pump, thermostat, radiator (this time with a new one), and the fan clutch. When I pulled the pump off, it too was full of rust flakes. I flush the block out as best as I could and put it all back together. Runs a lot cooler now, even with the underdrive still on it.

I would take a look at the condition of your cooling system. See how much drag the fan clutch has, calcium in the radiator? etc. While it is not overheating, it is running warm in my opinion.

 

[Moondog2178]

When was the last time you serviced your cooling system?

My 89 does not go past the half way mark anymore that I have noticed. When I first picked up my 89, it would get warm in stop and go traffic. It would go to the 3/4 mark or a little past. After it you got moving again, it would go down to the half mark or maybe a little above. Originally, I attributed it to the underdrive pullies that the car has. Shortly after the radiator started leaking. I had a used one so I put that in to get me by. When I tore the old one down for scrap, I noticed it was full of rust flakes at the bottom. Made it thru that summer with the used rad and then the original heater core let go. At that point, in addition to the heater core, I replaced the water pump, thermostat, radiator (this time with a new one), and the fan clutch. When I pulled the pump off, it too was full of rust flakes. I flush the block out as best as I could and put it all back together. Runs a lot cooler now, even with the underdrive still on it.

I would take a look at the condition of your cooling system. See how much drag the fan clutch has, calcium in the radiator? etc. While it is not overheating, it is running warm in my opinion.

Previous owner always maintained it. I just performed a coolant flush last week but I will have my mechanic check out everything you mentioned. Thanks for your input

 

[AeroCoupe]

Check and make sure the air deflector is still under the core support area on the car.



Fan clutch and serpentine belt would be the other usual suspects. These cars came with a 193 deg thermostat so they tend to run hotter than your 80's cars with 180 deg thermostats.

Also, low miles doesn't mean new and things will age in place.

 

[keel]

Factory coolant temperature gauges are known to be inaccurate sometimes.

 

[Moondog2178]

Check and make sure the air deflector is still under the core support area on the car.



Fan clutch and serpentine belt would be the other usual suspects. These cars came with a 193 deg thermostat so they tend to run hotter than your 80's cars with 180 deg thermostats.

Also, low miles doesn't mean new and things will age in place.

Thanks. Yes my air deflector is still in place. I’ll have my mechanic check over the entire cooling system to make everything is good

 

[Mustang5L5]

Factory gauge is notorious for being inaccurate, but the gauge roughly translates to something like this.

I checked my gauge against a mechanical and it does somewhat line up. Take it with a grain of salt.

 

[rednotch]

If you want to see how inaccurate the stock gauge is, turn the ignition to run, engine off then turn on the headlights, sit and watch the temp gauge climb on its own. It will peg the gauge on almost every Fox body.. Check it with a real gauge and note where stock one reads with engine running, it varies. Most of my cars don't even have the stock gauge connected any more but most never got past the half way point even above 200* in traffic with the AC on. alot never even hit the third line. Between the old wiring and what's left for sending units and them cheaping out on suppliers these days I would not put much trust in them.

 

[Moondog2178]

Factory gauge is notorious for being inaccurate, but the gauge roughly translates to something like this.

I checked my gauge against a mechanical and it does somewhat line up. Take it with a grain of salt.

Thanks for your input

 

[Moondog2178]

If you want to see how inaccurate the stock gauge is, turn the ignition to run, engine off then turn on the headlights, sit and watch the temp gauge climb on its own. It will peg the gauge on almost every Fox body.. Check it with a real gauge and note where stock one reads with engine running, it varies. Most of my cars don't even have the stock gauge connected any more but most never got past the half way point even above 200* in traffic with the AC on. alot never even hit the third line. Between the old wiring and what's left for sending units and them cheaping out on suppliers these days I would not put much trust in them.

Thanks for the info and your input

 

[FastDriver]

Air movement, water movement, and heat exchange capacity. It's always one of those 3.

If your car stays cool over 40 mph, it's probably air.

A lot of little things stack up on foxes and cause cooling system trouble. Itlf you're running the stock fan, underdrive pullies are a no-go. At idle, when the fan is just not pulling enough air to both cool the condenser for the A/C and the radiator. Incidentally, this is the hardest situation on the stock cooling system... Hot weather, low fan speed, hot condenser air being pulled slowly through the radiator.

The water pump needs to move water, which is also hindered by U/D pullies.

The basics of diagnosis are
- check the coolant for its level, any debris or contamination, & ensure proper ~50/50 mixture of antifreeze.
- Ensure shroud and deflector are in place
- check the radiator for debris or bent fins blocking airflow
- check the blocking airflow pump for leaks
- feel the upper pipe after start up while monitoring temps to ensure the t-stat is opening when it should
- Flush coolant and observe for contamination
- open the system and let the car warm up while watching for bubbles, or test for petroleum, which indicates a bad headgasket (coolant in exhaust, white smoke, is a dead giveaway). Air getting into the system can wreak havoc on the cooling systems ability to function.

Don't go crazy with changing t-stat temps. You need the oil to come up to 200+ degrees to ensure water, the natiral byproduct of combustion, evaporates or boils off. I like a 185* most, but I have a 180* stat in my daily.

People also get kinda dumb with their radiator recommendations, often citing how such and such radiator keeps their 1000 rwhp car cool. Well, hate to break it to ya, but a 1k hp car makes no more heat at idle than a 200 hp car, and a stock radiator would serve them just as well. Now, open track cars are a different story. They may be at WOT for 40 minutes, and need to keep the 400-600 hp that their motor actually produces for a long time cool.

I've found that while my daily struggled at idle with A/C on, now that I have an electric fan pulling up to 4k CFM as needed, those days are gone. U/D pullies are even working for me again.

I guess that's enough for now. It's not exhaustive, but it'll get ya started. Report back and we'll try to help you iron things out.

 

[Moondog2178]

Air movement, water movement, and heat exchange capacity. It's always one of those 3.

If your car stays cool over 40 mph, it's probably air.

A lot of little things stack up on foxes and cause cooling system trouble. Itlf you're running the stock fan, underdrive pullies are a no-go. At idle, when the fan is just not pulling enough air to both cool the condenser for the A/C and the radiator. Incidentally, this is the hardest situation on the stock cooling system... Hot weather, low fan speed, hot condenser air being pulled slowly through the radiator.

The water pump needs to move water, which is also hindered by U/D pullies.

The basics of diagnosis are
- check the coolant for its level, any debris or contamination, & ensure proper ~50/50 mixture of antifreeze.
- Ensure shroud and deflector are in place
- check the radiator for debris or bent fins blocking airflow
- check the blocking airflow pump for leaks
- feel the upper pipe after start up while monitoring temps to ensure the t-stat is opening when it should
- Flush coolant and observe for contamination
- open the system and let the car warm up while watching for bubbles, or test for petroleum, which indicates a bad headgasket (coolant in exhaust, white smoke, is a dead giveaway). Air getting into the system can wreak havoc on the cooling systems ability to function.

Don't go crazy with changing t-stat temps. You need the oil to come up to 200+ degrees to ensure water, the natiral byproduct of combustion, evaporates or boils off. I like a 185* most, but I have a 180* stat in my daily.

People also get kinda dumb with their radiator recommendations, often citing how such and such radiator keeps their 1000 rwhp car cool. Well, hate to break it to ya, but a 1k hp car makes no more heat at idle than a 200 hp car, and a stock radiator would serve them just as well. Now, open track cars are a different story. They may be at WOT for 40 minutes, and need to keep the 400-600 hp that their motor actually produces for a long time cool.

I've found that while my daily struggled at idle with A/C on, now that I have an electric fan pulling up to 4k CFM as needed, those days are gone. U/D pullies are even working for me again.

I guess that's enough for now. It's not exhaustive, but it'll get ya started. Report back and we'll try to help you iron things out.

Car is all stock. Thanks for all the great info