Car is overheating, usually when it’s hot and the engine idles.

I replaced catalytic converter, coolant tank, brakes so far. The car drinks coolant like crazy when it's hot outside, and then it overheats of course. There's brown sludge like stuff in the coolant tank. It doesn't burn oil, so I don't think it's a head gasket. It overheats only when it's hot and I'm idling. If I keep the car in neutral and rev the engine, it's fine for a while. My fans work; both of them come on normally. The heat works, so not thermostat issue.

My car has 182000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
You most likely have a transmission cooler that is leaking into the coolant inside the radiator. The transmission cooler is built inside the side tank of the radiator, and if it blew out, then you will have transmission fluid getting into the coolant and cause it to overheat. You will have to replace the radiator and flush out the cooling system to remove all the oil in the system.

How to Identify and Fix Common car Problems ?

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An overheating transmission usually means there is already some sort of internal damage or a transmission fluid issue, such as a leak, low fluid level or just old/dirty fluid running through the system. It can also happen with too much transmission fluid, which causes excess pressure within the transmission.
One common reason engines overheat while idling is a faulty or broken cooling system. This could include problems with the radiator, water pump, or fan belt. If any part of your car`s cooling system is not functioning properly, your engine may be at risk of overheating.
If you don`t have enough coolant running through the system due to leaks, ruptured hoses, loose hose clamps, whatever heat will build up, and your engine will overheat. So check the coolant level regularly, make sure the ratio of water to antifreeze is correct per your owner`s manual, and have it changed every year.
There`s a leak in the cooling system – In most cases, a leak in the cooling system is what causes your car to overheat. The radiator, hoses, water pump, head gasket, and thermostat housing are all cooling system components and can be susceptible to leaks.
The “transmission hot idle engine” message indicates a problem with the transmission in your vehicle. This message may appear when the transmission fluid is too hot and is not getting enough cooling or when there is a problem with the transmission fluid level.
If your car begins to overheat when idling, but the temperature gauge moves back down once you get going, it`s most likely due to a broken radiator fan. When the coolant goes to the radiator, it`s spread over a large surface area to cool it down. Airflow further cools it before it returns to the engine.
If this light turns on, it means that your vehicle has detected that the coolant temperature is too high. This indicates that your engine is likely overheating. If your engine is overheating, it is recommended to pull your vehicle over to a safe place and turn off the engine for at least 20 minutes.
The most common reasons a Ford Focus has a coolant leak are loose hose connections, a broken radiator, or a failed water pump. Search our network of RepairPal Certified shops near you to speak with a technician about your issue.
Normal coolant temperature will be around 195 to 220 Fahrenheit (approx 90°C) and anything above or below this can start causing problems.
External coolers are highly effective in keeping your transmission cool or at a regulated temperature, irrespective of the increased stress. External coolers will also work to minimize friction to the transmission, another cause of severe damage.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Car temp gauge is saying overheating , idle engine
ANSWER : Hi there. I don’t think that the V-Power gas has anything to do with your overheating issue. You indicated that when you turn the car off, you hear a sound as if the car is still running. That is most likely caused by near boiling water / coolant inside your radiator.

It looks like to me, from what you’re documenting, that you are having an overheating situation which could be caused by a radiator leak, bad thermostat, air trapped in the coolant lines, or multiple issues. This is a big deal, and I recommend that you have the overheating issue inspected by a professional mechanic as soon as possible to avoid further engine damage.

Car is overheating, usually when it’s hot and the engine idles.
ANSWER : You most likely have a transmission cooler that is leaking into the coolant inside the radiator. The transmission cooler is built inside the side tank of the radiator, and if it blew out, then you will have transmission fluid getting into the coolant and cause it to overheat. You will have to replace the radiator and flush out the cooling system to remove all the oil in the system.

Car is idling at high rpm’s and when the days are hot the car cranks but doesn’t turn on and also exhaust is smoking when i rev it
ANSWER : Hello – your symptoms suggest worn piston rings or valve stem seals (smoking), and a possible air leak in the intake, or idle air control valve sticking open (high idle). Both are signs of a higher-mileage engine with significant wear. I recommend an engine inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.

My car’s engine heat indicator goes up within 1 to 2 minute after I starts car. What is the reason for engine gets hot too soon?
ANSWER : It sounds like the cooling system is not performing as it should be. This could be due to a low fluid level, a restriction in the system, or a faulty temperature sensor. I would recommend having the coolant level checked first to make sure that it is full as this would be the most obvious sign of an overheating issue. I would then recommend having the temperature sensor inspected and tested by a qualified mechanic. Once this has been done, if the issue is not found yet, I would recommend having a coolant flush performed to remove any restrictions that may be in the cooling system.

My heat in my car stopped working two days ago and now my car is overheating. I put antifreeze in my car and it’s still overheating 2006 Pontiac Grand Prix
ANSWER : Hi there – you may have 2 related events here, a coolant leak, and a problem with the heater system. The current issue may be air inside the cooling system, which can cause overheating, and a lack of heater function. The lack of heater function could have 5 causes: the engine is not getting up to correct temperature (center of the gauge) due to a malfunctioning thermostat, the heater control valve is not letting hot coolant into the heater core, there is a restriction in the heater system that is preventing adequate hot coolant flow through the heater core, the heater fan is not working to transfer heat from the heater core to warm air for the passenger compartment, or the air blend doors inside the heater are not working properly to route warm air to the desired vents. I would recommend a heater system inspection](https://www.yourmechanic.com/services/heater-is-not-working-inspection) by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

Skipping engine, rough idle, shuts off during slow down & idle, overheating, white smoke from exhaust
ANSWER : Hi There,
It sounds like you may have a couple of separate issues going on here. Overheating can be caused by a number of things such as low coolant levels, a faulty thermostat, a clogged radiator or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. You may also have a water pump that is beginning to fail. Water pumps often times will begin to produce a bit of a whining sound when they are starting to fail. A common problem also associated with this is the water pump may begin to leak around the water pump shaft due to the seal being damaged. In addition to leaking around the pump, you may have a leak elsewhere in the cooling system coming from one of the hoses going to or from the radiator.

The rough idle and shutting off at slow speeds may be caused by a dirty or faulty idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. This is also an important function when starting the motor as it allows the motor to run and idle on it’s own once the motor fires. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed while adjusting the air/fuel ratio constantly to allow this to happen smoothly. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

The engine of the car runs, but when I push the gas pedal it does not accelerate, and the engine does not rev.
ANSWER : Hello. It sounds like you may have an issue with your throttle position sensor. This sensor sends a reference voltage to your power-train control module, which uses that to determine ignition timing and fuel trims. If the power-train control module is not detecting the proper signal from the throttle position sensor, the engine may not accelerate properly. It’s probably a good idea for you to have a professional mobile mechanic come to your location and complete a car is slow to accelerate inspection first, so they can pinpoint what is causing this issue to occur and they will recommend the right repairs be completed.

My car overheated while on the highway. I added coolant and let the engine rest and cool down. Now the car will not start. How can
ANSWER : Hi there:

Unfortunately, there is no exact reason we can offer to you as to why the vehicle won’t start now after your overheating issue; without first inspecting the vehicle. However, if the vehicle overheated on the highway there is a high possibility that major engine damage has occurred, which is possibly why the vehicle won’t start now. This damage could include head gaskets being blown, which can cause coolant to enter the internal portions of the engine and lead to additional damage. The best thing for you to do is have your vehicle towed back home, then contact YourMechanic.com to have one of our professional mechanics complete a car is overheating inspection.