WHAT ARE THE POSSIBLE CAURSES OF COOLANT OVERHEATING ON A BELL A20D

If your 2004 Infiniti G35 is still overheating after replacing the thermostat and cooling sensor, there may be a few other issues that could be causing the problem:

1. Radiator blockage: The radiator may be blocked or clogged, preventing the coolant from flowing through it properly. This can cause the engine to overheat. To check for a blockage, visually inspect the radiator for any obstructions or debris, and flush the radiator to clear out any buildup.
2. Water pump failure: The water pump circulates the coolant through the engine and radiator. If the water pump fails, the coolant will not circulate properly, and the engine can overheat. Check the water pump for any signs of damage or wear, and replace it if necessary.
3. Fan clutch or electric fan failure: The fan clutch or electric fan is responsible for cooling the radiator when the car is idling or driving slowly. If the fan clutch or electric fan fails, the engine can overheat when the car is not moving. Check the fan clutch or electric fan for any signs of damage or wear, and replace it if necessary.
4. Head gasket failure: If the head gasket is blown, coolant can leak into the engine cylinders, causing overheating and other problems. Check the head gasket for any signs of damage or wear, and replace it if necessary.

As for the no heat issue, it's possible that the overheating has caused damage to the heater core or other components. It's also possible that there is air trapped in the cooling system, preventing the coolant from flowing properly through the heater core. Bleeding the cooling system may resolve the issue.

do a compression test on cooling system just because no oil and water mix doesnt mean head gasket good ---keep an eye on fluid level possible can be burning the coolant also check flow new doesnt mean free from defects or improper installation [thermostat-water pump]

Steve, there's many causes of overheating. You say you have a new water pump and thermostat, so it's obviously not those at fault.

Just a question ... you say your car is not cooling, but is it actually overheating? A faulty temperature sender unit (it screws into the engine block, usually..) can give an incorrect reading on your gauge.

If it is overheating - steam/you can feel the excess heat - is your radiator fan kicking in? Is your car overheating as soon as you drive it? Or overheating when stuck in traffic .. and the fan isn't kicking in..?

Other things that cause overheating which spring to mind include a blocked radiator and/or a collapsed radiator hose.

Hot coolant enters your radiator via the TOP hose and cools as it goes down the radiator, then back into the engine via the bottom hose. Check both top and bottom hose after the engine has warmed - sometimes a hose can become 'flat' and blocked.

Another thing that causes overheating is a burnt head gasket/cylinder head problem.

Switch the engine on and look at your coolant bottle - a continuous 'bubbling' indicates that exhaust gases are finding their way (via a burnt head gasket) into the cooling system.

Any oil in the coolant bottle also indicates cylinder head problems. Also check the oil dipstick. If coolant (because of a defective head gasket/head) has found its way into the oil system the oil on your dipstick may appear a creamy/greyish sludge.

1. Make sure the electric radiator fan(s) is kicking in when the coolant temperature gets hot. If not that will be part of the problem and if the temperature sensor/switch is faulty the fans may not operate.

2. You may have a restriction in the cooling system that is significantly retarding the flow of coolant through the engine coolant passages or through the radiator. This can be caused by a build up of debris in the system so you cannot achieve optimum coolant flow.


3. You may have a combustion leak via a failed cylinder head gasket into the cooling system. This will cause hot combustion gasses to flow from the cylinder into the cooling system and the coolant will overheat. Bubbles showing up in the cooling system is a possible indication of that. A leak down test will show this up. This involves blowing compressed air into the cylinders one by one through the spark plug openings. If air enters the cooling system in this test bubbles will appear in the coolant and it is a sign of a failed cylinder head gasket and that combustion gasses are able to escape into the cooling system when the engine is running.

4. THE rough idle may be a low RPM miss fire in one or more cylinders. You need to have the vehicle scanned to see what fault codes the computer is generating. If you have rough idle once the engine has warmed up there will be one or more fault codes being generated. Once scanned and all the fault codes are found, the cause of the fault codes can be investigated and the problem fixed.



5. Do not hesitate to have the problem of the overheating checked out. Running the car with the engine overheating WILL cause expensive engine damage many times more than it will cost to fix the problem now. If you have been running the engine frequently in an overheated condition you may well have already caused failure of the cylinder head gasket but I hope this is not the case. Running the engine overheated can also cause the cylinder head to warp and crack. These are expensive engine repairs you definitely want to avoid.

6. You did not indicate the year, model of vehicle and engine type you have. Please provide this information if you have future questions as this normally has a direct bearing on the content of answers people are able to provide.

There are several things that can cause an engine to overheat. This is why the problem should be DIAGNOSED before spending a bunch of money replacing parts. You can go broke replacing parts and never fix the vehicle.

First, is your radiator cooling fan working? If not, then you must diagnose the cooling fan and cooling fan circuits to find out why.

Did you replace the coolant sensor for the computer or the one for the gauge? (Yes, there are two engine coolant temperature sensors) This brings us to the next question:

Are you sure the engine is actually overheating or is it possible that the gauge could be "lying" to you?
The actual engine temperature should be taken with an infrared thermometer to see if it agrees with the gauge.

When you changed the thermostat and the temp sensor, did you bleed the cooling system properly? There may be air trapped in the engine.

Has the engine been checked for a possible blown head gasket? If it has overheated at all, it is highly likely that you may have a warped cylinder head and/or a blown head gasket.

Is the water pump circulating the engine coolant like it is supposed to? You could have a damaged water pump impeller or a clogged radiator keeping the coolant from circulating properly.

It could be the water pump. First check and make sure the water pump drive belt is tensioned properly and not slipping. To test the pump, warm up the engine and let it idle. using your rag covered hand, squeeze shut the top radiator hose then release. You should be able to feel a surge of coolant as you release your hold. No surge? Probably a bad water pump. Corrosion between the pump shaft and the impeller blades can cause the blades to slip on the shaft, reducing the efficiency of the pump. Or the blades themselves can rust away and reduce the efficiency.

Sounds like you have a faulty head gasket or maybe a cracked head.This can cause overheating and the check engine light to come on.The code for the o2 sensor is probably caused by coolant getting into the exhaust system and coating the sensor.The coolant fan may work but it cannot remove enough heat from the rad to make the engine cool off.Try some engine coolant stop leak to see if it will help.This maybe only a temperary fix.Let me know if you need more.MOE

the viscous fan hub is a big problem related to overheating especially at lights or working slowly with high rpms
replace the thermostat as it is a requirement to stop overheating as well because with out it coolant passes to fast down the radiator cores and doesn't allow the heat to be transferred to the air
bubbling is boiling so check the temp gauge operation

The three most likely thing's cause overheating are faulty thermostat,electric fan or clogged radiator. Only at has been overheat so much it boils dry that it will cause engine trouble. Most common problem's are blown cylinder head gasket or a cracked cylinder head.
mixing coolant and water depends on where the gasket has blown or head is cracked. You will first need to check if it actually is overheating. The reason is. If the head is cracked or gasket blown then you can get a false boiling which is compresion from the cylinders blows through the crack in the head or gasket causing the coolant to blow out of the radiator cap.Fill the radiator to the top leave the cap off then start the engine.If the water blows out then you will need to remove the cylinder head check the gasket is ok. If its damaged replace if not get the head checked for crack's. If no water blow's when you start it check the thermostat is working properly. To check the thermostat put it a in a saucepan cover it with water bring the water to the boil. It should open before the water boil's but near boiling-point. If its ok then start the engine again leave it running until it boils and check the fan is running. If that's ok then its radiator problem. Their is no way to check if the radiator is ok you will need to get a new one. One last point. If the cylinder head or gasket are faulty it was caused by overheating so by just fixing the cylinder head problem is not a cure it will overheat again. Check the three things I mentioned at the begining and told you how to check them. Hope this help's. Cheer's

It sounds like you may have a leaking head gasket or cracked head. I would suggest you do a compression test.