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Discussion Starter #1
Hi to all of you there,
I have an e46 318i, M43 engine and had a problem with the expansion tank which i replaced a couple of weeks ago. Ever since i keep noticing the temp increasing nearly to the overheating level. I knew about the cooling water leakages ever since i bought the car but was always replacing the evaporating / lost water every couple of weeks without noticing overheating. I had replaced all pipes and plastic pipes in the cooling system and checked the system today for leackages and it turned out to be perfect. took the car for a spin and noticed the overheating once again. I have read in the forum about the correct way to bleed the air out of the cooling system but could be this the reason or could it be due to a blocked radiator or the fan not operating as it should. I ve also noticed that while in idle the car was overheating slightly and when the fan was switching on the temp gauge was still going up and then down and then up etc. I removed the temp sensor cable on the pipe from the radiator going to the thermostat and what i ve noticed was that immediately the fan was turning twice as fast and cooler air than before. of course it was not switching off until i placed the cable in the sensor. Even then the temp was going up and down without sense. Can anyone please help me out as am very very confused with this? could it be a defective temp sensor? could it be an electrical problem? could it be a blocked radiator or incorectly bleeding of the air out of the system?
The rattling noise i keep hearing is after i rev the engine up and it begins during the decrease in revolutions. It sounds like an exhaust leakage with the only differense that it sounds coming somewhere near the airflow meter which is impossible to trace.
I also keep hearing a whinning noise like its coming from the belts and tensioners which i dont think its related to those as i had them replaced (new belts and tensioners) and the noise is still there. i thought it might be the fan again as i first noticed it after the replacement of the expansion tank and i think the radiator wasnt put back and secured exactly in place due to breaking one of the securing bolts. This is only auditlbe when i first start the engine in the morning and then it stops.
i would appreciate any help.
thanking you all in advance
 

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Could be a faulty thermostat or an airlock in the system, or your engine cooling fan. I would suggest taking the car to a service centre and having the cooling system properly drained and refilled. If the heater is not providing hot air, it's a sure sign that the thermostat is gone or sticking - cheap and easy enough to replace. If the cooling fan is coming on, then it's obvioulsy working! I'd guess there is an airlock in the system and therefore not enough water circulating.
 

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Discussion Starter #4
The car has 105000 miles. The thermostat was replaced a couple of months ago but no sign of overheating till about a month after that. as i mentioned i replaced the expansion tank due to being holed and after that i had to fill up the radiator every couple of days. I then stopped the car and replaced every pipe / hose in the cooling system and when tested still i had some overheating with the symptoms described in my first message. I followed the instructions this morning and bled the air out of the system with the fan on at 32oC and seemed to work since i drove the car for 5km and noted the temp to be steady in the middle. hopefully my problem will be due to air in the system as am tired of the constant worry of overheating. I will take it for a spin in the highway this afternoon and see how it goes as it usual oveheats fast when i am driving at around 120km. The water pump wasnt replaced but i havent seen any signs of leakages to indicate the need for replacement. The a/c belts were replaced. What is the serpentine though and what does it do if you have the time to give me a short explanation.
thanks
 

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Hi to all of you there,
I have an e46 318i, M43 engine and had a problem with the expansion tank which i replaced a couple of weeks ago. Ever since i keep noticing the temp increasing nearly to the overheating level. I knew about the cooling water leakages ever since i bought the car but was always replacing the evaporating / lost water every couple of weeks without noticing overheating. I had replaced all pipes and plastic pipes in the cooling system and checked the system today for leackages and it turned out to be perfect. took the car for a spin and noticed the overheating once again. I have read in the forum about the correct way to bleed the air out of the cooling system but could be this the reason or could it be due to a blocked radiator or the fan not operating as it should. I ve also noticed that while in idle the car was overheating slightly and when the fan was switching on the temp gauge was still going up and then down and then up etc. I removed the temp sensor cable on the pipe from the radiator going to the thermostat and what i ve noticed was that immediately the fan was turning twice as fast and cooler air than before. of course it was not switching off until i placed the cable in the sensor. Even then the temp was going up and down without sense. Can anyone please help me out as am very very confused with this? could it be a defective temp sensor? could it be an electrical problem? could it be a blocked radiator or incorectly bleeding of the air out of the system?
The rattling noise i keep hearing is after i rev the engine up and it begins during the decrease in revolutions. It sounds like an exhaust leakage with the only differense that it sounds coming somewhere near the airflow meter which is impossible to trace.
I also keep hearing a whinning noise like its coming from the belts and tensioners which i dont think its related to those as i had them replaced (new belts and tensioners) and the noise is still there. i thought it might be the fan again as i first noticed it after the replacement of the expansion tank and i think the radiator wasnt put back and secured exactly in place due to breaking one of the securing bolts. This is only auditlbe when i first start the engine in the morning and then it stops.
i would appreciate any help.
thanking you all in advance
Rattling noise if probably from the DISA located between the map sensor and the intake manifold.? If that is the case replace it or rebuild it IMMEDIATELY !!!!! There is a pin the comes loose and gets sucked into the motor. This can cause complete engine destruction.....
I recommend a full coolant change and flush with water and radiator flush fluid from any parts store. Napa has some good products. Make sure you wait till the thermostat opens and water is circulating through the motor, and you have the heating set to max so fluid will circulate through the heater core, Refill with coolant and make sure the thermostat is open and heater is on Max heat.
Make sure you bleed the system completely. I add fluid from the radiator until I am just dribbling it in. Then fill the overfow tank and bleed from the screw on hte radiator.
 
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