Engine over heating with a full coolant reservoir
11-08-2011, 05:49 AM
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Engine over heating with a full coolant reservoir
The car is a 2004 A4 1.8t. It has an obvious coolant leak somewhere. The coolant level in the reservoir goes below the minimum mark after every 300-400 miles.
One day I was driving the car and noticed the temp gauge started moving past the mid point slowly. The low coolant lamp came on as soon as the gauge was nearing the red zone. So I quickly pulled the car over and turned it off. Thinking that it was just low on coolant, I opened up the hood preparing to fill the reservoir up (yes, I know it's a really bad idea to do that while the car is hot), but the level was already near the maximum mark. That same day, I noticed the heater inside the car was not working. Only cold air. I believe the two issues are some how related.
I barely made it back home that day. I drove the car in 2 minutes intervals (with a lot of coasting), in between multiple 10 minute cool off periods (with the engine off).
Does anyone have any ideas as to what can be causing this over heating?
One day I was driving the car and noticed the temp gauge started moving past the mid point slowly. The low coolant lamp came on as soon as the gauge was nearing the red zone. So I quickly pulled the car over and turned it off. Thinking that it was just low on coolant, I opened up the hood preparing to fill the reservoir up (yes, I know it's a really bad idea to do that while the car is hot), but the level was already near the maximum mark. That same day, I noticed the heater inside the car was not working. Only cold air. I believe the two issues are some how related.
I barely made it back home that day. I drove the car in 2 minutes intervals (with a lot of coasting), in between multiple 10 minute cool off periods (with the engine off).
Does anyone have any ideas as to what can be causing this over heating?
11-08-2011, 06:49 AM
#2
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First, how many miles, any recent servicing, etc would be good.
Over-heating is one of several things:
1) Leak casuing low coolant. Don't think this is it since you don't mention signs of leaks anywhere.
2) Thermostat stuck closed. This won't allow coolant into the engine and thus your heater core.
3) Water pump. One of the failures of cheap water pumps is the "cage" (the part of the pump that is inside the engine block) that creates coolant flow breaks and "freewheels" thus not creating any coolant flow through the block. This would explain your symptoms as well.
4) Worst case and check into the other 2 first!!!! Blown head.
The middle 2 are a guess unless you have replaced either recently. They cause the same problem which is no flow through your block.
Over-heating is one of several things:
1) Leak casuing low coolant. Don't think this is it since you don't mention signs of leaks anywhere.
2) Thermostat stuck closed. This won't allow coolant into the engine and thus your heater core.
3) Water pump. One of the failures of cheap water pumps is the "cage" (the part of the pump that is inside the engine block) that creates coolant flow breaks and "freewheels" thus not creating any coolant flow through the block. This would explain your symptoms as well.
4) Worst case and check into the other 2 first!!!! Blown head.
The middle 2 are a guess unless you have replaced either recently. They cause the same problem which is no flow through your block.
11-08-2011, 07:06 AM
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First, how many miles, any recent servicing, etc would be good.
Over-heating is one of several things:
1) Leak casuing low coolant. Don't think this is it since you don't mention signs of leaks anywhere.
2) Thermostat stuck closed. This won't allow coolant into the engine and thus your heater core.
3) Water pump. One of the failures of cheap water pumps is the "cage" (the part of the pump that is inside the engine block) that creates coolant flow breaks and "freewheels" thus not creating any coolant flow through the block. This would explain your symptoms as well.
4) Worst case and check into the other 2 first!!!! Blown head.
The middle 2 are a guess unless you have replaced either recently. They cause the same problem which is no flow through your block.
Over-heating is one of several things:
1) Leak casuing low coolant. Don't think this is it since you don't mention signs of leaks anywhere.
2) Thermostat stuck closed. This won't allow coolant into the engine and thus your heater core.
3) Water pump. One of the failures of cheap water pumps is the "cage" (the part of the pump that is inside the engine block) that creates coolant flow breaks and "freewheels" thus not creating any coolant flow through the block. This would explain your symptoms as well.
4) Worst case and check into the other 2 first!!!! Blown head.
The middle 2 are a guess unless you have replaced either recently. They cause the same problem which is no flow through your block.
If the thermostat is stuck closed, does it need to be replaced? Also, can the thermostat cause a coolant leak? I guess it could also be a bad water pump if the dealer replaced with a cheap one.
11-08-2011, 12:28 PM
#5
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Bleeding is typically only an issue with the heater, not running hot.
Even a cheap water pump should last that long. Based on all this, I would lean toward thermostat and no, you don't want to drive with a failed one.
Leaks? Don't think this would not be caused only by a stuck thermostat. Most leaks are from 1) aft coolant flange (rear of engine), 2) j plug (area of thermostat), or 3) the radiator itself (front of car), all of which you should see evidence of dried pink coolant. If the car is "eating" coolant and there is no leak, then the head comes to mind.
Even a cheap water pump should last that long. Based on all this, I would lean toward thermostat and no, you don't want to drive with a failed one.
Leaks? Don't think this would not be caused only by a stuck thermostat. Most leaks are from 1) aft coolant flange (rear of engine), 2) j plug (area of thermostat), or 3) the radiator itself (front of car), all of which you should see evidence of dried pink coolant. If the car is "eating" coolant and there is no leak, then the head comes to mind.
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