Accident, missing mysterious part - REWARD!
05-14-2013, 08:33 AM
#11
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P0128 code is almost always an indication that the heater coil in the thermostat has burned out.
Some modern cars, including the 545i, have a thermostat with the heater coil, which allows the cars engine control computer to accelerate the opening of the thermostat by supplying a voltage to this coil and accelerating the melting of the wax which physically opens the thermostat and allows the flow of coolant.
It is easy to check. Remove the electrical harness that connects to the thermostat and using a multimeter, measure the resistance between the two brass conductors exposed when the harness is removed. If the coil is intact it should measure around 16ohms. If the coil is burned out it will measure 1. The coil is tested each time the engine is started to ensure it is present, and if the connection is broken the computer generates the P0128 code. The thermostat will still work fine, so there is no urgent rush to replace it, but if the engine is driven hard before fully warmed up (not a smart thing to do anyway) the computer will not be open to quickly open the thermostat.
If the coil is intact you can continue your search elsewhere.
Some modern cars, including the 545i, have a thermostat with the heater coil, which allows the cars engine control computer to accelerate the opening of the thermostat by supplying a voltage to this coil and accelerating the melting of the wax which physically opens the thermostat and allows the flow of coolant.
It is easy to check. Remove the electrical harness that connects to the thermostat and using a multimeter, measure the resistance between the two brass conductors exposed when the harness is removed. If the coil is intact it should measure around 16ohms. If the coil is burned out it will measure 1. The coil is tested each time the engine is started to ensure it is present, and if the connection is broken the computer generates the P0128 code. The thermostat will still work fine, so there is no urgent rush to replace it, but if the engine is driven hard before fully warmed up (not a smart thing to do anyway) the computer will not be open to quickly open the thermostat.
If the coil is intact you can continue your search elsewhere.
I read someplace that different temperature of radiator hoses indicate a bad thermostat. I checked yesterday and after driving for 20 miles, top hose was definitely hotter than the one lower one coming out from the radiator to thermostat. Do you think it indicates just bad thermostat at all? Or maybe should I start with temp sensors?
05-14-2013, 09:08 AM
#12
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If the heater coil is gone the car won't take longer to warm up. The coil is designed such that if while the engine is still relatively cold and the thermostat is no where near opening (the wax is not yet melted) and there is a huge demand for engine power (you hold the accelerator down) the block can begin to overheat locally before the thermostat has a chance to open. The coil is designed to prematurely open the thermostat so that the water begins to move within the block and does not super heat.
Thermostat problems on the 545i can be divided into three groups: Thermostat stuck open, thermostat stuck closed and heater coil burned out. If the coil is burned out you should notice no difference in how the engine heats and cools.
The P0128 error does include an error after the car is started if there are large differentials between coolant temperature measured at different locations. Generally, the heater coil error shows up immediately after starting as measurement of the continuity through the coil is done on start up by the computer.
The fact that the car is not warming fully would lead me to believe that either the thermostat is stuck open or there is a defective temperature sensor.
Changing out the thermostat is an easy DIY. My suggestion is that you stay with the OE Wahler thermostat and don't buy an off-brand. I bought a Beck Arnley and was changing it out a week later when the heater coil burned out.
This is also a good time to bring up the question; Is your coolant system still original? If so you really need to consider a full refresh: water pump, thermostat, hoses, coolant tank and vent tube. Any 545i is old enough that, regardless of miles, it should be refreshed. Not only can this save you a tow someday or worse being stranded on a road trip in a location where you have to flat bed it out to civilization or overnight in parts. But worst of all you could overheat the engine if you can't immediately get to the side of the road.
The N62B44 engine is a leaky pig to begin with. Any overheating over-expands the aluminum components and stresses all gaskets. You want to avoid overheating and keep your oil fresh (I change every 5K miles) to have the best chance at maintaining gasket integrity.
Thermostat problems on the 545i can be divided into three groups: Thermostat stuck open, thermostat stuck closed and heater coil burned out. If the coil is burned out you should notice no difference in how the engine heats and cools.
The P0128 error does include an error after the car is started if there are large differentials between coolant temperature measured at different locations. Generally, the heater coil error shows up immediately after starting as measurement of the continuity through the coil is done on start up by the computer.
The fact that the car is not warming fully would lead me to believe that either the thermostat is stuck open or there is a defective temperature sensor.
Changing out the thermostat is an easy DIY. My suggestion is that you stay with the OE Wahler thermostat and don't buy an off-brand. I bought a Beck Arnley and was changing it out a week later when the heater coil burned out.
This is also a good time to bring up the question; Is your coolant system still original? If so you really need to consider a full refresh: water pump, thermostat, hoses, coolant tank and vent tube. Any 545i is old enough that, regardless of miles, it should be refreshed. Not only can this save you a tow someday or worse being stranded on a road trip in a location where you have to flat bed it out to civilization or overnight in parts. But worst of all you could overheat the engine if you can't immediately get to the side of the road.
The N62B44 engine is a leaky pig to begin with. Any overheating over-expands the aluminum components and stresses all gaskets. You want to avoid overheating and keep your oil fresh (I change every 5K miles) to have the best chance at maintaining gasket integrity.
05-14-2013, 10:35 AM
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If the heater coil is gone the car won't take longer to warm up. The coil is designed such that if while the engine is still relatively cold and the thermostat is no where near opening (the wax is not yet melted) and there is a huge demand for engine power (you hold the accelerator down) the block can begin to overheat locally before the thermostat has a chance to open. The coil is designed to prematurely open the thermostat so that the water begins to move within the block and does not super heat.
Thermostat problems on the 545i can be divided into three groups: Thermostat stuck open, thermostat stuck closed and heater coil burned out. If the coil is burned out you should notice no difference in how the engine heats and cools.
The P0128 error does include an error after the car is started if there are large differentials between coolant temperature measured at different locations. Generally, the heater coil error shows up immediately after starting as measurement of the continuity through the coil is done on start up by the computer.
The fact that the car is not warming fully would lead me to believe that either the thermostat is stuck open or there is a defective temperature sensor.
Changing out the thermostat is an easy DIY. My suggestion is that you stay with the OE Wahler thermostat and don't buy an off-brand. I bought a Beck Arnley and was changing it out a week later when the heater coil burned out.
This is also a good time to bring up the question; Is your coolant system still original? If so you really need to consider a full refresh: water pump, thermostat, hoses, coolant tank and vent tube. Any 545i is old enough that, regardless of miles, it should be refreshed. Not only can this save you a tow someday or worse being stranded on a road trip in a location where you have to flat bed it out to civilization or overnight in parts. But worst of all you could overheat the engine if you can't immediately get to the side of the road.
The N62B44 engine is a leaky pig to begin with. Any overheating over-expands the aluminum components and stresses all gaskets. You want to avoid overheating and keep your oil fresh (I change every 5K miles) to have the best chance at maintaining gasket integrity.
Thermostat problems on the 545i can be divided into three groups: Thermostat stuck open, thermostat stuck closed and heater coil burned out. If the coil is burned out you should notice no difference in how the engine heats and cools.
The P0128 error does include an error after the car is started if there are large differentials between coolant temperature measured at different locations. Generally, the heater coil error shows up immediately after starting as measurement of the continuity through the coil is done on start up by the computer.
The fact that the car is not warming fully would lead me to believe that either the thermostat is stuck open or there is a defective temperature sensor.
Changing out the thermostat is an easy DIY. My suggestion is that you stay with the OE Wahler thermostat and don't buy an off-brand. I bought a Beck Arnley and was changing it out a week later when the heater coil burned out.
This is also a good time to bring up the question; Is your coolant system still original? If so you really need to consider a full refresh: water pump, thermostat, hoses, coolant tank and vent tube. Any 545i is old enough that, regardless of miles, it should be refreshed. Not only can this save you a tow someday or worse being stranded on a road trip in a location where you have to flat bed it out to civilization or overnight in parts. But worst of all you could overheat the engine if you can't immediately get to the side of the road.
The N62B44 engine is a leaky pig to begin with. Any overheating over-expands the aluminum components and stresses all gaskets. You want to avoid overheating and keep your oil fresh (I change every 5K miles) to have the best chance at maintaining gasket integrity.
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