Hi everyone,
Today I pulled my M3 out of the garage to clean it up. I let the car run for a bit and noticed a grinding noise (like loose bearings spinning) from the engine bay. I used my stethoscope in an attempt to isolate the sound. I listened to all the pullies, etc. The water pump sounded fine on the top end. However, when I listened near the belt tensioner, I could hear a higher-than-normal frequency. When I climbed back into the cabin to shut off the car, I glanced at the gauges and noticed the temperature gauge needle was in the red zone. I shut the car off at that point.
A few hours later, I checked the needle, which was still reading high (at the entry of the red zone). I hooked up my scanner to check for any codes but wasn't able to detect any. The water pump isn't leaking fluid, and I couldn't feel any play. Additional checks:
The car and engine are currently sitting at 172kish miles. Here's when I replaced the water pump and thermostat last:
January 27, 2012 – Mileage: 103,682
Last coolant flush:
August 21, 2019 – Mileage: 164,683
What other diagnostics can I run to determine the root cause? I ideally don't want to replace parts through a process of elimination if I can pinpoint the issue. I'm leaning toward the water pump or thermostat but would welcome advice. Thanks for the help.
Update 8/14/23 (Post 30)
I had a chance to get back to diagnosing things. The week prior, I let the car run for a few minutes and saw the coolant gauge needle climb into the red zone again. The upper coolant hose warmed up, while the lower coolant hose stayed cool to the touch, but I didn't let the car run long enough to get it up to temp due to the needle position.
The car wasn't turned on in over a week. The needle was still pegged close to the red zone.
I pulled the thermostat and the water pump since I needed to perform a coolant flush. I checked the thermostat via the boiling water method, and it opened. I spun the water shaft and checked for play. There was practically no play, and it had resistance similar to new. This led me to believe the hardware (at least the parts I checked) is fine.
Update 8/15/23 (Post 34)
Viewed temps against ambient using a Schwaben scanning tool. The coolant temperature sensors were functioning fine.
Update 8/16/23 (Post 40)
Did a gauge cluster reset following this procedure. This seems to have solved the needle sticking in the red zone issue for now.
Will reassemble the cooling system and make sure everything functions as normal.
Update 8/21/23 (Post 46)
Reassembled the cooling system and got the engine up to operating temperature. Viewed temps against ambient using a Schwaben scanning tool. The temperature gauge needle climbed to 12 o'clock and stayed put. Everything appears to be operating normally again.
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My recommendation for diagnosing a temperature needle pegging in the red (in order of complexity)
Today I pulled my M3 out of the garage to clean it up. I let the car run for a bit and noticed a grinding noise (like loose bearings spinning) from the engine bay. I used my stethoscope in an attempt to isolate the sound. I listened to all the pullies, etc. The water pump sounded fine on the top end. However, when I listened near the belt tensioner, I could hear a higher-than-normal frequency. When I climbed back into the cabin to shut off the car, I glanced at the gauges and noticed the temperature gauge needle was in the red zone. I shut the car off at that point.
A few hours later, I checked the needle, which was still reading high (at the entry of the red zone). I hooked up my scanner to check for any codes but wasn't able to detect any. The water pump isn't leaking fluid, and I couldn't feel any play. Additional checks:
- Checked the coolant level - good
- Opened up the bleeder screw and ran the system briefly
- Upper radiator hose was very hot to the touch
- The aux fan did not kick on
The car and engine are currently sitting at 172kish miles. Here's when I replaced the water pump and thermostat last:
January 27, 2012 – Mileage: 103,682
- Water pump replaced with OE water pump
- Thermostat replaced with OE thermostat
- All water pump and thermostat gaskets/o-rings replaced with OEM
- Coolant flushed and refilled with Genuine BMW coolant and distilled water
Last coolant flush:
August 21, 2019 – Mileage: 164,683
- Coolant flushed and refilled with Genuine BMW coolant and distilled water
What other diagnostics can I run to determine the root cause? I ideally don't want to replace parts through a process of elimination if I can pinpoint the issue. I'm leaning toward the water pump or thermostat but would welcome advice. Thanks for the help.
Update 8/14/23 (Post 30)
I had a chance to get back to diagnosing things. The week prior, I let the car run for a few minutes and saw the coolant gauge needle climb into the red zone again. The upper coolant hose warmed up, while the lower coolant hose stayed cool to the touch, but I didn't let the car run long enough to get it up to temp due to the needle position.
The car wasn't turned on in over a week. The needle was still pegged close to the red zone.
I pulled the thermostat and the water pump since I needed to perform a coolant flush. I checked the thermostat via the boiling water method, and it opened. I spun the water shaft and checked for play. There was practically no play, and it had resistance similar to new. This led me to believe the hardware (at least the parts I checked) is fine.
Update 8/15/23 (Post 34)
Viewed temps against ambient using a Schwaben scanning tool. The coolant temperature sensors were functioning fine.
Update 8/16/23 (Post 40)
Did a gauge cluster reset following this procedure. This seems to have solved the needle sticking in the red zone issue for now.
Will reassemble the cooling system and make sure everything functions as normal.
Update 8/21/23 (Post 46)
Reassembled the cooling system and got the engine up to operating temperature. Viewed temps against ambient using a Schwaben scanning tool. The temperature gauge needle climbed to 12 o'clock and stayed put. Everything appears to be operating normally again.
__________________________________________________
My recommendation for diagnosing a temperature needle pegging in the red (in order of complexity)
- Perform a gauge cluster reset using this procedure. The reset is function 21.0 in the hidden onboard computer display. If the needle doesn't reset back to its home position (in the blue) while the engine is cold, the cluster may need to be pulled, and the needle may need to be manually reset. This thread explains that procedure.
- Check inlet and outlet temperatures using software. This can provide some indication that one of the sensors may not be functioning properly. The onboard computer can display live engine temp by selecting function 7.0.
- If the problem persists and hardware is believed to be the cause, check upper and lower radiator hose temps by measuring them with them an infrared thermometer. They can also be tested by physically touching the hoses - exercise extreme caution doing this. Read the rest of the thread for insights on this.
- Spin the water pump shaft freely (without the fan and belt) while listening for grinding and checking for wobbling/play. Worn and failing water pump bearings tend to exhibit noise and excess play in the shaft.
- Pull the thermostat and perform the boiling water test.
- Pull the water pump and visually inspect the shaft, impeller vanes, etc., for damage.
- Perform other cooling system hardware tests (radiator, etc.) as necessary if none of the preceding steps uncover the issue.
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