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Old 06-10-2019, 02:19 PM   #1
OkSoup
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M42 Overheating at idle/traffic

When my e30 sits at idle/in traffic the temp gauge will continuously rise. It's not an instant overheat, at the rate it goes I would need probably around 10 minutes of complete standstill traffic to get into the red. After a few seconds-a minute the check engine light comes on but will instantly go away when I rev. The second I start driving it starts to cool and when normal driving it's between 1/4-2/4. Revving or turning on the ac fan don't seem to help. My coolant levels are good but it looks like there's a very small and slow leak from the radiator. The car idles nicely, there's no obvious sign of damage. When I idle/sit in traffic my heat almost instantly turns to room temp air, I need to be driving for it to produce heat.
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Old 06-10-2019, 02:39 PM   #2
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First, check your WP belt tension. Second, find/fix your leak as you may have a loss of system pressure. Third, make sure your auxiliary fan is actually working.
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Old 06-13-2019, 03:24 PM   #3
Nairb
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A new radiator, new upper and lower coolant hoses, and if you have no idea when the thermostat has been replaced, you'll need one of those too. Don't forget the gasket. Flush the engine, finish off with some distilled water for the flush. Buy a few gallons from Wal-Mart, they're cheap.

When you refill after reassambly, you need to pop the upper radiator hose on and fill with distilled water until it won't hold any more. Then you are going to fill the radiator expansion tank. Then massage the lower radiator hose with the coolant cap off and see if water is going down in the reservoir. This "massage" technique has worked for me 100% of the time. Keep refilling the reservoir, with the car on idling, until water is consistently coming out from the top of the small hole under the radiator cap. When the car is warm, and thermostat opens, make sure that when you rev the engine (just push the throttle body from engine bay) that there is a consistent stream of steaming coolant coming out. Make sure reservoir is filled to appropriate level and then replace thermostat cap. Drive it for a distance and make sure coolant level stays consistent over time.

The mess under the intake is a whole other level of involvement. If you have leaks under there, look into it before you tackle that project. You can do it.
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Old 06-13-2019, 06:13 PM   #4
roguetoaster
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Quote:
Originally Posted by Nairb View Post
A new radiator, new upper and lower coolant hoses, and if you have no idea when the thermostat has been replaced, you'll need one of those too. Don't forget the gasket. Flush the engine, finish off with some distilled water for the flush. Buy a few gallons from Wal-Mart, they're cheap.

When you refill after reassambly, you need to pop the upper radiator hose on and fill with distilled water until it won't hold any more. Then you are going to fill the radiator expansion tank. Then massage the lower radiator hose with the coolant cap off and see if water is going down in the reservoir. This "massage" technique has worked for me 100% of the time. Keep refilling the reservoir, with the car on idling, until water is consistently coming out from the top of the small hole under the radiator cap. When the car is warm, and thermostat opens, make sure that when you rev the engine (just push the throttle body from engine bay) that there is a consistent stream of steaming coolant coming out. Make sure reservoir is filled to appropriate level and then replace thermostat cap. Drive it for a distance and make sure coolant level stays consistent over time.

The mess under the intake is a whole other level of involvement. If you have leaks under there, look into it before you tackle that project. You can do it.
No need to replace parts unnecessarily even if BMW considered them "maintenance items," cleaning the system, yes, 100%.

There should be no need to fill from the rad hose if the thermostat (which is not in the rad cap as you seem to be saying, but I know you know that ) bypass orifice is clear. Granted, it may have worked for you consistently, but it's not normally required.

Also, the MUTI clean up is no biggie, providing you can source a hose that goes from the plastic coolant pipe to the head port.

OP, did you do the stomp test to get the CEL to flash the code(s)?
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Old 06-18-2019, 06:04 PM   #5
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honestly it's probably just the clutch for the fan clutch is worn out if it's only happening at idle. But also fixing the leaks is probably a good idea
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