2006 temp question - BMW Luxury Touring Community
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post #1 of 4 Old Aug 12th, 2013, 10:09 pm Thread Starter
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Location: Granbury, Tx, USA
Posts: 136
2006 temp question

Changed the coolant, used BMW antifreeze at 50/50 mix.
I am pretty sure all the air is purged, left tank is full when I pull the cap at ambient temp.
Overflow tank is full to prescribed level.

Prior to coolant change the bike ran at 48% mark on the bar graph, and when stopped would rise to some other point, but cool rapidly to the "normal" point as soon as we had forward motion.

New condition is the bike runs at 51% of the bar graph, and temp rises when stopped as we'd expect, but cool down once we start moving is very slow.

Doing an IR scan after a ride shows both left and right radiators at the same temp +/- 5 degrees, which is normal.

I'm thinking deteriorated radiator cap. What say you all?
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post #2 of 4 Old Aug 12th, 2013, 11:12 pm
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Re: 2006 temp question

Just speculating, but doubtful that a somewhat deteriorated radiator cap will cause slightly elevated operating temperature without boiling, and prolonged cooldown. The radiator cap increases operating pressure to prevent the coolant from boiling, but it does not by itself improve cooling efficiency. If there is evidence of the coolant boiling, I would agree the cap is deficient. If not, there may still be air trapped in the system, in effect reducing coolant flow and leading to elevated temperature. The coolant level may be at the filler neck while there is still air trapped somewhere in the system. Also, if the new mixture is 50/50 and the previous was 40/60 (antifreeze/water) the cooling efficiency will be less and the engine could run at slightly elevated temperature. My first check would be to ensure there is no air trapped in the system.

Is it possible the 48%/51% could be due to higher ambients? That is also a possibility since the cooling system capacity is marginal. As such ambient temperature will have a more pronounced effect on coolant temperature.

Let us know what you find.

Andrť Strydom
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post #3 of 4 Old Aug 13th, 2013, 6:27 am Thread Starter
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Re: 2006 temp question

Also, if the new mixture is 50/50 and the previous was 40/60 (antifreeze/water)
I had this in the back of my head somewhere. In our climactic zone it would make sense not to use a 50/50 mix, which of course I did out of habit.

I have a cap on order so later this week a test ride will sort that out.
If the cap does not "fix" this, then it'll be a simple drain and re-fill now that I know the short cuts for doing this without disassembling the bike.
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post #4 of 4 Old Aug 14th, 2013, 9:44 pm Thread Starter
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Re: 2006 temp question

Updating Mikee's great adventure in maintaining the German monstrosity.

Drained the 50/50 solution of distilled water and BMW coolant. -40 degrees protection on my tester.
2.6 quarts from the radiator just as it should be.

Flushed the system 2x with pure distilled water.

Re-filled with a 65/35 ratio distilled water to coolant. -15 degrees protection according to the number of my balls floating. This equates to a very cold day in Texas. Shouldn't be an issue.

Air purged the system, ran the bike through a couple heat cycles while on the lift.
Checked the level in the radiator, zipped up the Tupperware and went for a ride.

Temp graph indicates about 46% while running 75mph, with a slight upward trend when at a stop.
This is followed by a very responsive cool down to the 46-48% level ( seat of the bike estimation here ) .
It is also possible to see the thermostat cycle between full open and just starting to close, so it looks like everything is right with the world.

This has been my very first experience with marginal cooling systems and I want to thank everyone for the education in coolant dynamics. It was a BIG help.
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