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Discussion Starter · #1 ·
I changed the coolant today on my 98 vt1100c. After filling it with fresh coolant I burped it several times. There were some largish bubbles and lots of smaller ones. I got the feeling that I could have burped it all day and there still would have been small bubbles rising. I guess my question is twofold: 1) the cooling system strikes me as a closed system, and therefore whatever air might be trapped in the system really has no way of working it's way out--correct? 2) if the coolant level drops some as the air works its way out, is coolant drawn from the reservoir to keep the level where it should be? Thanks in advance, Jon
 

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I believe there is a vent line from the reservoir tank to the atmosphere. When I changed the coolant in my 2001 Honda Shadow 750 ACE, I too still had a few bubbles coming up at the mouth of the radiator cap. Make sure there is coolant in the reservoir while bleeding the air out of the system. But once the bigger bubbles came out, the coolant level at the radiator cap no longer dropped. So then I topped the reservoir to the proper level and monitored the reservoir level over the next month. At first the reservoir level dropped a little and then remained steady. Then I added a little more coolant to the reservoir and it has been at the same level since.
 

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Discussion Starter · #3 ·
I believe there is a vent line from the reservoir tank to the atmosphere. When I changed the coolant in my 2001 Honda Shadow 750 ACE, I too still had a few bubbles coming up at the mouth of the radiator cap. Make sure there is coolant in the reservoir while bleeding the air out of the system. But once the bigger bubbles came out, the coolant level at the radiator cap no longer dropped. So then I topped the reservoir to the proper level and monitored the reservoir level over the next month. At first the reservoir level dropped a little and then remained steady. Then I added a little more coolant to the reservoir and it has been at the same level since.
Thanks, that's pretty much my plan. Had to check though because I acknowledge that there are folks on this forum who are mechanically much smarter than I.
 

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Small bubbles may not be a problem but you want most of the air out. The main issue with air is not that the coolant drops but that air + water = corrosion. There are inhibitors in the coolant that will reduce the corrosion so a little air is OK.

Answer 1: Yes it is a closed system and the system is under pressure with the rad cap relief valve actuating between 16-20 PSI.

2. Trapped air may or may not work its way out BUT if coolant does drop in the rad, coolant is syphoned from the reserve tank.

G.
 

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Discussion Starter · #5 ·
Small bubbles may not be a problem but you want most of the air out. The main issue with air is not that the coolant drops but that air + water = corrosion. There are inhibitors in the coolant that will reduce the corrosion so a little air is OK.

Answer 1: Yes it is a closed system and the system is under pressure with the rad cap relief valve actuating between 16-20 PSI.

2. Trapped air may or may not work its way out BUT if coolant does drop in the rad, coolant is syphoned from the reserve tank.

G.
Well alright then, guess it's going to be alright. Thanks
 
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