I have a bmw k1200s motorcycle. You suppose to fill in the coolant using vacuum. I usually fill it in at home, drive to a dealer and let them deal with the vacuum stuff. it didn't work out this time. right before the dealer, a hose to the radiator blew up and the coolant vapor started to come out.

It's all good but there was some blue gel. I think that might be because coolant overheated and started to become gel. is that possible?

another option is that because of high temperature, the hoses started to melt. the one that blew is deformed. and some rubber from the hoses mixed with coolant and became gel-like substance.

any ideas what happened or what should I do to make sure everything is alright?

1 Answer 1


I'm speculating that the under-filled condition resulted in the water pump being unable to move coolant through the radiator (maybe the water pump itself wasn't getting coolant, maybe the level was so low that it couldn't complete the circuit through the radiator and back).

Why you blew a hose is a bit of a mystery...if you were making too much pressure, the fill cap should have relieved this excess pressure. Maybe you had a loose clamp? A defective pressure-relief cap?

With regard to the "gel," sounds like a system flush is in order before you (or the dealer) refill the coolant.

  • you suppose to vacuum-refill the coolant on that bike. May be that eliminates the purpose for pressure-relieving fill cap. Dec 10, 2012 at 17:57
  • any tips on how to flush the system? i was going to just use a garden hose or refill it few times with water. Dec 10, 2012 at 17:57
  • 1
    Refilling with water from a hose is the typical way to flush a coolant system, but since the K1200 wants a vacuum fill, and you've found out that without that you get an incomplete fill, I'd imagine you'd end up with an incomplete flush this way. The dealer or a good owners group may be a good source of information here. I know there's a fantastic group for older K bikes like my K75 at www.motobrick.com, I'm sure theres similar sites for the newer fancier Ks.
    – mac
    Dec 10, 2012 at 19:39

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