Water getting pushed out of overflow [fixed]

[Turkish]

After a long run, I've noticed the water level in the reservoir "goes up". If I carry on riding it like that eventually it overflows via the pipe near the tail.

After taking the radiator cap off there is a large air gap. So it's migrating from one to the other...

Is this down to a dodgy radiator cap (original from what I can tell) or something more sinister?

Oil & water are otherwise as they should appear and no change in performance.
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ZX-6R G2
CBR125R RW6

[andym]

Have you tried flushing the coolant system and bleeding out any air?

I've had this a couple of times and it's been down to air in the system

[G]

If it's an expansion bottle not a reservoir, it should only get additional water when the pressure opens up the spring on the radiator cap.

The idea is that as the pressure reduces, the water should be sucked back up.

First thing to do is to top up the radiator - that may be enough to stop it overheating.

It's possible it's just the radiator cap, could be low on water and getting worse, or could be an underlying issue.

[misscrabstick]

When your in traffic is the cooling fan kicking in?

what's the temperature gauge doing?

You have a expansion tank system on this bike, when cold the rad needs to be full and the tank to its top mark.

The system works like this, when the coolant gets hot and expands the radiator cap lifts and coolant displaces to the expansion tank, as the engine cools after riding a valve in the cap will open under vacumn from the contracted cooler coolant in the radiator and engine and suck back in the previously expelled coolant from the expansion tank.

You may well have a bad rad cap, equally you may be running too hot due to a number of possible issues.

[Turkish]

Thank you for the replies. I changed the coolant not long ago and bled the system correctly - it has been fine for months.

I noticed it a few weeks ago and had to empty half of the water out of the expansion tank and put about the same amount into the top of the radiator.

By the sounds of it, instead of sucking the water back into the rad when it cools it is sucking air in through the cap instead.

Temperature gauge is a series of bars (8 I think). Normal riding/cruising it sits at 3/4, around town it goes up to 5. The fan comes on when it has been at 5 for a while - doesn't seem to do much though.

It went up to 6 before which is when I paid extra attention to the expansion bottle and realised what was happening - since I topped it up again it has been OK.

Should I order a new cap and change/bleed the coolant just to be on the safe side?
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ZX-6R G2
CBR125R RW6

[misscrabstick]

Try a new cap, possibly it is not sucking back the coolant from the tank correctly.

[Captain Liberious]

Hi mate,
Pushing coolant water out the overflow is a sure sign your head gasket is gone. Had this problem on a couple of bikes, basically pressure from the cylinder is leaking through the headgasket and over - pressurising the cooling system. The water goes the only way it can - out the overflow!
What bike is this?
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A squid eating dough in a polyethelene bag is fast and bulbous, got me?

[Shinigami]

[Clutchy]

[Richy CB1000]

Get a "sniff" test done, any decent garage would do it for you to see if there's any exhaust gas in the coolant.

[Ariel Badger]

Sniff test
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Bikers make great organ donors, get 115 on your licence today.

[Turkish]

So I fixed this.

It wasn't the cap.

Rad had small air leak under vaccuum. Pricey fix indeed but water stays where it should now.
____________________
ZX-6R G2
CBR125R RW6