Motorcycle Overheating after Coolant Change

[10kovako]

Hey!

So I’ve changed my coolant in my Suzuki GSF 650, flushed it, and got rid of any air (to my best knowledge).

Then the issues started happening. First I noticed after the 1st ride the overflow bottle filled to the max, then I noticed that the coolant started leaving the overflow tube after rides, and now the engine overheated, and after checking the bottle was nearly empty, and had to top up the radiator with 300ml coolant. Could this be the dreaded head gasket issue? Or not, as the coolant only leaks from the tube after I’ve stopped riding.

Any thoughts would be greatly appreciated!
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[Nobby the Bastard]

If it were behaving normally before you changed the coolent it won't be the head gasket.

There's exccess air in the system. Take the filler cap andleave it off after starting WHEN IT's COLD. Let the excess air bubble out and top up before it gets hot.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Kawasaki Jimbo]

Also check that the radiator fan comes on.

[10kovako]

I bought the bike about a month ago, so hoping it’s something I did! I’ll try that again tomorrow with it being cold.

Also yes, fan kicks on. The temp warning light also goes on but I’m guessing that’s from the reduced level of coolant!
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[10kovako]

[Nobby the Bastard]

It's an expansion chamber. It's supposed to allow for the expansion of a liquid.

If there is air in the system the air will expand a lot more than the liquid will and at a lower temperature, forcing excessive amounts of coolant into the chamber.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[10kovako]

[MarJay]

The coolant bottle is effectively an overflow. If you fill it, you're going to have a coolant leak.

It's also common to get an air lock after you change coolant, riding it will often 'burp' the system so the air is expelled. I'd open the radiator cap and see if there is any air in the top of the rad. If it's now full, and your expansion tank just has a little bit of coolant in it up to the minimum, ride it again to see if it overheats.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[10kovako]

[stinkwheel]

If it burped a big air bubble out, it would have to go somewhere first and that's into the expansion tank. The system has to be under pressure for the radiator cap to be opened against its spring which would allow coolant to flow both ways between the expansion bottle and the radiator. That't wont happen properly while there's air in the system because air is compressable.

It MIGHT be your head gasket, it's possible a bit of crud was all that was preventing if gassing through and the flushing dislodged it but as above, I'd refill and take it for a bit of a run and see if it's still doing it. If the gasket's gone, the gasket's gone. If it hasn't, you're fine.

Another wee test is to feel one of the coolant hoses as you rev the engine. If it goes hard as you rev it, that would be a bad thing.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MCN]

Radiator pressure cap off.
Fill the radiator until the level of coolant is at the top of the radiator filler neck/pressure cap flange.
Squeeze the bottom hose and top hose (if accessible) that should help to dislodge any air trapped in a corner somewhere. Or as Nobbers suggested, start the engine, the pump will circulate coolant around the system and dislodge air. But it might also Vomit it out over your good slacks.

Top up the radiator and repeat until you cannot top up anymore.
Radiator cap on. Make sure it is twisted over the detent to lock it in place too.

Adjust the expansion tank/bottle to the max level. Fitt the cap.
Run the engine until warm and the thermostat/regulator is fully open.
Raise the rpm blip blip to push the coolant around.
Shut off.
Check the level in the expansion tank.

BMW FYI recommend filling the cooling system via a vacuum device.
Coolant is sucked into to system from a container. (Physics l: Air pumped out of the system by the vacuum pump is relaplaced by coolant, which is pushed into the void by atmospheric pressure.
The vacuum is applied after the system is full.
The vacuum causes trapped air bubbles to expand in the lower than atmospheric pressure, when they get bigger they join up with other big air bubbles and can then roll out of the system easier.
The vacuum is released and the expansion tank topped up.
Vor Sprong Dork Teqnique.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[10kovako]

So, I’ve done as everyone has advised and ran with cap off etc.

Topped up to the max. No bubbles when revving, all seems good.

Went out for a hard ride, let the bike cool for a few hours, opened up the cap and water wasn’t to the top, but the expansion tank was definitely more full than before.

Did I let the bike cool enough for it so suck the coolant back up, or is there a leak in the return hose, or a faulty radiator cap?

Or is that normal?
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[10kovako]

Upon inspecting the hose at the bottom of the expansion bottle, I’ve found a little crack, could this be the cause? Coolant isn’t leaking out, but it could prevent vacuum from being made - thus allowing the coolant to dump into the bottle, but not be sucked back up?

Many thanks,

Kostya
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Let’s do this

[MarJay]

You're now looking for problems that aren't there. Ride it.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[10kovako]

[Nobby the Bastard]

In that case you are overfilling it. When you turn it off,all that heat in the engine is seeping into the water that is no longer being cooled so the coolent expands.

The small gap at the top of the radiator is probably because a vacuum forms whilst you are riding and when you take the cap off when cold you are letting air in.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[10kovako]

[10kovako]

[Nobby the Bastard]

You do realise there is a pump that will raise the level when the engine is running and it will lower again once you turn off the engine? Thats what pumps do...
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[10kovako]

[Nobby the Bastard]

if you have the cap off then it will raise the level. Thats why you were cautioned about water coming out of the filler hole onto your slacks.

Quite frankly, if you keep faffing with it and don't just ride it and see if it overheats then you're a lost cause.

Stop filling it up, ride it and see if something dramatically goes wrong.

If the expansion bottle overflows, wait until it cools down and then ride it again without topping it up.

Does it happen again?
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[jeffyjeff]

A functioning radiator cap will maintain pressure in the cooling system, allowing excess volume (due to coolant expansion when hot) to flow into the surge tank/expansion tank. As the engine cools, the radiator cap will maintain an airtight seal, and the coolant in the surge tank will migrate back into the radiator. Your symptoms suggest the radiator cap is allowing air into the radiator upon cool down. I suggest replacing the cap. The STANT 11233 is an aftermarket cap that works on many japanese bikes, and costs a fraction of the OEM cap.
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History shows again and again how nature points out the folly of men - BOC

[Nobby the Bastard]

If the radiator cap is letting air in when the bike is cooling, how is it maintaining pressure when the engine is hot? Bear in mind the whole point is that the pressure allows the coolent to go over boiling point and steam would get out the cap just as easily as air gets in.

It's not like the cap gets worn out by use....
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[jeffyjeff]

[jeffyjeff]

A leak in the surge tank tube above the coolant level could cause air to migrate into the radiator even if the radiator cap is functioning properly.
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History shows again and again how nature points out the folly of men - BOC