Cooling system problem

[Folcan]

Ive been having a problem lately with my VFR 400.. It seems to be fulling up the reserve coolant tank at the back of the bike. leaving the radiator with less coolant in it. and it just fulls up the reserve tank. ive had to transfer coolant twice so far, and also sometimes while riding I get a strong coolant smell for like 1 or 2 seconds, im not sure where its coming from on the bike.

I havent had the bike overheat or anything yet, but was just wondering what could be causing this. as the bike is supposed to automatically take from the reserve if the radiator gets empty no?

[vifferman]

This can be caused by an airlock in one or more hoses. You need to run the bike with the fairings off, take the radiator cap off, and squeeze the hoses, to get the bubble to move. Top up when you're finished.
Also, your radiator pressure cap could be stuffed. You don't necessarily need to buy one from the Honda dealer - a radiator specialist or an auto parts store should have the appropriate pressure cap for a lot less.

[Ixion]

This can be caused by an airlock in one or more hoses. You need to run the bike with the fairings off, take the radiator cap off, and squeeze the hoses, to get the bubble to move. Top up when you're finished.
Also, your radiator pressure cap could be stuffed. You don't necessarily need to buy one from the Honda dealer - a radiator specialist or an auto parts store should have the appropriate pressure cap for a lot less.

Wot 'e sed. But get y' girlfriend to squeeze the hoses , it's good practice for her.

[imdying]

Check the workshop manual, sometimes odd shaped motors liek V4s need to be bled in a particular way to get the air out.

[vifferman]

There is also a very slight chance that you have a blown head gasket, but this is unlikely.
I've just checked the Honda Common Service Manual - what I've said in my first post is correct. Blipping the throttle with the radiator cap off will help to get rid of airlocks.
What happens if the spring in the cap (this controls the pressure) is 'tired', it will mean the coolant can effectively boil at a lower pressure than it should, and the vapour pushes the coolant out of the system and into the reservoir. Having a blown head gasket can also do this, but in that case it's gases from the cylinder(s) doing it.

[Folcan]

If I have blown a head gasket I would notice oil in the water right? and I havent noticced any difference in the engine sound or performance

[vifferman]

If I have blown a head gasket I would notice oil in the water right? and I havent noticced any difference in the engine sound or performance
Not necessarily - it depends what'how the gasket is brukt. I had a Subaru with a cracked head - no oil in the water, or vice versa, just kept pressurising the cooling system and blowing the coolant out.
But yeah, you would more'n likely notice that. I just threw that in to make you start fretting. :blank:

[koba]

If I have blown a head gasket I would notice oil in the water right? and I havent noticced any difference in the engine sound or performance


Not necessarily - it depends what'how the gasket is brukt. I had a Subaru with a cracked head - no oil in the water, or vice versa, just kept pressurising the cooling system and blowing the coolant out.
But yeah, you would more'n likely notice that. I just threw that in to make you start fretting. :blank:

Take the radiator cap off and start the bike, let it run for a bit and give it a bit of a rev.
The water should start moving about more as it warms up. before it gets really hot turn it off.
If you see lots of little white bubbles form in the coolant adopt the following expression: :crybaby:
That will mean a leaking head gasket, but as said with the oil/water thing:
No bubbles is no garantee that the head gasket is fine.

Good choice of bike btw.

Hope that helps.

[cruza]

So you only noticed this after changing the coolant?? What level is the overflow tank when the motor has cooled down(overnight). over flow Tank level should drop as motor cools and sucks coolant back in to radiator. Does the overflow end up empty after a week or so?

[Folcan]

So you only noticed this after changing the coolant?? What level is the overflow tank when the motor has cooled down(overnight). over flow Tank level should drop as motor cools and sucks coolant back in to radiator. Does the overflow end up empty after a week or so?

No I havent changed the coolant.. I just noticed the one day that the reserve tank was way above high when I was doing one of my spot checks on the bike this was when the bike was cool. hadnt been ridden since the day before when I came back from work.

So I checked the radiator and noticed it was abit low.

Any other signs to look out for, for a broken gasket?


I tried squeezing some radiator pipes.. unfortunately I have to wait till the weekend to get all the fairings off

What you people thing the random smell of coolant while riding is.. maybe the pressure builds up and escapes somewhere. It doesnt happen every ride but when it does happen it happens in the same strech of road +/- a few metres.. then other times it doesnt happen at all... lately I havent had it happen at all

[kiwi cowboy]

ok strait out of left field here and im no mechnic but you might have a small crack in the overflow hose and when the engine heats up the overflow goes into the tank but a little goes out the crack onto something hot hence the slight smell and when the motor cools down it sucks air into the radiator through the crack in the hose.
just a thought anyway good luck

[Max Preload]

Check your radiator cap... on a coolant recovery system the cap spring is compressed by the pressure in the hot cooling system to allow coolant to transfer to the overflow tank via the small hose and then when the engine cools, coolant is drawn back in with the resulting contraction through a check valve in the cap. It sounds like that check valve is non-operational and the coolant cannot return.

[cruza]

ok strait out of left field here and im no mechnic but you might have a small crack in the overflow hose and when the engine heats up the overflow goes into the tank but a little goes out the crack onto something hot hence the slight smell and when the motor cools down it sucks air into the radiator through the crack in the hose.
just a thought anyway good luck

Yeah that is what I was think hence my questions, May be sucking air back instead of coolant, Would be nice, but there are the signs there of a leaking gasket , may pay to pressure test the cooling system too. First I'd be warming the bike up from cold to operating temp with fairing off without riding , looking for any coolant weeping out of the lines, A thumb over the end of the overflow line may help.

[Folcan]

Well after playing with the hoses it hasnt seemed to happen again yet. but ill keep my eye on it. and do some of the stuff thats been suggested just to double check

thanks for the help.