Coolant tank looks empty but radiator full to brim?

can Anyone help me with this one?
It has never lost any coolant since I've owned it, however I just noticed that the little coolant tank is almost empty so II took off the R/H fairing and opened the radiator filler cap but it was full to the brim. The bike had been parked all morning so the engine was not hot. I have been riding it around and it seems fine but the level in the tank is still below the lower line.The overheat light on the Rev counter has not com on. The engine doesn't seem overhot. Any Ideas? and of course.. is it safe to be riding it?
Thanks,
Simon.

top ur tank back up and keep an eye on it.

[DarrenSV650S]

As you fill the coolant, first the radiator fills up, then you fill the tank up. If you open the radiator cap when the tank is full it will all pour out of the cap.

Aah.. I will try that tomorrow. I foolishley assumed that because the rad was full that there was no more room for coolant, so I didn't put any in (D'oh!)
Well at least I know that it will work with no flippin coolant in it, for a while at least. Thanks for the tip :^)

[embee]

The coolant system is designed to run full, in other words the engine/hoses/rad should have more or less no air in the system. The rad cap has a spring loaded 2-way valve arrangement in it, it sucks liquid in quite easily but only allows liquid out when it reaches a certain pressure (typically about 1Bar or 15psi or thereabouts). This pressure raises the boiling point of the liquid and also minimises cavitation in the pump.

When it heats up the coolant expands and when it reaches a high enough pressure some is forced out into the "expansion bottle". It also vents any gas build up too, systems are designed to cope with some gassing.

Then when it cools and contracts again it sucks liquid back in to top up the system. That's why the pipe goes from the rad cap to the bottom of the expansion bottle. The coolant in the bottle should be between the hi-lo marks when cold.

[Luckypants]

Slight de-rail, but what should you top up the system with? Is normal car anti-freeze (£5 from ASDA) OK or should I go get some special bike stuff from the dealer?

[Biker Biggles]

I think thats normal to have very little water in the expansion tank when cold,as it will rise when the engine is hot.As long as the rad is full things should be fine.

[embee]

Coolant is as big a bag of worms as oil. Some will say it's all the same, others will differ.

Coolant does vary a lot in what it contains and how it behaves, the particularly significant aspects are corrosion inhibitors and whether it is silicate free, and it's how long the coolant keeps its properties.

FWIW I always recommend silicate free type, and for what it costs I use "ready to use" or pre-mixed stuff rather than dilute-it-yourself.
I use Toyota "Red" in everything I have (Red is for Japan built engines, Green for European built), it's a 5 year spec and costs around £15 for 5lts, and in my experience stays nice a fresh (some coolants smell very manky after a couple of years). This is not an OAT spec (does contain phosphates I believe), but in my experience it offers good protection and value for money. Toyota do use an OAT (pink) coolant but it is very expensive.

Audi/VW do a nice "G12+" which performs very well (OAT), and I'd also recommend Texaco/Havoline XLC (extended life coolant) which all the K-series users (Lotus etc) recommend.

Generally speaking, don't mix different types, and considering how little a bike holds it's well worth draining, flushing with clean water, and refilling with a good quality coolant every 3yrs, say.

If you are not actually losing coolant as such, but just need a slight top-up, then probably it has just lost some water due to evaporation, in which case simply use distilled or de-ionised water, or at a push tap water if it isn't too hard (clean rain water is usually fine too).

[yorkie_chris]

As long as rad is full and there is a little bit in the tank it will be right.

Mike just to top up just stick some distilled water in. I don't like adding random antifreeze if I don't know the 2 are compatible.

[Luckypants]

Originally Posted by yorkie_chris

Mike just to top up just stick some distilled water in. I don't like adding random antifreeze if I don't know the 2 are compatible.

Actually it's to completely change the coolant in Speedy's bike (I see my post very badly worded)... I top with water for the reason you state.