Overflow tank probs

[snuffle]

Was doing a coolant change yesterday and decided to empty the overflow tank, so took off the tube running up to the rad cap expecting all the gunk to run down - nothing happened. Tried pumping air into it, no good.coolant inside it is in awful shape. Any ideas about getting it out, pipe cleaner? Must be some blockage in there or at bottom of tank- cheers.

[Buzzin (^_^)]

Hmmm....if nothing else helps I think replacing it should be too expensive...
But you might want to remove it completely and try running water through it....if needed with a bit of pressure...

and remember to fill the system from the cap, not the overflow (but I guess that was clear already)

[McF]

It is a balanced system, so nothing will flow from the main system into the header tank unless it's under pressure.
Nothing will flow out from the Header Tank unless the level gets too high and it has a degree of pressure.

If there is fluid in the Header Tank and you piped some air in there, I'd expect the fluid to have drained, at least a little.
The outfall is only about 6mm dia, so it could easily block.

If you can figure out which pipe is the breather for the Header Tank, it will be worth taking a piece of wire and feeding it up and into the header tank. I'd suggest one core taken from a 240V multi core cable.

I would be very surprised if you needed a new header tank, but I'm pretty sure I have a spare if you do. They are a pig to remove or replace with the engine in situ though!

As for refilling, make sure you use the correct mix of coolant with distilled water (tap water has too many impurities for the alloys and mixed metals etc in the engine). Fill the main system to the neck of the filler/pressure cap, refit the pressure cap, then fill the header tank to the limits marked on the outside using the main opening.
Make sure all of the hoses are properly connected, refit all the other bits and pieces you removed to get at the engine, then start her up.

Once the engine reaches normal operating temperature, the coolant in the main system expands and opens a small relief valve in the pressure cap allowing coolant and probably a bit of steam to escape into the header tank where it is held.

When the engine cools down, the coolan cools and eventually pressure drops in the main system and creates a partial vacuum. This sucks coolant back from the header tank and into the main system. All of this helps to keep the system balanced.
The clever part of this is the two way relief valve in the pressure cap; take a look at it before putting it all back together.
Provided you fill the system properly and maintain clear tubes etc, it will all work perfectly.

Good luck and please report back

[snuffle]

Thanks for your replies, have noticed temp gauge will rise quickly when I stop after a spin on the motorway, bit worried that no coolant can reach the o/flow tank, good idea about the electrical cord! let you all know what happens.

[odie]

large syringe and a length of plastic hose (enema any one?), suck up / out what you don’t want, also works if you have over filled you engine oil or fork oil.
Rick

[snuffle]

Well I spent most of Saturday on this. Released the hose from rad cap and brought it under the o/flow tank, still no outflow. Took off the hose - nothing,got a bicycle cable into the tank and hurrah the muck started to flow. Started to rinse out the bottle but it kept getting blocked, decided to remove the bottle. Wheel off, shock off ( stupid mudguard positioning), bolts holding bottle on are a bugger! Bottle out and theres no way I can remove the crap inside, luckily I have my old 180,000 mile bike out the back, so same procedure and I have a clean tank. Installed it, flushed the coolant again and all seems fine. Wait till I tell you about my cooling fan woes!