Please help F650GS overheating

[kzrider]

My F650gs '04 first overheated when slowing after a long high speed run. I topped up the coolant resevoir plus radiator (and bled the system using the bleed nipple on the cylinder head). No improvement. So I removed the thermostat and checked it - it was sticking 'open' rather than closed. I decided to run the bike without a thermostat (whilst waiting for a replacement) assuming this would mean the bike was cooled from start up. The bike is still overheating. There is no weeping from the water pump drain hole and the pipe leading from it up to the radiator is getting hot so I think I am right in assuming theat the coolant is circulating. I have reset the ECU by disconnecting it for 15 minutes. None of this has worked - the bike still overheats. It is not a sensor problem - I know this because if I continue to run the bike when the warning light is on the pressure 'burps' back to the resevoir and vents through the pin hole in the top of the filler cap. I cannot fathom what is happening. If there are any sympathetic tekkies out there please help - I am at the end of my tether!

Aidan

[tonylester]

is your fan working?

[colebatch]

is your radiator blocked with mud?

[cy01]

Stripped the water pump gears a possibility.

[cy01]

I forgot to add should you have a problem obtaining a replacement thermostat.
Take your old one along to a car parts shop as its my understanding the thermostat from a VW Lupo or pre 2002 Golf will fit.

Good luck
Chris

[Tony P]

Failing Colebatch's suggestion of checking for a blocked rad (which he know all about from my Dakar!) I would follow cy01's suggestion of water pump area.

Although not weeping through the drain hole beneath (but you are not experiencing fluid loss are you?) that does not mean the shaft or impeller is turning OK.

A new shaft pump kit is about £25 from Motorworks and the two gear wheels about the same. It is a straightforward hour or so to replace - except on a Dakar where the oil pipe is a real bitch. Be prepared with a new clutch cover gasket - or the means to make one.

[navalarchitect]

Assuming you have checked the radiator is clear my thoughts of things in priority order to check before you assume a mechanical failure of the pump or other major problem:

(i) Check cooling fan is coming on - fan or its sensor could have failed.
(ii) Check radiator cap - a failing (hard or cracked) seal will stop system pressurising as it is suppossed to do and cause overheating. Best check is often replacement - they don't last forever.
(iii) In some car engines removing the thermostat can cause overheating - this is because it allows an accelerated flow rate through the radiator which gives insufficient time for the water to be cooled. So fit the new thermostat and check if that applies here.
(iv) Anti freeze is also an anti-boil fluid as it raises the boiling point of the coolant. If the mixture has become too weak due to periodic topping up with plain water (or from not changing it for many years) you can get over heating symptons.
(v) Similarly if the engine has been run for awhile without enough anti-freeze in the mixture - scale and corrosion in the passageways of the engine can be restricting flow. Descaling and flushing out engine and radiator with lots of clean water may then help.

If all of the above don't solve it then:
- could be failed water pump.
- could be a blown head gasket.
- could be an ignition timing issue ( but you'll usually notice lots of other symptons such as lack of power first).

Try the simple ones first - in my experience 90% of the time its one of those. Good luck.