the bike is a 2009 280 gasgas

i have taken the coolant cap off to check level was ok and found lots of oil in there, my radiator if full of thick gunk

does any one know why my oil is mixing with my radiator fluid

many thanks

Hi

I can only think of 2 ways that oil can come into contact with the coolant.

1. Cyl head o-ring failure
   
2. Water pump seal failure
   

Truth is though, in most cases where there is a seal leak you lose the water to the oil, not oil to the water. This is due to the water being at higher pressure than the gearbox almost all of the time when hot. The most common indication of this issue is milky coloured gearbox oil.

If it were a leaky cyl-head o-ring you would almost certainly be losing water gradually. This often coincides with a hard to start engine and overheating.

Hmmmmm.... did you fill the coolant last... there isn't a chance some oil got into the radiator or hoses during a stripdown??

Dom

the bike is a 2009 280 gasgas

i have taken the coolant cap off to check level was ok and found lots of oil in there, my radiator if full of thick gunk

does any one know why my oil is mixing with my radiator fluid

many thanks

Possibilities for a start:

Trans breather is blocked and pressure buildup has forced oil past water pump seal.

Clutch hub capscrew replaced with non-drilled type.

Aftermarket additive added to coolant that has congealed.

Head o-ring allowing combustion byproducts into cooling system (usually causes overheating).

Jon

water is always at a higher pressure than the oil so the mix technically should always be in the gearbox. i suspect congealed coolant additive

Problem was the head seals blowing combustion gases into coolant signs on this were removing cylinder head