oil in cooling water

[Klausen]

I bought a used EC 300 2009.
There is some oil (white film) in the water.
The piston, gaskets and o-Rings are new.
Where can I look for the leaking?

[wardy]

waterpump seal

[GMP]

First thing I'd do is drain/flush the coolant, refill with water, run it a bit and see if it returns. There is a chance its just some trace oil from top end assembly (sloppy?). Other than that I'd suspect a pinched inner head o-ring but usually that also causes pressurization of the system and what appears to be a boilover. Water pump seal or side cover gasket are also top contenders.

[Klausen]

OK I make some fotos of the cylinder and C head
I think there are a very bad casting - is this critical
I don't believe it was oil it was a white film may be aluminium corrosion
I don't know if the GG is boiling because I don't ride it a longer time
water pump seal was OK
side cover gasket I don't inspected

[Klausen]

[GMP]

Yes that is poor QC on that part. Its very close but the oring groove is not breached as far as I can tell. I would clean it up, flush the system, and run it with fresh good coolant. I never ride my new bikes with the factory coolant, and I have seen traces of contamination when removing the cap. To me this is no problem as I assume its just oil/grease traces from assembly. I think that if this were really leaking, your cooling system would be pressurized with combustion gas and appear to boil over very quickly.

Oh, your English is fine and better than my German, which consists of several old drinking songs taught me by a few German engineers when I worked for a TUV office here in the USA.

[Klausen]

my dealer say there is know problem - keep cool
the new 300 cylinder look the same
I will assamble the head and run the GG.

Oh, your English is fine and better than my German, which consists of several old drinking songs taught me by a few German engineers when I worked for a TUV office here in the USA.

thanks to www.leo.org

[jiauka]

Originally Posted by wardy

waterpump seal

+1, check BOTH seals

[GMP]

Could be, but my thoughts are always go where you have been last, or someone else has been last. Also, I would expect coolant in the oil before oil in the coolant for a bad pump seal. Bad pump seals on these bikes are rare, in ten years and four bikes I've never had one leak and only replaced one as part of a complete bottom up rebuild.

[Eric K]

Waterpump seals have failed for me a number of times.

On my '01 GasGas 300 (481 hours), I had to replace the waterpump seal 3 times since new.
On my '06 GasGas 300 (216 hours), I had to replace the waterpump seal 2 times since new.
On a friends '01 GasGas 300 he had to replace the waterpump seal once.

Most of the time coolant goes into the transmission oil. Once I had oil in the coolant.