Oil in the radiator!!! Where is it from?

[roverintherockies]

So I have a 2004 Kia Optima and the heater stopped blowing hot air a few days ago. I added some antifreeze. No change. I opened the radiator cap and mustard flowed out... The puzzling thing about this is there is no mustard in the motor... Is there an oil cooler line that goes into the radiator? and what is the possibility of that section of the radiator blowing and leaking into the antifreeze? Also just to let you all know I just had the timing belt changed about 4 months ago after it broke when I was sitting at a stoplight. Does this have any possible relation to the problem that I am having now? Please help me in any way possible it is my only car.

Btw it is the 4cyl (i cant remember the litter size)

[pulsar86]

Unfortunately you may have a water channel in the head that has corroded and is now in contact with a oilway. If it is milky white in the radiator this is the most likely cause, also check to see if you are getting bubbles in the radiator top tank when the engine is running. Pull out the spark plugs and check the condition and look for moisture on the plugs. If the plugs are getting wet I'm afraid the head will have to come off to investigate further. A compression test would confirm if the head is at fault. The only other thing I can think of that may cause a similar problem is that if your car is an automatic and has an oil cooler that is leaking into the radiator[ I'm not sure how transmission fluid would look if mixed in the coolant] but I think you could tell by the smell.. If the colour is mustard like you say I think it is more likely to be transmission fluid because engine oil would show up milky white.

[roverintherockies]

Thanks for the help... I checked the plugs no moisture... There is (I just double checked the oil dip stick) no milky substance in it... I checked the tranny fluid and no milk to that either... just in the rad... The color of the anti is like dijon mustard... a darker creamy yellowish color... Are there any diagrams of the cars cooling system around?

[pulsar86]

It doesn't sound like it is engine oil then , which is good. Are you registered on www.kiatechinfo.com it is free to register and will have online manual for your car[go to shop section after you register], plus a lot of other interesting things if you look around the site. Have you got any pipes for a transmission cooler leading into the bottom tank of your radiator? I would say that might be the problem [leaking trans cooler]