Oil from radiator

The bike is a 2003 wr450 f. Have been having problems with overheating since I bought the bike used. The over flow had been removed for unknown reasons, maybe the over sized gas tank took over the space need for this? Recently the problem became much worse. I noticed a bit of fluid coming from the "weep" hole on the pump. This quickly turned to water/ oil coming from some where in the body of the radiator ( behind the cooling fins). It is definitely oil, and I am definitely loosing oil level from the crank every time I ride/ check the level. My head gasket is a bit wet with oil but not so much so.

I am thinking the seal in the pump is shot and leaking oil to the radiator. I have not confirmed whether the pump is even working. I had a lower radiator hose come loose/disconnected during my last ride and there was no sign that fluid had been flowing from the hose when the bike was running ( I am assuming that the fluid would not flow with bike off?). My power/compression seems fine.

Replace seal?

Replace entire pump?

I have to assume the radiator needs replacing?

What other damage may have occurred from this condition? All help is greatly appreciated.

Edited by davidjay

I guess I will be the first and hopefully not the only to reply. After some investigating some around the engine with the tank off. I have found what looks like a an opening to the engine where I believe the oil was coming out onto the back of the radiator. I looked a t my sons yz and he has a cable for decompression going in to that exact spot. I did not have this function but have found some reference to a "decompression plug". Any one shed some light here?

Yup! Your looking at the area that on previous models, had a decompression lever there. The factory one in '03 has some issues in that it sometimes falls out. Seems like you need one to replace it! I believe ThumperTalk sells some.


Thanks for the feedback.

I took a look at the parts page for the decompression plugs. There are allot there. Can any one tell me what size would fit my 03 wr 450?

Sounds like you my have 2 issues: the missing decompression plug and a weepy seal on your waterpump.

I just searched eBay for a plug for my 04, easy to find in whatever color you want/need. Search for YZF decompression plug, takes 5 minutes to install. TT was out of stock and it was hard to pinpoint tge right one anyway.

Fix that, clean stuff up and see what's still leaking. It your dripping coolant sti out the weep hole, search waterpump seal replacement on here and you'll be golden.

FYI, the tank has nothing to do with the overflow bottle, it's supposed to be under the left side panel. The PO of my bike removed it as well for some dumb reason (it literally weighs ounces) so I re-installed it after purchase, no issue there either unless they replaced side panels with YZ ones; then you just have to cut out the "cast" in area where the reservoir passes through.

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