Hi all. Just had my timing belt and water pump replaced over the weekend. I was checking the coolant today to see if it needed to be topped off and found oil? In the overflow tank. I say it is oil but I am not sure. It is dark brown and somewhat sticky. I thought that oil when mixed in with the coolant would look kind of milky. This isn't, it is dark brown. I am beginning to think the previous owner might have added a can of stop leak to the radiator at some point though I can't see any indications of a leak. The tech that changed the belt and pump did say that the water pump was leaking. Has anyone ever seen this and should I be concerned? I plan to take the car to have the oil changed and brake fluid flushed soon and thought I would have the radiator pressure tested and possibly a citrus flush.

Any thoughts?

 

You are probably correct about the PO using stop leak, but I understand that the coolant has to be drained (at least partially) for a TB change. Did the mechanic mention the brown goo?
However, if it is oil, 2 sources come to mind;
1. ATF fluid leaking out of the transmission cooler.
2. Engine oil from some source - head gasket, etc.

 

At least get it all cleaned out. Drain some of the fluid out from the bottom and look at the condition. If it's dirty there too you need to stop driving and get it fixed.

 

when a headgasket goes the oil looks like chocolate milk.the coolant would look like sludge and the oil would stick to the overflow tank.bring a glass jar and have the person who is changing your oil fill the jar to see if there is coolant in the oil.good luck.

 

Thanks for the replies. I am leaning toward stop leak as it is dark brown and sticky, not oily feeling and not milky looking. Sticking to the walls of the overflow tank. When I removed some coolant it looked clean and pink. Does Lexus do a citrus based flush and do you think this would clean out stop leak, if that is what it is? I will have it pressure tested tomorrow if possible. I suspect the water pump was leaking (mechanic told me it obviously was) and the PO used stop leak instead of repairing correctly as they were trading in on a new LS460. Worst case, I hope, is that I have to replace radiator.

 

Get that all flushed out and new toyota red.