So I replaced the waterpump on my 02 dmax. Everything went really smooth. Re-filled the cooling system and verified no external leaks. Checked the coolant reservoir the next day and it looked very black inside. Checked the condition of the coolant and there appears to be oil in the coolant reservoir? I did not have oil in the reservoir before the waterpump was replaced. I have checked the oil level and it does not look like a milk shake and is not overfilling. Did I possibly get a bad waterpump? Have I disturbed the oil cooler pipe on the drivers side of the motor?. I did replaced the gasket for the oil cooler pipe to waterpump. Looking for any ideas.

The coolant system is pressurized, so oil going into it seems unlikely..........

I dunno what to say, I just wanted you to know someone looked at this post.

Oil in water?

Why did you replace water pump?

There is only one thing it could be.

Have fun with your NEW headgasket.

I have seen the oil cooler let oil in to the coolant before. Had to replace the oil cooler and flush the coolant system several times to get it cleaned up.

I thought about the headgaskets but,, when the engine is shut off, you would have 15 psi or so still in the cooling system and would the "push" the coolant into the crankcase. I never get coolant in the crankcase and never looks like a milkshake. I changed the waterpump due to leaking out of the weap hole. Is it possible the injector sleeve o-rings may be at fault? Never thought about the oil cooler however.Thanks for the input

That not exactly true.

I did mine at 149,000 miles and never had coolant in the oil.

I drove with a bad head gasket for 5000 miles before i fixed it and never had coolant in the oil.

When your truck is just shut off you will have some pressure, however, when it cools down you will have little to no pressure.

Get up in the morning and squeeze your upper hose. If it is rock hard, welcome to the gasket club. If not, your lucky.

good luck!

Oil cooler would be most likely source.

Coolant is pumped through the water pump outlet and through the coolant pipe to the engine oil cooler. The coolant flows around the oil cooler element and to the rear engine cover.

40-80 psi of oil pressure will definately overcome 16psi coolant system,but i would think coolant level would rise and overflow as the 16lbs cap vented?