Oil in coolant reservoir on 1998 Jeep Cherokee

I had the tranny cooling radiator replaced. I was getting light-brown sludge in the rediator and reservoir. Now I have dark-brown sludge only in the reservoir; radiator seems clean ( unless the sludge settles to the bottom). What's up?

Asked by for the 1998 Jeep Cherokee
1 answer
Clean out the coolant reservoir, maybe the oil from the trans cooler settled in the reservoir.