I just had the water pump replaced on my 93 SL1 and the coolant refilled (not flushed) after an overheating incident. But looking at the new coolant, it appears dirty and gray (not brown). There is a gray sludge on the surfaces of the tank. It doesn't smell like oil, but it's hard to be sure. There is no evidence of a head gasket leak, and so far the car's cooling system appears to run normally during both interstate and local driving.
What do those coolant pellets look like after they're dissolved? Is it possible that the shop added these and they just weren't added before, when the coolant appeared uniformly clear and green for years?
Or can refilling a system that has never been flushed before stir junk up (especially after overheating)?
Trying to decide whether to get a flush. Thanks.