Mixing coolant question
 

I am replacing my thermostat and the previous owner had green coolant. I was planning on putting yellow back in. I know there is still coolant in the system even though its been drained. Is it ok to mix the two?

just flush the system out with water, it doesn't take long.

Dont mix coolants otherwise it will turn to gel. Flush the system then add a 50/50 mixture of DISTILLED water and mercedes coolant.

Should be compatible.

If there's any question, put a bit of the old coolant in a cup, mix with the new coolant, and see if it thickens.

The old Dexcool aka: deathcool stuff that GM used did gel when mixed with regular ethylene glycol, but it was never green, I wouldn't worry.

There is a block drain on the right side just forward of the starter. that should get out a bunch of it.

Ditto on the Distilled water, flush it and 50/50 mix with Distilled water.

Maybe a good time for a Citric acid flush.

Charlie

Put a garden hose in to the upper radiator tube and run the engine for a minute.

green+ brown = sludge
 

definately do a thorough flush, just to be on the safe side. I have heard that the green stuff and golden brown stuff will turn into a gummy mess when they combine and heat up, all on the internals of your engine.