Rust colored & thick coolant in overflow tank?

[Red.1998.SLS]

just for everyone's info, I just went outside and looked at my coolant, changed 2 1/2 months ago, almost rust color, has some mud, looking sand, in it, if I were joezaier, I would follow Ranger's prior instructions and clean the stuff out of the coolant, watch my temp, don't overfill the coolant, if that helps, maybe change coolant, if not block test, but it sure sounds like maybe too many tabs or just time for a good change.

[submariner409]

Stop speculating and guessing, take the car(s) to a good shop or GM dealer and have them do a coolant change using their vacuum removal/fill machinery and work based on the latest TSB procedures. They get all the old coolant out, all the new coolant in with no air pockets or overheating problems, and you get a properly maintained car and some warranty out of the job. For an hour of your time, $140 and a cup of coffee in the waiting room, it's a no-brainer.

FWIW, my coolant was changed in 11/07. It has not changed in level one millimeter since, and is clear orange-red with no hint of sediment or "mud". The thermostat sits on 12:00 at 45 or 130 mph. It will go to 225 in heavy traffic with the A/C OFF: normal as fans are then commanded to slow by the temp sensor, not the A/C system.

[the recluse]

Now I know that you guys are saying that it's a common thing for the coolant to be "rusty" looking; but this doesn't sound right at all...

The problem is WHO changed the coolant last, did they flush it? did they reverse flush it? was the proper coolant in there before? was any coolant in there before?

If there looks to be "sediment" in the radiator, you should have to whole system flushed properly as I suggested before. If you've never done it, follow submariner's suggestion.

Some guys just "drain and refill" which doesn't get the sediments out of the block (sediments usually only form with either bad coolant or no coolant), then, with new fluids, the sediments get stirred up and end up in the radiator where they sit in the cooling tubes and block the radiator from cooling properly. Over time the sediments also form "clumps" that don't break up well and you need to have the radiator removed and steamed out or replaced...

[Ranger]

There should not be any sediment IF you use distilled water.

[Red.1998.SLS]

I think that the answer to the original question is that the coolant should be changed, check the codes, if the temp goes normal after change, drive the sh't out of the car and have fun.