Radiator issue?

I have a 97 XJ 4.0L. It is now getting hot on the freeway, but I can have it idle forever and it does not get hot. Last summer I replaced everything in the cooling system (Hoses, 3 row rad, thermostat, fan clutch, etc...) I did not have any issues until now, a year later. I noticed that there was some rust or dirt sediment in my reservoir. So I used the prestone flush and then replaced it all with new coolant and a new Mopar water pump (because I thought that was the issue ). The old pump appeared just fine. :doh: It has brand new coolant, a new water pump, and I even replaced the thermostat with a Robert Shaw balanced one that I usually use. SAME ISSUE!!! Gets hot on the freeway, but will idle cool and will even cool down the engine at idle after freeway driving. WTF!? After driving it around for a couple weeks, the coolant appears to remain sediment free and clean.

Do you think that rusty sediment crap could have already clogged parts of my one year old three row radiator?

I was thinking about the head gasket or head as a possibility, but there is not water in the oil or oil in the water. What do you guys think?

Unrelated I think: I found I had a broken engine mount while looking into the cooling problem. Replaced them both with the Brown Dog mounts.

Coolant sensor was the issue. Thanks for the input.:moon:

Mikey said:

Coolant sensor was the issue. Thanks for the input.:moon:

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Was the coolant sensor the reason your system was getting dirty coolant or the reason it was overheating on the highway? I have dirty coolant and am thinking of replacing the water pump but it does seem fine; possibly a leaky water pump gasket im thinking. I dont have overheating probelms but just dirty coolant. I saw you replaced everything and Im wondering if you'd do it over again.