creeping up engine temps on interstate - fan clutch? rebuild or new?

[outdoor7or24]

So I have noticed on last two vacation road trips that my Ultraguage is showing increased engine temps as get above 70MPH. At lower speeds my ultraguage shows temps of 190-195F, even under loads like going up hills in the mountains. At highway speeds 70-75MPH it is showing 203 to 208F. When I slow down the temperature decreases.

Truck has 250k on it. No idea if the fan clutch has been replaced. I know PO replaced radiator.

Fan will spin some when engine is cool, I need to test it when hot to see if it spins more....

1) should I rebuild it with new oil, it is hot here in SC for 5 months out the year OR does this mod using 10k silicon oil even help? From what I read on forum it appears to be very little help for the hundy.

2) If I go new it appears OEM or Aisin or can I get by with the local car parts store brand? Is there really a difference?

3) Anything else I should check?

 

[guardcompany]

Sub'd. I'm in the same boat. Just did a full coolant flush, hoses and new t-stat and still having the creeping up engine temp. Just got to 201F going up a small hill this weekend.

 

[outdoor7or24]

Cool. Hope to hear others chime in.

 

[Manhattan]

I wouldn't think the fan would be a factor at 75mph. But, that's just a guess... while you're waiting for someone, who actually knows what the hell they're talking about to weigh in

 

[jerryb]

my fix was the radiator. Everything minus the waterpump was new. It's funny to realize that it's easy to replace all the little things, but the ten year old or more radiator is still expected to be as efficient as the day it was installed as long as it doesn't leak. If your radiator is 8+ years old, replace it. It's cheap and easy. Anything else of unknown age ought to be replaced also.
If you have freeway creep, turn on the heater and see if temp falls. If it does, I would assume radiator inefficiency, debris in the fins or core, or maybe a hose that collapses at speed.

 

[abuck99]

Is 208f a problem in 95degree + ambient temps? I don't think so. 220's might start to raise some concerns.

This time of year my coolant temps range from 195-203f.

 

[jerryb]

I don't think 208 is a problem, it's just a sign.

 

[kelly saad]

This is exactly what I was thinking. The cooling system is still keeping it cool, there is just more heat being produced at times so the temps are up a little more during those moments. I wouldn't stress out if it cools off right away, and isn't really getting too hot. The fan is only doing its job at idle, so that's not it.


I have done the heater blower on trick, it can work. At least have the radiator checked, don't trust what the PO said.