89 k1500 gets warm only on the highway

[Nopainnogain445]

If you are doing the radiator, do the thermostat. The brown fluid also means that the inside of hoses are being eaten away. How old are the hoses? Temp sender?

Hell, as easy as it is, I would look at the impeller of the water pump. What quality is that 2 year old water pump?

It’s just an orileys water pump my dad threw one there before I bought it

 

[Nopainnogain445]

When doing very complete flush remove heat exchanger hoses, and use your garden hose to moderately power flush, both directions. And watch the crude blow out. The exchanger can like a settling pond , filling with crude . When flushing , block drains should be removed also, to flush low areas in block. Is top radiator tubes filling with crude reducing flow? Pull thermostat, in pan of water boil it , at what temp does it open? (Physical test of thermostat.) Test radiator cap, hold pressure, seal is good. That's a start.

When doing very complete flush remove heat exchanger hoses, and use your garden hose to moderately power flush, both directions. And watch the crude blow out. The exchanger can like a settling pond , filling with crude . When flushing , block drains should be removed also, to flush low areas in block. Is top radiator tubes filling with crude reducing flow? Pull thermostat, in pan of water boil it , at what temp does it open? (Physical test of thermostat.) Test radiator cap, hold pressure, seal is good. That's a start.

Forgot to mention I put a new rad cap on there, I also had tested my new thermostat and the old one, the new one opened up significantly sooner than the old one and seemed to open up more so I think it’s good

 

[GoToGuy]

Testing, meaning it opens at correct temp.

You must be registered for see images attach

 

[Nopainnogain445]

Testing, meaning it opens at correct temp.

You must be registered for see images attach

Had a thermal temp gun on there it opened up around 190 degrees

 

[Nopainnogain445]

I am guessing that it is a clogged radiator and heater core problem. Theoretically, you don't need a fan working at highway speeds because of the volume of air flowing over the radiator at that high speed. The fan clutch would pretty much go to neutral at highway speed and work much harder at slower speeds to pull air across the radiator.

Ok so I flushed the system and put some radiator flush in there and drove around a bit, then flushed that fluid out and dropped in new radiator, seems like it’s running cooler the temp got up to 210 on the steepest prt of the drive where it used to get up to 230 but dropped back down after, should it still be going up like that or should I flush it again, it’s just got water in it no coolant and a bottle of radiator flush right now.

 

[movietvet]

210 or under is ok. My 2005 Tahoe runs all over the place at just under 210 with no problems.

 

[Nopainnogain445]

210 or under is ok. My 2005 Tahoe runs all over the place at just under 210 with no problems.

I’ll flush it another time or two to get all the crud out of the motor and keep an eye on it

 

[GoToGuy]

Today down the highway, 75 to get to dentist on time. 195 thermostat, never over 200.
There are times when a direct reading thermometer is less prone to errors.
Empty truck , running that high ? You would think it would run cooler, good flush, thermostat, no leaks. Gauge error?

 

[Nopainnogain445]

Today down the highway, 75 to get to dentist on time. 195 thermostat, never over 200.
There are times when a direct reading thermometer is less prone to errors.
Empty truck , running that high ? You would think it would run cooler, good flush, thermostat, no leaks. Gauge error?

On the way to work downhill to work about 15 minute drive 65 mph never gets over 195 it’s only once I hit a steeper hill it seems then once it flattens out it’s fine, I don’t believe there is anything wrong with the guage, the water pump is completely rusted on the outside, I might replace that because it could be the same on the inside.

 

[Sean Buick 76]

I would call it a win and setup the coolant for -40 and call it a day.