Coolant temp rises on freeway (1 Viewer)

[HemiAlex]

I've been driving my truck daily after a serious refresh. Completely new cooling system with exception to the thermostat that is going in this week.

-New CSF radiator
-Aisin fan clutch
-Aisin Water pump
-New OEM hoses for coolant and oil cooler
-50/50 premixed coolant burped several times.


I drive 18 miles to work at 60mph. About halfway into that trip which is 95% highway I start to notice coolant temps rising at a constant cruise. I'm having a debate between the thermostat function acting up and being inconsistent or the airflow at speed not being able to keep up with the heat created by constant 2500rpm.

Either way, I am about the width of the pointer from being in the red after I get off the freeway and it slowly drops temp from there. If I hold the throttle at 1500rpm while at a stop, it comes down much quicker. Around town in 90* temps with the AC going in bumper to bumper traffic it never goes above half way.

Is this normal operation of the cooling system? Am I being too critical? This isn't the first old car I've had without an electric fan, but it is certainly the first with such a wide spread of operation on the temperature.

 

[Wingit]

Have you done a leakdown test?

 

[HemiAlex]

On the cylinder head or coolant system?

 

[Speen Shaytan]

Check the tension on your belts, I had something similar to this happen to me a while back. The lock nut and tensioner came off my alternator and let the belt slip a bit. Freeway driving would overheat, but lower RPM driving would cool very quickly. I put on a new lock nut and made sure the belt tension was good. No problems with it after that.

If that's up to snuff and there are no leaks/blockage in the cooling system, what else did you do on the refresh? Timing and AFR can also affect cooling.

 

[SteveH]

Are you going by the factory temp gauge or a quality aftermarket gauge? Overheating on the freeway is a classic 'clogged radiator' scenario, but in your case, perhaps a radiator hose is collapse or blocked, since your radiator is new. I would also do a compression test on the engine to double-check against a head gasket issue.

 

[Output Shaft]

Get a handheld IR temp gun. The next time the temp spikes, pull over and shoot the gun at the top front driver's side of the radiator, across from the inlet hose, pointing the gun backwards.

Verify the temp.

Compare that temp reading to what it says when the dash gauge reads "normal". The stock oem temp gauge has long and checkered past giving drivers incorrect temp readings.

 

[Elbert]

is fan shroud good? and what is the temp reading in "F" on the engine when the gauge shows close to red? no the temp gauge should not be close to the red mark, assuming the gauge is correct. Also do you have air in the cooling system?

 

[roscoFJ73]

Did you put a new radiator cap on it? Do the hoses get hard with pressure when its hot? If they don't hold pressure,the coolant begins to boil and make steam bubbles around the cylinders.

 

[orion]

I've read that big fog lights like I see in your avatar pic really screw up airflow on a 60...especially at speed. Turbulence, eddies, all that...effectively blocking air from flowing through the radiator.

Those still on the truck? Maybe try removing them, see if that helps.

- Brian

 

[TobyB]

When it's overheating, do a flying pullover and see if the lower hose is hot- like, way too hot to touch
(bonus points for IR temp readings)

If the lower hose is HOT, the radiator's underperforming. Time for new radiator. New radiators CAN be bad, but it'd be unusual. Unless it's blocked.

If the lower hose is cool, then
it could be
-head gasket, blowing coolant out of the block and head. (usually, you'll lose coolant if this is happening)
-thermostat sticking. Or not opening far enough
-slipping belt (I like this one- it's easy to fix)
-blockage inside something. This one is hard to find.

hth

t