Coolant temperatures while towing

[1998_K1500_Sub]

Here's what I have for AC under "System Parameters."

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So those numbers give an indication of where The General felt the ECU should begin taking evasive action against overheat.

 

[South VA]

Here's what I have for AC under "System Parameters."

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So the A/C shuts off automatically at 258.8º, correct?

Based on that, 225º doesn't sound so dire.

 

[1998_K1500_Sub]

So the A/C shuts off automatically at 258.8º, correct?

Based on that, 225º doesn't sound so dire.

Yup, sounds like it. 258F is 10F below boiling for 50/50 coolant. I have reason to believe those AC thresholds work; I've not tested the temp threshold but I have tested the RPM threshold (and it worked, at 3000RPM per my config).

Thanks @df2x4 for the aux fan numbers spec'ing a 225F turn-on.

 

[L31MaxExpress]

There is a fairly substantial fuel economy and power loss running that hot. If that truck has the basic 5 bladed steel fan I would upgrade to the 11 bladed fan or the 9 bladed early Duramax unit.

 

[1998_K1500_Sub]

Thanks for this. If I'm understanding correctly, the aux cooling fan comes on at a hair over 225º F, which is the highest temperature my Suburban reached on the trip to Richmond. It then went down to 221º after a short while. Is it fair to say that the aux fan coming on dropped the coolant temp those few degrees?

Maybe... it depends on your speed, if you were faster than the turn-off speed, then "no".

Both conditions need to be met for fan turn-on, speed and temp. If either isn't met, Mr. Fan is off.

 

[South VA]

Maybe... it depends on your speed, if you were faster than the turn-off speed, then "no".

Both conditions need to be met for fan turn-on, speed and temp. If either isn't met, Mr. Fan is off.

Interesting. It was above 50 MPH, so according to the chart the aux fan wouldn't come on. I wonder why it only stayed briefly at 225º.

 

[South VA]

There is a fairly substantial fuel economy and power loss running that hot. If that truck has the basic 5 bladed steel fan I would upgrade to the 11 bladed fan or the 9 bladed early Duramax unit.

Sounds like a worthy upgrade. Would either of those bolt right up to the 454?

 

[1998_K1500_Sub]

Interesting. It was above 50 MPH, so according to the chart the aux fan wouldn't come on. I wonder why it only stayed briefly at 225º.

Stupid question: Might your thermostat be functioning improperly? Partial opening at spec'd temp, wider opening at some higher temp? Just a wild guess on my part...

I know some thermostats are better than others. My Honda's OEM thermostat is a visually complex, dual-spring thingie that regulated temperature better than a cheapie replacement thermostat (ask me how I know).

Maybe a new 'stat should be part of your coolant service.

 

[South VA]

Stupid question: Might your thermostat be functioning improperly? Partial opening at spec'd temp, wider opening at some higher temp? Just a wild guess on my part...

I know some thermostats are better than others. My Honda's OEM thermostat is a visually complex, dual-spring thingie that regulated temperature better than a cheapie replacement thermostat (ask me how I know).

Not a stupid question, at all. Might be worth replacing that as well, when I flush and drain the coolant. I have no idea which thermostat is in there; probably not the original. Unless recommended otherwise, I'd probably go with OEM.

 

[L31MaxExpress]

Sounds like a worthy upgrade. Would either of those bolt right up to the 454?

Yes, with the right fan clutch being used. Is your current fan clutch attached to the water pump with 4 bolts or is it a thread on?