1997 LC heating up gradually only with A/C on. (1 Viewer)

Joined
Oct 24, 2007
Messages
135
Location
ELP, TX
Hi everyone. Here is the mystery of my truck. An overhauled was performed by a local shop. Engine runs smooth and everything is great until I turn the AC on. The temperature starts to slowly climb to almost 3/4 of the temp gauge (I turn the AC before getting to the red) But as soon as I turn the AC on it comes back to half and stays there. It has never spilled antifreeze nor has given me the smell of it.

So far, this is what I have done:

Water pump: new
Thermostat: new
Fan clutch: Aisin new (Planning on changing the oil to thicker viscosity as the blue clutch kit)
Electric fan: (turns on when AC is on)
Antifreeze: New
Timing: Checked to Factory spec.
Radiator: 1 yr old, but I still took it to get it flushed.

1.-Has anyone had this problem? if yes, how was it fix?
2.- Can this be a bad temp gauge?

Any pointers would be greatly appreciated.
 
Joined
Nov 18, 2019
Messages
328
Location
Albuquerque NM
Need more info. Is your temp gauge stock or modded? Do you get rising temps when idling or at freeway speeds, like going up a hill?
 
Joined
Nov 13, 2002
Messages
576
Location
The Saratoga slums, CA
Have you gone through the steps to burp the system of air?
With all of the replacements that you made it wouldn't surprise me that you might have air pockets trapped in the system.
 

flintknapper

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Joined
May 22, 2004
Messages
9,204
Location
Deep East Texas
The fact that the rising engine temperature only happens when the A/C is on (additional engine load) suggests your cooling system is right on the 'cusp' of being insufficient. The cause(s) of course, yet to be determined.

You've certainly taken sensible steps to remedy the problem.

Can you expand a little on what the 'overhaul' involved and the mileage on the engine prior to that?

I would definitely do the fan clutch 'mod' if you live in Texas (as I do). A new blue hub clutch with 20K cst silicone fluid should suffice. The 'new' radiator was what brand/type?

Be certain you have a new OEM radiator cap (I did not see that listed).

Timing (factory spec) is 3° BTDC......BUT if the timing chain was not replaced and IF it had any significant stretch.....you might benefit by advancing the ignition timing a few degrees.

You might already know...but the factory dash gauge has a HUGE 'dead spot' in it and I encourage everyone to acquire some form of aftermarket monitoring system (ScanGauge or something similar) that allows for real time readouts of coolant temps and more.

ScanGauge temp.jpg
 

rdcnj

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Joined
Jan 6, 2019
Messages
136
Location
NJ
I think the only way to start to determine the root cause of the problem, is to digitally monitor the temperature the computer is reading.

There you can compare the gauge movement to the actual temp the computer is seeing.

This helps you determine is the gauge is acting up or if the problem is stemming from something else.

From that conclusion, you can start to develop a plan of action.

We recently had a 1990's Corvette that appeared to go from mid range to overheating after driving a short while. When we used the method above, we found that it was really a 10 degree variation in temperature, which means the gauge was inaccurately representing the temperature... not the actual vehicle overheating.
 
Joined
Oct 24, 2007
Messages
135
Location
ELP, TX
Thank you guys. I will start by purchasing a digital monitor. Seems like most of you uses two brands and they basically do the same thing. Winter is here and everything looks fine. The timing is something that I do have to double check. My truck had 240k by the time I decided to do a full overhaul (top and bottom) . At idle it does the same thing (only heats up when AC is on).

The Radiator is not Toyota ( Will be corrected in the future). But that same radiator/fan clutch was working fine before the overhaul. So timing and bad gauge is what I have in mind.

Again thank you for your advice.
 
Joined
Oct 24, 2007
Messages
135
Location
ELP, TX
Have you gone through the steps to burp the system of air?
With all of the replacements that you made it wouldn't surprise me that you might have air pockets trapped in the system.
_______________________________________________________________________________________________________________________________________

How do you burp the system of air? I will research the concept. Thanks
 
Joined
Oct 24, 2007
Messages
135
Location
ELP, TX
Burping cooling system.

Step 1
Allow the engine to cool down to ambient temperature.
Step 2
Open the radiator cap.

Step 3
Turn the engine on and turn the heat to max. Turning the heat to max allows the radiator fluid to circulate through the cooling system to ensure that all air pockets are eliminated from the system.
Step 4
Rev the engine to 2,000 RPMs and hold for approximately 10 to 15 seconds and repeat two to three times. This will allow the radiator fluid to circulate throughout the whole system and ensure that all air pockets exit the radiator.
Gently squeeze the upper radiator hose approximately 6 to 12 inches from the radiator cap. Squeeze about five times. This will bring more air pockets up and out of the radiator and will ensure that the engine does not overheat.




References
 

REKCUT

SILVER Star
Joined
Jan 5, 2005
Messages
4,637
Location
Rogersville, Mo.
There are multiple choices for gauges from hard wired to blue tooth. I use the torque app and a blue tooth reader on my truck. I am going to hazard a guess that your truck has been running warm and on the verge of overheating but your factory gauge won't show that info. You will get better help once you install whatever choice you make on temp gauge.
 

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