Does your VX overheat with the A/C *off*?

[tom4bren]

Just curious, as it only happens to me when the a/c is on. It can be 110 degrees, sitting in traffic, and if the a/c is *off*, everything is okay. However, 90s, a/c *on*, the fun begins. I'm curious as to who has a VX that overheats *without* the a/c coming on?

Is it possible that the issue is an A/C issue, and *not* a coolant issue?

Another thing.....the corresponding model year Troopers don't overheat, and they share the same drive train.

This is probably not the answer that you are looking for but since I'm an Engi-nerd, it's what I do.

Refrigeration cycles are typically only about 25% efficient in automotive applications.

http://en.wikipedia.org/wiki/Heat_engine

That means 2 things when it gets really hot outside:

1. Your air conditioner is trying to dump 4 times the amount of heat energy than it is actually removing from the interior of the car. It's dumping all of that heat into the engine compartment. As you can imagine, as the outside air temperature rises, it gets more and more difficult to dump all that heat. Added to the problem is the fact that air can only hold so much heat, so even if your AC & radiator are in perfect condition, on a 110 deg day in TX, the combo is probably operating at it's limit.

2. Air conditioners use a lot of energy so your engine is working harder so it's also trying to dump more heat into that same thermally saturated air. Since the typical internal combustion engine is only 18-20% efficient (http://en.wikipedia.org/wiki/Internal_combustion_engine) there is a lot of waste there too. That waste is exhaust and heat.

OK, thermodynamics lesson over.

Any time that your engine overheats, start with checking the cooling system. Power flushing the cooling system and adding fresh coolant usually is all it takes. Sometimes the corrosion inside the radiator has built up to the point that a new radiator is needed. Since you are only overheating with the AC on, I'm guessing that the thermostat is OK ... but ... remember that it could only be partially opening so don't discount that as a problem either. I was told once that water pump impellers errode with use and could also be a culpret. I've never seen any signs of that in any of my cars though. Water pumps typically fail from leaking rather than any mechanical issues.

There ya go. My 2 cents worth.

BTW, several members have added supplimental electric fans to the system to help out on such occasions. Others have upgraded to aftermarket & custom radiators.

[eternal21]

This is probably not the answer that you are looking for but since I'm an Engi-nerd, it's what I do.

BTW, several members have added supplimental electric fans to the system to help out on such occasions. Others have upgraded to aftermarket & custom radiators.

http://www.vehicross.info/forums/showthread.php?t=22533