Cabin Air Gets Cooler???

Joined
Sep 18, 2002
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Location
VA
In my '98 LS400, I was starting to notice that the air would heat up to whatever I set it at. Maybe drive an hour and notice it would get cooler. Noticeably cooler. Just figured it was my old age, thin skin, etc. Well, one day my wife was with me and she said "Why is it getting colder? We haven't adjusted the temp controllers."

I change my coolant every two years (30k). The reservoir is full. Any suggestions as to where to look? I ran the temp gauge to MAX HOT and let it run for 5 minutes as we were driving down the road. I then went to MAX COLD and ran it for a little while. Week later I still get that cool feeling after I have been
driving a while. I really thought I was the problem until my wife said something without me ever mentioning it to her. Maybe we both are getting goofy.
 
Hey, I just remembered. When that guy fixed my car earlier, I wonder if he loosened that cap on top of engine to let any air out?
It's under that plastic cover and he might have not known about it.

I'm gonna check that first.
 
Just put a new thermostat in when changed timing belt and I am OCD on cabin filters. Don't know about cabin sensors.
 
I experience something similar in my Explorer. I don't have any testing to back it up, but I suspect the area around the interior temperature sensor gets heat-soaked after a certain amount of time (hot air running through the HVAC ducts, sustained warm air in the interior, etc.). If true, this would cause the temp sensor to be satisfied at a lower ambient interior temperature, and stop kicking out heat.
 
This just started happening after my last repair. FYI
 
Plus 1. If you don’t already own one, I suggest you buy a laser guided infra-red temperature gun available at most hardware store or amazon. Use it to check the components such as rad, block, heads, thermostat housing, and each hose.
 
Of course, one trick to make sure coolant is circulating properly, is to rev up the engine.

If you are using the auto temp selection, it may be that duct discharge temp is related to what the computer wants, and not what you want. It tries to maintain a specific cabin temp, not a specific duct temp.

I like to control duct discharge temp, as I like to manage the temp and velocity of the air blowing on me.
 
Of course, one trick to make sure coolant is circulating properly, is to rev up the engine.

If you are using the auto temp selection, it may be that duct discharge temp is related to what the computer wants, and not what you want. It tries to maintain a specific cabin temp, not a specific duct temp.

I like to control duct discharge temp, as I like to manage the temp and velocity of the air blowing on me.


I wonder if he has this on and doesn’t realize it? Good point.
 
Of course, one trick to make sure coolant is circulating properly, is to rev up the engine.

If you are using the auto temp selection, it may be that duct discharge temp is related to what the computer wants, and not what you want. It tries to maintain a specific cabin temp, not a specific duct temp.

I like to control duct discharge temp, as I like to manage the temp and velocity of the air blowing on me.
I "always" use Auto mode. It never did this till my last repair fiasco. I definitely understand your point. What is happening is the cabin all of a sudden gets noticeably colder. Back seaters notice it.
 
Here is something I saw and did yesterday. Y'all know I am an OCD maintenance guy that will probably die 3 years earlier due to my OCD.

The coolant reservoir had been full as I had checked it several times in the mornings. Yesterday I noticed it had fallen below "low." I took the plastic cover off the engine and loosened the 17 mm plug that sits on top of engine. I could see the red coolant but it wasn't at the top. I loosened the cap on the coolant reservoir to add more 60/40 (with distilled water of course) to fill it back up. After I filled reservoir up I looked back at the fill hole with the 17 mm drain plug and it was now as empty.

I filled it up, only took a small amount, and cranked the engine. Coolant overflowed the 17 mm fill hole so I tightened it down.

I gotta 2 hour drive today (My Mom needs her Colgate toothpaste) and am crossing my fingers there was just air in the system.
 
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