atropine

Other than a leaking heater core or a plugged AC box drainhole, what else could be causing my windows to keep fogging up? I bought my 94 LS400 used about 3 months ago, and have scrubbed the inside of the windows several times. But they keep getting foggy scum buildup after only a couple days. If I leave the windows cracked, no buildup. I don't really smell or feel any humidity. I also managed to get the water temp really hot in stop and go driving the other day, but once I got on the freeway it was fine. I replaced the thermostat today and tested the old one in a pot on the stove; it didn't open up til about 190-200 degrees but closed down about 180. I suspect that I may have a small heater core leak and just gradually lost enough coolant to make the car overheat. But I pulled up the passenger side carpet and I don't really see any evidence of a leak. Would it just leak out the bottom of the AC box and down the drain pipe? With the new thermostat and coolant fill, temp holds steady right in the middle right now. But I will have to watch it closely to see if I am losing coolant. Until then, just curious to know what else could be causing my windows to fog...

BTW, I blew compressed air up the AC box drainpipe and could feel air come inside the box, so the drainpipe is not plugged. I removed the cabin filter a few weeks ago and they were very dirty. Air flow has much greater volume now, but windows still fog...

deanshark

I would say you might have a leak in the heater core, even though you don't see anything on the floor. When mine leaked the windows fogged up all the time. When the coolant leaks from the heater core it leaks into the heater assembly and then steams out through the heating ducts, which in turn, fogs the windows. It's not really enough to notice the coolant level going down. Do the inside of the windows feel greasy? You might be able to tell if this is the problem by getting the car hot, turn the car off, about 5 minutes later see if there is steam coming from any of the ducts. Mine used to come out the front defroster and the side defrosters. (The ones in the side of the dash for the front door windows) If it's not that then you might have water in the car somewhere and b/c of all the humidity lately it fogs the windows.
The heater core is a BIG PITA to change, you could search my posts to see how to do it.

python

iTrader: (4)

what else can cause window fogging? having sex with ur girl with the windows up will do it most assuredly

Kansas

foggy scum on the windows inside is caused by only one thing -- leaking coolant in the interior ... but I like python's answer too.

emarknot

its your heater core.

atropine

I lol'ed when I read that and my wife was curious, so she had to read this thread. Her response was "well I don't remember it fogging up the windows in our other cars".

That's my girl...

atropine

I am not in the mood to change the heater core anytime soon. I am just gonna watch it closely and carry a gallon of coolant in the trunk just in case. I am thinking of just adding in a shutoff valve in the heater line as a diagnostic tool to see how much of the fogging disappears prior to even considering a heater core change. Anyone ever done this?

atropine

I just went outside to look at the heater hoses and found that there is already some sort of valve built into one of the lines. What is this and can it be manipulated to shut off flow to the heater core manually? Or maybe it already is, if the AC is set to max cold?

deanshark

You can bypass the heater core but you'll still have the coolant in it which might still leak out. There's a connecter just for that reason sold at any parts store. Ya take the 2 hoses off the heater core and connect them together. Do you have a pic of the valve you're talking about. Is it the actual heater valve or maybe something to flush the coolant?
Just as a heads up so you know, it took me 4 days to change my heater core. (In the December cold) The A/C lines need to be disconnected and drained.

python

iTrader: (4)

not a fun job by any means

deanshark

No it isn't!!! Here's my thread about taking out the heater core, post #7 tells what needs to come out.
https://www.clublexus.com/forums/ls4...ater-core.html
This thread post #4 has a pic of someone elses dash out which is about 3/4 of the way in to get the heater core out.
https://www.clublexus.com/forums/ls4...d-removal.html
Wow, after reading through that stuff again, the nightmares started coming back. Nothing I've changed on this car was ever easy, except the battery.

steve2006

If you're not losing coolant there may be another reason in that the AC filter is clogged up,this caused a similar fogging problem in my LS and replacing it sorted the problem although you can wash the filters and leave to dry before refitting.

deanshark

As he mentioned in the first post, he already removed the filter and still fogging. I tried washing my filters out, b/c I didn't want to spend almost $50 for a couple pieces of paper, and I couldn't get the dirt out they were so bad. One of them just fell apart. I spent 1.50 for a filter from Home Depot and made my own with the old plastic frames.

emarknot

interesting......what type of filter did you use? and did it affect the airflow pressure from the vents?

deanshark

I don't remember the brand but I used the same kind of filter as for my old oil furnace. Pretty much the same thing that was in there, almost. Ya know, the folded paper type filter. It's the same thickness as the OEM filters that I removed. I just cut it to size, used some industrial spray adhesive that we had at work, (like 3M but way more powerful) and then just for piece of mind I wrapped silver (not grey LOL) duct tape around the sides. Air flow feels alot stronger but the old filters were almost completely clogged. They were still good in Dec. (after 8 months) when I did the heater core.