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Condensation after service Lexus IS 250 2007

I just had the 30,000 mile service at a dealership, replaced a leaking water pump, front and rear brakes. The car has just 30k miles on it so it hasnt needed anythign major despite being 10 years old. Once I got it back the front windows and windsheild are fogging up. It doesnt seem to matter if the car just started or has been going for a while. We have had temperature changes and humidity changes in the weather, neither makes a difference. I have to drive with the windsheild defrost on all the time. The dealer said it isnt anything they did, but it started immediately after I got it back. Is it possible that they knocked soemthing and broke it? They want to see it again to see if they can figure it out. Any help in figuring this out is very much appreciated!

It’s possible you have a leaking heater core. That’s a mini radiator behind the dashboard that carries engine coolant to heat the interior.
Replacing the water pump allows the cooling system to build pressure to its proper level, which wasn’t possible when the water pump was leaking.
You should go back and have them pressure test the cooling system.
It’s also possible somebody at the shop spilled water on a seat (if they’re cloth and absorb liquids) or the rug on the floor.
The water pump failed prematurely, which suggests to me the coolant didn’t get changed by the recommended time/mileage.
I’m guessing your Lexus uses the same Toyota long life coolant that my 2006 Matrix uses, which is recommended to be changed at 7 years the first time (in 2014 for yours) on a vehicle which does not get much mileage (3300 miles per year in your case) and every 5 years after that.
Coolant wears out and can cause waterpump failure and corrosion throughout the system (including the heater core).
I did the first coolant change at 5 years and recently the second at the 10 year mark.


Thanks for replying!
So I will aks them to do a pressure test on the cooling system, check the heater core and I will ask when the coolant was last changed.
(The car has leather seats and weather tech mats so I dont think it is internal moisture unfortunatly.)
Any guess on cost assuming it is the heater core and coolant?
Thanks again!

Be advised that if your '07 is beyond the warranty period, you no longer need to use the dealership. If you’re happy with them, keep using them, but if you have doubts a reputable independent mechanic usually saves money.

Being as it was a Lexus dealer . . .
Did they detail it after service, before they returned it to you ?
THAT could be the residual moisture that is condensing.
Wipe some moisture with a paper towel and smell it.
Does it smell like coolant or cleaner ?
Leave the windows open a tad and let it air dry some more if it’s detailing residue.

Yes, I will check! Hopefully it is cleaner. I am guessing that if its not cleaner then its the heater core.

I doubt this has anything to do with the work you describe recently done. But a leaking heater core can cause this. If you feel the inside of the windshield with your fingers when this happens it will feel sort of greasy, or oily if it is the heater core. The substance on the windshield will usually have a definite sweet odor too.

If that all isn’t happening, and it just feel and smells like water on the windshield, then it is more likely just some water that has somehow gotten inside your car and is slowly drying out and condensing on the windshield. The shop may have parked it outside and forgot to roll the windows up or left a door open or the trunk open and rain got in. You or your shop should check under the carpets, especially the under-carpet padding – and the lowest part of the car, which is usually in the trunk area for dampness or puddles of water. In the meantime if you can figure out a way to do it, open the windows and use an electric fan to blow air through from one side of the car to the other for a few hours, sees if that helps. Open all the windows and let the wind blow through them when you’re driving if you don’t mind.

If it is a leaky heater core (I’ve had them do this and it’s exactly the complaint you describe), it can easily leak down the inside of the firewall and go UNDER your weather tech mats, so be sure, as @GeorgeSanJose said, to take those out and pull back the carpet and have a good look/whiff at the padding.

Hmmm ok, there is no odor or stickiness to the condensation. But it has been a couple weeks since the service. I guess I will haev them do a pressure test just to see if there is anything going on.
I got the car about 2 years ago from Florida, now Im in MASS. I dont know if it ever had the coolant replaced. But it makes sense that there might be a cooling problem.
Thank you to everyone for your ideas and help!

Best of luck.

This will happen in cooler weather with the ventilation system in recirculate mode.