Most here will likely know better, but I like to bring attention to a concern that comes up ( somewhat rarely ), primarily via people who are well intentioned but uninformed about the use of hot water on car paint . Some use it to melt snow and ice off the car, some use water a bit too hot in the wash bucket.

There's no denying that washing a car in the winter can be very UN-fun, so it's natural to want to warm things up a bit so your hands don't freeze. LUKE WARM water is generally ok, if it makes the job more palatable, but you have to keep it on the "luke warm" side and not leaning towards hot. It's the SUDDEN / instantaneous transition from cold to hot that causes the "shock" . Warming up the sheetmetal in the sun, even in winter, would help if you do use some warm water to wash.

Thermal stress can affect the resins in the clearcoat, or the resins in single stage urethane enamels as well (same paint, one is just non-pigmented). By applying anything hot onto a cold surface, the resulting thermal stress can and does cause tiny cracks (called "alligatoring) in the paint, also called "checking". The bad thing about it is-it may not happen right away. It can take weeks or even months to appear. I have seen it on a few cars over the years, although I cannot say with any certainty that hot water thermal stress was definitely the cause, because there are others.

So if you're out in the cold and want to warm up the wash bucket for the sake of your hands, just err on the "warm" side, and don't make it too hot. Wear dishwashing gloves as well, that will keep your hands from icing up and allow you to deal with the cooler water.

This is info I gleaned from a paint industry TSB ( technical service bulletin ) many years ago. The info came as a result of maunfacturers' finding various causations as to paint defects and warranty claims. This was one of the warnings they cited, and I wanted to pass it along.

Cheers

 

How hot is the water in those touchless/"laser" washes? That's where I "de-salt" my car in the winter time (purists will howl at me for risking swirl marks, but it beats severe underbody corrosion ) I'm guessing that it's not that hot, simply because the car wash operator probably does not want to pay the gas bill involved in getting the water up to a dangerously high temperature.

 

I don't know the answer to that one Squarehat, but I'll look it on of the industry tech boards and see if I can find out.

It would be a concern if it were too hot of water on a very cold day.
These are the kind of small details that can "slip through the cracks" within the industry, or worse, are disregarded in the name of marketing/selling a product or service. $$$ is often the bottom line for these businesses.The consumer needs to be informed on some of these arcane issues, but rarely is, that's part of my job here FWIW.

Thermal stress affects most things, as most of you know, driving your car with hot brake rotors through a cold puddle of water can warp them just like that, and paint isn't a whole lot different. Urethane enamel is pretty tough, and pretty flexible... It will depend on just how extreme the hot/cold issue is.

 

Excellent pointers!!!

 

Hmmmmm, need to try this out.
My car is really dirty at the moment.

 

When I lived in Buffalo,NY I used one of these heaters in my garage,and I was able to wash and work on my cars in a tee shirt when it was 20 degrees out side...........If you buy one make sure you get the right size for your garage............

http://www.comfortchannel.com/level....OVMTC=standard