CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Carwash threat to turbocharger?

Does a touchless carwash, with the high pressure spray and chemical detergents, present a threat to my engine?
I generally hand wash my car, but I make a point of visiting a touchless carwash with an undercarriage rinse during the winter. This always produces prodigious amounts of steam, which makes me wonder if there is any risk to engine components. Under normal driving conditions, it seems like very little moisture gets in the hood scoop, but the machine blasts soap and water straight in.
So I have a twofold question:
-do the detergents pose a threat?
-what is the safest way to remove winter road grime from the nethers?

Not unless you go through one with the Hood up.

You drive outside in the rain all the time. If that’s not bothering the engine what makes you think a car wash will???

Undercarriage washes are controversial. Many like myself believe that they force water into crevices that water would not otherwise be entering, many of these crevices not being designed to dry out well, and can actually promote rust. Others have done so without problems.

There’s lots of hot parts in your engine compartment, none hotter than your exhaust manifold and headpipe. IMHO it’s likely that the steam is coming from water splashing onto there rather than from your turbocharger. Detergents won’t pose a threat, but thermal-shocking might.

Additionally, if the wash is blowing water into your hood scoop you may be wetting the insulation under the hood. If so, that will rtetain water and cause rust. I’d check it out after a wash to see if it’s getting wet.

And then there’s the electrical components.

Bottom line: I’d either plug the scoop or stop the washes. There’s too much risk with blowing water into a hot engine compartment with no protection for the underhood components.