[Elderado82]

There is nothing wrong with using a power washer on your engine bay. Just be mindful of a few things:

1. Electrical wires and wiring harnesses, batteries, alternator, and fuses.

2. Don't flood the area of the engine where the spark plugs and ignition coils are. These should be sealed, and water shouldn't be able to get down into the cylinder head, but if it does, this can cause massive issues.

3. If you have a cone intake filter or open cold air intake, make sure to seal it off from the water.

Other than that, spray down the engine bay with a good degreaser, let it sit for about 10 to 15 minutes, and lightly brush any problem areas with a bristle brush, then rinse. I would personally shy away from using high pressure but instead use low pressure and focus on up-close, detailed cleaning.

You may get wet and experience splashback, so make sure to wear eye protection to prevent the degreaser from splashing into your eyes. The main thing is to be mindful of where you are spraying the water, and if you do get water in those areas, try to use compressed air to dry them out.

Also, it's a good idea to take the car for a nice long drive afterward to burn off any moisture that may be sitting. Water is corrosive and will accelerate corrosion and rust.

[Elderado82]

Originally Posted by 21X3M40

Question regarding the under-shield or under tray. On my 22 X5 a very large portion of the car is covered underneath, would it be prudent to remove the cover(s) before doing an engine detail/wash so the residue does not collect in the under tray(s)?

I know this would mean extra time and work to remove the undertray(s) before doing an engine wash. I am open to suggestions. TIA

No, these are made to properly drain. There are drain holes, and the tray is designed for water to drain out in the direction of the drain holes. You'll be fine. Just take the car for a drive, and it'll air out.

[NYG]

The only things you should know is:

Don't pressure wash connectors and wait till the engine is COLD before you spray cold water on it.

[bosstones]

You can use a 0° tip to really get into those hard to reach nooks and crevices.

(please don't actually try that)

[tracer bullet]

I think after reading all this again the answer is: If you're in doubt, don't do it.

The summary is that it's totally safe, as long as you don't do this, or this, or this, or this and be sure to also do this and this and this as well.

I'm well aware that these are all things that can be done, and it'll be OK, but the average person doesn't understand 2/3 of what all the things are that need to be done. I know where my engine takes in air, I know where my plugs and coils are because I've changed them, but the average person has NO idea what these things mean.

If you have to ask this question, the answer for you is probably going to be no, don't do it.

[Yuille36]

I would be reluctant to use a high-pressure washer, the problem is that water can be pushed up into connector causing electrical gremlins. Instead, I use your average garden sprayer that you pump up to create pressure. That and some degreaser or engine detailer would be fine, along with a brush to agitate the area. And some microfibers to wipe every down. But people will do what they think is best.