My oil pump, A/C compressor, etc. are all covered in thick carbon/dust. If I take the battery out, is it safe to flush the engine bay with water?

 

Keep the battery in. And start the car. Make sure not to spray too much around the intake. With the car running if you **** something up and the motor dies, youll at least know where you were spraying. But de-greasing a motor shouldn't be a huge problem. As long as theres no Electronics. Electronics are considered anything with a circuit board that might short out with water. Water will not hurt a battery. Theres actually water inside it.

 

Electronics is why I want to take out the battery--without the battery, the temporary shorting that could have resulted from contact with water should do no damage. This is not true?

 

Leave battery in place, spray away.

 

Just dont spray your alternator. That is about as close to an electronic circuit board as you can get inside the engine compartment.

Shorting field coils or the stator sucks, cover it with a grocery sack.

 

do not spray your engine with water with the motor running or power on!

with car turned OFF. spray degreaser everywhere. and spray the hose where ever. just leave the hood open in the sun and let everything dry before you try and start it.

the only thing to look out for is if you have an aftermarket intake. water could go through the filter and sit in the tubing. besides that. its fine. i do it all the time...

 

Yes, that could get messy.

You had me right up to the "let everything dry" part...in my experience, totally NOT necessary.
Ever looked at your engine bay after driving in heavy rain?
If a running engine and water was such a fatal combination, Mazda- and every other manufacturer- would have taken greater care to seal up the compartment and keep it dry.

 

I've done it a couple of times and I'm still zipping around perfectly fine. Although it might be safe to leave the battery in, I prefer to take it out and leave it out until everything is reasonably dry just to avoid blowing a fuse or something. like jjwalker mentioned, it would be safe to bag up the alternator and all the coils. Those things are just too expensive to risk.

 

Water does NOT conduct electricity very well, contrary to popular belief...
Salt or other impurities mixed in with water will conduct electricity.
Grease and oil do NOT mix with water.
Hence, the water will not short anything out.

Some points to note:
Cold water on a hot surface (exhaust manifold, etc.) may crack it.
Water corrodes ****.
Water may conduct the high voltage for spark plugs. (If you spray near your plug wires and see sparks or the engine misses, it may be time for new plug wires.) It also may get sucked up into any vacuum leaks... If the engine misfires during the washing or fails to start after washing, look at those places...


The way I've always done it is to warm the engine up just a little bit, then shut it down... Cover alternator and coils with a plastic bag... Spray with degreaser and let it soak in for a few minutes... Then hose it down... Lather, rinse, repeat as needed, hit the nasty areas with a brush...

While the engine is still wet, I'd fire it up and go for a drive around the block to dry the engine bay out faster.

 

use foaming degreaser, or steam to clean your engine bay.

 

Ive washed my engine bay every single time ive washed my car. all i do is leave the car running and go to town. never covered anything up nor has anything failed, sparked, stalled, blown, broken ect. One time i did wash the engine bay with the car off and when i i started it back up it missed like crazy for a few minutes then that was it. so now i just leave the car running like usual. Ive been doing this once a week or more for 2+years

 

Water sucks at conducting electricity. At 12 volts it isn't even a safety hazard, unlike 120. The current leaked through water would be miniscule, barely enough to harm some sensitive electronic components.

The spark plugs, wires and coils are high voltage, so water on them would conduct more power if it formed a solid water bridge to the chasis or engine. But that'd only short out the spark plug, making the engine miss until the water evaporated. That's it.