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iNeon 07-31-2005 04:30 PM

hot engine washing?
I read somewhere on this board that you shouldnt wash a hot engine?

after my oil change mishap(i forgot to screw the top car is a dalmatian!) i have got to clean it all up!

will i hurt the engine if i warm it somewhat to soften the crud?

whunter 07-31-2005 04:43 PM

Opinion is divided.
Depends how you do it.
Do not use a power washer on a hot injection pump.
Light spray/mist from a garden hose on a warm (not hot) engine should be ok.

Kerosene + a good selection of brushes on a COLD engine does great, then soap and water wash.

sixto 07-31-2005 04:43 PM

If you can keep your hand on the exhaust manifold it's probably cool enough to rinse with a hose.

Even on a hot engine it should be okay to use a light spray and keep it moving. There won't be enough water in one spot at one time to cause a big temperatrue drop. Do this at your own risk, of course.

Can you get a hose from your house water heater to the engine bay?

95 S420
87 300SDL

iNeon 07-31-2005 05:15 PM

well, i took the cheap route-

i had to clean the fenders and winshield wiper area, they had alot of oil dots on them(on a white car! diesel oil spots!!!)

i used some laundry degreaser my mom uses on my garage clothes and they wiped right off the fenders(and that stubborn spot on the door--it was a light grey from all the fingerprints!)

i used two cans of ether to clean the engine-- no wiping=) i rinsed with the garden hose and didnt warm the engine, it was stone cold from sitting overnight. i still have alot of clean up to do! boy i wont make that mistake in the near future again!

btw: i noticed the a/c compressor was some crazy brand remanufactured unit while i was unde cleaning it. it wasnt either of the two brands that are usually mentioned here. thats just an aside, though.

boneheaddoctor 07-31-2005 06:11 PM

I prefer to clean the engine while cold......then you take no chances of damaging it....then fire it up and let it warm up right afterwards to let it dry out ASAP.

iNeon 07-31-2005 06:12 PM

heh heh im not starting it till the ether has gone away for sure!

ive heard thats no good for it

kip Foss 07-31-2005 10:36 PM

If you can run your car through a puddle of water and have it splash up under the hood all over a hot engine you can certainly wash your engine when it is hot. That being said it is better to let it cool a bit if for no other reason than most engine cleaners are petroleum based and the heat will cause them to partially evaporate there by loosing some of their effectiveness. Oven cleaners work particularly well on warm engines esp. where you have a build up of heavy grease. There is nothing in your engine compartment that oven cleaner will harm. If there was it wouldn't withstand 25 years of hot oil, grease. road grime, cold, heat, etc.

tangofox007 07-31-2005 11:54 PM


Originally Posted by kip Foss
There is nothing in your engine compartment that oven cleaner will harm. .

Except paint and aluminum!!!

rg2098 08-01-2005 01:20 AM

The IP can't take the thermo shock of cold water on the hot metal with all the tight clearances .

Jim H 08-01-2005 09:20 AM


Originally Posted by kip Foss
...There is nothing in your engine compartment that oven cleaner will harm. If there was it wouldn't withstand 25 years of hot oil, grease. road grime, cold, heat, etc.

Maybe nothing made of cast iron or cast aluminum, but don't spill or splash that corrosive stuff on ANYTHING electrical! :eek:

SD Blue 08-01-2005 11:14 AM

Oven Cleaner? No, No, No!
Don't use oven cleaner! I am speaking from experience. Someone suggested this to me once and it seemed to be an inexpensive good idea at the time. Read the side of the can about use on aluminum. What a mess! Corroded aluminum and rust on the cadmium plated components. I took months to clean up to just reasonable. If you want an inexpensive cleaner, use biodiesel.

I repeat, do not use oven cleaner! :eek: :eek: :eek:

It is better to use a little more elbow grease. Water on a running hot engine should not cause damage. Water on a stopped hot engine is not a good idea due to too much thermal shock.

LarryBible 08-01-2005 11:20 AM

I have taken all kinds of cars with all types of engines to the carwash and washed the engine bay as a regular practice for over 30 years. The only ill effect I've ever had from this has been water in the distributor cap of a few gas engines such that I had to pull the cap and dry it out in order to get on my way.

I've washed engines this way when they were cold and when they were hot with little difference. It usually works better on a hot engine if you are trying to remove oil from a leak or a spill.

My $0.02,

iNeon 08-01-2005 01:33 PM

i just used some spray degreaser and cleaned the paintwork and then sprayed ether all over everything, it took it all off with no scrubbing.

im not an engine detailing kind of guy, i spray it clean so when im working on it i dont get greasy up to my elbows, but the engine isnt something i take pride in being able to eat off of.

except in the vws, they need to be cleaned so you can track oil drips and have a functional cooling system=)

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