Best way to clean Engine/Engine Bay

[Pajaru]

Back from trip up North and as normal the Engine/Engine Bay is covered in Bull Dust and a bit of mud. In the the past I have used a method suggested to me of using running water to wash down the Engine/Engine Bay. But I am now concerned about this method.

So, Is there a better method, How do others clean their Engine/Engine Bay.

[nj swb]

Car wash.

Make sure the engine is up to temperature - wash on the way home, not the way out.
Leave the engine running, to ensure it stays warm, to help heat drive out moisture.
Use the engine wash, high pressure soap, rinse. Be careful with the under-bonnet lining - it doesn't like the high pressure.
Leave the engine running while washing the rest of the car - help to dry things out.

[geopaj]

I’m actually the opposite (which is unusual - NJ & I are friends in the real ‘non internet world’ usually have similar thought processes).

I only wash the engine bay when it’s completely cold - I don’t like dousing hot engine components in cold water if I can avoid it).

I never use high pressure - just standard garden tap pressure. I don’t like the inoffensive high pressure water testing the electric’s seals.

I treat grease/oil with an aerosol degreaser (just the cheapest from Supercheap is ok). For general dirt I use CT18 Truck Wash as per the instructions (apply, let dry, them rinse off).

Then I dry everything visible with an old microfibre towel.

Then go for a drive to get everything hot and evaporate the residue moisture. Sometimes I get lazy and this is simply driving to work the following morning.

In my experience, (assuming everything is in good condition) everything under the bonnet can cope with a low pressure garden hose but I still use some common sense.

Given NJ and I use opposite techniques and haven’t had issues, you probably could conclude that either technique is ok.

[GHendo]

I was always told cold water on a hot manifold could crack it. I wash the engine cold, then started it to warm up and dry out.

Geoff

[Guest]

I spray degreaser over most things, pressure wash it off with soap then rinse. Making sure i keep away from main electrical connections, take it for a drive to dry it off. Spray the motor with tyre foam or tyre shine, polish the main bits. It makes it alot easier next time its dirty and looks like new. Found out that is what the used car dealers do to make it look good.

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[Garc]

I do cold engine. Make a spray of 10% liquid clothes washing soap in a small spray bottle. Soak everything with this then rinse off with garden hose gun on shower setting (no pressure). Then blow dry using leaf blower. Added bonus is that it smells nice!

[spot01]

Cold engine. I use a bucket of water & old chamois/spong. Gentle flow from garden hose when cold if you must. Don't spray water into electrical components & fittings, air intake, breathers, etc.

If using detergent, use one designed for cars, as household cleaners can be too harsh & may remove rust inhibitors, etc.

Then go for a decent drive to get it nice & warm to dry everything off.
Final wipe over with old damp chamois, rinsing in clean bucket of water frequently.

[Pushbike]

If you use a degreaser don't apply it to rotating shafts that may have oil seals, my experience is that some degreasers will shorten the life of the seal e.g water pump, timing cover seals etc.

[Onsan]

I’m with Geopaj. Cold engine, gentle wash (warm water if you like), run after.
Cold water on hot cast metal is generally not a good idea, if it was hot enough and you cool it quick enough you can crack or stress/distort the metal. Not good for seals either, cooling metal causes water to be drawn past seals, ruins boat trailer bearings. Probably unlikely to happen with the amount of water from a pressure washer and frequency of washes, but best practice and all...
High pressure and electrics...not a fan of either.



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[Pajaru]

Thanks for the replies Guys.

Some food for though there, although I would be inclined to go with the Low Pressure Garden Hose. I am not sure about degreasers though. I think the way to go would be to wash engine when cold, avoid electric components, dry with cloth then start engine and go for a 10 minute drive.

I have large garage compressor, I think it was 185l per minute. Could this be used to air dry after wash. Would the force of the compressor driven air drive water into seals etc.

Thanks

[Onsan]

Best way to clean Engine/Engine Bay

Would not think it’s likely.

Starting a wet engine is not an issue, throwing water on a hot engine is.

A wet engine that has heat applied to it has to first heat and evaporate the water before the metal itself gets much more than 100oC.
Think what happens inside the engine block, there’s cold water running around it the moment you start, the engine doesn’t really got hot until the cooling water is hot.

Pouring water on a hot engine is a different kettle of fish as cooling steel is a lot quicker than heating it. Think the time it takes to heat a piece of steel to red hot and the time it takes to cool it when quenching in water. Add to it that an engine block is not evenly heated, risk increases.


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[nj swb]

Would not think it’s likely.

Starting a wet engine is not an issue, throwing water on a hot engine is.

A wet engine that has heat applied to it has to first heat and evaporate the water before the metal itself gets much more than 100oC.
Think what happens inside the engine block, there’s cold water running around it the moment you start, the engine doesn’t really got hot until the cooling water is hot.

Pouring water on a hot engine is a different kettle of fish as cooling steel is a lot quicker than heating it. Think the time it takes to heat a piece of steel to red hot and the time it takes to cool it when quenching in water. Add to it that an engine block is not evenly heated, risk increases.

Drive through suburbia, pull into the car wash, leave the engine idling for a minute or two while getting ready. How hot do you think the engine is? How hot do you think the exhaust is?

[Onsan]

Engine is hot, don’t apply cold water to it directly.
Exhaust is rolled steel, not cast steel or alloy. Does not behave the same when quenched with water, does not have oil seals and is a hell of a lot cheaper to replace if you do damage it.

That’s my advice, I get that I and others have disagreed with yours, but I’m not here to argue with you, just a different opinion.
My advice is sound and reasoned, take it or not as you or anyone else see’s fit. It’s all good.


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[nj swb]

Engine is hot, don’t apply cold water to it directly.
Exhaust is rolled steel, not cast steel or alloy. Does not behave the same when quenched with water, does not have oil seals and is a hell of a lot cheaper to replace if you do damage it.

That’s my advice, I get that I and others have disagreed with yours, but I’m not here to argue with you, just a different opinion.
My advice is sound and reasoned, take it or not as you or anyone else see’s fit. It’s all good.

It comes down to language. The engine won't be above 100 degrees, I don't consider that to be hot (in the context of this discussion).

Using the spray wand isn't "quenching" anything - in the context of this discussion.

There is more danger utilising Mitsubishi's 700mm wading depth, where the engine is submerged in water rather than sprayed. What are the warnings in the owner's manual regarding this? When was the last time any of us heard of an engine cracking during a river crossing?

To each their own - I agree. But using analogies of quenching red hot steel is neither sound nor reasonable.

[Onsan]

It comes down to language. The engine won't be above 100 degrees, I don't consider that to be hot (in the context of this discussion).

Using the spray wand isn't "quenching" anything - in the context of this discussion.

There is more danger utilising Mitsubishi's 700mm wading depth, where the engine is submerged in water rather than sprayed. What are the warnings in the owner's manual regarding this? When was the last time any of us heard of an engine cracking during a river crossing?

To each their own - I agree. But using analogies of quenching red hot steel is neither sound nor reasonable.

Maybe your interpretation. I said 100oC in the context that wet metal will not get much hotter than 100oC before water has evaporated, it's just thermodynamics, liquid water can't get above 100oC at atmospheric pressure, so if it is present on the metal, the metal temp will not get much hotter than 100oC. My point was to provide reasoning to reassure.

I accept there's quite a few definitions of quenching, "the rapid cooling of heated metal with water" is what I had in mind, relevant to the context of the discussion, I did not think someone would take it as the specific application of heat treatment and submersion in water, my bad.
700mm is wheel height on most, which when a vehicle is driving through water would be not much more than sump height. It would expose diff seals to water ingress and I would guess that and other valid reasons is why MM put a warning in the owners manual stating

NOTE
• Because the inside of the vehicle is flooded
with water when crossing at a place where
the water is more than 50 cm deep, we recommend
you to have your vehicle inspected.
• Frequent crossing of streams can adversely affect
the life span of the vehicle; we recommend
you to take the necessary measures to
prepare, inspect, and repair the vehicle.
...

• After crossing a stream, be sure to have the
following items inspected at a MITSUBISHI
MOTORS Authorized Service Point and take
the necessary measures.
• Check the brake system and, if necessary,
have it serviced.
• Check the engine, transmission, transfer,
and differential oil or grease level and turbidity.
If the oil or grease is milky, it indicates
water contamination. Replace it
with new oil or grease.
• Grease the propeller shaft.
• Check the inside of the vehicle. If ingress
of water is found, dry the carpet etc.
• Inspect the headlamps. If the headlamp
bulb is flooded with water, we recommend
you to have it drained."

Sure, it can go 700mm or deeper even, no one argues that, but just because it can, doesn't mean you should or if you do, that there won't be the chance of an undesirable affect.


I'm erring on the side of caution by suggesting the least chance of a undesirable effect on someone else's pride and joy is to wash it when cool, forgive my wording if that point was lost.