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'83 300D
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Discussion Starter #1
Got into a discussion about the wisdom of washing off an engine that was covered in years of built up gunk.

His argument against was based on an idea that the combined oil, coolant, and dirt prevented leakage on older motors. He also presented anecdotal evidence of why washing off the engine is a bad thing by retelling an event where an individual bought a car from his family, immediately took it to the car wash and blasted everything under the hood, to include the ignition and inside the carburetor. New owner towed the vehicle back to coworker's house and demanded a refund (despite the problem being the headspace and timing between the steering wheel and seat).

My position being that you wash off the engine to find and repair the links, as well as prevent potential overheating.

Curious as to fellow members' thoughts on this.
 

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2001 E55 AMG
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3,294 Posts
I've steamed cleaned hundreds of those engines.....Newer ones are a different matter....Cover the alarm and dizzy with plastic bags and give it all a good dose of WD40 when you have finished.
 

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Daily Drive 82 240D 4 speed
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291 Posts
oil and diesel are great ways to fend off rust.....


or that's the excuse for my car :p
 

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1981 240D
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185 Posts
Cycobilly: There are three things to consider when thinking about washing your engine:

1. NEVER, NEVER, NEVER wash a hot engine. Even though car wash water is HOT, it is not as hot as an engine at operating temps. When you apply water to an engine that has reached operating temps you risk cracking or warping EXPENSIVE and HARD TO FIND parts, such as the block, head, etc. Some people may have differing 'opinions' on this statement, but the facts are based in science.

2. Legality; Some local governments have policies against washing engines. Also, any wash rack that is not equipped with an oil/water seperator will generally not permit engine washing. This is not a huge deal unless you get caught or you like to follow the rules.

3. Revealing leaks; someone touched on it in a previous post on this thread. Many times when you completely clean the engine off, you will find leaks. The caked on oil and grease seals the leaks in. I am not advocating ignoring engine leaks. Just because they are sealed in with caked on grease, doesn't mean they don't exist. My point here is, don't clean the engine off before you are prepared to address said leaks. When my mechanic completely degreased the engine on my 300SD, I ended up replacing the lower oil pan gasket. I recently degreased my 1981 240D and I have had no leaks.

As mentioned above in a previous post, degreasing the engine does allow the engine to cool properly. You reduce the chances of overheating and you keep vital parts clean and accessible. It is MUCH easier to work on a clean engine. You don't get as dirty, your tools function better and you can see what you are doing. Also, your engine compartment looks a lot better. Here is what I do when I clean my engine:

1. I make sure the engine has not been started for at least 6 hours prior. This ensures the engine is at ambient temperatures.
2. I use a bucket of hot water and Dawn dishsoap along with a stiff brush (not a metal brush. Plastic or plant based bristles are best) to scrub the engine. It is much easier to spray the engine down with degreaser, wait ten minutes, then spray it off with a garden hose, but you risk damaging parts this way (particularly gasket material, rubber gaskets and o-rings). You should do it by hand.
3. Remove the air cleaner assembly and any EGR/PCV hoses from the valve cover/turbo charger. I seal off all openings on the engine block with rubber gloves stretched over the holes. You can also use plastic and rubber bands. Make sure NO water will enter the engine, turbocharger, fuel lines, fuse box, etc.
4. Scrub each part area, then wash. If you scrub the whole engine then rinse, the soap will start to dry before you are done and some parts will have to be re-cleaned.
5. Start at the top of the engine and work your way down. Go around the head, transmission, block, oil pan, steering linkage, and drive train, carefully cleaning and rinsing each part.
6. When the entire engine is clean, look for places of standing water, such as the engine mounts, water drains, fuel injector recesses, etc. Make sure you dry this water up. Blow it out with compressed air or at least dry it with a shop towel.
7. Lubricate steering linkage, throttle linkage, CC cables, etc.
8. Allow your engine to completely dry before removing the protective barriers you used to block openings. Once it has dried, put your air cleaner assembly back on, run your engine up to operating temps and check for leaks.

A lot of people underestimate the effort required for this job. Just remember that water is no friend of engines, causes rust, and can interfere with electrical circuits. TAKE YOUR TIME! When I did my 1981 240D, it took me more than 4 hours, not including drying time.
 

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1982 300D Turbodiesel 212K or so, it doesn't work anymore :-)
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216 Posts
i wouldn't blast the top side with a real high pressure washer...i set mine to like 400 or 500psi when i wash mine and have no problem...simple green or purple power work great...do it while the engine is cold...

the older engines where everything is mechanical don't care about water so much as the engine is cold...

good call on soaking it down with wd40 or some other rust preventative.
 

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'84 300D/ dakota benz trk. Sold... miss it. "88 260E '91 190E 2.6 '89 Volvo 240DL "85 300D
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easy enough topic so i thought i would add my 2 cents... i have washed mine and others all the time. soak it down with any strong degreaser, straight, not watered down, wash it with pressure at least 1500 or so.
i like to do mine when the engine is warm, but NOT HOT, start it up and let all water burn off. i agree about bathing it with WD. i have always done that afterwards, i spray it down good...
 

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2001 E55 AMG
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3,294 Posts
easy enough topic so i thought i would add my 2 cents... i have washed mine and others all the time. soak it down with any strong degreaser, straight, not watered down, wash it with pressure at least 1500 or so.
i like to do mine when the engine is warm, but NOT HOT, start it up and let all water burn off. i agree about bathing it with WD. i have always done that afterwards, i spray it down good...
Thank you!...I use undiluted road and traffic film remover in a pump up sprayer.Then blast it with the steamer (jet wash) on HOT.
 

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Got into a discussion about the wisdom of washing off an engine that was covered in years of built up gunk.

His argument against was based on an idea that the combined oil, coolant, and dirt prevented leakage on older motors. He also presented anecdotal evidence of why washing off the engine is a bad thing by retelling an event where an individual bought a car from his family, immediately took it to the car wash and blasted everything under the hood, to include the ignition and inside the carburetor.
My position being that you wash off the engine to find and repair the links, as well as prevent potential overheating.

Curious as to fellow members' thoughts on this.
that guy is an idiot and the one who washed the engine should never pop a hood:surrender:

you wont really shouldn't spring leaks, if an engines that dirty it probably was abused
 

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1984 300CD, 1983 240TD Euro
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I don't wash mine ALL the time but I do. I use diluted Simple Green Lemon and a brush. Then I use a garden hose to rinse. Gord's on the valve cover and clean and lube the linkage with ATF. Oh yea, 251K
 

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1981 240D
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I don't wash mine ALL the time but I do. I use diluted Simple Green Lemon and a brush. Then I use a garden hose to rinse. Gord's on the valve cover and clean and lube the linkage with ATF. Oh yea, 251K
Holy Mole! You could eat off that thing! In addition to Dawn dishsoap, I also use simple green. I am not familiar with Gord's. Is it like Mother's polish? How does it work exactly? I am very envious of your bling!
 

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I don't wash mine ALL the time but I do. I use diluted Simple Green Lemon and a brush. Then I use a garden hose to rinse. Gord's on the valve cover and clean and lube the linkage with ATF. Oh yea, 251K
dear god i've never seen an engine with 251k on it look like that:thumbsup: that would easily raise the value of the car $1000 IMO
 

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85 Audi Coupe Quattro, 85 Audi Coupe GT, 71 BMW turbo 2002, 73 BMW 2002tii, 85 BMW 635csi
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I don't wash mine ALL the time but I do. I use diluted Simple Green Lemon and a brush. Then I use a garden hose to rinse. Gord's on the valve cover and clean and lube the linkage with ATF. Oh yea, 251K
Must be nice to have all that free time on your hands. :surrender:
 

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1984 300CD, 1983 240TD Euro
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Is that valve cover polished or chrome plated?
Holy Mole! You could eat off that thing! In addition to Dawn dishsoap, I also use simple green. I am not familiar with Gord's. Is it like Mother's polish? How does it work exactly? I am very envious of your bling!
Polished.
Gord's Aluminum & Chrome, Cleaner, Polish, & Sealer

Must be nice to have all that free time on your hands. :surrender:
Interestingly enough I am Always busy.
 

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1985 380SE
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I'd like to see how that Gord's polish works on the aluminum trim along the roof line and windows. My 240 has the all too common cloudy trim issue.
 

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W-1-2-3 Go!
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Washing the engine bay must be done only when you know that ALL vacuum lines have been installed properly and there are no open lines where water can get into. Also make sure the seal from the air cleaner to the turbo is properly sealed.

Otherwise, take precaution. The recommendations here are sound. The best part about using a degreaser is that it gets into the areas that are normally painstaking to clean.



Lubricate the linkages after the wash as Gary advised.

Cover the carb and distributor if you have a gasoline engine. The alternator, turbo and injection pump must be avoided. Cover them with a good thick plastic cover and seal it properly with a strong elastic so you know water will not get in.

Make sure the brake fluid reservoir is properly sealed.

Don't forget to degrease the wheel wells and pressure spray them with a good amount of water. Helps to keep rust from forming on the wheel arches when these areas are cleared of moisture trapping debris.
 

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Heh...i just degreased the 240 D engine earlier this week, but I didn't do half of what's posted here. Just sprayed it down with degreaser bought at Costco (after driving it to a self-serve car wash), then gave it a good rinse. Next time I'll take more precaution.
 

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1981 240D, 2006 S 430 4 Matic, 2007 GL 450 4 Matic
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137 Posts
engine

I used Simple Green and a steamer ( Like a steam buggy or other )
 
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