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Corrosion inside engine?

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Quick recap:
When I purchased the car it had Green coolant in it and leaking all over when run.
Over the course of the last few weeks I've drained the coolant, performed a Shout flush, then Citric acid flush.
I continued to see brown coloured liquid draining. It was pitch dark earlier and got to brown now.
Brown implies rust and I had been hunting for rust.

The water pump was also leaking so I had to replace it anyway. When I pulled the water pump I noticed this horror. The impeller was rusted and I noticed significant pitting on some of the other parts.
1. Could the green coolant have caused so much damage?
2. I hesitate because the first drain I performed it was clear green coolant. Wouldn't the green coolant also have some telltale signs?
3. Could it be something I did? I was only using gallons and gallons of distilled water, Shout, and Citric acid.
4. What do I do now? Just keep flushing with distilled water? I'm hesitant to use some vinegar considering the pitting I've already seen
5. Could some other parts be rusting out? I believe 78' have Aluminium blocks

Thank you in advance.

Caked green channels
Automotive tire Wood Bicycle part Gas Rim



Rusty impeller
Gas Automotive wheel system Auto part Metal Circle


Pitted inlet
Automotive tire Plumbing Gas Cylinder Plumbing fitting

Safety glove Finger Glove Personal protective equipment Gas
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· Outstanding Contributor , Bob's Your Uncle!
83 280 SL- 5 speed-The PIG
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35,278 Posts
You are servicing a system that, apparently, hasn't seem much love.

I'm pretty sure your block and heads are cast iron.

Your flush is the right way to do things...but I don't think it will ever run perfectly clean.

I say slap it all back together, put the correct coolant is and drive it for a couple thousand miles.

Then repeat your flush process.

That's what I did 17 years ago before I replaced the pump and rad.

Been good ever since..NOTE: I do a coolant replacement and flush about every 5 years.
 

· Registered
1978 450 SL
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96 Posts
Discussion Starter · #3 ·
You are servicing a system that, apparently, hasn't seem much love.
Oh man. That's what I was afraid of. First the tensioner, the timing offset, the bad oil, and now the coolant.

I'm pretty sure your block and heads are cast iron.
This has me confused. I checked with a magnet after seeing your comment. Don't see any excitation.

it will ever run perfectly clean
/me cries tears. Tears of rust

correct coolant is and drive it for a couple thousand miles
I'll take that advice nobby. Seems like the only reasonable course of action. Especially since I don't want to leave the system with no corrosion inhibitors in coolants.
 

· Registered
1985 380 SL
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616 Posts
Looks to me that in addition to the wrong coolant somebody put in a lot of stop leak at some point. The block is cast iron but just about everything else in the engine that the coolant touches is aluminum. I would thoroughly flush everything separately (engine/rad/heater core) to try to get it all out.
 

· Registered
1983 380SL R107, LH drive
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254 Posts
Any old coolant will turn acidic, regardless of color. To my knowledge, the colored coolant (except the old traditional green) is mostly simply an environmentally friendlier product.
I had the same age-old coolant in mine too, and my WP looked similar to yours. After replacing the pump, thermostat, fluid, etc, everything was working fine until I learned of a small leak it had developed. To your question of corrosion, my leak came from the very middle of a section of the manifold behind the rear driver's cylinder. The sand casting had developed a pinhole leak, and it was quite evasive... hidden underneath a steel loop bracket (for hoisting engine). At first I thought it the bolt leaking, as it went through the manifold and threaded into the block.
I diligently cleaned the pinhole leak area and dabbed some JB Weld onto the area. It's holding. I did not bother to replace the steel bracket, so the 2 bolts show the sealant I used.
So the short of my story, is- yes, likely you have some corrosion and you can probably handle it.
 

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· Registered
1979 450SL UK spec
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2,734 Posts
I'm not very surprised about what you see, probably not uncommon on any old/expensive to maintain "cheap" car.

Mine looked like this when I stripped it. This was after detergent and citric acid treatment.

Automotive tire Wood Motor vehicle Gas Machine


There was also a fair bit of aluminium pitting.

Jewellery Silver Door Metal Automotive tire


Eventually to get all the gunk out.....

High-visibility clothing Workwear Hard hat Road surface Infrastructure
 

· Registered
1979 450SL UK spec
Joined
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2,734 Posts
The sand casting had developed a pinhole leak, and it was quite evasive... hidden underneath a steel loop bracket (for hoisting engine). At first I thought it the bolt leaking, as it went through the manifold and threaded into the block.
I diligently cleaned the pinhole leak area and dabbed some JB Weld onto the area. It's holding. I did not bother to replace the steel bracket, so the 2 bolts show the sealant I used.
I think this must be a common weak area on the head leading to coolant leaking to the bolts and corroding them and or leaking. One of my bolts had to be cut through via the gasket as it had seized.

Wood Font Gas Auto part Metal
 

· Registered
1978 450 SL
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96 Posts
Discussion Starter · #9 ·
I'm not very surprised about what you see, probably not uncommon on any old/expensive to maintain "cheap" car.

Mine looked like this when I stripped it. This was after detergent and citric acid treatment.

View attachment 2782768

There was also a fair bit of aluminium pitting.

View attachment 2782769

Eventually to get all the gunk out.....

View attachment 2782772
Man that pitting makes me cry. By no means are these cheap to maintain, especially through years of neglect.
Charging ahead!
 

· Registered
1973 450 SL, 2014 GLK 350
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132 Posts
I started burning coolant in mine so it seemed head gaskets were the order of the day. When the aluminum heads came off they were so corroded it turned out they were the problem. Fortunately we were able to weld up the bad spots, machine and put back together with a top end rebuild,water pump, thermostat, hoses and recored the radiator. Not to mention chain guides. Chain and sprockets were fine, no stretch or wear. My mechanic even loveingly restored and detailed the entire engine compartment, painted many items.

Naturally, the chain tensioner is going on me now, but that's another story.
 
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