Have M20 on engine stand, want to clean coolant passages

[CubbyChowder]

I'm in the process of prepping an M20 to swap into my '87 325is and I noticed that the coolant passages are filled with chunky and flaky gunk everywhere when I removed the water pump. I'd like to clean this all out as good as I can before I start putting stuff back together, but everything I've seen says you need to get the car up to operating temp several times.

Does anyone have any tips or methods on how I could go about cleaning all of these passages out with the motor on a stand? Could I fill it and soak it with a solution overnight or something like that and then flush it all out? Any help would be appreciated.

Here's how it looks with the water pump removed

[TimeMachinE30]

Break it down more?

[SkiFree]

Mikey...

Option 1: Hot tank the block
Caveots: Requires engine tear down, ruins intermediate shaft bearings

Option 2: CLR (diluted hydrochloric acid) flush
Caveots: Keep it away from aluminum

Hope that helps!

[jlevie]

I'm with SkiFree except that I'd use Oxalic acid, which is reasonably safe for aluminum on short exposure. However, for it to work the engine will have to be hot and you will have to circulate the solution. So basically there isn't a practical way to do this without the engine installed and running.

See http://www.r3vlimited.com/board/show...07&postcount=8 for a flush procedure.

[CubbyChowder]

Hey guys thanks for your input.

I am not planning on tearing this engine down any further than I already have (as pictured), so the hot tank solution isn't really an option for me unfortunately.

It seems like I will likely have to flush everything out once the motor is back in the car so I can get it up to operating temps and really clean things out, several times.

What concerned me this evening is that I pulled the drain plug on the passenger side of the block and found that it was completely clogged with black debris that resembled oily dirty grime buildup that always accumulates over the years on the outside of the engine. It went pretty far back too.



Would a standard chemical flushing procedure pull most of this out of the coolant passages? Sorry for all the questions, this is just my first time performing this. Thanks

[Panici]

Let me preface with: I've never dealt with this before.
Is it possible to knock out the freeze plugs, then scrub everything you can see by hand? Then put in new freeze plugs?

Just food for thought.

[jlevie]

Finding the block drain being plugged isn't uncommon and indicates poor maintenance in the past. A "standard flush" using a commercial compound will clean up the block pretty well, but it won't remove the rust.

[tim88325is]

Evapo-rust is awesome stuff to use, google it, I have found all the claims to be correct.

[jlevie]

From what I can find, it seems that Evapo-rust isn't aluminum friendly. It might be okay on a bare block, but I'd hesitate to try it on an assembled engine. Basically you'd have to submerge the block and eliminate air pockets, then hope it doesn't damage the intermediate shaft bearings.

[dnguyen1963]

^ This. You can wrap a piece of aluminum foil around a stick. Immerse it in Evapo-Rust overnight and see how much of the aluminum foil is left in the morning.

[ForcedFirebird]

Etch N Prep, Por-15, Ospho, or any other phosphoric based solution will convert the rust, and is safe for short term aluminum contact. What you have is common on these 30yr old engines, see it often and a good flush after install takes care of it. Long handle engine brushes and some elbow grease goes a long way if it's on a stand, though.

[CubbyChowder]

Thanks for all the input everyone. I think I have decided that I will perform a few chemical flushes once the engine is installed and running properly. I don't think my situation is as bad as I had originally thought.

[tim88325is]

http://www.evapo-rust.com/product-info/faqs/

[tim88325is]

"This. You can wrap a piece of aluminum foil around a stick. Immerse it in Evapo-Rust overnight and see how much of the aluminum foil is left in the morning."

I am curious if this is something you have already done? What was the result?

[dnguyen1963]

"This. You can wrap a piece of aluminum foil around a stick. Immerse it in Evapo-Rust overnight and see how much of the aluminum foil is left in the morning."

I am curious if this is something you have already done? What was the result?

I have done this with other rust removal products, but not with Evapo-Rust. If the product is not compatible with aluminum then you would see the foil is pocketed.