Cleaning Rusty Clay Like Substance (Cooling system)

[thescreensavers]

I got a 1983 BMW E21, the car definitely sat for a while.

Anyhow we removed the radiator to remove the condenser and all the water cooling pipes have a nice coating of rusty clay like substance previous owner might not have used antifreeze.... What is the best way to clean this out? Ideally not removing the engine.

Some people pour in Metal Ready into the cooling system is that a good way to do that?

 

[monkeydelmagico]

lime away or CLR for metal. Replace the rubber.

YMMV this is off label use

 

[thescreensavers]

^ my friend mentioned CLR too hah for like an Hour then dump it guess we will go that route.