Cleaner for coolant system

[TwoC400s]

Question: what's a good ABS plastic safe solvent to get rid of oil that's gooped up with coolant.

Back story:
I'm helping my son clean up a bit of a mess. His 2016 Mazda 3 2.0L had a head gasket go and it over heated. He paid a shop to swap in a pulled engine that allegedly had much less miles. This all happened outside of my view and hundreds of miles from where I live (he was visiting friends out of state).

Anyway that's the back story: head gasket popped, engine was replaced, and now the warranty on that work is over.

Today he was by the house and I was just looking the car over (it's a habit) and I noticed sludge in the overflow tank.

He told me the shop said that the sludge was pretty much everywhere in the cooling system, and unless he paid to replace every component of the cooling system as well, that sludge would show up in the over flow for a while. It looks like the sludge has been there a while.

I removed the overflow tank, but this stuff is really caked in the bottom of the tank. right now I'm just soaking it in hot, soapy water, but it's taking forever.

 

[Timmastertech]

Back when GM 3.1 and 3.4 intake gasket failures were a regular occurrence and would occasionally mix oil and coolant in the cooling system, GM had us clean up the oily ones with Cascade dishwashing machine detergent. Fill the cooling system with water and add soap and run the car til it gets clean. Id usually go a half hour or so, dump the cooling system and repeat. You will likely wind up replacing at least some hoses as the rubber hoses swell when they see oil.

 

[Nick1994]

Empty what you can and soak with some gasoline and shake it.

 

[maraakate]

Empty what you can and soak with some gasoline and shake it.

You mean kerosene? Never use gasoline to clean parts. Every service manual specifically warns you not to do it.

 

[jetman]

Its in a plastic container?

 

[TwoC400s]

Its in a plastic container?
View attachment 332242

The sad thing is, this jug costs almost twice what a new reservoir would cost from RA.

 

[ripcord]

Throw some nuts and bolts in the reservoir and agitate to clean the caked on stuff.

I've done the Cascade detergent flush to remove oily residue from the cooling system like Timmastertech mentioned. It works, but I would pull the thermostat and flush well with a garden hose to really rinse it out well. You should do a final round with distilled water after that if you have hard water where you live.

 

[jjblbi]

Cascade for oil residue, CLR for rust and/or mud. Flush well and fill with the proper mix of the correct anti-freeze and distilled water.

 

[PandaBear]

I used to use the Prestone stuff, but CLR should work as well as at least back then CLR was also something like a citric acid.

I would be careful of anything else in the coolant loop just in case it cause other problem after flushing out the goop from say head gasket. I might run a garden hose through it without any other chemicals.

 

[joshuawes1984]

I've poured simple green in my 6.0 Powerstroke's cooling system when doing a flush. Whole gallon jug of simple green, filled the rest up with tap water, and ran it up to temp. Then dump and flush, flush, flush, flush, flush and flush some more before the refill. Amazed me what came out.