Rb20 coolant turns brown :/

[Liquidus]

So, my coolant gets pretty gross really fast. Just had the system flushed, but now it looks bad again. Is this for sure a head gasket issue, or could it be the turbo? What's the best way to figure out which it is. Did a compression test, all cylinders tested well. Not sure what else to do before pulling the head.

[OutToWinPAHC]

Do a coolant pressure test, they have them at loan a tool at advanced, oreilly, etc they cost about 300-350. Test at 1.1-1.3 bar and see if she holds pressure (car off of coarse). Let it site a good 30+ minutes if pressure drops there is a cooling system leak somewhere.

But could just be a rusted bloack from running only water in the past. If it check out, just keep flushing it and use a mix of at least 30% coolant.

Dont forget to bleed the system after coolant pressure test and flushings.

[Carl H]

are you running straight water?

[Ramius83]

Have you always had this problem? My RB26 sat for who knows how long before I bought it and the coolant that was left in the block rusted over and turned brown. Multiple and multiple and multipe flushes were done by me at my dealership, kept turning dirty in a matter of days. Problem finally went away when I built the engine and had the block/head vatted/cleaned. This will keep happening until the block/head corrosion/rust heats/bakes off over time.

[rblover]

its normal, the block is iron and any water and air mix will cause rust to form, use nissan blue coolant or honda blue, the blue coolant has much better anti-corrosion properties, so do a few flushes then when you think you got most of the nasty rust out, fill with the blue 50/50, I just rebuilt my rb20 and it was alot better in the block ports than my first rb rebuild, still had light rust but no chunks of rust like the first time.

[opticnerv]

I read somewhere that you can clean the inside of the coolant jackets with some type of acid. Someone please confirm this. My RB has the same issue I'm afraid the rust chunks may create a clog somewhere ! haha

[rblover]

i don't recommend using acid on an assembled engine, only bare components were you can rinse the acid off after treatment

[bmart]

I used citric acid to flush mine because it was doing the same thing. I put 5lbs mixed with water in the coolant, ran it untill it was warm (~20 minutes), then flushed it with a garden hose with the thermostat removed. All the rust was gone and the thermostat housing/block looked new. I haven't had a problem with it since I did it.