What is the brown sludge in my radiator

[leroylucky]

Im just completing a sbc swap. I put new head gaskets, intake manifold, and radiator. I have run the motor a few times but have not driven it. When getting ready for the maiden voyage today I checked the coolant and found brown sludge on the cap and in the radiator.(Looks like baby boo boo)

I checked the dip stick and the oil is like new.

What is it? And how do I fix it?

[z2go]

What does the baby doodoo smell like? What is the history of the coolant? Has the proper ratio of coolant to water been used, and changed at a reasonable interval? There's a lot of unknowns here. You might also have luck checking on the world wide web for troubleshooting like this, especially on a chevy.

[leroylucky]

It doesn't smell like anything. Maybe battery acid smell.

The coolant is new as I just completed the swap.

I used 30% coolant @ first but after chasing down a small coolant leak on the intake manifold its probably like 10% coolant.

[z2go]

Did you flush the system before changing the radiator? It might be sludge that came out from the block. Possibly rust? If the engine sat for a long time with water in it, that's possible. If it were me, I would clean it up, flush the system and check again after running it. If it's gone or starts to go away, it was probably just gunk that was stuck in the engine, if it comes back full force, you know you have a problem.

 

Caveat: I am not a professional, I would still check with a mechanic for other possibilities.

[getoffmyinternet]

Rust.

[jasper]

BROWN:

Could be RUST.

Could be OIL.

Could be BARS LEAK ,(branded radiator,etc. sealer)

If it is OILY in nature, drain, remove thermostat, fill with water and SIMPLE GREEN.

Run, drain, repeat. This WILL clean the system. Hoping it's old/residual contamination.

Flush by removing upper hose at radiator, fill radiator with hose while running, till running clear.

Refill with 50/50 mix, and thermostat. If contamination recurrs, you've got oil getting into thecooling system.

Either engine oil or trans fluid(if auto trans).

 

PS: may also be baby boo booo sabotage!!

Edited January 13, 2011 by jasper

[280zNHChris]

Just hope your coolant isn't acting like a bong and filtering lost compression through the head gasket into the coolant passage. If it's like baby poop, it could be the oil and gas blowby. When you shut the motor off is there a gurgling sound from the radiator area? Just a guess... Good luck.

Edited January 13, 2011 by 280zNHChris

[hoov100]

It's most likely aluminum/iron shavings from someone trying to cure a coolant loss problem.

[1993_570ZX]

Last time I had a nasty coolant, like... Ive flushed it 3 times and after a week it comes back brown from rust. I went and poured a quart of CLR with distilled water into empty cooling system. Drove it like that for 3 days. Then ran it with a hose in one end. Then flushed 2 times with distilled water, running the engine each time to get flow. Making sure to clear out any remaining CLR and no crap water. Refilled with 50/50 mix distilled and coolant, and been beautiful ever since. I got some nasty crap out with the CLR. works great.