What causes rad fluid to discolor??
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
What causes rad fluid to discolor??
I remember draining the fluid out of an old GM 250 straight six after about 70,000 miles and it was as clear as the day it was put in. (almost) I run it in my 350 V8 and it is green/brown after about 500 miles... what is up with that?
I know that if the engine has aluminum heads/intake, running the diff metals can do this but I am sure mine is all iron. :confused:
I know that if the engine has aluminum heads/intake, running the diff metals can do this but I am sure mine is all iron. :confused:
Instructor
Joined: Jul 2002
Posts: 110
Likes: 0
From: sarasota fl
Re: What causes rad fluid to discolor?? (KJL)
had this same problem.put a new motor int the car and kept having discolored radiator fluid.after looking over everything found that the old overflow tank had brown goop in it.after replacing it with a new tank the fluid has been fine for 8,000 miles.
Melting Slicks
Joined: Dec 2000
Posts: 2,635
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From: Union Ontario
Re: What causes rad fluid to discolor?? (jn79vette)
I say the brown is rust that you disturbed when you flushed the system out. FLush again( with water only), and it will probably do the same thing. keep on doing it until it stays fairly clear the put antifreeze back in.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
Re: What causes rad fluid to discolor?? (jn79vette)
I don't have an overflow tank but now that yall mention it, the system could probably use a good flushing. I bet the bottom of my rad has about an inch of mud in it!! I have only had the car for about a year and a half and flushing the rad kind of fell off the "to do" list!! 
Safety Car
Joined: Apr 2001
Posts: 4,795
Likes: 1
From: Regina Saskatchewan, Canada.
Re: What causes rad fluid to discolor?? (SmokedTires)
You can get rust from the spring inside the bottom rad hose which can cause discoloration ;) .
Safety Car
Joined: Oct 1999
Posts: 4,101
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From: NorCal
Re: What causes rad fluid to discolor?? (KJL)
It's definitely rust. It starts when Coolant is old and turns acidic (we use Ph dip papers to check it), and while it still looks green, it starts to eat freeze, plugs, waterpump plates, those springs in the hoses, etc... Different cars, for no particular reason, do it more than others. My Vette has it bad (from the previous owner) and I've been flushing and adding new coolant since I got it. I use distilled water and name brand coolant, and it's slowly getting better, but I've probably done it 6 times in the last 2 years! I mostly worry about the freeze plugs and the heater core.
Hans
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