Brown coolant
Thread Starter
Instructor
Joined: Feb 2009
Posts: 191
Likes: 0
From: Woodstock IL
Brown coolant
Ok I just bought a 93 corvette LT1 6spd. After driving it 1600 miles to Chicago I noticed my coolant was brown. And in the bottom of the coolant resevoir is some brown chunky residue. Thus far the car is not over heating at all and runs pretty cool. However, it does seem that the coolant in the resevoir gets lower and lower every day. So far I have noticed no coolant leaks. In fact the only leak is an small oil leak out of the front main seal.
What is the cause of this? Why is my coolant brown with chunky residue
What is the cause of this? Why is my coolant brown with chunky residue
Last edited by rogerdoger1993; Mar 7, 2009 at 08:50 AM. Reason: Grammar, spelling and added information
Instructor
Joined: Jul 2008
Posts: 218
Likes: 0
From: Utah County Utah
http://forums.corvetteforum.com/c4-t...is-engine.html
Instructor
Joined: Feb 2001
Posts: 117
Likes: 1
From: Acworth Ga
Your comments indicate the cooling system hasn't been taken care of regularly. Flushing every several years does wonders in keeping the corrosion down. Check very carefully for small leakage around seals and hose connections when the engine is at normal operating temp. I could be that you are losing coolant through evaporation leakage without liquid residue showing up. Also get some radiator flush, like from Prestone, and flush it out thouroghly. You might have to do it several times to clean out the chunky stuff.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
As mentioned above, it sounds like neglect. You just missed a really good thread on how to properly flush out your coolant system:
http://forums.corvetteforum.com/c4-t...em-for-c4.html
http://forums.corvetteforum.com/c4-t...em-for-c4.html
Thread Starter
Instructor
Joined: Feb 2009
Posts: 191
Likes: 0
From: Woodstock IL
Ok I am starting to feel better now. I just bought the car last weekend. And I thought maybe the previous owner sold me a car with a bad head gasket. Ok I will try to flush it out and refill it. And if it happens again ill let you guys know for sure.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Assuming good compression and driveability, I'd assume that someone added GM Coolant Sealing Pellets. They were called for in most Service Manuals and GM used them when they took asbestos out of the gaskets fearing that systems would develop leaks during the warranty without them. Later, they issued a Service Bulletin stating that they weren't used and that they did little other than make the gunk you've found. (Dealerships still seem to have an array of the things sitting out on the Parts Counter). Flush everything - consider taking the Radiator to a shop to have it rodded out - start over.
Navigator
Joined: Dec 2023
Posts: 9
Likes: 1
From: Houston
Not trying to sound dumb but when I first got my c6 I worked on it like it was my Camaro thinking it went radiator—->coolant resevoir. Windshield fluid on the other side of the bay and brake fluid near the back and I thought I had dark brown “coolant” only to find out that wasn’t the coolant reservoir lol it’s the brake fluid, the reservoir is under the radiator. This post is old and I’m sure you didn’t mess up like I did but this thread comes up first results for dark coolant so I thought I’d say my dumb experience so no one else has to look stupid at a mechanic asking for a flush haha
Melting Slicks
Joined: May 2014
Posts: 2,898
Likes: 592
From: New Port Richey FL
Brown oily coolant with brown slime at bottom of tank and radiator= Bars leak coolant system sealer a couple doses, is there a slight haze always in the windshield. Odds are precious owner had a slight leak somewhere (heater core possibly) and double dosed for the sale so clean out flush and start looking.
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Drifting
Joined: Oct 2020
Posts: 1,398
Likes: 438
From: Marlton NJ
For brown coolant I would be very inquisitive to see what the block looks like. I have to believe that the coolant passages in the block have not been flushed out in a long time. As others have said flush the system but don’t do just the radiator
Safety Car
Joined: Mar 2017
Posts: 4,215
Likes: 1,333
From: LeClaire Iowa
Shop vac flush works! - CorvetteForum - Chevrolet Corvette Forum Discussion
I had the same thing on my 96. This method cleaned it out. Dan
I had the same thing on my 96. This method cleaned it out. Dan
Pro
Joined: Jun 2018
Posts: 532
Likes: 104
Flushing might help, it might not. It did not help me. Key is not just that it is brown, but that you are losing coolant as well. That means it has to be leaving the car somehow, unless it is leaking on to the floor or the ground, it is either going into the crankcase or more likely into the combustion chamber and out the exhaust.
That to me implies a head gasket leak, which are common on these cars. It can drive fine like this for years, tens of thousands of miles. As long as you don't mind the color you just need to fill it when it gets low.
If you want to be sure get one of the kits that tests for combustion gasses in the radiator.
That to me implies a head gasket leak, which are common on these cars. It can drive fine like this for years, tens of thousands of miles. As long as you don't mind the color you just need to fill it when it gets low.
If you want to be sure get one of the kits that tests for combustion gasses in the radiator.
