brown sludge in my coolant
Thread Starter
Pro
Joined: Jun 2018
Posts: 532
Likes: 104
brown sludge in my coolant
So I have brown oily sludge in the coolant on my 89. I have flushed it twice now. Have not flushed the passengers side block because I broke the knock sensor trying to get it off and after I paid $400 to get the stud extracted did not want to screw with it again. The sludge floats on top of the coolant, so it is lighter than water.
The rest of the engine other than the passengers side block has been thoroughly flushed and a leaking heater core has been replaced, so the heatercore is brand new. I still keep getting blobs of oil like "scum" showing up in the coolant.
My first thought is a head gasket, especially since it has aluminum heads but: There are no bubbles in the coolant, no noticeable water in the oil, no white smoke, no overheating, good compression on all cylinders, it does not lose coolant.
Could it be a really really mild case of a blown head gasket with no other symptoms?
Could it be that there is just that much crap, scale and rust in the block on the passengers side?
Could be a leak inside the oil cooler with oil leaking into the coolant? I would think I would get some coolant back into the oil, especially since the cooling system is pressurized for a while after you turn the car off.
The rest of the engine other than the passengers side block has been thoroughly flushed and a leaking heater core has been replaced, so the heatercore is brand new. I still keep getting blobs of oil like "scum" showing up in the coolant.
My first thought is a head gasket, especially since it has aluminum heads but: There are no bubbles in the coolant, no noticeable water in the oil, no white smoke, no overheating, good compression on all cylinders, it does not lose coolant.
Could it be a really really mild case of a blown head gasket with no other symptoms?
Could it be that there is just that much crap, scale and rust in the block on the passengers side?
Could be a leak inside the oil cooler with oil leaking into the coolant? I would think I would get some coolant back into the oil, especially since the cooling system is pressurized for a while after you turn the car off.
Last edited by auburn2; Nov 26, 2020 at 09:22 PM.
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
So I have brown oily sludge in the coolant on my 89. I have flushed it twice now. Have not flushed the passengers side block because I broke the knock sensor trying to get it off and after I paid $400 to get the stud extracted did not want to screw with it again. The sludge floats on top of the coolant, so it is lighter than water.
The rest of the engine other than the passengers side block has been thoroughly flushed and a leaking heater core has been replaced, so the heatercore is brand new. I still keep getting blobs of oil like "scum" showing up in the coolant.
My first thought is a head gasket, especially since it has aluminum heads but: There are no bubbles in the coolant, no noticeable water in the oil, no white smoke, no overheating, good compression on all cylinders, it does not lose coolant.
Could it be a really really mild case of a blown head gasket with no other symptoms?
Could it be that there is just that much crap, scale and rust in the block on the passengers side?
Could be a leak inside the oil cooler with oil leaking into the coolant? I would think I would get some coolant back into the oil, especially since the cooling system is pressurized for a while after you turn the car off.
The rest of the engine other than the passengers side block has been thoroughly flushed and a leaking heater core has been replaced, so the heatercore is brand new. I still keep getting blobs of oil like "scum" showing up in the coolant.
My first thought is a head gasket, especially since it has aluminum heads but: There are no bubbles in the coolant, no noticeable water in the oil, no white smoke, no overheating, good compression on all cylinders, it does not lose coolant.
Could it be a really really mild case of a blown head gasket with no other symptoms?
Could it be that there is just that much crap, scale and rust in the block on the passengers side?
Could be a leak inside the oil cooler with oil leaking into the coolant? I would think I would get some coolant back into the oil, especially since the cooling system is pressurized for a while after you turn the car off.
Drifting
Joined: Feb 2017
Posts: 1,274
Likes: 399
From: Tacoma WA
2024 C4 of the Year Finalist - Unmodified
Mixing of the green coolant with the orange Dexcool will do exactly what you are experiencing. You can change from one to the other but the system has to be flushed completely to avoid mixing of the two types. Is it possible someone mixed the the two types?
Racer
Joined: Oct 2020
Posts: 271
Likes: 83
GM also used to sell these brown pellets that went in the coolant. My 91 Eldorado had it basically from the factory I flushed that multiple times and replaced the heater core twice cause it kept plugging with that mud.
Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 276
From: Melbourne, Victoria, Australia
So I have brown oily sludge in the coolant on my 89. I have flushed it twice now. Have not flushed the passengers side block because I broke the knock sensor trying to get it off and after I paid $400 to get the stud extracted did not want to screw with it again. The sludge floats on top of the coolant, so it is lighter than water.
The rest of the engine other than the passengers side block has been thoroughly flushed and a leaking heater core has been replaced, so the heatercore is brand new. I still keep getting blobs of oil like "scum" showing up in the coolant.
My first thought is a head gasket, especially since it has aluminum heads but: There are no bubbles in the coolant, no noticeable water in the oil, no white smoke, no overheating, good compression on all cylinders, it does not lose coolant.
Could it be a really really mild case of a blown head gasket with no other symptoms?
Could it be that there is just that much crap, scale and rust in the block on the passengers side?
Could be a leak inside the oil cooler with oil leaking into the coolant? I would think I would get some coolant back into the oil, especially since the cooling system is pressurized for a while after you turn the car off.
The rest of the engine other than the passengers side block has been thoroughly flushed and a leaking heater core has been replaced, so the heatercore is brand new. I still keep getting blobs of oil like "scum" showing up in the coolant.
My first thought is a head gasket, especially since it has aluminum heads but: There are no bubbles in the coolant, no noticeable water in the oil, no white smoke, no overheating, good compression on all cylinders, it does not lose coolant.
Could it be a really really mild case of a blown head gasket with no other symptoms?
Could it be that there is just that much crap, scale and rust in the block on the passengers side?
Could be a leak inside the oil cooler with oil leaking into the coolant? I would think I would get some coolant back into the oil, especially since the cooling system is pressurized for a while after you turn the car off.
It should be as others have mentioned, I would test it with fresh 50/50 mix coolant concentrate and water after flushing the block thoroughly don't forget heater hoses and oil cooler hoses.
the only way oil could get into the coolant would be under pressure, a blown head gasket would not give you an oil supply. Usually you would get cream / chocolate colour under the oil filler cap if coolant leaked via blown head gasket, not oil into the coolant.
Compression test will show if you have a blown head gasket, if the coolant had been changed regularly you should not have a head gasket issue with low miles.
Cheers
Gerard
Safety Car
Joined: Mar 2017
Posts: 4,206
Likes: 1,325
From: LeClaire Iowa
https://www.corvetteforum.com/forums...ush-works.html
I had the same problem. The bad part about just draining the block through the knock sensors is the is no agitation of the scum. All that drains out is the scum in suspension. It does nothing for what is coating the sides. Once I did this there is NO scum left. Dan
I had the same problem. The bad part about just draining the block through the knock sensors is the is no agitation of the scum. All that drains out is the scum in suspension. It does nothing for what is coating the sides. Once I did this there is NO scum left. Dan
Le Mans Master
Joined: Aug 2017
Posts: 6,943
Likes: 1,490
From: New Jersey
That's only an issue if you're using non extended life coolant. The green prestone is chemically identical to dexcool... I called them and asked. And have hD it mixed a couple times. Aside from it being an orange green color it didn't make sludge in the 7 years it was in there. Back in the 90s when there was a difference it was however an issue but since most coolant is extended drain now they all have the same additive aside from color and are for the most part compatible.
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
Someone probably added some sealant to fix a leak in the past . Also when the coolant hoses start to deteriorate from the inside you will see something like this. Pics would help. If it has the original hoses, change them with the flush.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Pro
Joined: Jun 2018
Posts: 532
Likes: 104
It is not overheating, so I am not too inclined to worry about it if this is it.
Last edited by auburn2; Nov 27, 2020 at 06:35 PM.
Thread Starter
Pro
Joined: Jun 2018
Posts: 532
Likes: 104
Hi
It should be as others have mentioned, I would test it with fresh 50/50 mix coolant concentrate and water after flushing the block thoroughly don't forget heater hoses and oil cooler hoses.
the only way oil could get into the coolant would be under pressure, a blown head gasket would not give you an oil supply. Usually you would get cream / chocolate colour under the oil filler cap if coolant leaked via blown head gasket, not oil into the coolant.
Compression test will show if you have a blown head gasket, if the coolant had been changed regularly you should not have a head gasket issue with low miles.
Cheers
Gerard
It should be as others have mentioned, I would test it with fresh 50/50 mix coolant concentrate and water after flushing the block thoroughly don't forget heater hoses and oil cooler hoses.
the only way oil could get into the coolant would be under pressure, a blown head gasket would not give you an oil supply. Usually you would get cream / chocolate colour under the oil filler cap if coolant leaked via blown head gasket, not oil into the coolant.
Compression test will show if you have a blown head gasket, if the coolant had been changed regularly you should not have a head gasket issue with low miles.
Cheers
Gerard
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
In the same boat, just not as bad. Maybe youll get lucky wtih something but these 113s are known to spring head gasket leaks.
Pull your radiator cap and test your cyl pressure or do a leakdown test. Ck plugs esp numbers 7 and 8 see if they are extra clean.
Do you have any kind of miss or stumble at idle? Ever get a whiff of coolant?
If you hold your hand over the exhaust does it feel damp and oily?
Once had a van that used to have orange coolant..I put green in it and it looked pretty nasty keep us posted.
Pull your radiator cap and test your cyl pressure or do a leakdown test. Ck plugs esp numbers 7 and 8 see if they are extra clean.
Do you have any kind of miss or stumble at idle? Ever get a whiff of coolant?
If you hold your hand over the exhaust does it feel damp and oily?
Once had a van that used to have orange coolant..I put green in it and it looked pretty nasty keep us posted.
Thread Starter
Pro
Joined: Jun 2018
Posts: 532
Likes: 104
In the same boat, just not as bad. Maybe youll get lucky wtih something but these 113s are known to spring head gasket leaks.
Pull your radiator cap and test your cyl pressure or do a leakdown test. Ck plugs esp numbers 7 and 8 see if they are extra clean.
Do you have any kind of miss or stumble at idle? Ever get a whiff of coolant?
If you hold your hand over the exhaust does it feel damp and oily?
Once had a van that used to have orange coolant..I put green in it and it looked pretty nasty keep us posted.
Pull your radiator cap and test your cyl pressure or do a leakdown test. Ck plugs esp numbers 7 and 8 see if they are extra clean.
Do you have any kind of miss or stumble at idle? Ever get a whiff of coolant?
If you hold your hand over the exhaust does it feel damp and oily?
Once had a van that used to have orange coolant..I put green in it and it looked pretty nasty keep us posted.
I did smell coolant when my heater core was leaking but not since then.
Last edited by auburn2; Nov 28, 2020 at 05:38 AM.
Safety Car
Joined: May 2001
Posts: 4,759
Likes: 1,647
From: Fairfax Virginia
I had a Buick develop the brown sludge type stuff appeared in my overflow bottle. Less than a month later my head gasket blew out. I used the Red DexCool and my engine did get hot once when the cooling fan died. The mechanic told me that the sludge was the gasket material breaking down from my Dexcool Coolant being 8 years old. Some of the materials used in DexCool change PH when exposed to high heat and become acid.
Today they make heater cores out of aluminum instead of brass like the old days. The aluminum gets eaten by the coolant if not changed on schedule. Our 2011 Camaro had the Heater Core go at around 37,000 miles and 6 years old. It was the junk aluminum that started to leak. Now it even MORE important to keep these new cars coolant flushed every five years.
Today they make heater cores out of aluminum instead of brass like the old days. The aluminum gets eaten by the coolant if not changed on schedule. Our 2011 Camaro had the Heater Core go at around 37,000 miles and 6 years old. It was the junk aluminum that started to leak. Now it even MORE important to keep these new cars coolant flushed every five years.