Carbon in Coolant

Colo Bird

Registered User
I'm the original owner of an 89 SC with ~90,000 miles and original head gaskets. I have noticed that I'm getting unburned carbon in the coolant overflow tank that's coating the inside - also collects on the radiator cap. However, I notice no exhaust gas bubbles in the coolant or coolant in the oil which would be typical for a blown HG. There is some consumption of coolant which is steadily getting worse the past few thousand miles- no external leaks.

Is this a definite sign of a impending HG failure? Note that I had the supercharger top off recently and noticed some unburned carbon and oil in the housing which was probably coming from the PCV system. Gas mileage is bad currently which probably contributes to the carbon. Have replaced both O2 sensors and tested the coolant and ACT sensors. Checked the fuel press regulator for leakage into vacuum line. Can't seem to find reason for why gas mileage has dropped recently from 19-20 avg to 13-14 but the car is running rich even though the engine idles smooth (although low manifold vacuum at Denver's elevation) and I have plenty of power...

Any help is appreciated - I would like to keep this car in my garage and on the road.
 
Do you see little tiny black particles floating around in your overflow reservoir? That's what I'm experiencing lately. It made a scum ring around the top of the water level. I thought it may be paint from my new radiator cause it smells weird.
 
Do you see little tiny black particles floating around in your overflow reservoir? That's what I'm experiencing lately. It made a scum ring around the top of the water level. I thought it may be paint from my new radiator cause it smells weird.

Yes mine are very fine black particles forming a film in the reservoir. But I have done nothing to my coolant system lately except change the water pump and hoses. Looks like a fine soot or carbon. I may do a test on the coolant to see if it contains exhaust gases which would be a sure sign of HG failure. I have seen some minor oil in the coolant when the engine was very new. However, what worries me now is the coolant consumption is increasing dramatically although I don't see it as white smoke in the exhaust yet.
 
Thanks, but...what about the carbon in the supercharger? Isn't this possibly blowby from the combustion chambers through the PVC system?

I think you're looking at two, unrelated problems. Dave is right; your H/G's are going. I had a 90 LX that exhibited the same condition (particles in the coolant).

You would be doing yourself a big favor by taking the car out of service now until you can get the H/G's changed. If the gasket blows into the oil passage(s), you'll likely trash the bottom end of the engine. Coolant and bearings don't mix.

There's a lot of info on this site about doing this common project. As a matter of fact, I just finished one of my cars last month. It wasn't exhibiting any symptoms, but at 110K miles, I knew I was on borrowed time. The prospect of wiping out the bearings comepelled me to get this done. Attached is a link where I listed all the parts I used for the project that might help you out.

http://www.sccoa.com/forums/showthread.php?t=86529 (list is near bottom of post).

I replaced many things during my project that weren't head gasket-related, but you can pick through the list and find the applicable parts. I would, however, recommend changing the motor mounts, spark plugs and plug wires, at a minimum.

I did a lot of research before selecting these parts and I hope it saves you some time/money. You'll need a couple of special tools to get the job done, but they're not expensive or hard to come by. PM me if you have any questions.

Good Luck,

JD
 
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