When I checked my coolant I noticed that I have a black clay like build up in my radiator cap. I cleaned it off 2 days ago and it's back. Its not the common brown sludge that you see when dexcool goes bad. This is a '04 supercharged SS with only 46,000 miles on it. Can bad dexcool cause this black carbon like buildup or is there something else like bad manifold gaskets or head gaskets that could cause this? And can this crap be flushed out or will I need to replace the radiator and heater core? Thanks.

Den

 

Hm.. I would guess head gasket, intake gasket, or maybe somebody put stop-leak in the radiator at some point?

 

I did a Google search on this and I seen others complain about stop leak being added causing a black clay residue to buildup on radiator cap. I don't have any white smoke coming out of exhaust or coolant in my oil. The car runs perfect and the temp is below the halfway point on the gauge with the AC on in 90 degree weather. I'm gonna have a Chevy dealer do a flush and refill. They only charge $140. And I'll bet the intake gaskets are shot as well.

 

Have some more stop-leak handy. That flush will probably re-open the original leak. If you don't know when it was flushed last then it is still a good idea. And if it leaks, at least you know the stop-leak will work (again)

 

Yeah if it leaks that's ok. A new radiator cost $128 at Rockauto. There's a little coolant on my lim. I wouldn't be surprised the car dealership where I bought the car probably put stop leak in there cause the intake gaskets are bad and that's what's causing the black gunk. Cause I only drove the car for a month last summer and I didn't see any black stuff. But this summer I'm noticing it. Like I said, the car runs perfect and runs cool despite it being hot as hell here in Jersey. And its 15 years old. Damn nice car.

 

Same thing happen to me .. The cause of mine was that the transmission cooler cracked into the radiator .. So it was leaking trans fluid into the water that was cooling the engine .. Mine never got hot eather but the trans would start slipping from being low got a new radiator took care of the problem .. Had to flush the engine about 5 times to clean it out ..

 

wow . Did you see anything wrong with your tranny fluid? Did your tranny fluid look any different? I've looked at my trans fluid on this dipstick and smells and looks like it should. But I've got to get it flushed right away and have the dealer inspect the radiator, heater core and the trans. Thanks for posting this.

 

Black gunk on radiator cap. This amount of gunk builds up in a few days.

 

No .. The trans fluid look fine .. Just got low leaking into the Rad .. Have had no problems on either issue since the Rad change .. Take care ..

 

Lastnight I rechecked my trans. fluid with the engine fully hot and the trans fluid was right were it was supposed to be on the dipstick. Plus it wasn't burnt or discolored.