Black grease in radiator

[Bowed]

About a month ago I bought a 98 GMC short bed with a 305/auto and 85k miles . I notice the inside surface of the radiator is covered with a black grease . If I stick my finger down inside there and rub around , the finger comes out all black and greasy . I drew some coolant from off the top and even though it's not perfect , it's not all that bad either . There are no signs of oil in the coolant that I could see . The coolant level seems to stay constant and no drip at the tail pipe to indicate a head gasket. I also notice that even though the coolant level is exactly where it should be , every once in a while , right after the truck is parked , it spits out a little coolant on the ground . This slight spill is not coming from the reservoir overflow tube and no leaks are apparent at either top or bottom of engine , water pump , radiator or freeze plugs . It is not AC drip either , it's coolant . I am at a loss to where it is actually coming from and like I said it's not all the time . Well , do we have any ideas .

[GASoline71]

Is there coolant in the oil?

Gary

[HarrisonTX]

That is weird. I wonder if its some sort of "STOP LEAK" coating??

Since you say there's a leak you cant find, maybe the previous owner poured some stuff in there to "seal it up''?

[clinebarger]

Originally Posted by Bowed

About a month ago I bought a 98 GMC short bed with a 305/auto and 85k miles . I notice the inside surface of the radiator is covered with a black grease . If I stick my finger down inside there and rub around , the finger comes out all black and greasy . I drew some coolant from off the top and even though it's not perfect , it's not all that bad either . There are no signs of oil in the coolant that I could see . The coolant level seems to stay constant and no drip at the tail pipe to indicate a head gasket. I also notice that even though the coolant level is exactly where it should be , every once in a while , right after the truck is parked , it spits out a little coolant on the ground . This slight spill is not coming from the reservoir overflow tube and no leaks are apparent at either top or bottom of engine , water pump , radiator or freeze plugs . It is not AC drip either , it's coolant . I am at a loss to where it is actually coming from and like I said it's not all the time . Well , do we have any ideas .

On the coolant leak, its probably the intake gaskets. 96-98 vortecs are notorious for leaking intake gaskets. The black grease, im not sure. chould be sediment mixed with the dex-cool coolant. Even though it only has 85K its still 12 years old.

[clinebarger]

Originally Posted by HarrisonTX

That is weird. I wonder if its some sort of "STOP LEAK" coating??

Since you say there's a leak you cant find, maybe the previous owner poured some stuff in there to "seal it up''?

I agree, Trying to stop the intake leak.

[Bowed]

Originally Posted by GASoline71

Is there coolant in the oil?

Gary

Thanks for answering ... No coolant in the oil .

[ChevLoRay]

What I noticed my '96 Silverado radiator neck had an orange crust in it and that the reservoir kept going empty, I figured out it was the organic antifreeze mixing with air that caused the crust. Replacing the intake gaskets solved the problem.

Now, if someone mixed the green and the orange coolants, could it produce that crud that you found? Maybe that and something like Bar's Leaks....

[Bowed]

Originally Posted by clinebarger

On the coolant leak, its probably the intake gaskets. 96-98 vortecs are notorious for leaking intake gaskets. The black grease, im not sure. chould be sediment mixed with the dex-cool coolant. Even though it only has 85K its still 12 years old.

The coolant is not Dex , it's the yellow stuff . The small spill does not happen all the time , just once in a while and it lands directly under the engine . I can't find a coolant track anywhere . Thanks .

[Bowed]

Originally Posted by ChevLoRay

Now, if someone mixed the green and the orange coolants, could it produce that crud that you found? Maybe that and something like Bar's Leaks....

Sorry , I'm real slow at typing and didn't see your post before I answered Clinebarger . So .. yellow and red don't go together unless you want a messy radiator . Guess the PO didn't know that either . I will get a can of flush , clean it out and then replace the coolant . Thanks .