residue on bottom of radiator cap.

TbirdSCFan

Registered User
Wonder if any one else has seen this. I have a layer of black gummy residue on the bottom of my radiator cap. Original HGs BTW and I plan to replace them.. is this a sign that I should do it sooner rather than later ?
 
That black goo is a combination of rubber parts breaking down and exhaust gas residue. Sounds like your HG's are starting to weep.
 
head gaskets

I could be wrong as I'm not an expert...
I've read and experianced first hand it was white crap in the cap as well as other symptoms that indicated it was a blown head gasket?.
Like I said I'm no expert but I personally would replace them....especially if your over 100,000 miles.
Hope this helps,
Bryan
 
That all depends on where the HG's are leaking. White scum means theres a leak of the water jacket into the crankcase. You can also get the white scum without any HG leakage into the crankcase by running the engine in cold temps and not letting the engine get up to full oporating temp for a period of time needed to evaporate the water condensation in the crankcase that you get as the cold engine starts to warm up. The warming engine will sweat on the inside causeing moisture to form. You need to let an engine run long enough in very cold outside temps in order to burn off the condensation in the crankcase or you will get that white scum.
Should the HG leak between the combustion chambers and the water jackets you get hot burnt gasses into the cooling system and it forms a black goo.
Theres more than 1 way a HG can fail and theres not 1 single symptom that gives you clues as to if there going or not, there can be different symptoms for the same problem.
 
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