Hey guys, 2010 assault, got back from the mountains a while back and just noticed my coolant reservoir bottle has a black film of carbon on the inside. Doesn't appear to be any oil in the coolant / no discoloration, it is a dry film, you can scrape it off with your finger and looks like exhaust carbon. No discoloration on the plugs, boro scoped the pistons, no coolant leak that i could see, coolant level isn't dropping. Was thinking maybe head gasket or o rings allowing some exhaust gas in? water pump going? some crap in the coolant system? sled runs like a champ 350 miles on full rebuild, mtntk fix kit, new cylinders, full slp exhaust, slp coolant bypass, pcv5, etc... Sled got pretty warm on the trail on one day rose to almost 170 but, not for long (low snow and climbing in elevation), was 120-130 for the rest of the time. Any insight?
Carbon on inside of coolant reservoir?
- Thread starter Assault81
- Start date
What did you do to fix it or did you just let it be? mine is a stock head, so i'm thinking new head gaskets and o rings, kinda weird though cause they're pretty new.
If there is grey color inside to coolant bottle, THAT IS THE REASON.
its jet black in color looks exactly like exhaust carbon when I scrape it off with my finger but, sounds like the problem, before next season I'll replace the head gasket and o rings. Thanks guys 
