kevinski Use a careful low pressure flush,it''ll act like a water heater you'll get some dirty water then run clean---not even close to clean !!IF IT FLOWS AND HEATS GOOD better leave it alone. On your block some time when you have the head off you can hurt that sludge that piles -up around 5 and 6 with a big screwdriver and hammer. Outside of that be glad it will run cool !!
