i just picked up a used 8870 , 1995 model , 5300 hours . the crankcase is getting pressure in it . i have removed the breather and it seems fine from the filter out . i.ve thought , maybe head gasket , but when i pull the oil bung after it sitting for 5 or 10 min. and it still has pressure , i have to think it is still a breather issue . has anyone else had this issue . thanks in advance for any help .