Pontiac Repair: 1998 pontiac bonneville sle, pontiac bonneville, coolant temp

Question
the coolant temp on my bonneville fluctuates from about 200 down to 140 and the heat is not very warm and i just put a new thermostat in that is set at 195. what can be another issue?

Answer
Hey Blake:

Did this ever over heat? If is then I would start looking for a possable head gasket issue if it ran hot enough it may have blown a gasket. Was this low on coolant before it may have over heated? These enegines are a bit touchey when they run hot. The opper part of the engine is made of plastic and they warp and distort and start leaking coolant into the engine and that can be the root cause of an overheat issue. These engiens are also heard to bleed air out of the system. You may have an issue where it has an air pocket trapped in the system. there is an air bllled er screw on the thermostat housing you can get it up to opertaing temp and then crack open that screw untill you just get a steady stream of coolant and no air. MAke sure the mixture of coolant is 50/50 and no more no less it affects the way the coolant works not only for freezing but for tempature absorption from the engine. did you use a factory termostat or an aftermaket one? cheap aftermarket ones will do wierd things and will no cycle fast enough and you can get a huge temp swing. was this issue the reason for the t/stat change in the first place? good luck :)