Vehicle make/model = 1998 Pontaic Transport
Mileage = 230000 km
Engine size = 3400
dash lights = No
codes = No
work done prior = None
work done to repair = Thermostat was replaced but problem still there
tech = JK
question = Hi, I have a 1998 Pontiac transport montana. The heat will
go from hot to cold then back from hot to cold then the temp will rise
to hot then drop down to about 60 d then to about 100/110 and the heat
will blow hot for about 5-10 min then same thing all over again i
replaced the thermostat and the problem still there any help will be
appreciated thank you
JK
Sounds as if you are getting air in the cooling system. Some common causes of this are
leaking lower intake gasket, or blown headgaskets. The rear headgasket is prone to this
condition. From under the van, the pass. side of the rear cylinder head may show signs of
leaking externally. If that is the case, it may also be pushing compression into the cooling
system. Air in the cooling system will affect the heater in the manner you have described.
You may want to let engine run with radiator cap off and look for bubles. Or remove the
spark plugs and inspect for signs of burning coolant.
It is possible that the replacement of the t-stat fixed the heater problem, but you have air
in the system from that procedure. This would act as if you still have the same problem,
but in fact just need to bleed system.
Back
Mileage = 230000 km
Engine size = 3400
dash lights = No
codes = No
work done prior = None
work done to repair = Thermostat was replaced but problem still there
tech = JK
question = Hi, I have a 1998 Pontiac transport montana. The heat will
go from hot to cold then back from hot to cold then the temp will rise
to hot then drop down to about 60 d then to about 100/110 and the heat
will blow hot for about 5-10 min then same thing all over again i
replaced the thermostat and the problem still there any help will be
appreciated thank you
JK
Sounds as if you are getting air in the cooling system. Some common causes of this are
leaking lower intake gasket, or blown headgaskets. The rear headgasket is prone to this
condition. From under the van, the pass. side of the rear cylinder head may show signs of
leaking externally. If that is the case, it may also be pushing compression into the cooling
system. Air in the cooling system will affect the heater in the manner you have described.
You may want to let engine run with radiator cap off and look for bubles. Or remove the
spark plugs and inspect for signs of burning coolant.
It is possible that the replacement of the t-stat fixed the heater problem, but you have air
in the system from that procedure. This would act as if you still have the same problem,
but in fact just need to bleed system.
Back
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