I have a 2001 pontiac montana, we had to replace the thermostat. when we started the van up it would idle between 2 and 3.we changed the iac nothing no check engine light.now it idles between 3 and 4.

SOURCE: replace thermostat 2003 pontiac montana

yes but with the right shaped wrenches and tiny hands it can be done without removing the exhaust crossover pipe

SOURCE: 2002 Pontiac Montana Thermostat replacement

check the coolant level fiirst...if that is low it wont give you any heat.....to change the thermostat you have to follow the top radiator hose to the engine.at the send of it you will see a clamp take it loose...then you will see the thermostat housing its held in place by 2 bolts . once you remove them you have the thermostat....make sure you clean all the old gasket material off both the housing and mount.also make sure you get a new gasket.

SOURCE: 2001 pontiac montana overheating no warm air when heat is on

Might be a weak or failing water pump... Does it leak antifreeze or do you have to add antifreeze very often? When the engine gets to operating temperature squeeze the top radiator hose and see if you can feel pressure from the water pump forcing water through it.

SOURCE: need to replace thermostat on pontiac montana van.

public library...Chilton or Haynes auto repair manuals or collisionrepairadvice.com     make sure you bleed the system

SOURCE: how hard is it to change the thermostat on a 2001

Hello, it's not very hard at all. Here are some instructions to help you decide if you want to try and do it;

To replace the thermostat in most vehicles yourself;

Remove the hose from the housing, then remove bolts from the housing and lift the housing off
to access the thermostat. Pay attention to witch side is up on the thermostat that you remove, the
new one will have to go in the same way. Also look at the temperature rating that is stamped into
the thermostat that you take out, and make sure the new one has the same temperature rating.
(failure to do so can cause false readings by some sensors, and may start triggering error codes)
Install new thermostat, right side up, put housing back on and bolt back down, hook hose back on
to the housing. Check the coolant level. Start the engine and let it run for 6 to 8 minutes to reach,
"normal operating temperature", and look for any leaking. before you turn the engine off turn your
heater wide open and listen for a click. Most of the time when a thermostat opens you can hear a
click and may hear the coolant flowing through the system. Shut the engine off, wait for it to cool
down and then check your coolant level one more time. ( do not fill all the way up, only fill to
FULL line on resrvior.)

The location of the thermostat for most vehicle.

Stand in front of the car with the hood open, you'll see a black hose hooked to the upper side of the
radiator.( about 2 inch in diameter, newer vehicles about 1 and 1/2 inch, and newer small cars
about 1 and 1/4 inch. ) Follow the hose to the other end, it connects to the thermostat housing. The thermostat is inside of the housing.( the hose usually goes to the air intake manifold, but some
housings are on the side or back of the engine. )

I hope this helps you, and good luck!
Donnie