1999 Montana Overheating

I have a 1999 Pontiac Montana that is overheating. There is no heat coming out of the vents. Can anyone give me some ideas of what is wrong?

Have you checked the coolant level?? How many miles?? Do you notice any coolant on the ground where you park the vehicle?? Need more history.

I have a 1999 Pontiac Montana that is overheating. There is no heat coming out of the vents. Can anyone give me some ideas of what is wrong?

You could have air in the system, you need to bleed it out. You should have two purge valves on the van. Open them while the van is running until coolant starts to come out then tighten th up!
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I had a prevous GM Sunbird that would do the same thing. It's thermostate needle would go up, hold, then suddenly drop. Almost acting like a stuck thermotate. Sometimes heat would come out of its inner cabin vents and other times its head didn't work at all. My local mechanic changed its thermostate. He even drained the air out of its RAD system twice. Once during thermostate replacement and 5 days afterwards. For its needed "air lock" removal for the 3rd time, he called me over and showed me the root cause of the problem.

Steps he used:
- With cold engine, take the RAD cap off.
- Start engine and let idle for 15-20 minutes (until engine in warm).
- With rad cap off, rev engine up/down several times - to ensure proper water flow, and thermostate is working properly.
- Take a bright flashlight and look down the removed rad cap opening. Even at idle with warm engine, one should see the fluid move around (inside the RAD).
- Continue to look down its rad cap opening. If bubbles start to float up, then something isn't right. For example, a blown had gasket - that is allowing air to get into the cooling system.

If wondering, my old Sunbird's rad had bubbles floating up. Not much. But during 30-60 second time cycles, one can see the bubbles float up at idle engine (while looking down - into the Rad's open spout).

Since getting its head gasket replaced (and its heads planed) was more expensive the vehicle's re-sale value, we traded the vehicle in a few days later. I pitty the person who bought that used car (from our dealer who accepted the trade in).

Hope these "air bubble" inspection tests help you as well....

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I have a 1999 Pontiac Montana that is overheating. There is no heat coming out of the vents. Can anyone give me some ideas of what is wrong?

The heater core may be plugged. Are BOTH heater hoses HOT when the engine is at operating temp?

Have you been slowly losing cooloant from the reservoir?

Any leaks around the intake manifold?