02 montana cooling fans off

[Brady 895]

Hi on my 2002 Pontiac Montana, the cooling fans don't run unless I unplug the temperature sensor. I have replaced the temperature sensor switch, the radiator cap and had the engine scanned for errors, with no luck. Any help would be appreciated!

[GregA]

Originally Posted by Brady 895

Hi on my 2002 Pontiac Montana, the cooling fans don't run unless I unplug the temperature sensor. I have replaced the temperature sensor switch, the radiator cap and had the engine scanned for errors, with no luck. Any help would be appreciated!

Welcome to the forum!

Do the fans come on when you switch on the Air Conditioner?
Are there any other symptoms (temp gauge in the red, etc.)?

I have some information about how the cooling system should work at the link below. Maybe it will help.

GM Van Cooling System

Take Care,

[Brady 895]

Yes, the fans come on when the a/c is on, the temp gauge stays normal.
Thanks!

[GregA]

Originally Posted by Brady 895

Yes, the fans come on when the a/c is on, the temp gauge stays normal.
Thanks!

So everything is cool (pun intended) ?
I know that the fans don't come on (at low speed) until about 225 degrees (F).

Take Care,

[Brady 895]

Im not sure if the water pump is working. I don't know how to check it. If the temp. sensor is plugged in the the van does over heat badly but the temp gauge stays normal. Before I replaced the temp. sensor the temp. gauge would max out. I am 100 per. sure its overheating because I back the cap off to the safety and boiling coolant goes into the overflow tank. Thanks for the info you gave me.
Jim

[LMP]

If overheating, consider possible head gasket failure. My brother just had his 02 Montana engine overhauled for head gasket failure 2 weeks ago. Known and common problem accompanied by all kinds or erratic gauge/fan/heater behaviour.

[cdru]

Originally Posted by Brady 895

Im not sure if the water pump is working. I don't know how to check it.

It's next to impossible for your water pump not to be working. It's connected to the serpentine belt directly. It would require either the pump drive shaft to have broke or the impeller blades to have corroded off...and neither happen under normal circumstances. Feel the upper or lower radiator hose. If either are warm, your pump is working fine. You won't feel anything though until the engine reaches normal operating temp and the thermostat opens. The fact that boiling coolant gets to the reservoir pretty much confirms that the coolant is moving anyways.

If the temp. sensor is plugged in the the van does over heat badly but the temp gauge stays normal. Before I replaced the temp. sensor the temp. gauge would max out. I am 100 per. sure its overheating because I back the cap off to the safety and boiling coolant goes into the overflow tank. Thanks for the info you gave me.

You need to get a better idea at what temp the coolant is at when it overheats. The radiator cap increases the boil over temperature 3 degrees for every pound of pressure. If memory serves me, it's a 13PSI cap so that's about an extra 40 degrees so just because it's boiling in the reservoir doesn't mean it's too hot.

Normal operating temperature is about 195 with air flow from just driving around. Fans won't kick on until around 225 degrees as Greg mentioned. On my gauge, that is nearly into the red (98's have a different gauge then the 02's).

[Brady 895]

That's good info. I am going to take it to a different shop tues. I am assuming a head gasket or intake manifold gasket. I have lost all antifreeze now so I am going to put a gallon in. I just can't take a chance on burning up the engine. If antifreeze stops the over heating that would be great but I don't think it will. I will keep in mind what you said about them running hot to start with. Thank you for all the help.
Jim

[GregA]

Originally Posted by Brady 895

That's good info. I am going to take it to a different shop tues. I am assuming a head gasket or intake manifold gasket. I have lost all antifreeze now so I am going to put a gallon in. I just can't take a chance on burning up the engine. If antifreeze stops the over heating that would be great but I don't think it will. I will keep in mind what you said about them running hot to start with. Thank you for all the help.
Jim

Jim,

You say "I have lost all antifreeze now" - From where? The overflow bottle or the radiator? Is it leaking out somewhere?

The proper procedure for filling (or refilling) the cooling system is the allow the engine to cool (completely), and fill the radiator (at the radiator cap) up to the top of the neck. Put the cap back on.

Then put enough coolant in the overflow bottle to come up to the FULL MARK.

Then run the engine & bleed out any air that may be in the system (there are two bleed screws - one near the thermostat and one on the other side of the engine).

If you can, please take a look at the following page and let me know at what temperature your gauge is at when it overheats.

Temperature Gauge with numbers

Take Care,

[Brady 895]

254 if my gauge looked like the one in the picture. If I have 95 percent water in the car now is that alone enough to overheat it. When I release the cap to the safety the coolant pushed out the cap. Thanks Jim

[Brady 895]

It was the intake manifold gasket. So im out $500.00 but its good I did not burn the engine up. Thanks Jim