Overheating/Heater blowing cold. Please help!

[rn4l21]

'96 Tahoe here. When I have the heater on, it blows cold after awhile and the car temp goes past 240 and the "Check Gages" light comes on then once warm air starts blowing again, the temp goes back to normal.

The engine will smoke a little here and there when idling. Any ideas what could be wrong?

 

[RED TAHOE LS]

I would start by replacing the thermostat, it controls all the water flow to the heater core to create heat,as well circulation to keep temperature normal.
David g.

 

[Auto Parts Guy]

Firstly, I see no reason to let the engine get past 220. You risk blowing the head gasket or worse when temps go 240+.
You either have air in the coolant system, a blockage somewhere in the coolant system, a leak, a bad heater valve, a bad water pump, a bad thermostat, or a combo there within.

 

[rn4l21]

I replaced the thermostat and it's still overheating. I refilled the antifreeze and it started leaking. I haven't driven the car since this was posted but there's a puddle of antifreeze along the bottom on the fan. [emoji53]


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[TigerEyz3]

Cold air blowing when the "heat" setting is engaged, could be an air bubble in the heater core.

The fact that your system is going to 240* could be related to air/cavitation around the water pump (impeller spinning air rather than moving coolant) and/or a bad thermostat (not allowing coolant to move from block to radiator).

Since you've replaced the thermostat, I'd drain the system (I know it's a pain) and start over... if you can elevate the front end, you'll be better off - air rises and can more easily exit the radiator as the system "burps."

 

[TigerEyz3]

Another thought.... make sure your hose connections are correct.

I recently installed a new radiator (with electric fans) and moved the heater hose nipple from the intake manifold to the radiator (so I could use the intake location for the temp sending unit). Needless to say, I no longer had cabin heat. My rig didn't overheat at all... quite the contrary. Never really got up to temp. After I plugged the radiator bung and used a t-fitting in the intake (temp sending unit on the side and heater hose outlet on top) everything worked as expected - cabin heat worked, electric fans worked, and coolant temp was in the 195* range.

 

[rn4l21]

I was able to pinpoint the leak to the water pump so I'm in the process of replacing that and the hoses, just in case. I'll have to keep you posted, if anything.

 

[rn4l21]

So I replaced the water pump and the car is still overflowing and is leaking this brown fluid. It might be oil but it only leaks when the car is running and it comes out like crazy. Could it be a head gasket?

 

[TigerEyz3]

Where is the "brown fluid" coming out? Pics would be nice.

 

[rn4l21]

Where is the "brown fluid" coming out? Pics would be nice.

Yeah. I thought about that after. Sorry. I will post pics.


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