This 2005 Chevrolet Tahoe came in with the complaint that the heater was working erratically. The customer stated that when she started the engine in the morning there would be no heat while idling and driving down her driveway. Once she had been driving at highway speed for several minutes heat would start coming out. When she got in traffic it would come and go. She thought that her Tahoe had some sort of terrible electrical problem.
Well, it turned out that the main problem was that the coolant level was low by one gallon. The coolant reservoirs become stained over time with neglect and at first glance it looks like there is something in the reservoir.
You can see the color change slightly above the halfway seam in the tank.
Removing the pressure cap (following proper safety procedures) revealed that there was no coolant on the reservoir tank. You may need to click on the picture below to enlarge it, to be able to see.
I installed a 50/50 mixture of Dexcool and distilled water. It took one gallon.
You can see the shadow is now darker and you can see some orange color in places.
A much better view of the coolant level from the driver’s side of the vehicle.
Another view from the firewall side of the tank. This is the general full level for a warmed up engine.
I did a little bit of checking and found a coolant leak at the heater hose tee where it connects to the front heater core and the lines for the rear heater core. Normally a leak in this area would be attributed to a leaking intake gasket but not so in this case. The drip on the ground was at the passenger rear side of the engine and that is where a leaking intake gasket normally drips on these engines.
She says she will have me change the tees and heater hose connectors but we will have to wait and see.