2001 Silhouette overheating

I have a 3.4L, 6-cyl, automatic, approx 140,000 miles on it. It had been occasionally overheating, then the red "hot temp(?)" light came on. Took it to a shop they replaced the thermostat and did a radiator flush. It seemed ok for a few days then started sporadically overheating again.

One thing I noticed the first day I brought the van home after the repairs; I shut the engine off it made a "gurgling sound" on the inside of the passenger compartment like it was coming from the heater. It still makes this sound if I've been running the heater.

When this happens the temperature rises very quickly. It can be 40 or 70 degrees out and been driving for less than 5 mins. I've also noticed that sometimes when I put the heater on to try to bring the temp down it blows cold air instead of hot.

There's no rhyme or reason when it overheats, totally sporadic.

Sounds like there is air trapped in the cooling system. Take it back to whoever flushed it and have them bleed and top off the cooling system.

Thank you. I'll try that first.

Update on the overheating. I took my van to the GMC dealership instead of the place that did the radiator flush. They ran a test and said I have a leaking head gasket that's causing the problem. They couldn't explain to me why the overheating is so random, however it is getting more consistant :(

They couldn't explain to me why the overheating is so random, however it is getting more consistant .

That's because the leak is getting worse.......when you have a leak like this, you create an air pocket in the engine......this can prevent flow through the heater core, and when this happens, you do not get heat from the heater core....It can be an external leak(gaskets are known to leak in these vehicles at #1 cylinder).....or it can be an internal leak.....have seen the leak cause coolant to seep into a cylinder.......when you go to start, the vehicle starts, but may run rough until the coolant is burned/pushed out of the cylinder......and because you basically have a closed system, this loss of coolant creates an air pocket, which causes the overheating.....my money is on the head gasket at #1 cylinder...

They couldn't explain to me why the overheating is so random, however it is getting more consistant .

That's because the leak is getting worse.......when you have a leak like this, you create an air pocket in the engine......this can prevent flow through the heater core, and when this happens, you do not get heat from the heater core....It can be an external leak(gaskets are known to leak in these vehicles at #1 cylinder).....or it can be an internal leak.....have seen the leak cause coolant to seep into a cylinder.......when you go to start, the vehicle starts, but may run rough until the coolant is burned/pushed out of the cylinder......and because you basically have a closed system, this loss of coolant creates an air pocket, which causes the overheating.....my money is on the head gasket at #1 cylinder...

Nice, TechII!

Thank you for the explanation. The dealer wants $2100 to do the job, the van's not worth it since I'm having problems with the TCS as well :(

This is my first time using the forum so I'm not sure how to thank people correctly. But a big heartfelt thanks to those who responded to my crisis.:)

ANd with the 3.4, this problem is not an "if " but rather a "when". AT 140k miles. you are in the lucky gang...