Hello,

i have a 2nd gen trailblazer 2001 4.3 V6.
today the check gauges light went on. I realized that the engine temperature was very high. Whenever I stopped it went up again, when i drove it went back to normal. I checked cooler fluid level and saw that it was kinda low. I refilled but the temp still rises while im standing. When i shift on p while standing and increase the rpm the temp also goes down immediately. I checked the ventilator and its still turning.
Also since I own this car the heater does not work. It blows out, but only cold air.
anyone of you guys has an idea what could be wrong with the car?
thanks in advance!

 

Possible thermostat, possible partial clogged radiator, air still in lines, clogged heater core

 

Yeah, I was thinking heater core or thermostat.

 

Thank you for your replies.
I just ordered a new thermostate and I will change it to see if anything changes.
If not, I will change the heater core next.
Is it a pain to replace it?

 

Here's a quick vid on the heater core...

 

This may work, I`ve done it. Buy some hose that fit the heater core fittings (2 different sizes) reverse the flow using a garden hose on the outlet and make sure the inlet hose is long enough to reach over the side of your truck. Slowly increase pressure and reverse flush the core. It works

 

Definitely try this before spending any more money on parts.

 

I would definitely try flushing the heater core. what I did was use a funnel connected to the hose and poured a small bottle of CLR in. Waited 10 minutes and flushed it both directions until it ran clear. The stuff that came out was black. I have had good heat ever since.