Chevy & GMC Vans

I am hearing gurgling sounds coming from the passenger side under the dash when I rev the engine. What is that?

Water.



You have air trapped in the heater core and need to burp the system.
Start with a cold system, rad cap off, heaters turned to high and hot, (if you have rear heat run it too) front passenger side jacked up.
Jack it, drive up a hill or partway up a ramp, whatever, but passenger side is high. Run like this until the thermostat opens and keep the radiator filled. After it will take no more water put the cap on tight and go for a short drive. When you shut it off top off the over flow tank to the hot mark and let cool. It should drop to the cool mark, if it's low from this mark add water to the cool mark and no more. After this you should not need to open the rad cap just watch the level in the overflow.

Just to clarify…don't use water…use a minimum 50/50 mix of antifreeze/water. Woodbutcher is right though in you are low on antifreeze. Next question to ask is why? Look for a leak somewhere.