Since I bought this vehicle I have begun to notice what sounds like water running throught my dash. If I get on the thing from a standing stop it sounds like a waterfall. Is this normal for these vehicles? It's a 2000 S10 Blazer. 85k miles

That is air in your heater core. The AC DELCO radiator caps that originally came on these vehicles are defective, the seals leak and allow air into the system. If not caught soon enough, it will cause all kinds of problems. Check your coolant for signs of sludging:

If it looks good, change the cap with a Stant from Advance Auto (stant is the best, but any one other than AC DELCO will work) and flush your system soon if it hasn't been done already...you are past due.


If there are signs of sludge you will need to get your cooling system flushed immediately and refilled with fresh and then replace the cap.

Yip, what he said. ^^^^^

Blazee is my Blazer jedi in training. :lol:

if air in heater core and hoses ... you can buy fitting to cut and clamp at high spot of hose that has lid or valve to bleed out air while motor running. otherwise, disconnect hoses from heater core tubes under hood, using funnel of some kind, fill heater tubes up with coolant, as well as hoses, keeping hose end covered with finger, reattach it to tube ... or maybe better, since core tubes have weak solder seal to core, making messing with them dangerous ... do same from motor side of heater hoses, holding hose up, filling, reconnecting.

if air in heater core and hoses ... you can buy fitting to cut and clamp at high spot of hose that has lid or valve to bleed out air while motor running. otherwise, disconnect hoses from heater core tubes under hood, using funnel of some kind, fill heater tubes up with coolant, as well as hoses, keeping hose end covered with finger, reattach it to tube ... or maybe better, since core tubes have weak solder seal to core, making messing with them dangerous ... do same from motor side of heater hoses, holding hose up, filling, reconnecting.

No, that is not needed.

It is a closed pressurized system and all that is needed is to install a new non acdelco rad cap and the heater core will eventually purge itself of its own air.

No, that is not needed.

It is a closed pressurized system and all that is needed is to install a new non acdelco rad cap and the heater core will eventually purge itself of its own air.

Yep, you learn fast. :)

A properly working radiator cap will remove the air after a few run cycles. When the temperature rises the the coolant expands, creating pressure that pushes the air out past the rad cap and into the reservoir. The air escapes the reservoir through the vented cap. When the engine cools, the coolant contracts pulling more coolant in from the reservoir, to replace the air. After a few cycles the air will be gone. The AC Delco caps do not seal well so during the cooling cycle they draw in more air instead of coolant.

Keep a very close watch on the coolant level. This noise is also a sure sign of low coolant. Check the level in the radiator to start with, and keep the reservoir full. If losing coolant and no apparent leak, it might be internal, that's bad.