Guys I need some assistance. I went to warm up my 77 cutlass today and I let it idle about a good 15 minutes. All good at this point. Before going to drive I gave it a few good revs and thats when it happened. BIG COOLANT explosion. It was pouring out from the passenger side by windshield from top of intake. Well I didnt have the heater on during the warm up and rev. The car has been sitting a week in very cold temps here in Colorado. I found where it is coming from but I dont know the name of the part. It looks like a plug that goes into the intake and on top of the plug it have a diafram looking part. I hardly had to pull on it and it came loose from the top of the plug that goes into the intake. What is this called? what do I need to replace and why did this happen?

 

That's the heater control valve. Install a new one.

 

Thank you so much. why did it blow out when reving? Is this a sign my heater core is bad? it does make a bit of noise on low. like a pissed chipmont is in there.

 

It blew out because the plastic valve aged and cracked. Pressure in the cooling system goes up slightly with engine speed. Don't read too much into this. This is not an uncommon failure. That's why replacements are easy to get. The best valves are all metal.

 

Has nothing to do with the condition of your heater core. If it came apart that easily, it was just due to deterioration of the part.

I'm guessing the "chipmunk" sound you're describing is the heater blower motor? May be time to replace that, too.

 

$18 at local Napa. Part will be in tomorrow. This is why I love classic vehicles. This is also why I love this forum. Priceless. Thank you for the help. One cant help but shiver when smoke is billowing and coolant spraying.

 

That chipmunk sound could be a leaf that has worked its way inside the squirrel cage blower. In any event it has nothing to do with the heater valve. I would get a metal one for sure.