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Discussion Starter · #1 ·
That term “if it isn’t broken, don’t fix it” truly fits my current situation. HELP!

so I have a 70 Chevelle with a 502 bbc. It’s all stock, has a 4 row radiator and the fan is just a mechanical one. When I bought the car it had the “green stuff” in the radiator. I would always see my tempt hovering around 200-220 degrees and never any overheating issues. Just felt it was still running pretty hot. The car had a 195 degree thermostat and had heater hoses going to heater core and radiator. Here’s what it looked like:
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So I wanted to change a few things, I got a 160 degree thermostat, decided to block off the heater core and remove the hoses while capping the top of the intake and radiator portion as well. I drained the green stuff a few times (3 times) and I know it wasn’t completely flushed out. I would add hose water and attempt to flush out the remainder of the green stuff. So after draining it once more, I added new coolant. I added two gallons of Zerex G05 50/50. Went for a short drive and holy hell my temp gauge shot past 250 and saw radiator fluid on my way back home. Got home and the lower radiator hose was pulsing from how hot it was. Haven’t checked it since. And here’s what the motor looks like now:
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Did I just not add enough coolant back in? When I added those two gallons, it filled the radiator up to the top. I’m assuming there wasn’t enough coolant, but then again what do I know.
 

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Take the thermostat out, go drive it again, and report back.

Where is your temp sensor located? How accurate is it?

200 is not a problem, 220 is pushing it. Some insist on 180 always, but oil needs to be hotter than that to burn off the moisture in the oil, especially for those that sit more than they are driven. And short drives too.
 

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Discussion Starter · #3 ·
Take the thermostat out, go drive it again, and report back.

Where is your temp sensor located? How accurate is it?

200 is not a problem, 220 is pushing it. Some insist on 180 always, but oil needs to be hotter than that to burn off the moisture in the oil, especially for those that sit more than they are driven. And short drives too.
I’ll have to do the check back tomorrow, currently pulling my hair out. But as far as the temp sensor, I’m assuming it’s fine. Considering it would sit around 200-220 and then shoot straight up to 250 with the car overheating after I did whatever the hell I did.
 

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you do know the heater core does bleed off some of the heat as well? It should not make that much of a difference though. I would say you had a air pocket or did not run the engine after filling it up with the cap off to make sure the system was full.
 

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Discussion Starter · #5 · (Edited)
you do know the heater core does bleed off some of the heat as well? It should not make that much of a difference though. I would say you had a air pocket or did not run the engine after filling it up with the cap off to make sure the system was full.
Damn, now that you mention it I did not run the motor with the cap off before driving it.

Update: just started it up, cap off and added more coolant. Sat for about 7 mins and hit 250 degrees and spilled over. Shut it off and all the coolant spilled out.
 

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I think the best way to eliminate an air pocket is to idle for 10-15m with the cap off. Put a fan in front of the radiator so as to prevent coolant starting to bubble out. Shut it down quick if it does.
 

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Discussion Starter · #10 ·
I think the best way to eliminate an air pocket is to idle for 10-15m with the cap off. Put a fan in front of the radiator so as to prevent coolant starting to bubble out. Shut it down quick if it does.
Yea tried to do this and it began to bubble out around 7 mins. Shit it off real quick and a shit ton of coolant spilled out
 

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Your heater core was doing the same thing before deleting.
With the hose coming from the intake before the t-stat, going through the heater core, and returning to the radiator it was purging the system.
 

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Did you by any chance move the water temp sending unit from the intake manifold over to one of the cylinder heads? If so, then move it back to the intake manifold, and your gauge might any longer climb so high. I think on BBC engines, the use of the water temp sending unit in the cylinder head can give you a false reading since it's too close to one of the exhaust valves.
 

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Don't know if you have the block full, one way to be sure is to pull the thermostat and fill the block/radiator from the thermostat housing until the coolant is just below where the thermostat sits. I've done this for a long time and never had issues.
 

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Do your research (maybe you already did) but I personally would put nothing but "the green stuff" in my Chevelle - not ZEREX and NEVER DEXCOOL!
Agree 100%. I won't use Dexcool in ANYTHING, but under NO CIRCUMSTANCES should it be used in a vehicle that doesn't have a pressurized coolant reservoir. Dexcool and air is a BAD BAD BAD combination.
 
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