Stop Leak In Radiator

So at the shop this is how we would tackle a clogged heater core.

Remove both hose off of the heater core, plugging the lower one after it drains. Then we'd fill the heater core with flush chemical. We have been using the prestone stuff. All coolant flush is pretty weak compared to some of the old fashion stuff that was made with acid, so you really don't have to worry about the modern stuff doing damage. Leave it in for at least 1/2, and hour is better. Then flush the core in both directions, and don't be stingy with the water or amount of time of flushing. Never used hot water as we just have a hose near one of the doors. Some guys will try to blow compressed air though the core, but please don't. I've never seen a heater core damaged from a water back flush, but I've seen guys blow them out when they jam 100+ psi of air in there.

It'll work, but in my experience typically it's only a bandaid and 6 mnts to a year later it's clogging up again.

SirRobyn0 said:

So at the shop this is how we would tackle a clogged heater core.

Remove both hose off of the heater core, plugging the lower one after it drains. Then we'd fill the heater core with flush chemical. We have been using the prestone stuff. All coolant flush is pretty weak compared to some of the old fashion stuff that was made with acid, so you really don't have to worry about the modern stuff doing damage. Leave it in for at least 1/2, and hour is better. Then flush the core in both directions, and don't be stingy with the water or amount of time of flushing. Never used hot water as we just have a hose near one of the doors. Some guys will try to blow compressed air though the core, but please don't. I've never seen a heater core damaged from a water back flush, but I've seen guys blow them out when they jam 100+ psi of air in there.

It'll work, but in my experience typically it's only a bandaid and 6 mnts to a year later it's clogging up again.

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That's basically what I'm going to try. I've heard sometimes it works sometimes not. What may help is the radiator is relatively new, just the heater core appears to be plugged.

Jimbarry said:

That's basically what I'm going to try. I've heard sometimes it works sometimes not. What may help is the radiator is relatively new, just the heater core appears to be plugged.

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I would say yes that may work in your favor. I've never had a back flush completely fail to restore at least some heat, on a recently plugged core but think of it like this.

There is no way stop leak alone will clog a heater core tubes, but if there is a bunch of calcification in there and the tube entrances and exists are narrowed from the calcification then yes stop leak can seal those shut. Calcification is a calcium deposit that hardens in time, so what your going to get out of the core with a back flush will be the stop leak and loose calcification, the hard stuff cannot be removed, unless the core is boiled out in acid or rodded out. Either of those treatments may expose leaks which would need to be soldered up. So those tubes will become functional at least to some extent after the back flush resulting in heat again, but they'll likely clog again down the road.

As long as you had heat and after the stop leak you lost it, I have full confidence you'll get heat back after the flush especially if you let a flush solution sit in there for a bit.

The blocked rads and heads I've seen were leaky on and off for a long time and very most likely had BarsLeak dumped in more than once.
"Hey of a little is good..."

Rusty Nail said:

I dunno exactly what SBC cooling system line pressure usually runs but the radiator caps are 16 pounds or so yeah?

I imagine 16psi of water pressure goin through one inch diameter coolant hose at 195°... Good luck with diagnosis!

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15 according to one owners manual for these trucks, I dont remember the year or engine choice (if that would matter even)

Is the HC in the 83 brass? If desire to use chemical, be careful for solder safe stuff or just not too harsh you may just make new leaks where you wouldnt ever want lol

Thanks for the info all. Good stuff. I'm also thinking changing the intake may have contributed, even tho I covered the ports. Hard to get it 100% clean in the backyard.

Ah Ha!

Could be!

Removed the thermostat and heater hoses, flushed backwards and forwards, this is what came out of the first 2 cups of water on the backflush. I'm soaking in a light solution of water/vinegar and will reflush in a couple of hours. So far no leaks inside which is a very good sign and water appears to flow freely now.

Completed this AM, heat works really well so, on to the next problem.

Cheeeittt. Was so proud of the heater I played with it on and off and broke the mount at the end of the control cable. NEVER say on to the next problem.

Is your truck AC equipped?

I cheated when my lever thing broke, put a on-off switch inline the power cable from that speed switch.

I can still change it from floor to defrost and not hot to hot, one smells more like dead mice than the other (floor) and one gets nice and hot and one i dont bother touching lol(I grab the cable and push in or slide out the thing)

Kewl idea but mine broke on top of the blend door. I pulled the glove box and can fix it I think.

AuroraGirl said:

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Is your truck AC equipped?

I cheated when my lever thing broke, put a on-off switch inline the power cable from that speed switch.

I can still change it from floor to defrost and not hot to hot, one smells more like dead mice than the other (floor) and one gets nice and hot and one i dont bother touching lol(I grab the cable and push in or slide out the thing)

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Just in case it also disconnected at the control box, can you remove it without removing the Guage cluster? The pic looks like you can.