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Old 12-17-2012, 04:50 PM   #1
Longhorn 70
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Testing Heeater Core before reinstall.

I am going to replace the AC/Heater box under the hood. I wanted to test the heater core prior to reinstall. I have the inner fender out and am ready to go with the new box, gaskets seals and such. I also have a good blower moter ready to go in....

The heater core looks good. I was going to just hook it to water supply pressure in the yard. We have 30 lbs+ of water pressure. Will that make it blow up like a baloon? Is there a better reccomended way?

Does it matter if it is hot, cold supported for testing?


Edit: BTW the one that is in there is a Stant core from 92. It has been disconnected for a couple of years due to bad heat valve that kept it on all the time....
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Last edited by Longhorn 70; 12-17-2012 at 04:56 PM.
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Old 12-17-2012, 04:57 PM   #2
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Re: Testing Heeater Core before reinstall.

You can tell by simply capping one end with the palm of ur hand use ur mouth to blow as hard as you can in the other side. Even a pin hole will be obvious to you. Never tried a water hose before. I'm sure there are better ways. If you can cap an end and use compressed air in a bucket of water??
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Old 12-17-2012, 05:11 PM   #3
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Re: Testing Heeater Core before reinstall.

I do have a 5/8 cap that came off a new water pump I bought several years ago. I wondered why I held on to that thing. GOOOD IDEA. I'll cap, clamp and put about 20 of air pressure in it....


Wish me luck.

Thanks.
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1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar

And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9
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Old 12-17-2012, 05:19 PM   #4
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Re: Testing Heeater Core before reinstall.

Longhorn 70 what are the replacement heater cores made out of? Copper or alum?
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Old 12-17-2012, 08:37 PM   #5
sameyrasmea72
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Re: Testing Heeater Core before reinstall.

I would take it to a radiator repair shop so they can pressure test it. Call and see how much it would cost to test it first.
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Old 12-17-2012, 09:00 PM   #6
Daner
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Re: Testing Heeater Core before reinstall.

I would be wary of using too much pressure to test your core. I probably wouldn't go too far past what your cap psi is. Be a shame wreck a core that would have worked fine.
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Old 12-17-2012, 09:04 PM   #7
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Wink Re: Testing Heeater Core before reinstall.

Pressure cap is what 15 pounds on a radiator. I wouldn't get to happy with it. Like they said would be asham to mess up a good one by over pressuring it.
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Old 12-17-2012, 10:28 PM   #8
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Re: Testing Heeater Core before reinstall.

Buy a new one and be done, you don't want to do it twice.
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Old 12-18-2012, 09:43 AM   #9
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Re: Testing Heeater Core before reinstall.

I'd be inclined to make one of the caps with a regular valve stem in it and use a bicycle tire pump. Toss the whole thing in a bucket of water and see if any bubbles come out at about 10-12psig.
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Old 12-18-2012, 10:16 AM   #10
bk2life
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Re: Testing Heeater Core before reinstall.

last heater core i bought was 19 dollars. with a warranty.

rad cap only has 15psi. i wouldnt put any more than 10-15 in it. even then id err on the side of 10 psi. thats alot under water.
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Old 12-18-2012, 10:23 AM   #11
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Re: Testing Heeater Core before reinstall.

I just got a DUH moment.

I will just start the truck with the hoses on the core but not installed yet..... Just set it on the tire, start the truck and let the pressure build. I only have water and a rust preventative in it right now until the core goes in. Once it's up to temp, turn it off and let the pressure build as the coolant soaks up heat.

THEN if all works, I'll install, drain, fill with antifreeze and be on my way.

Thanks for the help guys.
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1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar

And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9
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Old 12-18-2012, 11:33 AM   #12
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Re: Testing Heeater Core before reinstall.

I used the pressure reducer from my RV and tested my radiator. They only cost around $10 and keep the water pressure from blowing the seals in a RV when you hook up to a water faucet.
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Old 12-18-2012, 11:38 AM   #13
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Re: Testing Heeater Core before reinstall.

Recently replaced a core in a 80's S-10 without testing from O-Rielly's. A real pain in the rear to do. New outta the box that leaked. Yeah sure it was exchanged but wasn't fond of the amount of work involved to pull it a second time around. Pre-testing for leaks before installing it is time saved for peace of mind. Not to mention the damage it does to new carpet on the floor, of course they don't cover that part.
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"You can wash a pig, soak it in most expensive perfume. In the end it is still just a pig."

ODD BALL build thread http://67-72chevytrucks.com/vboard/s...d.php?t=478629"
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Old 04-01-2013, 03:04 PM   #14
Longhorn 70
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Re: Testing Heeater Core before reinstall.

My final DUH moment, well at least on this subject.....

I have the A/C box under the hood off to replace the box. Why don't I just hook up the hoses and see what happens? If I hook up the hoses and warm up the truck, maybe a little hotter than normal, and run it for a while and it doesn't leak, I'll put it together. ANY sign of leakage and I mean any I'll replace with one that matches the one in there. Not one that's close, one that matches. The one in there is brass tanks with a copper core. I have seen new ones that just don't look the same quality.
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1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11.
1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar

And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9
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Old 04-01-2013, 04:08 PM   #15
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Re: Testing Heeater Core before reinstall.

if i went thru the effort to setup a pressure test i'd b checkin at least 40-50lbs to make sure of the extreme limit testin



in the end i'd probally just keep turnin it up till i could blowit up on the second one i'd know the limit to not cross in the service test
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