Roger L

I noticed a slight drip on firewall and wasn't sure if leak was from heater core or hose clamp, the clamp felt tight. I didn't want to dismiss the leak and later find anti freeze inside the car and associated mess.
I went to plumbing supply and purchased a Gas Line Test gauge that plumbers use to pressure test the gas lines before service is installed. The gauge cost $20 and has built in Schrader valve. I needed to add a 3/4" hose barb to gauge with short piece of 3/4" hose, and block off the other heater core tube with a 5/8 hose plugged on other end.
I drained the coolant level down, disconnected the existing heater core hoses, applied a little grease to heater core tubes and clamped down the hoses. Pressurized heater core to 29 psi and will let it sit for a day, if no drop in pressure then I know heater core is OK (at least for now).
Thought I would pass this along as it was simple solution to a common problem, plus it adds another tool to the box- LOL.
Roger

Tampa Jerry

Looks like a great diagnostic tool. If you find you must replace the core, check your new one prior to putting it in the car. Once out, it is easy to check, just add pressure and put it in a tank of water and look for bubbles. Also, is 29 lbs. a little too high for a core? I'm thinking that most systems top out at less than 20 lbs. Jerry

TheSaint

Are you doing this test on a new heather core?

I ask because when i ordered a AC heather core made in Mexico(which i understand most are)i asked the seller if it was true what i had heard that the heather core should be re soldered around the pipes and the seller agreed that i should have the new heather core resoldered before i installed it in the car

stingrayl76

Roger,

Good test but how did you determine 29 psi? That seems a little high for a cooling system that is designed to function at 13 to 15 psi.

Dave

Bluestripe67

I had my new one tested by a reputable shop. They go to 20lb for testing. Dennis

Roger L

Regarding pressure, I arbitrary selected 29, as Bluestripe67 posted 20 pounds would be safe. I just wanted an ample safety factor past the 15 psi of the system. I'll keep my fingers crossed when I check it tomorrow, not looking forward to removing heater housing based on what I read on forum.
I will use the same gauge to check a new core, as definitely wouldn't want to do it twice. Just want forum members to know that this was an inexpensive way to test it.

67vetteal

This same Pressure Gauge Tester is suitable for adapting to testing POA Valves in 67 A/C Systems. The POA is adjustable and this Gauge set up allows you to check the POA for opening PSI. Al W.

colter

I'm making one of these as I couldn't find a local shop to pressure test a new heater core off the car. So looking around and I came across this posting.

Though took a while to get the gauge to quit leaking out the teflon/screw part of the barb fitting. Ended up taking 7 wraps of the thin teflon tape and tightening it down to get it to quit leaking bubbles there.

mcb55-210

In the past, I have taken an old bicycle tire tube, cut out a 16" section with the valve stem in the middle, clamped either end on the two heater core nipples, and pressure checked it that way. A little more time consuming (having to periodically check psi) but got the same results.

Mike

colter

I think the gauge is better because it's easier to see if there is a PSI drop as well vs. just looking for air bubbles.

Though if you just care to look for bubbles, then the tire tube would probably work fine with it aired up.

I'm working on a C4 though and these aftermarket heater cores don't have the tubes bent right.

tuxnharley

I think he meant that you can use a tire pressure gauge on the bike tube valve stem. How else do you check the pressure on a bike tire?

Pilot Dan

Leaks on the engine side are generally the result of a bent heater core tube, if the core was leaking through the cooling vanes, you would see it in the passenger footwell. Trying to go back to a corbin clamp (original style) after bubba cranked down with a worm type is usually the cause of a leak on the engine side. Pilot Dan

BB767

For Teflon tape try Blue Monster PTFE Thread Tape:


They recommend at least 3 wraps with it but it's by far the best stuff going out there. The ubiquitous white teflon tape made today doesn't work very well.

Thomas

colter

I don't know how he'd be checking the psi in his example, but every time you connect a tire pressure gauge like when checking tire pressure, you always lose some pressure by connecting/disconnecting it. So I think all he'd be doing is making sure it's still pressurized as you can't really look for psi drop that way with such small psi.

Better to do it like the OP by having a gauge constantly attached so you don't have to keep meddling with it once you get it to the psi you want it at.

Then again, you can just look for air bubbles using the inner tube method and not bother monitoring psi drop.

Also you can buy an adapter kit for the Mityvac to test heater cores with.

colter

They've actually got tape for "gas" sealing. It's yellow. I guess it's supposed to seal gas better than regular tape that is supposedly more for sealing water.

I figured I'd keep trying what I already had before buying the "gas" since I would barely even use it.

SS409

That's a great idea Roger using air pressure to rule out any future leaks.
I'm a licenced plumber and we use these gauges all the time on gas lines. The gauge will bleed down a small amount overnight which is normal. On something as small as a heater core, I wouldn't expect it to drop more then a 1/4 psi. I always give the gauge a little flick with my finger to "set" the needle. We sometimes get a bad gauge so if the pressure does drop, take some soapy water and a small paint brush and apply some foam around the gauge before you replace the core....

mcb55-210

I was checking the condition of a spare heater core for a '37 Chevy. Aired it up, dropped it in a tub of water, and looked for bubbles.

Told me exactly what a gauge would have.

Mike

Maxo

Thank You Roger

colter

The reason for the gauge is because they say you can have a real slow leak. So you can leave it in the water for a day or however long to look for bubbles but to also see if the gauge is dropping as well to help detect a slow leak that might get missed when looking for bubbles.

I know I sealed off the gauge to check itself for leaks first. And had issue of air leaking past the teflon/threads. But it was a slow leak and a bubble would form, but it would take a while for the bubble to float up. But I could tell it was leaking by looking at the gauge slightly dropping as it sat.

Now that was pretty easy to see a bubble forming on the gauge, but that slow bubble would probably be more difficult to detect with a heater core and all of it's fins and you having to flip it to check other side which could cause that slow bubble to float off while flipping it and you not notice it.

The gauge I got was a 15psi gauge, so it would be easier to notice the needle dropping compared to a 30psi gauge.

stratplus

This past winter I replaced my heater core and control valve on my 60.

I read something from JohnZ to test a new core. I never would have thought to test a new one. I brought both the heater core and the valve to a radiator shop. Sure enough, the control valve had a leak in it, the core was fine.

They used 8PSI to do the test. He said that 8 PSI was enough to see any bubbles. It was, you could see the bubbles on the top of the control valve. I re-soldered the top of the control valve, brought it back to the shop and it was OK, just "bubbleishish" Oh, that's radiator tech talk