1997 Heater Core disconnected - how to test? - Ranger-Forums - The Ultimate Ford Ranger Resource

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Old 08-10-2016
Thread Starter
Join Date: Aug 2016
Location: Livermore
Posts: 2
1997 Heater Core disconnected - how to test?

Hi all,

New here - and new to working on cars. My son wanted a truck to take down to school later this fall, and so we bought a used and somewhat beat up 1997 Ford Ranger Extended Cab with the 2.3L 4 Cylinder engine.

I did my normal shakedown during the test drive, but I missed something kinda big. When the previous owner mentioned that the heater didn't work, I figured that the blend door or blend door actuator was probably the culprit based on my old '96 which met an unfortunate end at the bumper of a cement truck...Knowing that it could be rigged up to work by going in through the glove box etc. I was ok with just using it as a bargaining chip to get a lower price.

But upon further inspection I see that the heater core has been bypassed completely and so now I suspect that the heater core may have been leaking at some point. I didn't find any water damage on the floor or anything, though, so who knows?

So, is there a good way to test the heater core for leaks so I know if it needs to be changed? I'd hate to tear out the dash and find out that the core is fine.

On the plus side student is heading to San Diego, so having no heat isn't the end of the world - the project may wait for next summer.

Thanks in advance...

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Old 08-11-2016
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Join Date: Jan 2014
Location: Vancouver, BC
Posts: 7,281
Heater core needs to handle about 16psi of pressure, Radiator Cap rated pressure.

Put hoses on the core and seal one hose, then blow into the other hose and see if it holds pressure.
Your lungs can generate about 2psi of pressure.
Do NOT use an air compressor, or you will for sure need to replace the heater core.

If core can not hold 2psi pressure then it will need to come out.
If it can then give it a try, but keep your eye on it.

And have your son carry a connector/splice 2 hose clamps and a screwdriver just in case it does leak and he needs to by-pass it again
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Old 08-12-2016
Thread Starter
Join Date: Aug 2016
Location: Livermore
Posts: 2
Thanks for that, RonD

I spoke with the fellow who sold it to us while dropping off some paperwork, and he seemed genuinely surprised that it had been disconnected. He suggested that there was one mechanic who told him after another service that his heater was bad and needed to be replaced, which he declined because of the warm climate and the cost the mechanic quoted. He wondered aloud if that mechanic bypassed the heater needlessly to try and get him to pay for a "new" heater core while just reconnecting the system.

I'm not sure I buy it, but I'll try the lung pressure test and take it from there.

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Old 08-18-2016
sheltonfilms's Avatar
Join Date: Apr 2010
Location: Knoxville, TN
Posts: 631
As stated above a pressure test is needed.

Bicycle pump will be good to use.

BTW you can make your readings more sensitive by adding water to the heater core.

The smaller the air chamber the more a small leak will show on the gauges.
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