Hunting a Leak

[lothian]

2006 Hyundai Sonata

Issue:
System will not hold vacuum, post-replacement. System equalizes from vacuum in just 30mins, which suggests (to me) a rather large opening... somewhere.

I realize that negative pressure indicates an opening in a system, while positive pressure reveals it. I lack the equipment to put the system under positive pressure. What do I need to get? ...and what is the exact procedure?

The Story:
The 20yo compressor died in our stalwart Sonata. The system had zero pressure.

The Details:
I'm a fair wrencher, so I decided to perform the replacement. It's a big job but definitely not complicated. I replaced the compressor, condenser, expansion valve, desiccant bag (Genuine Hyundai), LP line, all o-rings, both schrader cores and caps—all new Denso components. I thoroughly flushed the evaporator and individual lines ONLY and confirmed (with filter) that zero contaminate was present. Only OEM parts remaining: HP line, comp-to-cond line, pressure transducer, evaporator. I confirmed neither the manifold and vacuum lines, vacuum pump, nor quick connects are the source of the leak.

I'm at a full stop, of course, until I determine the source of the opening to the system.

[Cusser]

Issue:
System will not hold vacuum, post-replacement. System equalizes from vacuum in just 30mins, which suggests (to me) a rather large opening... somewhere.

I realize that negative pressure indicates an opening in a system, while positive pressure reveals it. I lack the equipment to put the system under positive pressure. What do I need to get? ...and what is the exact procedure?

What equipment do you have? Some would add a can of R134a and use electronic sniffer and soap bubbles to find the leak. Or add some UV dye and 1 can of R134a and use UV light and yellow goggles to find the leak.

[Tim]

Issue:
System will not hold vacuum, post-replacement. System equalizes from vacuum in just 30mins, which suggests (to me) a rather large opening... somewhere.

I realize that negative pressure indicates an opening in a system, while positive pressure reveals it. I lack the equipment to put the system under positive pressure. What do I need to get? ...and what is the exact procedure?

What equipment do you have? Some would add a can of R134a and use electronic sniffer and soap bubbles to find the leak. Or add some UV dye and 1 can of R134a and use UV light and yellow goggles to find the leak.

With such a significant leak, you should be able to tell quickly when adding a little refrigerant. I'd also look for oily spots at connections.

[lothian]

Did either of you read my post all the way through?
The first test of a new system is to see if the thing holds vacuum.

I need to pressurize the system with nitrogen. If I use shop air or add refrigerant prematurely I risk ruining the desiccant.

...

[Tim]

Adding the correct refrigerant for a pressure test won't harm the desiccant; Nitrogen does work, too. If you must open the system for a repair, cap the drier.

[Cusser]

Did either of you read my post all the way through?
The first test of a new system is to see if the thing holds vacuum.

I need to pressurize the system with nitrogen. If I use shop air or add refrigerant prematurely I risk ruining the desiccant.

...

Yes, I used my Chemistry degree, Phi Beta Kappa, Magna cum Laude little brain and read the post all the way through.

Since you stated you lack the equipment to put the system under positive pressure (nitrogen) it would be CONSIDERABLY easier and less expensive to use a can of pure R134a than get a nitrogen cylinder set-up. You may even be able to hear refrigerant hissing out your large leak.

Shop air will contain moisture and ruin your desiccant, adding R134a will not.

I'm NOT an AC professional so your attempt at insulting me does not other me, but Tim IS an expert, so watch your language.

NEVER ADD ANY SEALANT OR REFRIGERANT CONTAINING SEALANT.

[JohnHere]

2006 Hyundai Sonata...Issue: System will not hold vacuum, post-replacement. System equalizes from vacuum in just 30mins, which suggests (to me) a rather large opening... somewhere.

How many miles has this vehicle logged?

It's unlikely that any of the new parts you installed have such a sizeable vacuum leak. However, you didn't replace the HP line from the condenser to the TXV, or the evaporator.

A few questions: Is the metal HP line routed down low near the bottom of the condenser? Is it subject to road splash? Do you live in an area in which the DOT applies ice-melt chemicals to the roads in winter? If so, the line might have corroded-through.

The evaporator could also have corroded-through due to leaves and other moisture-retaining gunk that have accumulated in the lower part of the plenum, especially in a 20-year-old vehicle.

Some additional thoughts: Are all of the o-rings you replaced the correct size? Did you use a dab of Nylog Blue on each o-ring and threaded joint to ensure a leak-free seal?

Since the system will not hold a vacuum in its current state, that means air and moisture have been introduced into the system, requiring a second desiccant change and thorough evacuation. This presumes that you found and fixed the leak beforehand.

[tbirdtbird]

By far and away, IMO, the best way to detect leaks is by charging with a partial can of refrigerant, and then using a sniffer to find the leak. Most of the other methods are antiquated IMO. That is what we do in our shop. Areas to be suspect of are the evap (20 yrs old) and its O-rings. Evaps are famous for leaks and are unfortunately very difficult to get at.

I seem to recall your user name, if you have been on here before then you know the quality of those that respond.