AC Leak Differential Diagnosis and Treatment Plan

[highway_star]

Looking for informed opinions on AC leak.

This has been present since I bought the car in 2021 or so. Initially I topped off the AC and it was fine for a couple of years with just that. Next top off lasted 2 months, so I decided the "watchful waiting" was over and it was time to fix.

Car is a 2006 Lincoln Town Car. So AC system is 20 years old now.

Service manual says dye is in the system from the factory, I also added some extra UV dye. I can see a small amount of dye by the connection to the condenser and the pressure switch. No visible dye elsewhere.

I didn't have any luck with the sniffer tool initially, so I recharged the system again to get the pressure up. After doing that, I get a slight reading in all of the following after running the AC for a few minutes

• HVAC Vents in Dash
• Floor Area of vehicle
• HVAC condensate drain location
• Pressure Sensor Area
• Connection to condenser
• Connection to compressor

The only strong reading I get is over the high side Schrader valve when the protective cap is off.

My interpretation of these results is that after 20 years the o rings are likely a bit weak and connections in general seem to be leaking, the high side valve is leaking, and there is a leak in the evaporator. However the weak readings make me hesitant to assume all of this.

Part 2 of the question is what to do treatment wise. Given that I have to evacuate refrigerant and draw a vacuum and recharge, etc. for any opening of the system I'm leaning towards replacing anything which by age or indication might be leaking. I would hate to put everything together after fixing one component only to find others leaking. So for anything cheap and relatively low marginal effort that would be my approach.

This would amount to o rings at connections and the evaporator and high side valve.

Any opinions?

 

[JHZR2]

Evaporator leaks are horrible. I have lots of old cars that still run original AC systems, even R-12. But I won’t buy a car that I think has an evaporator leak because pulling dashes on old cars is rough. Modern ones I imagine may be worse.

I’d replace everything you could, including the valves in the service ports. Leak test with pressurized nitrogen with a trace of refrigerant. Buy a refrigerant sniffer.

 

[bullwinkle]

Look for dye/leaks underneath the insulated accumulator-they rust out & leak. The one on my MGM was rusted out when I bought it.

 

[Nukeman7]

Looking for informed opinions on AC leak.

This has been present since I bought the car in 2021 or so. Initially I topped off the AC and it was fine for a couple of years with just that. Next top off lasted 2 months, so I decided the "watchful waiting" was over and it was time to fix.

Car is a 2006 Lincoln Town Car. So AC system is 20 years old now.

Service manual says dye is in the system from the factory, I also added some extra UV dye. I can see a small amount of dye by the connection to the condenser and the pressure switch. No visible dye elsewhere.

Unless you spilled dye in that area, it has to be coming from a leak/pinhole/micro-crack in that area. Clean the area with brake cleaner and re-examine in a week to see if the dye returns.

I didn't have any luck with the sniffer tool initially, so I recharged the system again to get the pressure up. After doing that, I get a slight reading in all of the following after running the AC for a few minutes

• HVAC Vents in Dash
• Floor Area of vehicle
• HVAC condensate drain location
• Pressure Sensor Area
• Connection to condenser
• Connection to compressor

The only strong reading I get is over the high side Schrader valve when the protective cap is off.

Here is my easy and inexpensive repair of the high pressure Schrader valve that you should start with. Buy a $10 Dorman 902-025 brass plug from Amazon or O'Reilly Auto Parts. Install it on the high pressure port using Teflon tape on the threads. Unlike the plastic dust cap, this plug will 100% seal the port from leaking. It is very possible that the other "weak" readings that you are getting on the sniffer are simply a result of the R-134a diffusing from the high pressure port.

My interpretation of these results is that after 20 years the o rings are likely a bit weak and connections in general seem to be leaking, the high side valve is leaking, and there is a leak in the evaporator. However the weak readings make me hesitant to assume all of this.

Part 2 of the question is what to do treatment wise. Given that I have to evacuate refrigerant and draw a vacuum and recharge, etc. for any opening of the system I'm leaning towards replacing anything which by age or indication might be leaking. I would hate to put everything together after fixing one component only to find others leaking. So for anything cheap and relatively low marginal effort that would be my approach.

Let's not jump to a nuclear solution until you eliminate the obvious and most probable causes. Occam's Razor does have merit in most situations.

 

[Chris142]

The front seal on those compressors often leak. Take the front hub off to see it.

 

[highway_star]

Unless you spilled dye in that area, it has to be coming from a leak/pinhole/micro-crack in that area. Clean the area with brake cleaner and re-examine in a week to see if the dye returns.

Here is my easy and inexpensive repair of the high pressure Schrader valve that you should start with. Buy a $10 Dorman 902-025 brass plug from Amazon or O"Reilly Auto Parts. Install it on the high pressure port using Teflon tape on the threads. Unlike the plastic dust cap, this plug will 100% seal the port from leaking. It is very possible that the other "weak" readings that you are getting on the sniffer are simply a result of the R-134a diffusing from the high pressure port.

Let's not jump to a nuclear solution until you eliminate the obvious and most probable causes. Occam's Razor does have merit in most situations.

Brass plug is an interesting idea. If nothing else, it might allow a test of if the bulk of the leak is from that valve or elsewhere. If 90% of the leak is that valve then the time between charges on the rest might be years in which case we could go back to watchful waiting.

However, the other weak readings are definitely not due to the valve on the high pressure. I have 1 "bar" of reading ambient, and along lines, under the orifice tube, etc. Even reasonably close to the valve on the line. But the passenger floor, vent, HVAC condensate drain, etc. are 2 "bar" readings specifically. I'm a little skeptical of the floor as there is the possibility its picking else on something from the carpet, but these are not ambient readings due to a leak at the valve. But I'm unsure if their magnitude is significant.

I basically never intend to get rid of this car, so I know at some point a total system replacement is likely, but delaying 5 years might mean doing that in an air conditioned shop with a lift instead of the current improvised facilities.

 

[highway_star]

Evaporator leaks are horrible. I have lots of old cars that still run original AC systems, even R-12. But I won’t buy a car that I think has an evaporator leak because pulling dashes on old cars is rough. Modern ones I imagine may be worse.

I’d replace everything you could, including the valves in the service ports. Leak test with pressurized nitrogen with a trace of refrigerant. Buy a refrigerant sniffer.

Already have the sniffer, that is where most of my diagnostics have come from thus far.

The Town Car does not require the dash to be pulled to do the evaporator, its a box with the blower under the hood. Incidentally, I have pulled the dash on it to fix 2 $30 actuator motors for the AC duct work however, and it was not a fun job.

 

[highway_star]

Look for dye/leaks underneath the insulated accumulator-they rust out & leak. The one on my MGM was rusted out when I bought it.

I've heard that is a panther issue, although mine doesn't show any dye or trigger the sniffer. Southern car with little rust to speak of is likely a factor in its longevity.

 

[bullwinkle]

I've heard that is a panther issue, although mine doesn't show any dye or trigger the sniffer. Southern car with little rust to speak of is likely a factor in its longevity.

Thought an ‘06 Town Car was a Panther? I was surprised when mine was rusted out, because it was garaged in Nashville, TN in winter & spent summers in MN before I bought it, but it was a typical Ford design, insulated steel, so it would never really dry out.

 

[highway_star]

Thought an ‘06 Town Car was a Panther? I was surprised when mine was rusted out, because it was garaged in Nashville, TN in winter & spent summers in MN before I bought it, but it was a typical Ford design, insulated steel, so it would never really dry out.

It is a panther, I meant I had heard that was an issue so I was sure to check that area for leaks with the sniffer.

 

[14Accent]

I've heard that is a panther issue, although mine doesn't show any dye or trigger the sniffer. Southern car with little rust to speak of is likely a factor in its longevity.

The rust doesn't come from the environment, it comes from the condensation on the accumulator itself. The original steel part sweats and soaks it's foam insulator, which collects on the bottom and rots the accumulator from within the plastic casing.

Not saying that's the cause of your issue, just an FYI.

 

[Donald]

Replace all the o-rings and service valves. Then start looking for other leaks.

 

[The_Eric]

Try looking for dye on the condensate drain too.

 

[Marcozi]

Here's my take: drive the car to a reputable automotive AC shop. Have the shop refill the system with refrigerant and dye. Bring the car back to the shop when the AC stops working. Have the tech find and fix the leak. Replace the dryer as the car's AC system has air in it.

 

[highway_star]

Here's my take: drive the car to a reputable automotive AC shop. Have the shop refill the system with refrigerant and dye. Bring the car back to the shop when the AC stops working. Have the tech find and fix the leak. Replace the dryer as the car's AC system has air in it.

Not looking to spend what that would cost or have those people touching my good car.
I do everything myself for a reason, even if it takes a bit longer or some effort.

 

[highway_star]

The rust doesn't come from the environment, it comes from the condensation on the accumulator itself. The original steel part sweats and soaks it's foam insulator, which collects on the bottom and rots the accumulator from within the plastic casing.

Not saying that's the cause of your issue, just an FYI.

Ok yes, that makes sense. I may replace that as well since some of the sources I see indicate that moisture entry to the system occurs when opened for service and the dryer should be replaced as part of that.

 

[14Accent]

Ok yes, that makes sense. I may replace that as well since some of the sources I see indicate that moisture entry to the system occurs when opened for service and the dryer should be replaced as part of that.

That's a solid plan, the desiccant in your original accumulator is likely past it's serviceable life regardless so installing a new one is smart.

If you want to stick with OEM, it looks like RockAuto has the Motorcraft accumulator complete for $66.79 which includes a new mount. For that price, that's the route I'd take.