Out of ideas on how to find my freon leak...

[rothsean]

I have used a sniffer.....nothing, but a few false positives.

I have used a black light, there is some green residue mixed with dirt on the high pressure line coming out of the compressor, but I cleaned it and nothing has re-appeared. It could be from an old leak that was fixed last year by DMCH (they said the compressor seal was bad and they replaced the compressor).

Schrader valves are not leaking.


I have checked every possible line and connection in the front and rear. I looked over the condenser with the black light, nothing.


The only thing I have not checked is the evaporator. Is there an easy way to check that?

[LordFly]

I would think with the dye and black light it should be pretty easy to find. If not, it must be a pretty minor leak....

[Jonathan]

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."

(I thought that was originally a Mr. Spock quote until I googled it and it comes up under Sir Arthur Conan Doyle/Sherlock Holmes... huh, fancy that)

...OT... if you seem to have ruled out every known place you could be having a leak, save the evaporator, perhaps the system isn't leaking? And I just mean that perhaps whatever way you are using to measure/test/evaluate whether there is enough freon in the system has a defect in it? If indeed there is no leak to be found.

What are you doing to test or measure the freon pressure in the system?

[David T]

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."

(I thought that was originally a Mr. Spock quote until I googled it and it comes up under Sir Arthur Conan Doyle/Sherlock Holmes... huh, fancy that)

...OT... if you seem to have ruled out every known place you could be having a leak, save the evaporator, perhaps the system isn't leaking? And I just mean that perhaps whatever way you are using to measure/test/evaluate whether there is enough freon in the system has a defect in it? If indeed there is no leak to be found.

What are you doing to test or measure the freon pressure in the system?

A common leak is the service valves. You don't normally test them because you have your hoses on them while you are looking for leaks. Get some metal caps to put on them and you should replace the valve cores. If you put dye in the system run the A/C till it makes water and see if the dye is in the water. if it isn't, the evap coil is not leaking.
David Teitelbaum

[Bitsyncmaster]

How long does it take to leak (AC stops cooling)? Slow leaks that take months will not show up with leak detection if a hose is leaking over the total length of the hose.

Mine turned out to be the hose from the condenser to the accumulator. That leaked about 12 oz. in 3 months. Hose replacement is less work than evaporator replacement.

[David T]

How long does it take to leak (AC stops cooling)? Slow leaks that take months will not show up with leak detection if a hose is leaking over the total length of the hose.

Mine turned out to be the hose from the condenser to the accumulator. That leaked about 12 oz. in 3 months. Hose replacement is less work than evaporator replacement.

Which is why to test you pressurize with Nitrogen to 250 psi and use leak detector solution. When the system is not running the whole system balances out to around 70 psi. Double what the low side runs at but very low (less than 1/2) what the high side runs at.
David Teitelbaum

[DavidProehl]

To check the evaporator, look at the evaporator drain. It will have some dye present. When my evaporator was leaking, there was only minimal dye making it very hard to detect, likely because the water also flowing from the evaporator box washed it away.

[rothsean]

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."

(I thought that was originally a Mr. Spock quote until I googled it and it comes up under Sir Arthur Conan Doyle/Sherlock Holmes... huh, fancy that)

...OT... if you seem to have ruled out every known place you could be having a leak, save the evaporator, perhaps the system isn't leaking? And I just mean that perhaps whatever way you are using to measure/test/evaluate whether there is enough freon in the system has a defect in it? If indeed there is no leak to be found.

What are you doing to test or measure the freon pressure in the system?


The system worked fine since last September when the new compressor was installed and the system was pressured up again.

A month ago the A/C stopped blowing cold air and was warm with a hint of cold (and the compressor was cycling on and off every 5 seconds). I added 9 ounces of Freon (R12) and the pressure was up to 40 psi / 210 psi (low/high) and it cooled great.

Now it is barely cooling, pressures are 24psi/170psi. It is definitely leaking somewhere and that does not seem like a small leak since it took a month or less to drop again. It was down to 35psi/190psi within 1 week of adding Freon.

All of my pressure tests were done on 90 degree days.



I need to find the leak. I am going to turn on the system and let the evaporator water drain into a cup and see if it is greenish..

[Jonathan]

The system worked fine since last September when the new compressor was installed and the system was pressured up again.

A month ago the A/C stopped blowing cold air and was warm with a hint of cold (and the compressor was cycling on and off every 5 seconds). I added 9 ounces of Freon (R12) and the pressure was up to 40 psi / 210 psi (low/high) and it cooled great.

Now it is barely cooling, pressures are 24psi/170psi. It is definitely leaking somewhere and that does not seem like a small leak since it took a month or less to drop again. It was down to 35psi/190psi within 1 week of adding Freon.

All of my pressure tests were done on 90 degree days.



I need to find the leak. I am going to turn on the system and let the evaporator water drain into a cup and see if it is greenish..

Gotcha. Thanks for detailing that.

You might very well be right there is a leak somewhere of significant size that needs to be found. As David said also, could be the service valves being problematic too.

Maybe one other thought on the pressure tests though... when we test the pressures of these sorts of systems, are we not also counting on a certain performance or set of characteristics from the compressor or other components to make those pressure numbers be good or be bad?

What I am getting at is, if we were measuring the discharge pressure on a water forwarding pump (an example a little more up my alley), we factor in the suction pressure as we measure the discharge pressure and also the temperature like you have done. Then you look it up on the pump curve to see where it should be. Perhaps the fluid we are pushing too if it is significantly different enough in terms of specific gravity or what not. The part I was curious what the group felt about was if you saw low pressures on a forwarding pump, you would often start to question or investigate whether the pump impeller had gotten worn down or cavitated, or whether there was some sort of pump seal problem letting water go back where it came instead of out, or perhaps even whether the motor running that pump was putting out less than it should.

Applied to a DeLorean A/C system, could any of these considerations affect your pressure readings and throw you off course in your troubleshooting? In our case, the motor driving the pump is the belt driving the compressor. Could there be something going on there with your car/any car that would give it a little less umph than needed? The temperature one is also quite likely rather important in much the same way your average gas pump will indicate that it is calibrated to 15 deg C. Or perhaps like any other process flow system, if you have downstream restrictions that aren't normally supposed to be there, it may build unnecessary back pressure on the high side yet cause a low pressure situation on the suction side.

Just some ideas... as we "think outside the box" (... put that expression in the annoying thread too, lol).

[rothsean]

Gotcha. Thanks for detailing that.

You might very well be right there is a leak somewhere of significant size that needs to be found. As David said also, could be the service valves being problematic too.

Maybe one other thought on the pressure tests though... when we test the pressures of these sorts of systems, are we not also counting on a certain performance or set of characteristics from the compressor or other components to make those pressure numbers be good or be bad?

What I am getting at is, if we were measuring the discharge pressure on a water forwarding pump (an example a little more up my alley), we factor in the suction pressure as we measure the discharge pressure and also the temperature like you have done. Then you look it up on the pump curve to see where it should be. Perhaps the fluid we are pushing too if it is significantly different enough in terms of specific gravity or what not. The part I was curious what the group felt about was if you saw low pressures on a forwarding pump, you would often start to question or investigate whether the pump impeller had gotten worn down or cavitated, or whether there was some sort of pump seal problem letting water go back where it came instead of out, or perhaps even whether the motor running that pump was putting out less than it should.

Applied to a DeLorean A/C system, could any of these considerations affect your pressure readings and throw you off course in your troubleshooting? In our case, the motor driving the pump is the belt driving the compressor. Could there be something going on there with your car/any car that would give it a little less umph than needed? The temperature one is also quite likely rather important in much the same way your average gas pump will indicate that it is calibrated to 15 deg C. Or perhaps like any other process flow system, if you have downstream restrictions that aren't normally supposed to be there, it may build unnecessary back pressure on the high side yet cause a low pressure situation on the suction side.

Just some ideas... as we "think outside the box" (... put that expression in the annoying thread too, lol).


I just tested the pressures again. The low side was 32psi and the high was 175psi. Within spec for today's temps.


Even though it is within spec it still does not feel very cold. I do not have a temp gauge, I will get one. Maybe I am being too picky and this is just a DeLorean A/C in the Texas summer heat. But, 3 weeks ago I put enough Freon in to make the low pressure 40psi and the high side 210psi and it cooled great for a few days, very cold air.

So to me it means that some has leaked out since then (3-4 weeks ago).

Also, the compressor stays on at idle but when I am driving it is kicking on and off every 3-5 seconds, very annoying.




I checked the Schrader valves, no leaks there. The sniffer did not smell it, I don't hear it, no dye around them and I also took small balloons and put them on the valve stems and they did not inflate at all in 1 hour. They were very small balloons, about 2 inches long and 1cm wide.






Sean

[Jonathan]

Hey Sean,

Maybe one other possibility would be if the cold air you are expecting is actually getting generated, but is getting mixed with warmer air before it gets to you? This is one area on my/our cars I have not ever taken apart, so it's a bit of a guess, but would there be anything going on in the way of valves or flaps that go from one supply of air to another that could be letting some warm air from either the cabin or normal car heating source mix with the cold stuff and it comes out warm/cool?

Maybe someone else can chime in to confirm? I was just thinking that if it all checks out for pressures per today's temperature, than maybe there is something else going on here. That is if you are measuring temperatures at your front vents for example with a temperature gun/sensor you know to be calibrated. I know these kinds of things can often be "relative" to the conditions, much like a booster pump adds to the suction pressure so it will go up and down based on the supply pressure. If it gets hotter and hotter ambiently, I would imagine the A/C can't get down to near freezing temperatures because of that.

[Jonathan]

Just one other thought...

Did you do any stereo upgrade/deck and bracket replacement work recently?

The reason I ask is because when I put my new DIN bracket in and stereo and all that jazz, everything had to come out, including the center vents. They have these rubber sleeves that connect the vents attached to the bracket to the air source pipe openings behind the console. When the new stereo and bracket were going back in, it can be a bit goofy making sure these rubber sleeves line up with the edges of the vents and if say one portion was flapped over, it might create some sort of "venturi" type syphoning that could pull in warm air from behind the stereo in with your cold A/C air.

Who knows, stranger things have happened with these cars...

[rothsean]

21261

I found the leak, it is on the high pressure hose after leaving the compressor where it changes from a metal hose to the rubber hose (see pictur, glowing green near center of photo on metal).


Now, my question is.... I guess I should replace both hoses from the compressor right? Who should I buy them from? Also, what else should I replace while I am doing this job?


I have R12 Freon that I can use and a can of Freeze 12. Should I buy more oil for the system too?

[David T]

21261

I found the leak, it is on the high pressure hose after leaving the compressor where it changes from a metal hose to the rubber hose (see pictur, glowing green near center of photo on metal).


Now, my question is.... I guess I should replace both hoses from the compressor right? Who should I buy them from? Also, what else should I replace while I am doing this job?


I have R12 Freon that I can use and a can of Freeze 12. Should I buy more oil for the system too?

The high side hose coming off the compressor to the condenser coil has to handle the highest pressures and the highest temperatures. It is not unusual to see a leak at either end or the hose (and crimps). If the hoses are original they should all be changed, otherwise just change the high side hose. Measure the oil level. To be safe I would just pour it all out and refill with fresh.
David Teitelbaum

[Nicholas R]

Mine leaked from the evaporator core itself. I pulled the blower fan and stuck the sniffer inside and it went off. Not a fun place to find a leak. The evaporator was only 3 years old too from specialTAuto. I replaced it with one from DMCMW and its been great since.

[rothsean]

The high side hose coming off the compressor to the condenser coil has to handle the highest pressures and the highest temperatures. It is not unusual to see a leak at either end or the hose (and crimps). If the hoses are original they should all be changed, otherwise just change the high side hose. Measure the oil level. To be safe I would just pour it all out and refill with fresh.
David Teitelbaum

Do I need to take the compressor off in order to drain the oil from it? What about the oil that is in the dryer?

My understanding is that once I take off the two large hoses and remove the oil from the compressor, I need to add 6 ounces of oil into the system? Do I add into the hose itself or do I have to add it into the low pressure Schrader valve where Freon goes?

[David T]

Do I need to take the compressor off in order to drain the oil from it? What about the oil that is in the dryer?

My understanding is that once I take off the two large hoses and remove the oil from the compressor, I need to add 6 ounces of oil into the system? Do I add into the hose itself or do I have to add it into the low pressure Schrader valve where Freon goes?

If you are replacing hoses you undo them and remove the compressor to drain it. You remove the large brass plug on top to drain, refill and check the oil. If the oil is clean and the insides of the hoses are clean you do not have to worry about any oil still remaining in the system. If the dryer/accumulator is original it should be replaced. Look in the Workshop Manual for the procedures, it is ALL in there.
David Teitelbaum

[Ron]

$.02

I think you should allow for oil in replaced hoses considering that the Sanden manual wants you to allow .5 oz even for a drained compressor. It's .3 oz for hoses on a typical system and it's a loooong way from one end of a D and back...

There is a procedure to determine if the oil charge is correct, but you have to reclaim the refrigerent in the process...
(If you can do this, and IF you can get the pressures and cooling right first, I would check what is currently in it... )
See: 13.4 Oil Charge Determination for Long Hose Applications (http://dmctalk.org/showthread.php?353-Sanden-SD-AC-Compressor-Service-Manual)


FWIW- So far, it sounds like you developed a leak and have been going from overcharged to undercharged ever since.
See: http://dmctalk.org/showthread.php?7921-AC-Pressure-Charts-Reading-Gauges-(R12-and-Retrofit)


Are you using a variable orifice?

[rothsean]

So, I just want to make sure I am 100% clear on the A/C system. I keep hearing about the oil in the system and oil in the compressor. Is that the same oil system or do A/C systems have 2 separate oils systems?


If it is a single system, then why does most of it hang out in the compressor? I would think that if it is mixed with Freon that it would be equally spread throughout the Freon system.


Can anyone recommend any oil for the r12 systems? I am about to change all of my hoses and accumulator, vacuum the system down and put in new r12. Does the average auto part store carry the mineral oil and dye for the r12 systems?

[Ron]

There is only one system and it uses Mineral Oil (https://www.google.com/webhp?source=search_app#fp=99b9cfc034d2c57c&q=R12%20mineral%20oil).
It is carried by the refrigerant throughout the system (and why you must match types ie Mineral for r12, PAG for 134a, etc).

[rothsean]

There is only one system and it uses Mineral Oil (https://www.google.com/webhp?source=search_app#fp=99b9cfc034d2c57c&q=R12%20mineral%20oil).
It is carried by the refrigerant throughout the system (and why you must match types ie Mineral for r12, PAG for 134a, etc).



Thanks

[rothsean]

When I vacuum the system, do only do the low side or the high side? I am assuming that I just connect on the low side and vacuum the system, and that will vacuum the high side too. I just want to make sure.


FWIW, I installed my SpecialTAuto hoses today, high, low and condenser-evaporator hoses. Took me 3 hours and I am a novice. I am also very picky and this time includes using zipties to neatly hang hoses under the car. Also included removing the compressor and draining the oil.

[DMCMW Dave]

When I vacuum the system, do only do the low side or the high side? I am assuming that I just connect on the low side and vacuum the system, and that will vacuum the high side too. I just want to make sure.
.

It's a looped system (I.e. inside is inside) so technically it doesn't matter. As a practical matter, open both valves, does a better job of extracting moisture.

[David T]

It's a looped system (I.e. inside is inside) so technically it doesn't matter. As a practical matter, open both valves, does a better job of extracting moisture.

Actually the way to do it is with both the high and low side and use a valve extractor to withdraw the core on the low side so you aren't trying to suck through that tiny valve. Also helps when you are filling. When I do systems I replace the cores, change the oil, add dye, and pressurize to 250 psi with Nitrogen before evacuating. When I evacuate the system I use an electronic vacuum gauge that reads in Torrs, much more accurate than the compound gauge. You can actually see when you have all of the moisture removed. Takes about 1/2 hour if the system was clean and tight. To evacuate I first open the valve to the high side and watch the low side come down. When I get low I then open the low side and finish. After about 5 minutes I shut both valves and see if the vacuum holds. If it does then I open both valves and let it run till I get all of the moisture out. Once you have removed all of the air you are boiling the water vapor and that can take a while. When you see the vacuum won't get any lower you are done and then you shut the vacuum pump and immediately get some refrigerant in there to get you to at least atmospheric.
David Teitelbaum