2004 BMW 325i (E46) Typical Leaks Locations?

[McLugnuts]

2004 BMW 325i base model. Automatic Transmission. 106K miles . Purchased three months ago.
Intermediate auto repair level with very limited auto HVAC knowledge and experience.

Trying to find information on typical leak locations for this vehicle. A/C ice cold and blowing on all and vents on purchase. Three weeks after purchase I had the car on jack stands for five days performing coolant system repairs (issue within itself). On first drive after coolant repairs a/c not cold and compressor not engaging. Brought to local, independent BMW mechanic that used software/pc to engage compressor, switches and other parts of car. Compressor engaged, so he did a vac and recharge. He pulled vacuum for 30 minutes and said pressures were very even and did not drop. He filled correct amount of freon and said if there is a leak it's most likely very small.
Two weeks later encountered the same scenario with car on jack stands for a few days for repairs and a/c out again on first drive. Brought to another mechanic that I explained previous failure and he did a vac and refill with dye. He said he couldn't see any leaks with UV light and to bring it back in a few days. He also stated if it's an evaporator leak it will most likely show in condensation on ground. I monitored condensation and did not see any. Brought it back to him three days later and he inspected with UV light and again he said there aren't any noticeable leaks. Three days later warm air coming from passenger side only which, through Google searches, indicates low refrigerant level. Yesterday my daughter was on a two hour road trip and she said a/c not working.. blowing warm air through all vents at all speeds and levels.

Seems to hold a charge for roughly 7 to 14 days. I've researched a lot online for possibilities and they are listed below:
1) High and Low side schrader valve fittings: pour water over fittings and check for bubbles.
2) Compressor shaft
3) Evaporator; usually accompanied with musky smell in cabin but, car doesn't have that.
4) Expansion valve: The day after I purchased the car I noticed frost coming out of vents for a brief period when I shut the engine off.

While I'm posting i may as well ask do products like this work: http://www.cliplight.com/automotive/sup ... l-premium/
I spoke to one of their technicians and he said if it the car's a/c system can hold a charge for two weeks the product may work to seal pin-hole sized leaks.
He explained to me that it would need another vac and recharge first before applying the sealer. I asked him if it would damage shop's vac/recharge machine and said modern machines have filters that protect them and should be okay.

All replies, tips, comments appreciated

[GM Tech]

If you put sealer in it--no respectful mechanic will work on it-- they do not wish to plug up their expensive recovery equipment....

A leak that big can be easily found with a good sniffer, dye and black light with UV glasses...

[McLugnuts]

If you put sealer in it--no respectful mechanic will work on it-- they do not wish to plug up their expensive recovery equipment

That's definitely understandable and why I am asked here first.

A leak that big can be easily found with a good sniffer, dye and black light with UV glasses...

I think i need to bring it to an automotive a/c specialist. Neither mechanic used a sniffer. The UV glasses is a good suggestion.. any particular brand or type?

[Cusser]

I think i need to bring it to an automotive a/c specialist. Neither mechanic used a sniffer.

UV light and UV goggles get used in the dark or near-dark. An automotive AC specialist will use/have a combination of techniques to pinpoint leaks: UV dye, electronic detector ("sniffer"), soap bubbles....

Remember too: good service valve sealing caps are very important to retaining the refrigerant !!!

[McLugnuts]

I think i need to bring it to an automotive a/c specialist. Neither mechanic used a sniffer.

UV light and UV goggles get used in the dark or near-dark. An automotive AC specialist will use/have a combination of techniques to pinpoint leaks: UV dye, electronic detector ("sniffer"), soap bubbles....

Remember too: good service valve sealing caps are very important to retaining the refrigerant !!!

I'm tempted to go ahead and replace the schrader valves and caps. Inexpensive and easy to do. Do you know if Santech products are good? or should I stick with OEM: https://www.ecstuning.com/ES250000/?gcl ... gQodPDAN3A
I watched a video in which a mechanic used balloons to test for leakage from the valves. Since it seems the freon is low or completely out again it seems like a good time to replace them.

[wptski]

I'm tempted to go ahead and replace the schrader valves and caps. Inexpensive and easy to do. Do you know if Santech products are good? or should I stick with OEM: https://www.ecstuning.com/ES250000/?gcl ... gQodPDAN3A
I watched a video in which a mechanic used balloons to test for leakage from the valves. Since it seems the freon is low or completely out again it seems like a good time to replace them.

Santech is one of the biggest names in the business.

[Cusser]

I'm tempted to go ahead and replace the schrader valves and caps.

I watched a video in which a mechanic used balloons to test for leakage from the valves. Since it seems the freon is low or completely out again it seems like a good time to replace them.

I would use soap bubble solution on the caps area first. you should be able to see if leaking there. If it was, I would try good-quality caps first (bubble check those too) before I monkeyed with the valves.

I have seen valve caps where the rubber seal had cracked, allowing refrigerant to escape.

[McLugnuts]

I'm tempted to go ahead and replace the schrader valves and caps.

I watched a video in which a mechanic used balloons to test for leakage from the valves. Since it seems the freon is low or completely out again it seems like a good time to replace them.

I would use soap bubble solution on the caps area first. you should be able to see if leaking there. If it was, I would try good-quality caps first (bubble check those too) before I monkeyed with the valves.

I have seen valve caps where the rubber seal had cracked, allowing refrigerant to escape.

Are the caps the seals or does the valve itself seal or a combination of both?

[Cusser]

Are the caps the seals or does the valve itself seal or a combination of both?

Combination of both, but GM Tech and others here say the cap is the true seal.

[McLugnuts]

Are the caps the seals or does the valve itself seal or a combination of both?

Combination of both, but GM Tech and others here say the cap is the true seal.

I just spoke with the mechanic and he said he did spray valves and cap with soapy water and no bubbles seen.