I was thinking of pressurizing the AC with compressed air to see if it holds pressure, and if if really lucky, finding where the leak is. It's empty now and I have other problems so I'm just checking things.

It's for a 1998 C230.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

I'm not sure thats a good idea. The idea is to keep air and humidity OUT of the system. Thats why you should pull a vacuum for leak tests.

I understand WHY you want to do this, though.

I've always looked at all fitting connections and look for oil residue. Have you replaced the compressor itself? The front seal under the clutch is a prime source of leaks.

Afterthought: Air in your receiver-dryer is bad.

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My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

The only way you will ever find it is with a stethoscope and then you will have to replace the receiver....don't waste your time. Pressure with R22 and a few oz of Nitrogen + sniffer or pull vacuum and use stethoscope that way listening.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

NO! Don't do that! You will be contaminating the system with moisture and other contaminants from the atmosphere. Pressurize the system with Nitrogen, refrigerant, CO2/Argon, etc.

It's not even good to blow out flushing agents with compressed air. Much better to use an inert gas as above.

If you do this, you will NEVER get the contaminants out with a vacuum pump.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

I think ps meant to say pressurize with Nitrogen and a few oz. of R22, not the other way around. It only takes a few ounces of R22, pressurized by nitrogen, to make it HIGHLY detectable with an electronic sniffer, even one of the old technology ones.

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

The OP said he wanted to pressurize with compressed air.

Definitely NOT a good idea.

__________________
My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

Yes, and I emphatically said that in the post previous to the one you quoted.

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

I have an 83 240D. It's black, so the AC is a must have. I used DuraCool two years ago and it's cooling well. I ran some of their sealer, without bothering to look for leaks, as I don't care where they are as long as they are plugged.

I got the deluxe kit, with gauges for about $70 CND.

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I choose to be happy, even when the Mercedes is being awkward, lol

I'm not picking on you Smiffy, but anytime the subject of sealer comes up, I feel compelled to make a point:

Using a sealant is a REALLY risky thing to do with your auto a/c. If the sealant is nothing more than a seal sweller you will usually be okay. For the use of most sealers, however, you run the risk of completely wrecking your a/c system and make it untouchable by most shops.

The non seal swelling sealers will COMPLETELY WRECK most recovery/recycle machines. The shops are NOT anxious to destroy a multi thousand dollar machine in the course of effecting a few hundred dollar repair. Not much profit in it.

As a result they will check the system for sealants before connecting to their machine. If sealant is detected they will NOT connect to the machine for recovery, thus it is ILLEGAL for them to service the system.

Just want to make sure everyone is aware of this. I am NOT one who is a proponent of making things illegal, but if they were to pass a law making a/c sealants illegal I would certainly not protest.

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Never use leak sealer in an A/C system.
I replace too many compressors and other components wrecked by stop leak every year.

This is an especially BAD idea on the newer compressors that have a speed sensor.


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__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Most air compressor output is wet (condensation) and seriously contaminated with random particulate.

Nitrogen, R12, R22, and vacuum are safe.

Rule of thumb if there is no rush:

* Vacuum the system 12 - 24 hours.

* If the system will then hold vacuum without loss for 12 hours it is OK to re-charge.


.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/