1999 E300 AC question - Page 2 - PeachParts Mercedes-Benz Forum

Deplore · #16 06-12-2016, 05:07 PM

Also, did you flush the system by pulling a vacuum? I have a ac vacuum pump that will pull -30 psi, and the system will maintain that vacuum for over an hour (with the pump disconnected and gauges connected) And then I pump in refrigerant with 8oz of oil, and the pressure rises nicely to 7-15 bar, depending on outside temp.

funola · #17 06-12-2016, 08:59 PM

Quote:

Originally Posted by dhake2

UPDATE: It was 90 deg yesterday and I hooked up the gauges before starting the car and the pressures on low and high side was reading 120. I relieved the pressure down to 100psi and started the car. The pressures are now 35/325. .................

I don't think this is normal. The vapor pressure should remain the same whether the system is over/ under/ or correctly charged. i.e. letting out some refrigerant should not change the pressure reading. Maybe there is moisture in the system which is contributing to the "extra" pressure?

Per this R134a calculator R134a Refrigerant Pressure Temperature Calculator , at 90 F the vapor pressure should be 103 psi.

leathermang · #18 06-12-2016, 10:28 PM

Quote:

Originally Posted by Deplore

Also, did you flush the system by pulling a vacuum? I have a ac vacuum pump that will pull -30 psi, and the system will maintain that vacuum for over an hour (with the pump disconnected and gauges connected) And then I pump in refrigerant with 8oz of oil, and the pressure rises nicely to 7-15 bar, depending on outside temp.

It will help if you start using accepted standard nomenclature for discussing the AC system.

Pulling a vacuum does not ' flush ' the system according to what is accepted naming. It is the method for boiling off the moisture in the system. To flush you would need to run a liquid through the parts in question.

The amount of vacuum you can pull is dependent on barometric pressure.. which varies according to temperature, elevation compared to sea level and atmospheric conditions.... You probably can not pull a ' perfect ' vacuum on an automobile system because it is not hermetically sealed...

You do not pump refrigerant into your system if you have pulled a vacuum .. you allow it to be pulled into the system by that vacuum and may help that procedure by running the compressor.. which again is letting the system pull it in....

dhake2 · #19 06-13-2016, 08:28 AM

To answer a few questions:
1) When I installed the new compressor my recollection was that the directions said to turn the compressor over to pour out the oil while turning the compressor 10 revolutions. I turned the clutch; not just the pulley. I did not drain from a plug.
2) I flushed the evaporator by using compressed air with flushing fluid with the expansion valve removed. I flushed long enough for the fluid to be "near" clean but cant say it was completely clear.
3) When filling the system I pulled a vacuum to about -30 for about 45mins then put in 2.2lb of R134.

tjts1 · #20 06-13-2016, 10:09 AM

I guess the instructions to put in 2.2lbs are just wrong.

funola · #21 06-13-2016, 11:08 AM

"When I installed the new compressor my recollection was that the directions said to turn the compressor over to pour out the oil while turning the compressor 10 revolutions. I turned the clutch; not just the pulley. I did not drain from a plug."

Looks like too much oil is in the system, resulting in over charge of refrigerant.

funola · #22 06-13-2016, 11:17 AM

How do you remove excess oil without starting from scratch?
Would this work?

1. Hook up manifold gauge set.
2. Stick yellow line into a 16 oz bottle half filled with water
3. Start engine and run AC
4. Open high side valve (just a little, not too violent to blow water out) to vent refrigerant + oil mix into water.
5. Shut high side valve and let the oil float to the top of water.
6. Repeat steps 4 & 5 till the desired amount of oil is removed.
7. Charge with the amount of refrigerant that was vented.

Zulfiqar · #23 06-13-2016, 11:39 AM

Quote:

Originally Posted by dhake2

To answer a few questions:
1) When I installed the new compressor my recollection was that the directions said to turn the compressor over to pour out the oil while turning the compressor 10 revolutions. I turned the clutch; not just the pulley. I did not drain from a plug.
2) I flushed the evaporator by using compressed air with flushing fluid with the expansion valve removed. I flushed long enough for the fluid to be "near" clean but cant say it was completely clear.
3) When filling the system I pulled a vacuum to about -30 for about 45mins then put in 2.2lb of R134.

The rotate 10 revs while pouring oil in the compressor inlet is for older style compressors which were found in the W124s and 201s. The W210 uses a variable stroke compressor and has a drain bolt to remove and add oil.

You can rotate the compressor clutch all day long and it wont make a difference, you need to remove the crankcase bolt to change/charge the oil. If it was a new compressor which is not OE Denso or MB you need to change it twice to ensure you have clean and fresh PAG46 oil only in there, Aftermarket replacements are shipped with a shipping oil in them.

dhake2 · #24 06-15-2016, 08:10 AM

I went on a 4hr trip in 95deg weather and the vent temps were about 43deg. The car was chilly with the fan on low. The AC works great but am sure the system has too much oil from the discussion here. Is there any harm in running it this way? I second Funola's question: At this point, what is the best way to get the right amount of oil in the system?

tjts1 · #25 06-15-2016, 09:51 AM

Too much oil is not a big deal. Enjoy your AC.

leathermang · #26 06-15-2016, 10:41 AM

Quote:

Originally Posted by tjts1

Too much oil is not a big deal. Enjoy your AC.

Too much oil is a huge problem...
You need to do some general AC research ... not right to be advising others off the cuff.

Off

https://www.google.com/#q=auto+ac+too+much+oil

tjts1 · #27 06-15-2016, 10:47 AM

Stop making a mountain out of a molehill. AC is not rocker science. His AC was over charged, he fixed the problem, move on.

leathermang · #28 06-15-2016, 11:42 AM

Quote:

Originally Posted by tjts1

Stop making a mountain out of a molehill. AC is not rocker science. His AC was over charged, he fixed the problem, move on.

'Rocker Science' never heard of that....... no it is not... but there is a reason the MB FSM AC manual specifies a certain amount of oil ...and even that it be distributed around the system when installed... these threads are not just for the OP.... all sorts of people will be reading them of all sorts of experience levels... and we have an obligation not to leave them with a bad information.

dhake2 · #29 06-15-2016, 05:07 PM

I learn a ton from this site. What is the danger of too much oil? When it gets cooler I am willing to drain some oil and getting the correct amount in the system. Any suggestions on how to get the correct amount out and back in? A big thanks to all on this.

leathermang · #30 06-15-2016, 05:18 PM

Quote:

Originally Posted by dhake2

I learn a ton from this site. What is the danger of too much oil? When it gets cooler I am willing to drain some oil and getting the correct amount in the system. Any suggestions on how to get the correct amount out and back in? A big thanks to all on this.

I would guess that it acts an an insulator if too much is in there... you want an interaction between the refrigerant and the metal inside the condensor and the evaporator to be unrestricted .. read ' fast' ... so you really only want the amount of oil needed to keep the parts lubricated that depend on the oil which is mixed into the refrigerant ......
The second question hits right at the big problem...
I know of no one who has come up with any way to determine how much oil is in the system without taking all of it out... flushing... and re installing... which is a relatively huge job...

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