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#16
07-23-2009, 12:46 AM
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[QUOTE=whunter;2252798] a good vacuum pump will remove the moisture./QUOTE]
No vacuum pump is able to remove the moisture which has attached to the drying media under oil in the receiver dryer. Removing it via vacuum relies on dropping the boiling temperature of the water and it can not get to the water in the media due to the cooling effects of the oil. All the manuals agree on this point and the instructions on the receiver dryer would say to vacuum it if it had been open.... but they say discard instead because the physics is not there to get the water back out. Just minimize the open time. Kmoysob, water can be removed from the silica jell if you cut open the receiver dryer and take it out... wash with a solvent and then oven dry... Silica Jell is used to dry flowers...and is recycled many times by oven drying.. something can be added to it so that it shows blue or pink depending on the moisture content as an indicator of when to put into the oven. I have several pounds of it in the garage. You also see it on walls in weather indicators along with barometric pressure indicators. In that case ( not under oil ) it is able to respond to the ambient moisture conditions by changing colors without needing artificial drying.
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html 
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#17
07-23-2009, 08:50 AM
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Answer
[QUOTE=leathermang;2252809]
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#18
07-23-2009, 08:56 AM
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So is it better to add oil to other parts of the system rather than the drier before sealing it up and pulling a vacuum? That way the dessicant remains oil free until the refrigerant starts bringing it to the drier.
__________________
 Current Mercedes 1979 maple yellow 240D 4-speed Gone and fondly remembered: 1980 orient red 240D 4-speed Gone and NOT fondly remembered: 1982 Chna Blue 300TD Other car in the stable: 2013 VW Jetta Sportwagen TDI / 6-speed MT
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#19
07-23-2009, 10:46 AM
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__________________
Chad 2013 Jeep Unlimited Rubicon OBK#44 "Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.) SOLD 1985 300TD - Red Dragon 1986 300SDL - Coda 1991 - 300TE 1995 - E320 1985 300CD - Gladys 2006 Nissan Pathfinder LE 1998 Acura 3.0 CL
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#20
07-23-2009, 11:02 AM
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#21
07-23-2009, 11:03 AM
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Well, I thought a bit about it, and it seems like if you put oil in the drier as soon as you uncap it, the oil should protect the dessicant to some degree. Granted, the different oils have differeing degrees of hygroscopicsity (:?), but in general, the oil should prevent water from getting to the dessicant if it is sitting on top of it. There will still be water in the air space above the dessicant, but you could remove all of that with the vacuum. So (BTW I am doing this this weekend in my wagon, too) I think I am going to uncap the drier and put some oil in ASAP before putting the drier in place and sealing the system. and assume that I am protecting the dessicant the best I possibly can.
I have a vacuum pump, so I can immediately pull a vacuum. Have you considered renting one from AZ or similar so you can pull a vaccum and cap it before you drive to the shop? That way you could really minimixe the amount of time air is in the system.
__________________
Current Mercedes 1979 maple yellow 240D 4-speed Gone and fondly remembered: 1980 orient red 240D 4-speed Gone and NOT fondly remembered: 1982 Chna Blue 300TD Other car in the stable: 2013 VW Jetta Sportwagen TDI / 6-speed MT
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#22
07-23-2009, 11:24 AM
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#23
07-23-2009, 11:57 AM
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__________________
Current Mercedes 1979 maple yellow 240D 4-speed Gone and fondly remembered: 1980 orient red 240D 4-speed Gone and NOT fondly remembered: 1982 Chna Blue 300TD Other car in the stable: 2013 VW Jetta Sportwagen TDI / 6-speed MT
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#24
07-23-2009, 12:52 PM
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This is well written....
and mentions changing the receiver dryer as a time determined maintenance item in addition to when the system is opened up. Who has cut open one lately ? Used to be the pellets were in a sack...which would deteriorate with time and vibration... but I thought the actual containers had been changed to something like a brass sieve like deal... That does not mean that the actual beads might not need changing even absent the old sack like container. But it has been a very long time since I have seen this even mentioned .... Although I did mention a while back that I was hoping to route TWO receiver dryers into my 240 by using Rotolock valves which would allow one at a time to be changed out without having to evacuate the refrigerant in the system... This talk about the oils picking up moisture.... remember that the prudent thing to do is to break open a new supply of Cold flow 500 oil at the same moment you open up the new receiver dryer , put in the oil. close up the system and start the vacuum.
__________________
1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html
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