I will be replacing the manifold seals on my 85 300D R4 compressor. This appears to be the only leak spot, and system works good when recharged with R134. I hope to have the system open only a few minutes if all goes as planned. Car received full R12-R134 conversion in 2003, and hopefully a new dryer was then installed. Must I replace the dryer? Is this a must anytime the system is opened??? I plan on having it evacuated and recharged and oil added shortly after I replace the seals.
Gene

It's so inexpensive, why wouldn't you?

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

On my car it is.

I guess I have been wondering about this too. I have heard this from everyone and it is in the Haynes manuals. I've never been given an explanation though. So off to a search engine. First hit gave me this:

http://www.forparts.com/techreceiver.htm

Which says that the receiver drier should be thought of kind of like an oil filter in that it needs to be replaced often. Even when you don't open the system up. Apparently there are some pellets involved that "desiccate" the system and these get used up, or break down due to too much moisture when the system is open. When that happens, it just becomes a reciever, not a reciever drier.

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Jackson

1984 300d 223k
1994 Jeep Cherokee 2.5L 88k

"She may not look like much, but she's got it where it counts, kid. I've added some special modifications myself." -- Han Solo

"Would it help if I got out and pushed?" -- Princess Leia

OK, I'm sold. Sounds like compelling evidence and good advice.
Thanks,
Gene

If your system has leaks, then replace the receiver dryer.

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Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi

Is it possible to change the dryer without evacuating the system? I have the system charged up with r-12, and would hate to have to pay someone to suck it all back out, then pay them to fill it back up again. If I do have to have it evacuated, how much am I looking at to have someone do it for me?

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head

Well, if you let them keep the R12, you can probably get it done for free.

EDIT- Why do you want it changed? If you haven't opened up the system, it should be fine.

Because he read Miners post about replacing it as a maintenance item. Which should be taken with a grain of salt.

The problem with leaking systems is you always lose oil with the refrigerant and you have no way of knowing how much.
You stated that your going to "Recharge and add oil". How much oil were you planning on adding?

The correct way to do it would be to flush out the whole system. That way you can start with a known amount of refrigerant and oil.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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Indeed. If their was too much water in the system to start with, then the drier will be toast. If not, more water will not enter the system. Even if you have a leak, water shouldn't be entering the system until ALL of your refrigerant has leaked out.

I had not thought about flushing the system in that context before. How much oil will a commercial flush remove? I have read that they are insufficient to remove all of the metal shavings in the event of a compressor failure.

You can never be certain to get everything. But the receiver/dryer has a catch area and a screen to trap particles too. The more you clean, the more you get out, but you'll never get it all.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

." Even if you have a leak, water shouldn't be entering the system until ALL of your refrigerant has leaked out."-Tabor

That is not true. You are assuming things about pressure in the system without taking into account the dynamics of the pumping ,pressures, and thermal dynamics. The MB AC manual says that if any leak exists you are to assume moisture has entered the system.
If you placed the proper hardware.... before and after the receiver/dryer you could switch it out without all that work.. otherwise you can't. --Greg

Greg is right. A low charge can be enough to make the pressure switch on the dryer allowing the compressor to run. That same charge can be insufficient to keep the suction side from cycling into a vacuum, which can draw in moisture, especially over time. BTW, good to see you're still kickin Greg, haven't heard from you here in a while. Sometimes I feel like the only old fart online at this forum.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I beleive that the expansion valve also has a screen in it which should be cleaned when the system is evacuated. Also, if your system has a leak, what difference does it make if you lose the r12 over time or all in one hit? The longer you leave it leaking, the higher chance of the internals becoming corroded.
This includes the evaporator!

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Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi