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O-rings - what sizes required for Mercedes system?

br1anstorm on Sun September 07, 2008 7:10 PM User is offline

Year: 1990
Make: Mercedes Benz
Model: 560 SEC
Engine Size: 5.6 ltr
Refrigerant Type: R12
Country of Origin: United Kingdom

I need some quick help with part numbers and 'O' ring sizes. I need to replace the expansion valve and receiver-drier in the (R12) aircon system of my 1990 Mercedes 560 SEC. I have the new parts, but neither comes with new 'O' ring seals for the connecting pipes.

First, I believe I ought to fit HNBR rings - which are normally green in colour.

But the main problem is that I haven't yet removed the old parts, so can't check the sizes. I think I'll need three rings for the connections at the receiver-drier, and four for the expansion valve connections. They are NOT all the same size...

Can anyone help by telling me what sizes I need? I understand that normally replacement 'O' rings come in standard sizes labelled #6, #8, #10 and #12 (are these the diameter in mm, I wonder?). I don't have an autoparts store down the street, so I have to order the O rings I need before I start - and for that, I need to know the sizes!

Thanks in advance...

br1anstorm

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br1anstorm

Chick on Mon September 08, 2008 10:32 PM User is offlineView users profile

You might be better off ordering an assortment, it's difficult to tell what size they are without seeing them.. They are cheap enough to order a few of each.. Hope this helps..


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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

retrofit on Tue September 09, 2008 1:00 AM User is offline

The numbers used to describe tubing, hose and o-rings in U.S. automotive A/C have nothing to do with the metric system, they are shorthand for English measurements in sixteenth inch increments. So the outside diameter of #6 tubing is 6/16" (3/8"), #8 is 8/16" (1/2"), #10 is 10/16" (5/8") and #12 is 12/16" (3/4").

There are variations in o-ring size for particular applications so you may see #6 standard, captured or G.M. special for example. Metric o-rings used on European made vehicles are not the same as those used on U.S. vehicles.

Here are some o-ring dimensions for the 1990 Mercedes 560SEC listed by a U.S. domestic auto parts supplier:

A/C O-Ring/O-Ring Kit;8 x 12 x 2mm, green ; Receiver / drier to expansion valve & to ; Cpe, 4 Per Veh; Years: 1990-1991;Qty Per Vehicle:4;

A/C O-Ring/O-Ring Kit;11 x 15 x 2mm, green ; For expansion valve 126 830 03 84 ; Cpe; Years: 1990-1990;Qty Per Vehicle:1;

A/C O-Ring/O-Ring Kit;15 x 23 x 2mm - Green ; For Expansion Valve# 126 830 03 84 ; Cpe; Years: 1986-1991;Qty Per Vehicle:1;

Since you only need a few o-rings it might be less expensive to get them at the dealer than to buy a whole assortment like the one shown here:



Edited: Tue September 09, 2008 at 10:04 PM by retrofit

Pete.L on Wed September 10, 2008 9:29 AM User is offline

Have a word with your nearest Merc dealer. I've always found them helpful, their knowledge of a/c stuff is poor, but they will fax or email sections from their epc so you can identify the seals needed. Prices are around £1.00 per seal and some dealers will post to you to save you having to collect. I know they are expensive seals, but in the overall scheme of things it's peanuts!

br1anstorm on Wed September 10, 2008 4:49 PM User is offline

Thanks to all for responses, and especially to retrofit - who has given me exactly what I think I need! Interesting that some of the sizes are odd numbers (11 and 15).

Pete L., your idea is logical, but I fear that the local MB dealer (in chilly Scotland!) won't carry any a/c parts, and the problem is then that while the O rings may cost a dollar or a pound each, the charges for special order will be a great deal more!

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br1anstorm

Edited: Wed September 10, 2008 at 4:55 PM by br1anstorm

tony1963 on Sun September 21, 2008 3:45 PM User is offline

My experience with MB vehicles is that the o-rings used are of a special size, not off-the-shelf sizes. I go to the dealer to get the proper o-rings.

You can try to use standard sizes, but you will be disappointed. Been there, done that.

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Grove Automotive Group, Inc.

An Alabama Corporation

TRB on Sun September 21, 2008 4:43 PM User is offlineView users profile

Quote
Originally posted by: tony1963
My experience with MB vehicles is that the o-rings used are of a special size, not off-the-shelf sizes. I go to the dealer to get the proper o-rings.

You can try to use standard sizes, but you will be disappointed. Been there, done that.

Standard or Metric is all I have ever needed! Nothing special about MB o-rings.



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Edited: Sun September 21, 2008 at 4:43 PM by TRB

tony1963 on Sun September 21, 2008 6:30 PM User is offline

On the older models, the o-ring between the compressor and line set has a unique tab to hold it in place.

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Grove Automotive Group, Inc.

An Alabama Corporation

Pete.L on Mon September 22, 2008 11:17 AM User is offline

I've never been charged for a "special order" for O rings from Merc.

Merc dealers carry almost no a/c stock, it's virtually all ordered in for specific jobs, so order one day and with them the next - I think pretty well all car dealerships are the same.

Give them a call and ask - even in chilly Scotland!

tony1963 on Mon September 22, 2008 11:37 AM User is offline

I do the same thing. I get the diagram and show the dealer each o-ring that I need. They order them, have them the next day, and mark them for me.

I would not recommend trying to make it work without, but to each their own.

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Grove Automotive Group, Inc.

An Alabama Corporation

TRB on Mon September 22, 2008 1:29 PM User is offlineView users profile

If you have the correct o-ring I see no need for a specific MB o-ring. Nothing odd about a A6, R4 or York O-ring.

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Contact: ACKits.com

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