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Old 08-25-2003, 01:41 PM
Registered User
Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
A/C Repair Questions

Hi All,

Iím replacing the main A/C hose, receiver-drier and expansion valve on my 86 300E and I have a few questions that I hope some of you might be able to help me with.

I have the Service CD, but I canít find anywhere in the Climate Control section where it details replacing the hose assembly. Does anyone know where I can find it?

The system has already been evacuated of freon. When I remove the hose assembly and receiver-drier, should I drain and measure the amount of oil that drains out so the A/C shop can refill it with the same amount, or is there some other way of determining when thereís the proper amount of oil in the system?

On the main A/C hose there's a canister arrangement with a couple of threaded fittings (see circled area in pic below), apparently for cooling the gas before it reaches the fuel distributor. The hose fittings appear to be difficult to reach from either above or below.

Can anyone whoís done this job tell me the easiest way to get at them, requiring the least amount of additional disassembly.

When I refit the gas hoses do I need to bleed the air out of the lines? If so, is it done at these connections or further upstream? Whatís the best way to do this?

Iím also replacing the expansion valve (just because itís relatively cheap and available). Itís tucked in against the firewall on the other side of the brake booster.

Any tips on tools and techniques to disconnect and replace it? I believe the valve body is attached to the evaporator by a couple of screws, but it doesnít look like thereís room to fit any kind of screwdriver in there. Would a ľĒ drive ratchet handle with a screwdriver bit do the job? Does it need a flat-blade, phillips or allen bit?

When replacing the o-rings, do I need to use any type of sealant or lubricant? What type, and where can I obtain it?

Any other tips, info or advice would be welcome.

Thanks in advance,

Attached Thumbnails
A/C Repair Questions-ac-hose-circled.jpg  

Last edited by Phalcon51; 08-25-2003 at 01:52 PM.
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Old 08-25-2003, 03:40 PM
Registered User
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,512
Can't comment on the manifold assembly, as my diesel is mercifully lacking this added bit of complexity.

The expansion valve looks a bit daunting on the 124, but is actually pretty easy. On the diesel there is a heater hose exiting the firewall a bit above and in front of the expansion valve. Detaching this an moving it aside greatly eases access. You may also have some vacuum lines which are in the way.

The hoses are held to the expansion valve via a single 8mm nut. Use a plain old wrench to break it loose and back it off. Because you *really* don't want to be dropping that nut, I recommend loosening it the final few turns with the fingers of one hand while holding a magnetic pickup tool on it. I have a pen shaped magnet which is great for such tasks.

Move the hoses out of the way. This may required loosening some clamps on the forward firewall, under the alarm horn.

The expansion valve is held to the evaporator via two 3mm allen head screws. Use a small allen key to break them loose and back them out. The magnet tool is again handy for removing them.

At the very least give the new o-rings a generous coating of refrigerant oil. I prefer nylog, a specialty o-ring lubricant/sealant for a/c systems. It can be purchased from

Good luck,

- JimY
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Old 08-25-2003, 07:01 PM
Registered User
Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490

Thanks for the info on changing the expansion valve and the tip on Nylog. I've never heard of this, but it sounds like a good product.

Does anyone know where I can buy Nylog sealant over the counter in the L.A./San Gabriel Valley area? I'd prefer not to pay shipping for just one bottle of stuff.

I know that the R12 system needs a mineral oil, but Is there a recommended brand that should be used in this car? If so, I'd prefer to buy it and supply it to the shop that's going to recharge the system than just rely on what they might have sitting around.

Anyone able to address some of my other questions?
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