Hey guys, I recently purchased a beautiful 1985 300SD. I bought the car and Ohio so I did a very thorough inspection checking for any rust or corrosion. The car has been garage kept its whole life and is absolutely immaculate with only a 140,000 miles. I didn't noticed a little corrosion around some of the fittings under the hood and bolt heads in various places but the body and frame and entire car checked out and was in great condition.

The AC of courses didn't work so, which I knew before purchasing. Immediately after getting the car I took it over to my trusted mechanics shop to have the AC compressor, drier, and manifold hoses replaced. Norrmally I wouldn't replace the manifold hoses but the fittings and mounting bracket show some ugly corrosion so I decided I wanted to go ahead and replace it.

Well the mechanics called me today and said the AC system is all tested and in full 100% working condition. I put the system under vacuum over the weekend and it held the vacuum all weekend long so we're all good there.

However they were not able to replace the manifold hoses because the fittings were corroded in place. Despite soaking the fittings with penetrating oil they were unable to disconnect the hose from the firewall or the condenser.

So we just decided to keep the existing manifold hoses who knows maybe they could last another 20 years the system holds vacuum great and the AC works now.

They said they could cut the lines but then the condenser and the expansion valve under the dash would need to be replaced and this would be expensive. So we left the original AC manifold hoses is in place.

Anybody have any ideas for how to remove these siezed manifold lines?

I don't have any suggestions on getting those off, however:
The expansion valve is probably not expensive. I just replaced that in my w123 300td and it was about $20. Though if you're using R12 you may not find one at any price. The ones in production are all for R134a.



I replaced the condenser too; it was about $60, and it's a better condenser than the stock one because it's parallel flow.

Just because it held vacuum all weekend long doesn't mean you're "all good".
You don't leak check an ac system with vacuum. Have a competent and experienced shop pressure test with nitrogen and if they don't have equipment to do this, go to an ac specialist who does. Non-609 certified guys shouldn't be messing with their air conditioning.

Take it to a better mechanic. Preferably a classic mercedes specialist. Someone who knows how to remove difficult hoses/connections and doesn't need their customer (you) to post on a public forum and do their job for them. You're paying your mechanic and he should figure out this for you(not the other way around).

As someone with years of experience running a shop full time and encountering all sorts of difficult to remove nuts/bolts at awkward/odd angles with all sorts of obstacles in the way, I can always find a way to do it.

BTW, There is one manifold in this ac system and that is directly behind the r4 compressor, which always leaks. Under the evaporator, is the expansion valve. That is not a "manifold".

50/50 mix of ATF and acetone is an excellent penetrant.
Apply your choice of penetrant daily over a few days.

Apply the flare wrench to the flare nut fitting.
Apply the open end (counterhold) wrench to the fitting with the schrader valve.
Angle the open end wrench a bit diagonally so there is a greater area of contact between the jaws of the wrench and the flats of the schrader valve fitting.
Offset the handles of the wrenches by 20 degrees or so.
Lightly tap the jaws of the wrenches (on the fitting) with a small hammer.
Gently try to tighten (yes tighten) the fitting by squeezing the wrench handles together (turning the flare nut clockwise...just a tiny bit)

Then crack the torque, reposition the wrench handles about 20 degrees apart to loosen the union by squeezing the handles together (turning the flare nut counter clockwise...just a tiny bit).

Applying a little heat from a hand-held hair dryer may also help, if the union is being really stubborn in releasing the clamping torque.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I did not read all of the posts so this could be a repeat.

Since such fittings don't seal on the threads they can take a dremel tool and use the little cutoff wheels and cut through the length of the Nut on each side stick a screwdriver in the groove and twist and the Nut should split into 2 pieces. Of course you would need a new Hose with fittings.

Or they could drill one or more holes into the middle of one of the flats on the Hose Nut down to the threads and use that as a place to squirt in Penetrating Oil and use some heat with a propane torch to wick the Oil into the threads.
If done carefully it allows you to reuse the hose.

Attached pic of a real Dermal tool with a cut off wheel on it. I have some generic versions one from Harbor Freight.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

I have never seen the parts you are speaking of but am wondering if it is going to be a issue like on the Oil Cooler hose connection where the aluminum nipple corrodes to the steel hose nut. Then as happened on mine when I turned it a piece of the oxidized aluminum thread was stuck in the threads of the steel nut and when I turned the hose nut it acted like a cutter and cut up 2 and 1/2 threads on then end of the aluminum oil cooler nipple.

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84 300D, 82 Volvo 244Gl Diesel