Stripped Expansion Valve Nut - Cannot get valve out 300D - PeachParts Mercedes-Benz Forum

rhodes2010 · #1 04-30-2006, 12:05 AM

1980 300D. Under the passenger foot well and removing the expansion valve.
Bottom two nuts are steel, no problem.
Top two are brass, left side no problem, right side is now round.

So, expansion valve is still in car (original one), brass nut is now rOund.

Since I have to replace the nut I will need to drop the part up in the
dash area.

That is the question - what am I supposed to do to get out the part of the AC
that is in the dash ? I have replaced heater cores before, I imagine it
is something like that.

If you are wondering how I did this stupid thing:
Used a thread release like PB blaster on the fitting threads.
Used a line wrench of appropriate size (19mm).
Rounded the corners first.
Then used a vise grip. This brought the soft brass to round.
Before going to vise grip I tried several wrench sizes to find one with a oh-so-snug fit. I have everything but wentworth sizes.

I could cut away expansion valve, but the nut needs replacing now.
So, out with the AC core .

Can anyone give me some directions ?
Thanks everyone.

rhodes2010 · #2 04-30-2006, 12:31 AM

All right - I did just check the manual for removal of the AC Evaporator.

If anyone has done this - any shortcuts ?

Complete dash removal - not looking forward to.

dannym · #3 04-30-2006, 10:26 AM

I hate to be the one to tell you but I and lots of people here have warned many, many times that flare wrenches are a must for this job.

You can't cut those lines. Look at the lower lines that you removed. You'll see the end is flared with channels for the o-rings. How are you going to duplicate that after you cut it?

At this point you can either replace the evaporator or find a way to remove those fittings. Channel locks, vice grips. Use them backwards if you have to. Maybe a small belt wrench?
Keep trying. You'll get it. With the left side off you should be able to get it to move away far enough to get a wrench in there.

Danny

tangofox007 · #4 04-30-2006, 11:08 AM

Quote:

Originally Posted by dannym

I hate to be the one to tell you but I and lots of people here have warned many, many times that flare wrenches are a must for this job.

A line wrench and a flare nut wrench are one in the same.

rhodes2010 · #5 04-30-2006, 11:46 AM

Thanks tango.

Tried to cut away the expansion valve only. Thinking that the flare nut would stay intact. Did not work.

My donor car has half the dash out anyway, and a pristine heater/AC core box.
No dust and a car that was apparently garaged a lot.
(my car has spent at most 2 years of its 26 in a garage).

When trying to release this soft brass nut (why steel on the bottom only ?)
you just keep thinking, no problem, it will pop loose. All the other three came
loose with ease, my expectation was the same for this one. Had no reason
to believe that it would not.

So today I begin removing the AC evaporator from donor.

dmorrison · #6 04-30-2006, 02:16 PM

Yes flare nut wrenches are desired but I'm not to sure they will fit near the expansion valve connections. I used standard SEA wrenches on all my Ac work.

SOOOOO. You will have to remove the evaporator box and replace the evaporator. This requires removing the center cosole and dash area to remove the evaporator box.

By the way ALL fittings on the W123 AC system are SAE, not metric. So get a set a large SAE wrenches for the job.

Dave

rhodes2010 · #7 04-30-2006, 03:04 PM

The good news is I own flare nut wrenches in both SAE and Metric.
My tool kit is fairly extensive - close to 30 years of collecting standard and specialty tools.
Interestingly the MB manual calls for SAE sizes on those fittings.

Got the donor evaporator out in about 2 hours.
The thing about non-reassmbly work is it goes faster. You might call it destructive disassembly, no damage, just not destined to be reassembled.

Back to evil expansion valve. I am sort of going down two paths, one
trying to repair the bad connection, the other path is prepping for a complete
AC Evap replacement.

So this morning I tried propane heat to expand the valve and get the nut loose.
No work. So get ready to CRINGE!! I had made up my mind that the last resort
would be a clean cut on the copper line. I did and its out.
So I put the expansion valve in the vise, put a pipe wrench on the nut.
It took a tremendous amount of force to release the nut, seriously.
I use a torque wrench often, and suppose if I had to guess, that nut took 200 lbs or more
to get loose (probably more - but no one would believe me).

So, to all those that want to believe I just didn't have to destroy this,
I disagree.

I had some discussions with a few folks about how this could have happened,
and maybe what should have been done.
Due to lack of decent facilities I replaced a AC compressor some 16 years ago
and probably left moisture in the system. But the car also sat for 10 years
with the lines unpressurized and possibly contaminated. (This car was just revived in December 2005).
The thought is that some reaction took place between the expansion valve and brass nut. I also wonder if the first owner's mechanic might have cross threaded it (but that is a far stretch - too hard to believe).

I would crack the nuts on the expansion valve if ever my system gets discharged and is going to sit for a while. The nuts on the donor car were
tremendously easy to loosen, just the way these should have been.

So I might just try and solder in a union/splice on the copper with a new flare nut, and see if it holds vacuum, then pressure test with air, just to see if it can be done.
Then I'll go on to replace the AC Evap, and the heater core since I am in there. Car has close to 300K and 26 years, should buy some piece of mind for the next 20 years of service.

And the removed expansion valve ? - clean inside, perfectly clean.