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Removal and Replacement of Expansion Valve
1989 560 SEL (W126)
Considered a dreaded
project by some, removing and replacing the expansion valve (located a few
inches above the gas pedal) is not as bad as it seems. It took me about 5 hours,
much of the time spent simply trying to figure out how to remove three components
(steps 9, 10 and 11). Had I had this documentation here, I would
probably have done it in much less time. Had I not had the kind help and support
of my dear friend Chuck Taylor of Falls Church, Virginia, I would have taken
I recommend reading over
the entire procedure before tackling the job.
The following instructions
assume an empty system (no refrigerant in the system) and do not include the
refilling of the system.
The following tools are
this model, a 19mm and a 22mm crowfoot wrench (more on that later)
the normal stuff, in particular a 17mm open end box wrench
metric socket set with extensions (as usual on these cars, 13mm and 10mm are
instrument cluster pullers (about $14 at a Mercedes Benz dealerships as of
May 2004) (More on those later)
The following parts and
accessories are needed:
air conditioning oil (more on that later)
(not covered here)
ties (large ones needed)
tape (more on that later)
Notes before getting
The two important aspects
of getting this job done involves the loosening and partial removal of a support
bar, with one of the bolts holding it in place being behind the instrument
cluster, and getting the new expansion valve in place correctly.
One technician at a Benz
service center told me that the vital challenge in doing this job right involves
the correct setting of the threads when installing the new valve. He mentioned
that too many of these Benzes have the job done cheaply at a corner shop, only
to have the car come into his hands because some mechanic cross-threaded the
hose and pipe connections. He then echoed what another technician told me: when
installing the new valve, tighten the four connections by hand first. Keep
everything loose (halfway down the threads at the most) until you have all four
connections in correctly, then tighten all four all the way down the
threads by hand, and then apply the wrench.
About the crowfoot
I have been given different
specs on different wrenches needed, going all the way to 24mm. On this model
year, I now know for certain that you only need two crowfoot wrenches, 19mm and
22mm. However, the shape and thickness of the wrenches matter. I bought an
entire impact set for about $36 on the web, only to find out that they were too
fat to fit, and had a nasty shape problem that kept them from sliding onto the
I found that the Sears
Craftsman 19mm worked nicely. I did not get a chance to try a Sears Craftsman
22mm (don’t even know if they make one), but found Snap-On’s 22mm to work
perfectly. Both of these had simple “U” shaped
(open end box wrench) openings.
About the A/C oil:
I am assuming you know
about A/C systems, their oils, etc. Never ever mix and match r12 oils with 134a
oils, unless you know exactly what you are doing. Use the same oil type that is
in your system. For this part of the job, you will be oiling the o-rings only.
You will need more oil to add to the Receiver-Drier before refilling the system
(not covered here).
I found a drain hose in
need of repair (Figure 5 “D”). I did not have the part handy, so I followed
Tom Ridge’s advice of solving the problem temporarily with duct tape. Since I
would not be surprised if this part had deteriorated on other models of the same
vintage, I would apply the old motto “be prepared”. I have ordered a
Benz Instrument Cluster
You can make your own with
thin steel rods. I have experimented with several materials, including coat
hangars. Short of getting the actual tools, by far the best material I found are
the control rods for model airplanes, found in hobby stores. They are thin yet
Below is a picture of what
the Benz cluster pullers actually look like:
Total length without
handles is 6.5”. Hook length is ¼ inch measured from the outside of the rod,
slightly bent upwards at an angle. The dimensions of the hook are important. The
depth marker is at 3 13/16” from the top (or roughly 2 ½ “ from the
bottom), right by the tip of the pen. You can create you own mark using magic
marker on your homemade tool.
you have a telescopic steering column, move it all the way out.
the battery (keeps all the lights off, and is a good practice anyhow).
all driver’s side floor matting (admitted, I did this later, but doing it
now is a great idea. Read on and you’ll know why! Also, some of the
pictures were taken out of the sequence I am describing here.)
the lower dash: The lower dash comes in two parts – the soft vinyl part
closer to the driver and the hard plastic part over the feet. Removal is
out the gray plastic Philips slotted retainers (Figure 2 “A”)
out the Phillips-headed metal screw (Figure 2 “B”)
the plastic strip moldings over the coin basins on both sides of the
steering wheel by gently prying them away with a small
screwdriver. They pop right off.
the screws underneath the moldings you just removed (Figure 3 “A”). Do
the same above the ignition key.
upper part of the lower dash may fight you a bit – not to worry, it’s
stapled to the hard plastic bottom part, though not tightly. I found the
best thing is simply to remove the staples (example in Figure 2 “C”)
for good – the grey plastic retainers hold both the upper and the lower
portion in place.
upper part of the lower dash should come right off.
lower portion is held in place only by a metal “T” sliding along a
long slot. I had to bend the “T” a bit to aid in removal….
will now be able to see the expansion valve, with the insulated cover, as
shown in Figure 4. Chances are it’s been leaking refrigerant, oil, and
dye. The lower plastic portion of the lower dash you have removed probably
has some drippings, and since you thankfully have removed the floor mats as
described in (1) above, the drippings are now going on the floorboards
rather than the carpet! Note that by now you have probably worked for only
about 15 minutes.
a breath, look at the project. You will notice that there is a big duct
(Figure 4 “A”) in the way – it needs to go (more on that later). You
will notice that there is a plastic duct (Figure 4 “C”) behind the big
round metal duct – it needs to go. You will also notice a black steel bar
(Fig 4. “B”) conveniently placed right by the expansion valve –
you’ll have to loosen it and move it out of the way (you can’t remove it
completely because there are too many cables wrapped around it at another location –
more on that later). The expansion valve cover is probably soaked with oil
- a perfectionist would replace it (I did not).
the center console side panel. There is a Phillips-headed screw (Figure 2
“D”) that needs to be pulled. The panel is very flexible and can be
carefully removed after moving the driver’s seat back all the way.
CAREFUL: There are several plastic tabs that go into the molding of the
center console – don’t break anything!
ductwork “A” in Figure 5 by removing screw “B” and sliding duct
“C” out of the way.
the instrument cluster:
a good idea to use Scotch tape to cover the wooden portion of the
dashboard. There are sharp corners on some of the connections on the back
of the cluster that can scratch the woodwork.
the MB tools into the cluster on points “A” and “B” up to the
markings on the tools.
the tools to grip. (Figure 6)
out the cluster (Figure 7). This will take some force and wiggling.
DANGER: Do not damage the instrument cluster housing. It’s soft, and
I’ve had a home-made tool bury into it (fortunately in a spot that
can’t be seen with the cluster in place). You don’t want to add vinyl
repair to the project…
the positions of all the connections carefully – they are quite logical,
but the better you understand them, the easier it will be to put them back
connections may need the help of a small flathead screwdriver to create the
first break away from the pins. Remove all connections and remove cluster.
plastic duct (Figure 4 “C”). It simply pulls out and is not retained by
anything hard. Some twists and turns and it will be right in your hand.
round duct. It is held in place by two nuts (Figure 8 “A”) and by a bolt
on a bracket off the steering column accessed from below (hard to see
at first, but approximate location behind and above duct in Figure 9 “A”,
and easy to get to once spotted)..
Also remove the grey Phillips headed fastener on the right of the duct holding
in place the plastic duct manifold (Figure 10)..
After closely examining the steering column mount of this duct you will find that it comes off the bracket by pushing it towards the driver’s side, thereby clearing the tab. You may need a screwdriver to pry the mount away from the column to clear the tab..
– now you have a better view! Time to loosen the black crash bar:
the bolt behind the instrument cluster (Figure 11 “A”)
the bolt under the steering column (Figure 12 “A”)
the fasteners by the center console. Figure 13 shows some of the locations
(Figure 13 “A”) with the nuts already removed.
position and remove the twist ties (Figure 13 “B”) and the other items
(Figure 13 “C” are some that just pull right out) that may be impeding
the movement of the bar.
foam covering the valve is split and can be easily lifted. (If you tear it
off (as I did) you can tie it back on later with a cable tie). Look at
figure 14 (valve removed) and check the size of the wrenches needed.
can now remove the fittings. Don’t be too violent – they come off easily
(no high torques), and you don’t want to damage the top pipes that go
straight into the evaporator! After removing the last connection, the unit
should fall right into your hand. Tips on removing (as shown in Figure 14
left – 22mm Crowfoot
right – 19mm Crowfoot
left – 22mm Crowfoot
right – regular 17mm open ended box wrench
the old black o-rings and clean the fittings. Oil the new o-rings with the
A/C oil you bought and place them over the fittings.
If you are NOT replacing the receiver/drier, you need to add the right
amount of oil into one of the hoses before connecting!
- Remember the two top connections (22mm and 19mm) are rigid, and the bottom ones loose hoses. Screw in the top connections about half way (no more and no less – you want the part to wiggle, yet you want to make sure you are not cross threading) into the new valve.
the bottom hoses. This is the tricky part, and you may have to loosen the
upper connections further again to get the valve into the correct angle.
all connections all the way down by hand. This guarantees you are not
cross threading before applying the wrenches, and will actually save you
time in the awkward spots. Apply the wrenches. Remember that these were
not too tight connections when you loosened them.
insulation. In my case, I used a long cable tie to go around the back
insulation and back to the front to hold the front pad in place.
close up the job, reverse steps 1 – 11.
receiver/dryer, with correct amount of oil.
and fill the system.
Note: Oil quantities on
this model called for a total of 40 ml, with refilling system requiring 10 ml and replacing the
receiver/dehydrator 30 ml
© 2004 FunnyYouAsked.com
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