These instructions are for a renewal of the hydraulic fluid for the convertible soft top system on your OG 9-3, involving several extraction and refill sequences.

Work completed for your reference here was done on my 2001 9-3 Viggen convertible. The car is (was) nearly 20 years old and has clocked 110,000 miles. I have some service records from the previous owner which details some microswitch work done on the top by a reputable Indy shop in 2018, but no record of any sort of hydraulic work being done on the top. The top works just fine, even if there is some visible weeping from the driver’s side cylinders. I reckon that a fluid renewal will help me keep her in good operating order.


Tools needed:

  • drain pan or other means of spill protection
  • small funnel (optional)
  • fluid extraction/transfer pump
  • 13mm socket
  • ratchet driver
  • phillips-head screwdriver
  • trim removal tool or screwdriver
  • knee pads (optional)
  • flashlight/torch


Parts/supplies needed:

  • 1 liter fluid
  • rags, empty plastic bottles (for used fluid)

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Difficulty rating (scale of 1 to 5): 1 – Easy

You’ll be working on your knees in the back seat area, and manipulating a button to raise/lower the soft top several times. This is about as easy as it gets.


Time Estimate: 1-3 hours, depending on your mechanical skills and the number of times you wish to repeat the extract & fill sequence.


References:

There is a very helpful video from 2019 on YouTube that demonstrates the process and concepts involved here. A must watch! Also, you may wish to refer to the WIS information on the convertible top for your specific year/model at www.saabwisonline.com, which outlines a procedure to check and then “top up” the fluid. We’re gonna do something abit more involved, and I’ll be aiming to add to the WIS information rather than repeating most of it.


Type of hydraulic fluid and interval:


Saab used a synthetic ‘central hydraulic fluid’ (aka CHF) as factory fill for the OG 9-3 convertible system, different from the fluid used in the classic 900 verts. The current part number for this fluid is 93160548, and is described in the GM fluid catalogues in Europe as CHF 202. SAAB did not specify a change interval (ie they considered it a lifetime fluid).

SAAB 93160548 – SAAB/GM/Opel/Vauxhall “Transmission Oil power steering”, made in the EU. Curiosity got the better of me, but even after some significant research I was unable to determine who manufactured this fluid, or if it is still being manufactured/packaged under some GM branding (given GM’s departure from Europe I doubt it).
$15.39/liter bottle at eSAABPARTS.com, plus shipping

Fuchs Titan ZH-3044, ultra high performance central hydraulic fluid, made in Germany. Note that Fuchs now owns Pentosin and is combining CHF products under the Titan brand name.
$12.95/liter bottle at eSAABPARTS.com, plus shipping

Pentosin CHF 202 – long-life hydraulic fluid, synthetic, made in Germany
$13.44/liter bottle at fcpeuro.com, plus shipping.

Now, as is life with topics such as oils, plenty of folks suggest just using the CHF11S fluid spec'd for the power steering system in the soft top system as well. Both fluids are synthetic, though I’ve seen reference to CHF202 being “partially synthetic”, whatever that means. Both fluids are also compatible from a mixing standpoint with each other and comparing Pentosin’s specifications for each doesn’t reveal much difference (at least to a layman such as myself). There are also more than a few multi-specification PSF products which meet the SAAB 93160548 specification like Prestone Euro (AS268Y), Lubeguard Complete (23232) and Amsoil Multi-vehicle (PSFCN). Don’t think you can go too wrong here – any quality CHF you put in will undoubtedly be better than the old stuff that’s in there.
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The OG 9-3 soft top hydraulic system capacity is 550ml in total, and roughly half of that is held in the reservoir at the Max line (with top in open/lowered position).


Procedure

Vehicle placement. Ideally you’ve got a level area that also will allow you to safely open and close the soft top. I did my work in the garage - shade means cool(er) – but the overhead door and lighting meant I had to pull the car out of the garage several times to operate the soft top.
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Checking fluid level. You can eye the soft top’s hydraulic fluid level from the trunk. Lower/fold/open the soft top, folding it into the storage bag. Remove the four (4) bristle-type plastic pushpins holding in the trunk floor carpeting.
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This exposes two round holes – the lower right one for shining a flashlight into the torsion box and the left upper hole to view the soft top system’s milk-white translucent fluid reservoir. Now, I had a heck of a time as I couldn’t really see where the fluid sat. Turns out the fluid level was pretty low, too low for me to see it in the view hole.
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Accessing the hydraulic unit. The hydraulic unit contains the pump and valve blocks and lives in the “torsion box” below the trunk pass-through area behind the rear seat. The pump block includes consists of DC electric motor and integrated fluid reservoir (the target of our little operation here).

To access, first remove the rear bottom seat cushion and then fold forward the rear seat backrest (removing the bottom seat cushion will allow the backrest to fold down flat). Next, remove the plastic cover in the trunk pass-through using the screwdriver and trim tool to remove the six (6) expanding rivet clips and the circular cap/plug over the manual operating valve.
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Fold the flap of carpet covering the hydraulic unit back into the trunk area.
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The mounting plate for the hydraulic unit is now fully exposed, secured in place by nine (9) 13mm bolts, and two tongues protruding from the rear edge of the mounting plate. These tongues sit in slots on the rear/trunk side of the torsion box. The bolts should be easily removable even with a ¼” drive ratchet.
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The hydraulic unit can now be lifted from the front edge of the mounting plate and rotated a full 90 degrees up and back towards the trunk area, pivoting on the tongues/slots on the rear edge. The front edge of the mounting plate will end up tucked firmly underneath the soft top storage bag.
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Tip#1 – With the soft top open/lowered into the storage bag, its much more difficult to rotate the hydraulic unit back and fit it underneath the “full” storage bag. However, with some careful pushing of the storage bag up while rotating the hydraulic unit back, you’ll get the unit on its side and thus the reservoir plug in the top/vertical position with the benefit of having the most fluid available for extraction. On the other hand, it is much easier to position the hydraulic unit under the empty storage bag if the top is closed/up, but there will be less fluid in the reservoir to extract as more of it is in the lines/cylinders. Your choice though.

With the hydraulic unit rotated up from the torsion box location, you can much more easily assess the fluid level in your system. From the picture you can see just how low the fluid in my system was, and it was still operating fine.
Remove the 13mm brass plug from the unit’s reservoir. Note the o-ring on the plug.
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Extracting waste fluid. Insert the suction end of the hand pump ($12 or less at your friendly local auto parts store) into the reservoir hole and pump the old ‘waste’ fluid into a suitable container. Here I’m using Performance Tool W1139 transfer pump, purchased at O’reilly Auto Parts and my review posted here, along with a 20floz/591ml sports drink bottle with a hole drilled into the cap to insert the pump outlet tubing (small air hole also drilled into cap). Pump/extract as much fluid as possible from the reservoir.
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Tip#2 – Get yourself something to catch any drips/spills that might occur, as you don't want this stuff on the carpet or seatback. I'm using a disposable aluminum pan taped to the edge of the torsion box, along with a shoprag placed in the torsion box underneath the reservoir. Also, turn the hand pump upside down and continue pumping into your used fluid container to fully empty the pump.

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My fluid level was quite low, so first drain was only ~100ml of fluid

Filling new fluid. Insert the suction end of the hand pump into your bottle of new CHF and place the outlet tube into the reservoir. Pump new fluid into the reservoir – I chose to pump new fluid up to the Max line. Alternately you could use a small funnel and pour in the new fluid.
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First fill took ~290ml of fluid out of my 1 liter bottle.

Finally, reinsert the brass plug and tighten. Remember its PLASTIC, and there’s an o-ring to boot, so not much more than finger tight here.


Cycling the system. First we’ll rotate the hydraulic unit forward until it rests down in the torsion box (no need to bolt it down).

Tip#3 - Be careful not to tear a hole in the soft top storage bag while you’re doing this little maneuver, as the leading edge of the cover plate is sharp (enough). Ask me how I know.

Now turn the ignition to ON (or start the car if you’d like), then raise and lower the soft top several times. Our aim here is to “mix” the new fluid in the reservoir with the old fluid contained in the lines and cylinders. I completed three (3) successive raise/lower cycles of the soft top in this first sequence.

As a discussion point, the degree of fluid mixing between the cylinders and reservoir could be rather small. This is the theory in a closed hydraulic system anyway, as the fluid is not really “flowing” or circulating in the same manner as does say engine coolant or even the fluid in your power steering system. In order to really get the old fluid out of the cylinders and lines we’d have to disconnect and drain them, similar to how you would flush/bleed your brake system. Of course, your brake system has these very helpful things called bleeder valves that are readily accessible on the calipers, thereby making a brake fluid flush pretty easy. In contrast, your soft top system doesn’t, and it’d be a PITA. So no, a complete soft top system flush is not in the scope of this exercise, at least for me.


Repeat extract/fill/cycle steps. Repeat this 3-step sequence as many times as you feel it’s productive. I did four (4) of these extract/fill/cycle sequences in the course of a few hours one afternoon, and a single 1 liter bottle of fluid was enough for this.

Step
First
Second
Third
Final
Extract 100ml 225ml 230ml 220ml
Fill 290ml 210ml 200ml 185ml
Cycle (up/down)
3X
3x
4x
Ongoing…

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1st and 2nd drains 3rd 4th and New fluid

The first two sequences were productive I’d say, the last two didn’t seem to show very much difference between what I filled and what I subsequently extracted. My take, two sequences is likely enough.


Button it back up. Once you’re satisfied with your extract/fill/cycle sequences then here’s a quick checklist:

  • Final fill to the desired level in the reservoir
  • Reinstall brass plug, tighten lightly and carefully. My o-ring was fine, and if you didn’t find any leaks in the torsion box yours is likely fine too.
  • Place the hydraulic unit back down into its home in the torsion box. Reinstall the 9 bolts holding it in place. Hand tighten.
  • Put carpeting back in place over the mounting plate, and reinstall the plastic cover into the trunk pass-through with the six (6) expanding rivets.

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  • Fold up the rear seat backrest and lock into place. Reinstall the rear seat cushion.
  • Reinstall the trunk floor carpeting, securing with the four (4) bristle-type push pins. A poly-head hammer will assist in seating these pins.


I think I’ll look to do a single extract and fill sequence once a year, or maybe every other year, as a means of giving new and old fluid an opportunity to mix abit more. Assuming my hydraulic cylinders and lines don’t fail, knock on wood.

Don’t forget to properly dispose of your oil fluid. Its oil, so your local auto parts store should take it.