Well, my first boost leak test revealed that a motor with what I am assuming is the original motor combination down to the nuts and bolts and a total of 190,000km's is now starting to show it's age; being 17 years old. I have found leaks at the BISS screw (O-Ring), the TB shaft seals (leaks behind the throttle return springs), and a few other little spots at vacuum hoses. So, rather than live with these little headaches while I am tracking down another problem, I decided to pull the whole TB assembly off the engine and get it freshened up.
A trip to NAPA revealed that ordering the TB shaft seals they list for the 1G 90 DSM at VFAQ.com (as submitted by Club DSM Canada members), will yield results in a few days coming out of Montreal, or Toronto at the farthest. I ordered the small/large seal combination oil seals as was appropriate for the 89 4g61t TB and the 90 4g63t DSM TB.
Part #'s that NAPA needs to look things up are as follows:
Large seal = CR 3930
(Chicago Rawhide) CR 10x14x3 (mm) HM4 R
Small seal = CR 3030
(Chicago Rawhide) CR 8x12x3 (mm) HM4 R
(Something to note is that the CR part could not be sourced readily at the time of order, so you will see the SKF box in its place
but with the same sizing information!! It doesn't really matter what company you get the seals from if they are indeed "oil seals" with the above dimensions.)
EDIT 05/17/2008 GBS (Global Bearing Supply in Canada) can get the small sized seals for under $5 CDN, over the counter. If you can't find the smaller sized seals or even the larger ones locally, try a local bearing supplier and use the Chicago Rawhide numbers, as they interchange with SKF and other oil seal brands. They should be able to order them based on that, if not have something in stock for you.
Remember these seals look just like camshaft and crank seals just without the metal (spring) ring inside to keep tension on the area that contacts the rotating shaft.
The only headache I found was the price - $10 per seal!!!!! Ouch, but better than hunting down numbers at the dealer only to find the same pricing or worse, just because Satan can.
So, this is what a dirty TB will look like after an exterior/interior clean (without going into the guts) and 5000 km's since that light cleaning.
Grab some tools on the list here and prepare to wrestle with some tight screws:
3/8" drive 10mm socket
1/4" drive 8mm socket
Long handled #2 Phillips screwdriver with a GOOD tip for proper contact
HD Degreaser spray bottle or equivalent (pictured below)
Alright, now you are ready to tackle removal of the various external parts that bolt on/screw into the TB casting. First we'll start by removing the TPS (throttle position sensor), but remember to mark/score the casting and the plastic to realign the two parts in exactly the same position. 2x 8mm bolts to remove the TPS sensor.
Next you can remove the nut holding the throttle cable guide in place. Be sure to mark the springs with white out or something that will stick to them while you are working to get them back in at the proper tension and locator spots.
Make note of where this little rubber spacer goes, I believe it goes in the white plastic housing pictured next ---->
An important step will be to file down the ridge on the butterly shaft, that the butterfly screws make when they get peened in place at the factory. This ridge will potentially scrape the internal walls of the TB casting. I lightly scored the walls on my TB so this will help save people some headaches. You can just see the circular ridges at the top of the butterfly shaft in the photo below.
Click Here to see the shaft cleaned of ridges/burrs from the peening process.
Now that you have the both ends of the Butterfly shaft cleared of sensors or otherwise appendage type pieces, you can proceed to remove the seals, spacers, and the Circlip ring. To remove the Circlip ring you will have to expose the ring by pushing from the other side of the shaft to more the Circlip past the housing flange that covers it. The Circlip is accessible after picture 5, at which point you would remove the rubber seal shown on the red glove, but also shown again on the shaft for orientation before it came off.
Order of removal: Black Seal -> Circlip -> Plastic Spacer
These are you new seals for reference, you can see how brittle the large seal got; even with gentle handling it crumbled in the one section. The old seals are not holding to the shaft the way they did originally = air leak in/out.
So, with cleaning of the TB casting comes removal of the port covers on the ISC air path. Pictured below is the air channels feeding the ISC circuit. The cover is shown in Picture 1, with the screws loosened to show orientation of the factory wiring setup. The following steps will show the process of dirty ports / clean ports.
Remove the port with 3 screws holding it in place. Notice the wiring layout as well.
Clean this port really well too.
If your casting is really clean everywhere but where the seals get put back into place, make sure to clean these areas (x2).
If you want to replace any seals/gaskets that close off the covers you have removed, you will have to source those from the dealers most likely or another vendor who supplies Mitsubishi parts over the internet, as the aftermarket most likely will not have these for sale. Correct me if I am wrong on that point of availability though, and I will make changes to this thread appropriately.
Seals like the FIAV, etc, available through the following dealers:
<- incredible rebuild work if you are too squeamish to attempt this yourself. Machining services available if required.
<- Great service and can find you almost anything for your Mitsu, but most importantly, your gaskets!
Time for reintallation of everthing you have removed:
Reinstall the ISC motor to it's home and torque the bolts/scews down.
Reinstall the 2 plates you removed to access the ISC air channels, 1 panel with 5 screws and the other with 3 screws. Take not of the wiring setup and where the holder tabs went under the screw heads
Reinstall the butterfly shaft in the correct orientation, and get the correct ordering of the seals/washers/circlips/seals all setup per your notes at the time of removal, as this is key for proper tension and sealing of the butterfly shaft.
Reinstall the Butterfly shaft, but be sure to lubricate it with some Dielectric grease or similar to help the shaft ride it's entire length into the casting, the whole while passing across the sealing surface of the large seal.
Reinstall the butterfly plate (circular brass plate) in the correct orientation, should be obvious as it will not fit the wrong way in.
Reinstall the two butterfly retainer screws with some loctite (your choice of Blue(light)/Red(strong)).
Reinstall the seals and washers etc, such that you can get the TPS sensor back in position and screwed down. **Your marking is now key for orientation of the sensor.**
Reinstall the throttle return spring assembly *double wound* with the rubber spacer I mentioned ealier, and that is also pictured in the same section.
Reinstall the Throttle Cable Plate and finger tighten the nut in place.
Before the butterfly nut has been tightened with a ratchet, you are ready to check for proper movement of the butterfly shaft. It should be smooth like butter and snap back with a reassuring CLEAN metal tapping sound. It should NOT bind in any way, or be too loose as this is indication of improperly installed parts or incorrect spacer placements, or improper installation of the return spring assembly.
***** Take extreme care when tightening the nut on the shaft with a socket/ratchet as it only gets a fraction of the threads to grip, unlike would a normal nut/bolt combination. You can strip this easily if forced too much, and I can attest to that fact!!!!*****
Double check you have a new O-ring on your BISS screw and find one of those BISS screw caps while you are at it, and you'll never look at this spot for trouble again.
Reinstall the TB assembly on the intake manifold along with the elbow joint, and enjoy the lack of hissing you were used to hearing on a boost leak test!