Hey kids, Well, I think I done goofed. I was changing the timing belt on my 1993 Mitsubishi Minicab Van with the 12 valve 3G83. I followed the Danko engine manual to a T for reinstallation. With the belt on, I thought I would just run the engine just for a second to see if it all looked fine. Well, my torque wrench must need calibrated because the tensioner moved and the belt skipped a few teeth. I shut it down the second I saw the tensioner move. So I redid everything and lined all the marks back up per the manual. Now it is all back together and it just does not seem right. It idles fine and does not seem like it misses or anything. Thinking maybe I hit a valve? So I did a compression check and I get 165-170psi on all 3 cylinders. Tested each cylinder 3 times and got the exact same results each time. Maybe I averted disaster and did not hit the valves. I checked all the alignment marks like 20 times and they seem spot on. What else should I be looking for?
With such good and consistent compression numbers like that, do you think the valves avoided damage? I picked up an endoscope and am going to get a close look at the valves. If the valves are all seated properly, I am going to check the timing marks again. I had heard from someone that sometimes timing belts can be a little off and that my ignition timing may be a little off. This is the first I am hearing of such a thing. Is it possible?
With the numbers you are getting, I seriously doubt that you had any damage to the valve train. Contacted between the piston and valves is generally catastrophic. So I doubt you have any damage. I guess the timing belt could have minor errors in manufacture. But the odds are very low, and any errors would be quite minor. If the cogs on the belt don’t match the slots in the wheels pretty closely, it will just chew them up in short order. If you have a compressor I would recommend buying a bleed down tester. It will tell you if the valves are seating, and endoscope will not. If you go with the endoscope you would look for damage to the piston, because it will be much more visible.
Leak down is my next test. With the endoscope, I saw no evidence of contact on the pistons. They had no marks or divots and the slight carbon coating from combustion was undisturbed. Everything looked pristine inside. I suppose I could be off a tooth. When I drove it, there did not seem to be a loss in power. It just seems to grumble and vibrate more. Maybe I am off a tooth on the balance shaft? Either way, it is all coming back apart. I will report back with what I find.
I did a leak down test and I got under 20% leakage across all three cylinders. Looks like the valves are ok. Now to pull the timing cover and recheck. Maybe I am off a tooth or something. But it seems I have avoided introducing the valves to the piston.
I got it all back together and it seems to be running just like it used to. I may have been off a tooth on the balance shaft. The raised dots on the case we hard to see the first time around. So this time, I cleaned them up and hit them with my fluorescent paint marker. I think I got really lucky and did not trash anything internally. May run out and buy a lotto ticket or invest some money into a start up. I do have a question about the timing belt tension. The James Danko service manual states to use a screwdriver to apply pressure to the tensioner when doing the initial tightening. Doing it that way seems too tight and it caused the belt to whine very loudly and there was no whine before. Even if I used very slight pressure on the tensioner, the timing belt still whined. What I did instead was I installed the tensioner spring and then got the nut as tight as I could with my fingers. Next, I pushed the tensioner down with my thumb to be sure it was not binding on it's mounting stud. I rotated the engine by hand around several times to ensure all the timing marks were still lining up correctly. Once all the marks returned to their proper alignment, I torqued the tensioner to spec. The belt had about 3/8" of deflection from the cam cog to the balance shaft cog. There is no whine now and there seems to be little deflection from the belt when running. Is my procedure ok? Or, if done the other way, will the whine go away with time?
Wes, Please go to your Signature in your Profile and tell us what you have! Your procedure seems to be correct to me, unless I'm missing something! As long as your sure your, belt is back in the proper teeth,(grooves)! I was kinda surprised when you said your torque wrench might be off, because when your tightening your bolts, pay attention to the feel factor, and tighten it by your own feel knowledge and then use the torque wrench to test it out! An old timer taught me that trick yrs ago, and it really works! I know it sounds crazy, but when your really gettin in to it you really to acquire a feel for things! Limestone
Awesome! I actually read that was the procedure on the Subaru Sambar. Belt teeth are in the proper grooves, timing marks all line up correctly, and it seems to be running nice and smooth now. I also found out it was less my torque wrench and more my math. I had to convert KGF/m to ft.lbs. Then my ft.lbs torque wrench did not go low enough and I had to switch to my in.lbs torque wrench and convert ft.lbs to in.lbs. Forgot to carry the 2 lol...
Wes, Glad that's all it was! Hey half the time this is what happens as were trying to figure this stuff out! We've all been there, and will be there again, I can guarantee that! LOL! Limestone
I thought I would add to this in case anyone else in need stumbles upon this thread. While I did purchase the Mitsubishi 3G83 Engine Manual Translation made by James Danko, I found the translation a bit vague in some areas and the images are not the greatest quality. One major component that was missing in the timing belt section was how to properly tension the timing belt. Now, I have changed a few timing belts in my time, but this was the first that did not have an automatic tensioner. So I needed proper specs for tension in this case. The Danko manual simply states to "Use a flat screw driver to pry on the tensioner while tightening the tensioner nut." That is it. There is no other information to check or test for proper tension. Doing it this way made the belt far too tight and cause a very loud whine. I then found a thread related to the Sambar that talked about how to properly tension the timing belt. That is detailed in a response above. Then I discovered that the 3G83 was also used in a utility cart that was sold in the U.S. The Toro Workman. The manual for it is readily available online for free here: https://www.manualslib.com/products/Toro-Workman-3000-Series-10745917.html The timing belt procedure starts on page 3-48. It has much higher quality diagrams as well as a much more detailed description of the timing belt installation procedure. Albeit, it is for the 6 valve 3G83. But the Danko manual does not list a separate procedure for timing belt install between the 6 valve and the 12 valve. I think this, used in conjunction with the Danko manual would do well for others servicing their Minicabs.
