Mr_Clean Posted August 27, 2011 Share Posted August 27, 2011 Well I'm changing my timing belt today and the saying "something will always come up" holds true... pull off the crank gear to replace the seal and the slot that the wooddruff key goes in is blown out on one side... Any suggestions? I'm thinking either replace the seal and tack weld the key in and just plan on a new crank if I have to tear back in, or fill weld in the chip, and file it down as best I can... neither seem like a great option, but replacing the crank at this time isn't an option either... additionally, I found this sensor that is disconnected on the front of the drivers side head. Any idea what it is? Thanks, -Scott Link to comment Share on other sites More sharing options...
BrianD Posted August 27, 2011 Share Posted August 27, 2011 Sorry I can't answer your question about the crank - Wud sum one PLS tell how U post these large pictures? I wud like to add pix but can't find answers anywhere - Sorry man - Newbe here. Link to comment Share on other sites More sharing options...
Mr_Clean Posted August 27, 2011 Author Share Posted August 27, 2011 Sorry I can't answer your question about the crank - Wud sum one PLS tell how U post these large pictures? I wud like to add pix but can't find answers anywhere - Sorry man - Newbe here. I just post my photos on photobucket and put a link in my post. Link to comment Share on other sites More sharing options...
Precise1 Posted August 27, 2011 Share Posted August 27, 2011 By the marks, it looked like the harmonic balancer has spun and galled the crank journal. From what you said, I would go with fill weld, match file (Pretty easy to do, when the pulley goes on, you are done) and tack weld the key in. One option you haven't considered is to cut another woodruff key slot 180 degrees from the damaged one. Then there is a combination of the two which is fill weld the entire existing slot and recut it in the same place... B Link to comment Share on other sites More sharing options...
Mr_Clean Posted August 27, 2011 Author Share Posted August 27, 2011 I went with option 1. Fill weld, file it down smooth, and file out the key slot. Fits with no play now! Looks like crap, but fits tight. WHEW! Link to comment Share on other sites More sharing options...
Precise1 Posted August 28, 2011 Share Posted August 28, 2011 Cool, good job!! A proper weld will hold... (not a welder, but I know this) B Link to comment Share on other sites More sharing options...
Tungsten Posted August 28, 2011 Share Posted August 28, 2011 How does @!*% like this even happen? Link to comment Share on other sites More sharing options...
adamzan Posted August 28, 2011 Share Posted August 28, 2011 ^^ same here. I wanna know how this happens. Kinda wanna check mine now. Link to comment Share on other sites More sharing options...
sewebster Posted August 28, 2011 Share Posted August 28, 2011 My timing sprocket key slot was damaged when I rebuilt my engine too. I didn't do anything about it because I didn't properly understand the ramifications of failure the. It looked like someone had gone at it with a dremel for some reason. Anyway the key still went in tight so hopefully it is fine! There shouldn't be TOO much force on the sprocket anyway, right? Link to comment Share on other sites More sharing options...
JamesRich Posted August 28, 2011 Share Posted August 28, 2011 It looks like the balancer didn't spin but just the timing belt gear. This usually happens from the crank bolt not being tightened enough. The sensor on the head looks like a cylinder head temp sensor which your 95 truck shouldn't have. My guess is the key sheared and let the timing belt slip and probably bent all the valves. So the PO got a set of head off of another vehicle to put back on. The CHT switch on older pathys is usually yellow so the heads probably came from some other type Nissan with a VG. Welding the chipped area is your best solution. If your key is tight you should have a permanent repair. Just make sure your crank bolt is torqued properly. Link to comment Share on other sites More sharing options...
sewebster Posted August 28, 2011 Share Posted August 28, 2011 Why would a loose crank bolt cause the sprocket to spin? Isn't the sprocket always free to move forward and backward somewhat (except for the fact that it is a tight fit)? Maybe I'm missing something on mine, but if I were to push mine back too far then it would rub on the oil pump (there is actually a washer type thing in between). Link to comment Share on other sites More sharing options...
Mr_Clean Posted August 28, 2011 Author Share Posted August 28, 2011 (edited) i've been wondering that same thing (what causes something like this to happen)... Edited August 29, 2011 by Mr_Clean Link to comment Share on other sites More sharing options...
ahardb0dy Posted August 28, 2011 Share Posted August 28, 2011 Well at least the newer cranks have 2 slots, my 87 hardbody only had one that the timing gear and dampener had to share, my key was messed up one time and I had a friend replace the timing gear and dampener with OEM parts, he tightened everything to spec and a month later it happened again, so instead of replacing the crank I had him put a JDM engine in, Engine made the truck feel better than new. Plus like my friend and I discussed way back never know what else you would find when pulling the old crank out. Good fix! Link to comment Share on other sites More sharing options...
Precise1 Posted August 28, 2011 Share Posted August 28, 2011 It looks like the balancer didn't spin but just the timing belt gear. Yes, you are absolutely right, I realized I had it backwards when I looked at it again... B Link to comment Share on other sites More sharing options...
Mr_Clean Posted August 28, 2011 Author Share Posted August 28, 2011 It was the gear that spun, but it's all back together and running fine again. At least now I know what all is going on in there... timing parts and water pump looked good, probably could have gone another 50K, but you never know when buying a used vehicle when the PO says "I don't know when it was changed" Thanks for all the help! -Scott Link to comment Share on other sites More sharing options...
JamesRich Posted August 29, 2011 Share Posted August 29, 2011 Why would a loose crank bolt cause the sprocket to spin? Isn't the sprocket always free to move forward and backward somewhat (except for the fact that it is a tight fit)? Maybe I'm missing something on mine, but if I were to push mine back too far then it would rub on the oil pump (there is actually a washer type thing in between). If you look close at his picture of the crank, there is a shoulder right in front of the oil pump seal. When you tighten the balancer down it pinches the timing gear against this shoulder and holds it solid. A keyway is for indexing only and not for holding something in position. If the balancer is not tight enough it allows the timing gear to bounce back and forth on the keyway until something like this happens. The balancer could have spun to but it is more of a press fit instead of slip fit. Also the balancer is turning the accessories so it has a constant force in one direction holding it against the keyway. If you ever turned a camshaft by itself you'll see it has three positions it wants to stop in from pressure from the valve springs. These positions cause the cams to want to bounce back and forth when its running. James Link to comment Share on other sites More sharing options...
sewebster Posted August 29, 2011 Share Posted August 29, 2011 (edited) Ah, I see, yeah, makes sense. On mine, when I pushed the timing sprocket all the way on by hand it started rubbing on the washer behind it, so I pulled it back out and used the balancer tightening to push it into what I figured would be the right position. I used an impact wrench, and I'm confident the bolt is quite tight. It doesn't rub now that I can hear, so I guess the tightening squashed the washer into the right shape or something. I suppose another possibility is that I'm missing some sort of spacer... I guess I'll make sure to check the next time I have that opened up. Edited August 29, 2011 by sewebster Link to comment Share on other sites More sharing options...
MY1PATH Posted August 29, 2011 Share Posted August 29, 2011 Ok to save the mile of quote links I just decided to post without them. That mystery sensor on the right head is a head temp sensor for the ECU there is a coolant passage right next to it but the sensor itself stays dry. In pathfinders this sensor was only used in TBI's as both gauge and ecu sensors were moved to the coolant neck for MPFI pathfinders. Did your engine come from another vehicle previously? normally that spot is plugged. Good job on fill welding the snout, that's what I had to do. THE REASON it happens is because the key slot in the balancer and gear are too deep. they Key sometimes migrates out of its keyway(in the crank) and deeper into the key slot by about a mm and then begins wearing on the wall until it folds over. There are TWO solutions I have done for this; The first is insert a 1mm shim on top of the key so it cannot migrate away from the crank. Later on I machined my key way to a lager radius but of the same depth and used a larger key. Lastly, Sewbster that shoulder pictured above needs a washer pressed against it before the gear goes on and a second one on the other side of the gear. These washers are a little taller than the gear and give the t-belt something smooth to rub on. they are meant to rub just a little. Link to comment Share on other sites More sharing options...
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