KOMAT’SU WA 600 FRONT AND LOADER WA 600-3 S/N 52419 ENGINE. SAA 6D170E-3 S/N 316219 At 26,000 HRS Engine develop a problem on 6th cylinder. The exhaust valve hit the piston and one valve got broken, we decided to repair the cylinder damaged, and started the engine the same problem happen again just after 30 seconds. We decided to stop the engine so that we could do major over haul. When we received the parts and start assembling is when we noted a big Back hole on the Crank shaft gear. we decided to pull it out and noted a huge wear on the crankshaft key way which indicates , this had been a problem which develop to wear engine things which therefore affected by the valve Train and Hits the piston. This is very strange phenomenal A CRANKSHAFT GEAR which is a press fit. Sea attachment photo. QUESTION: Is this wear on the Crankshaft key way normal or is a factory defective
Gear appears to be bronze or brass, the different heat expansion characteristics of steel and brass make it a poor choice for the purpose. Even as a press fit if it heated faster than the crank then it could loosen to the crank and do just as pictured. I would see if there is/was a change to a steel gear setup to later units engines.
Are those bolt holes in the crank the front of the engine or the rear? I don't recall ever seeing a brass or bronze timing gear in a modern diesel engine and sure don't remember any in a Komatsu engine. As I recall all the drive gears on the cranks on Komatsu engines were cut into the crank. That is a big gear train though and there could be lots of load on that one gear. The only thing sure though is that you need some expensive repair work before putting that engine back together.
It's kind of hard to say it's a factory defect at 26,000 hours. I'd guess that gear started moving on the shaft within the last couple thousand hours. I think that color on the gear is a little oil, "varnish" or just the camera. Looks like steel to me. Not sure about the other picture either, if that's the right end or not. I'd definitely get a new gear, but a good machinist can probably fix your crank one way or another. I'm curious why only one piston hit a valve if this was the cause. Was there any evidence of a bent crank? tapered bearing? stretched #6 rod? really loose old #6 rod bearing? Do cams ever bend???
The gear is steel not brass, and the gear is onthe rear of the engine were timing is done, the wear was so huge, that it could move the timing mark in the camshaft more than two teeth, which ofcourse will affect the valve train, the crankshaft is straight not bend and all journals are standard.
As Delmer says a good machines shoould be able to salvage the crank. Just make sure he knows that this key is what times the crank to cam. I'm assuming the wear is all on one side of the keyway so should be able to determine the original location with some percision. I too was wondering why you only had a problem with valves hitting on one cylinder. I'd be checking rods, pistons and vavle train very close. Check cam for wear on lobes too. I'm thinking your WA-600 has a Komatsu engine? We have one with a KTA-19 Cummins and it has just over 24,000 hours. Ours had a valve spring break on on cyliner last summer. We were very lucky and it did not drop down enough to get hit hard by piston and we were able to just pull heads and get them rebuilt and put back on and it's running fine as I write. Good Luck.