Nissan Repair: knocking noise, mobil 1 synthetic oil, plastic particles

Question
QUESTION:
Hello,
We are sorry, but Calvin Iwashita wasn't able to answer your question:

I have a 1997 Nissan xe pickup with four wheel drive that has 130,000 miles. Other than a clutch and an alternator this truck has run and preformed perfect. I always change the oil on a regular basis and use Mobil 1 synthetic oil. I recently started the truck one day and heard this very loud rapping noise for a few seconds and then it was quiet and ran fine. The next day about 5 miles from the house it had this chain rattling while driving.On inspection I found that the stationary trimming chain guide was missing the plastic on it. I went ahead and put all new chain, guides, oil pump, water pump and thermostat, the hole nine yards if it came off to do the chain it was replaced with new genuine Nissan parts. As far as the plastic off the chain adjuster I never found any of it in the pan (as far as I could tell as could not get pan totally off truck), the pickup, the pump, nothing. So I put it all back together and now I have this new knocking noise. I kind of sounds like a rod knock but only in the number 4 cylinder and only at 15 hundred rpm and higher at both load and no load. The knock does get louder and more rapped with higher rpm's but at idle the motor sounds and runs perfect. Now that you have the back story I have three questions. Could the plastic particles have wiped out the rod bearing on just one cylinder and nothing else? What is the easiest way to get the oil pan totally off the truck (as I am limited on tools and rolling around on the ground to do this)to make sure the deep end is also free of debris? Could this knocking noise be something else that would sound like a rod knocking.

   Thanks for the help
         James


ANSWER: James,

It does sound as if the rod bearing on number 4 has spun.  The only way to get the pan off is to unbolt the engine to raise it, in the vehicle.  That is, support the vehicle where you can get under it.  Then, use a jack under the harmonic balancer to jack it up enough to remove the pan.  If you have a hoist you can lift the engine that way.  Remove the rod bearing cap and inspect the bearing.  You could get lucky and have caught it before there was rod damage.  If there is rod damage you need to remove the piston and rod and get another one.  Or, have that one resized and reinstall it.  Another cause would be that it jumped timing and number four has a bent valve or a broken ring land from impact with the valve.  But, I feel that it would be more than just one cylinder if that happend.

---------- FOLLOW-UP ----------

QUESTION: First of all thank you for answering and confirming my questions. Second the factory manual I ordered finally came today and I found that it says to run the truck for 20 minutes at 1,000 rpm to bleed all the air out of the oiling system. I did not do that as one did not know I had to do that and two when I heard the noise that sounded like a rod knocking I shut the motor off so as not to damage it farther and inspect it for a problem. Could the knocking just be that there is air in the system (remember new oil pump) and I need to run it for that 20 minutes to get it all out and it will quiet up after everything is good and oiled with continuous oil pressure? When I do get this pan off (still want to make sure there is nothing at all in the deep end to cause problems latter)I am still going to pull the rod cap and check the bearings and depending if it looks good or not I will check the other three also as I am already there and want to be sure. As for jacking the motor up to get the oil pan off do I need to take the motor mounts loose or will it move far enough in the rubber to get the room I need? As I said I am limited on tools here at the house and the mounts look like a pain to get to not to mention the fact 11 years of rust on the bolts. I can get the tools I will need it would just be nice to already have them there so as not to waist another day.
     
       Again thanks for all your help
         James

Answer
James,

Bleeding the air from the oiling system simply allows the tensioner for the chain to tighten up so there will not be chain noise.  If your noise is a number four then the oil is bled and we are back to number four.  Yes, the motor mounts need to be unbolted to get the engine high enough to get the pan off.  If you did the chain this is going to be much easier.  Even with the rust, just use lubricant and hopefully you have air tools.  With hand tools it is going to be a pain getting the motor mount bolts loose.  A box end wrench and a socket with a breaker bar would help.