Tapping/clacking sound coming from front-underside of engine

[j3ff]

Title says it all.. I have a rattling sound coming from the front/underside of the engine, and its very harmonic.. not constant, sort of rattle tap tap rattle tap tap, rather than tap tap tap tap tap, if you know what I mean.

Any ideas on what this could be? Its been present for a couple of weeks now, is particularly noticeable when the engine is cold, and seems to have gotten slightly louder.

[DCColegrove]

Lot of miles on it?

also is the oil full and what oil do you have in it?

Possible chain tensioner or stretched chain... Try a tensioner first, if you do it yourself make sure you also remove the valve cover and release the tensioner and prime the oiling system before you try and run it.

[j3ff]

176k miles, new chain, sprockets, tensioner, guide rails, etc about 10k miles ago. I'm running 10W-30 Mobile 1 in it.

[gearheadE30]

I run 10w40 and it seemed to quiet the engine down a bit. I don't think this is your problem, though.

M42 oil pumps are known for having loose bolts. You will probably have to pull the lower oil pan, and you may find a few bolts in it. Use locktight when you reinstall them, and make sure you use the proper torque values. If you are really unlucky, the oil pump pickup can suck a bolt in and at best cause the pump to cavitate or at worst suck the bolt into the pump and shatter most of the front end of your motor.

[tjts1]

I'm running 10W-30 Mobile 1 in it.

Wrong oil. M1 10w30 is actually thinner than their 0w30. Pour in something that ends in the number 40. Also drop your lower oil pan and fish out all the loose oil pump bolts.

[peerless]

M42 oil pumps are known for having loose bolts. You will probably have to pull the lower oil pan, and you may find a few bolts in it. Use locktight when you reinstall them, and make sure you use the proper torque values. If you are really unlucky, the oil pump pickup can suck a bolt in and at best cause the pump to cavitate or at worst suck the bolt into the pump and shatter most of the front end of your motor.

The bolts fall out of the upper front pan rail, not the oil pump. In this case the gasket can get pushed out and suck air, quickly destroying the engine.

Its physically impossible for a bolt to get sucked into the pump as the pickup has a very stout metal screen built into it.

Check m42club.com for more information on the subject.

Also to the OP, it could be possible that the thrust bearing is completely wiped and the crankshaft is basically moving back and forth creating some of the noise you are hearing. Might be worth hooking up a mechanical oil pressure test gauge to see what your oil pressure is. Just a thought, but these M42 in stock form are very self destructive.

[dashboardmonkey]

Rod?

Andy

[gearheadE30]

The bolts fall out of the upper front pan rail, not the oil pump. In this case the gasket can get pushed out and suck air, quickly destroying the engine.

Its physically impossible for a bolt to get sucked into the pump as the pickup has a very stout metal screen built into it.

Check m42club.com for more information on the subject.

Also to the OP, it could be possible that the thrust bearing is completely wiped and the crankshaft is basically moving back and forth creating some of the noise you are hearing. Might be worth hooking up a mechanical oil pressure test gauge to see what your oil pressure is. Just a thought, but these M42 in stock form are very self destructive.

Hmm, looks like I checked the wrong bolts when I had the lower pan off...crap.

As for the little grate thing, apparently they can move. I didn't believe it either, but some guy on M42club had the oil pump suck up a bolt. I'll have to check it again, because now I don't trust my memory.

[j3ff]

Welllll damn. I took off the lower oil pan.. the good news is that there weren't any bolts in it. A couple of the bolts attaching the upper oil pan were a little loose, so I tightened them properly. Put everything back together, but 10W-40 in it this time, and its still making the same sound (that's the bad news). I really hope this thing isn't about to blow up.. that would suck majorly.

[EN318isPDX]

My guess is tapping lifters? Time for a rebuild

[j3ff]

My guess would've been tapping lifters too, except for the fact that the sound is definitely coming from the bottom of the engine. I'm thinking that the comment about the thrust bearing being shot is the most plausible right now.. That really sucks though. This engine has been meticulously maintained with the oil changed every 3-4k miles.. always Mobile-1.

I'm not really sure what to do next.