Engine diagnosis

[Hogback Fabrication]

Not a Chevy I know

'94 Civic, 1.5L, makes a noise that really sounds like a rod knock to me. Sounds perfect when its in neutral.

It makes a knocking type noise under load (when in gear, at lower RPM's, say 1500-2500 RPM). As RPM increases (and load decreases) the noise goes away.

The noise is also noticeable when you let off the throttle with the car in gear, sounds like metal on metal contact.

Again, the noise is only apparent under load and is not speed related (its engine RPM related but pushing in the clutch gets rid of the noise). Its definitely some part of the motor or something directly related to it. The noise is not consistent, it comes and goes based on load (silent when in neutral).

To me, no noise at idle rules out any valve adjustments (which I've checked and were good).

I pulled the pan, no metal to be seen and the bearings look fine to me (an example of the bearings, they all looked similar and the crank had no significant marks):

Could this still be a bearing knock? Should I measure bearing clearance before I put the bottom end back together? Could this motor be knocking and not create damage to the bearings?

 

[oatsk5]

Is it a stick and could it be the clutch/pressure plate.

 

[Hogback Fabrication]

Is it a stick and could it be the clutch/pressure plate.

Its a stick, clutch and pressure plate are brand new but I believe it made the noise before the clutch was replaced.

 

[oatsk5]

Hmm how bout the rod bearings.

 

[Hogback Fabrication]

Hmm how bout the rod bearings.

That's what the second picture is (this motor has one big bearing cap that holds all the main bearings).

 

[nsxxtreme]

Sounds like valve train to me.

I purchased a 94 accord long ago and end up replacing all the rod bearings because of this noise. Noise remained.
Does you civic have vtec? If so you have a rocker in there that floats until the oil pressure reaches a certain level then it locks in place and rides on a seperate cam lobe. My guess is this noise is comming from your valve train.

 

[Disciples Performance]

from what i can see the bottom end appears to be good no gauling on the bearings, no pitting, so from that stand point your good. Now as for the noise nsxxtreme could be right about the valve train. pull the cover have a look at the lobes and inspect the tolerences of the lobe of the cam to the spec indicated by factory.

 

[4X4HIGH]

My vote is for a bad input shaft bearing in the trans. The pics of the mains and rod bearings are good.

 

[Jason4x4]

Its a stick, clutch and pressure plate are brand new but I believe it made the noise before the clutch was replaced.

I would verify that, if it wasn't, I bet the flywheel bolts are loose.

 

[Hogback Fabrication]

The problem is still there, I've checked the rocker/valve clearance and readjusted the timing belt tensioner. Cam looks perfect.

I did the clutch myself, thoroughly cleaned and applied loc-tite to all the bolts. If the flywheel bolts were loose wouldn't it make noise in neutral too?

I'm 95% positive that this noise was there before the clutch replacement (it was a friends car and I do remember it making a noise like this). The thing is, when I got the car the clutch was so burned up it couldn't put enough load on the motor to get it to make this noise (the car could just barely move at all).


I kinda doubt its the trans input bearing because the seal isn't leaking and, while I didn't intentionally look for a bad input bearing, I know I handled the trans by the input a bit and I didn't notice any play.

So does anyone have any other ideas? I'm going to pull the belts and see if one of the accessories is making the noise.

 

[Jason4x4]

Distributor?

 

[Hogback Fabrication]

Distributor?

Bearing or spark knock?

I haven't really dealt with spark knock before but I don't think this is what it sounds like.

 

[Jason4x4]

bearing, I dunno why it would matter under load though.

 

[diesel4me]

I vote for a worn thrust bearing surface on the main bearing that controls the end play,causing too much crankshaft end play...thats why pushing in on the clutch silences it,it keeps pressure on the crank,and wont let it walk back and forth and cause the rattle..the crank itself may be worn too ,on the thrust surface where it contacts the bearing..pull in and out on the flywheel or balancer,I bet you find its got 1/8" or more of end play,should only have a few thousandths..

 

[Hogback Fabrication]

I vote for a worn thrust bearing surface on the main bearing that controls the end play,causing too much crankshaft end play...thats why pushing in on the clutch silences it,it keeps pressure on the crank,and wont let it walk back and forth and cause the rattle..the crank itself may be worn too ,on the thrust surface where it contacts the bearing..pull in and out on the flywheel or balancer,I bet you find its got 1/8" or more of end play,should only have a few thousandths..

Haven't checked that yet, but the noise is not there with the car in neutral (clutch out).

 

[jms]

...So does anyone have any other ideas?...

Nope, except to say that we missed you at the 'Bash.

 

[Hogback Fabrication]

Nope, except to say that we missed you at the 'Bash.

I know, I was really sad I had to miss it this year

Next time