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Damian
10-23-2013, 03:59 PM
Ever since I rebuilt my Jeep motor and fired it up for the first time, its always had a knock under light load around 2000rms and up. It will knock every once and a great while at idle. Ive done as much as I can think of to figure this out with no results. This is a mechanical issue.

Things Ive done so far:
Pulled the oil pan, no metal shavings
Re-torqued everything, and I do mean everything!
Pulled the valve cover off and re-torqued all the rockers (no adjustment to them)
I pulled the timing cover off, verified timing and nothing hitting the cover.

Then I found out if I pull the injector plug or plug wire off of #3 cylinder, it knocks continuously at idle. #3 is the only one that knocks when I do this. So I then pulled the brand new hydraulic lifters, rockers, and pushrods and swapped them with #2 cylinder. No change what so ever. I swapped injectors with #2 and #3, nothing. Swapped spark plug wires with #2 and #3, nothing. I even changed out the #3 rod bearing and it didn't change, didn't even need a new one either.

One thing that I did do that made a change was loosen the rocker bolts for the intake and exhaust with the injector plug off and it changed the sound. It got quieter, but didn't go completely away. Im getting plenty of oil flow, well equal to the other cylinders, out of the pushrods through the rockers.

Info about the motor is that the only internal moving parts that are old are the rods and crank. Everything else is brand new. The head is a brand new head that came fully assembled. I did reuse the old rockers, but that's it. Everything was machined/replaced for just a normal rebuild, nothing crazy on this one. I cant think of anything else to do besides pull the head off and take a look. If I had a borescope to use, that might help some. Anyone have any other ideas? Im completely lost.

BADDASSC6
10-23-2013, 11:17 PM
Does it have headers or an exhaust manifold? If it has headers you can you a pyrometers to check the exhaust gas temps when it's knocking at idle to see which cylinder is causing the problem. I'm assuming that you already pulled and read the spark plugs. It sound like you are confident that it's not a mechanical knock and could be detonation.

Damian
10-23-2013, 11:57 PM
It has the stock exhaust manifold. From everything I've done so far, I know it's cylinder #3. I just don't know what else to check. I know it's not the rockers, lifters, pushrods, injector, spark plug, plug wire, distributor cap or rotor, or the rod bearing. The piston easily moved on the wrist pin before install, the rings all have the correct gap, it's not piston slap because tempurature makes no difference either. I think my last thing to do is pull the head and look at the valves on that cylinder.

I should add that it's a 98 Wrangler with the 2.5L I4. It runs just fine other than the knock. It even passed smog too.

94cobra69ss396
10-24-2013, 09:11 AM
Did you mic the bearing clearance when you put it together? How about the valve to piston clearance?

Damian
10-24-2013, 02:45 PM
I mic'ed all of the bearings. I didn't check the piston to valve clearance since I'm using stock replacement pistons that have the same dished shape as the stockers did. I would have done that if I were running some aftermarket higher compression pistons, but these are stock compression which is 8.5:1 if I remember correctly. Plus, if one cylinder was off, Id expect them to all be off.

I also did a compression check the other day and it has 140psi, minimum is 100psi.

94cobra69ss396
10-24-2013, 03:40 PM
Just because it has the same dish doesn't mean that the compression height is the same on the replacement pistons as it was on the stock ones. You could have one piston that wasn't right and is sitting higher in the bore than the others.

Also, you said you bought a head that was already assembled, did you remove the rockers from cylinder 3 and rock the valve to see if it moves? Maybe there is an issue with the guides on cylinder 3.

Damian
10-24-2013, 05:45 PM
I just pulled the head off, I was really hoping I didn't have to do that. The pistons look fine, no nicks or anything. Same with the valves. The cylinder walls look like they are brand new.

I just went out and tried to move the valve and I cant, but the springs are still on it. Im pretty sure my neighbor has a spring compressor, so Ill take the springs off on that one and see. The valves appear to be seated flat though.

With 2 and 3 pistons at TDC, there is no difference from a straight edge on the top of the block to the top of the highest point of the pistons.

BADDASSC6
10-24-2013, 11:22 PM
How about swapping fuel injectors to see if the knock follows? You could have a stuck open, clogged, or failing injector. It definitely a long shot, but quick and easy compared to pulling the head.

Damian
10-24-2013, 11:35 PM
I tried that as well. I even swapped in my Typhoon stock injectors with no change.

Vettezuki
10-25-2013, 12:20 AM
Pulling this out of my ass. Small crack in the manifold around 3 causing it to take in more air and go lean to the point of knocking?

Any way or reason the timing could go way advanced on 3?

Damian
10-25-2013, 01:42 AM
I didn't see any cracks on the manifold anywhere. Timing is computer controlled, but has no knock sensor (weird IMO).

The part that I don't understand is that #3 knocks ALL the time if I pull it's plug wire or disconnect it's injector. The only way I can get the knock to change is if I loosen the rockers. This is all during idle of course.

Vettezuki
10-25-2013, 02:40 AM
Rod bearing on #3 rod. The slightly higher revs/load reveals slop in the tolerance?

94cobra69ss396
10-25-2013, 07:52 AM
Rod bearing on #3 rod. The slightly higher revs/load reveals slop in the tolerance?

That's what I think as well especially after the issue he had with bearings during assembly.

Damian
10-25-2013, 10:04 AM
That's what I thought but I plastigauged it with the new bearing and it was within spec.

94cobra69ss396
10-25-2013, 10:08 AM
If you still have the head off rotate the engine by hand and see if you feel anything catching. Also watch the #3 piston to see if rocks or does anything different than the rest.

Damian
10-25-2013, 10:51 AM
I did that when I first pulled the head off but I'll do it again. It rotates nice and smooth, which is making me lean towards the valves. I'll pull them out later today when my neighbor gets home from work.

Damian
10-25-2013, 04:29 PM
There is no movement with the piston as far as side to side goes. I also turned the crank to get #3 to start its downward stroke and pushed on the piston and it didn't move.

Damian
10-25-2013, 04:45 PM
Went back to the listing where I bought the head from and found this:

Details:
Brand new heavy duty stronger casting than factory
All parts are reconditioned factory pieces
Head is assembled with new valve seals
Head is complete and ready to install

Being that the parts are reconditioned, I wonder if they used something that wasn't good.

94cobra69ss396
10-25-2013, 06:09 PM
They check everything so I doubt it. Did you listen with a stethoscope before you took it apart to see if you could pin piont the knock?

Damian
10-25-2013, 06:57 PM
I tried to pinpoint it but wasn't able to. I just know it was internal and related to #3.

Damian
10-25-2013, 08:35 PM
I pulled the valves of off #3 and didn't see anything wrong. I'm done with this damn thing. I'm just gonna bolt everything back up and drive it till it dies. It will eventually stop knocking sometime. I've already spent over a grand on it already and countless hours, I'm done. Unless someone can think of something by 9pm tonight, I'm putting it back together.

Damian
10-27-2013, 10:58 AM
Put it all back together last night. It doesn't knock anymore when you disconnect the injector but still knocks around 2k rpms.

94cobra69ss396
10-27-2013, 09:23 PM
Can you get video of the knock? Now that it's back together, does it sound like it's coming form the top or bottom of the engine? Have you tried swapping the injector on 3 for one further away like 6 to see if it's a noisy injector?

Damian
10-28-2013, 12:44 AM
I've swapped in a completely separate set of injectors with no change. I can try and get a video tomorrow.

I've been reading some more and some people have had issues with their knock sensor causing a knocking like mine, so I ordered one from good ol Rockauto.

Damian
10-28-2013, 01:52 PM
O2 sensor, not knock sensor.

Damian
10-29-2013, 07:19 PM
Finally, the video: http://i53.photobucket.com/albums/g45/meclipsegt/BB3B4072-B54D-4F32-B91C-01460F2701C5-262-0000005700A586D4_zps630f8469.mp4

The new O2 sensor didn't do anything but make the idle a bit smoother.

I've changed the oil 3 times now and the knock stays the same. I've even added Lucas and STP oil additives and no change in the sound. No clue anymore.

Vettezuki
10-29-2013, 10:34 PM
Can you find a source to temporarily swap out the head assembly? If you replaced the whole upper half and it stayed the same, you'd at least be cutting that out. :huh:

Damian
10-30-2013, 12:47 AM
I would but the 2.5 head isn't easy to find at the junk yards and I had to ship mine back to the vendor I bought the head from. If someone has a 2.5 head lying around, I'd swap it in. Would only take a couple hours.

I can't pinpoint the exact location of the noise but it is coming from the top end.

Vettezuki
10-30-2013, 01:20 AM
What year? I traded my 91 2.5 with enkeivette for legal retainer. Not sure what if anything he's doing with it at the moment. I don't want to volunteer anything for him, but if it's compatible, hit him up, he might not mind if it's just sitting around at this time.

Damian
10-30-2013, 09:57 AM
Mine is a 98, I believe the only difference is his is carb'ed and mine is fuel injected. Not are if the head is the same casting though.

Damian
10-30-2013, 06:24 PM
I bought a engine stethoscope and I isolated the noise to the front bottom of the engine. I pulled the timing crap out again and nothing, but I was a tooth off somehow. Put it back together and same shit. One of the many things I've read is a bad harmonic balancer. The timing marks match up perfect though.

Damian
10-30-2013, 07:51 PM
My harmonic balancer is taking a shit. The rubber is starting to come out the sides. I don't know how I never noticed that, especially since Ive pulled it off a few times now. Plus my serpentine belt has had a slight squeak to it, and now I know why. Before I buy a new one, anyone have a good one I can swap in really quick? The 4.0 and 2.5 use the same one, but it has to be a Tj.

94cobra69ss396
10-31-2013, 03:46 PM
Did you replace the timing chain?

Damian
10-31-2013, 04:29 PM
New chain and sprockets as well as a tensioner.

94cobra69ss396
10-31-2013, 05:55 PM
If you listen to the timing cover, does it sound like the noise is coming from there?

Damian
10-31-2013, 10:11 PM
I can hear it there but it's much louder on the bottom of the cover where the oil pan bolts to it.

94cobra69ss396
10-31-2013, 10:24 PM
To me from that video it sounds like a rod knock.

Damian
10-31-2013, 11:56 PM
That's what I thought too at first but the oil pan is metal shavings free. I'm going to get a new balancer tomorrow and see how that goes.

Damian
11-01-2013, 06:40 PM
Looks like Ill be pulling the motor sometime soon.

Damian
11-07-2013, 11:53 PM
Pulled the motor in the Jeep today, found all the rod bearings were shot. Crank was unharmed thankfully. The standard bearings were too loose, took some measurements and got the right ones. Plasti gauged everything and it's right. Should have the motor back in tomorrow. I don't understand it though, I tried the .010" the first time and they were way too tight, now they work perfect. Maybe they were the wrong size in the packages I got??

Vettezuki
11-08-2013, 12:41 AM
I don't mean to brag, but . .

Rod bearing on #3 rod. The slightly higher revs/load reveals slop in the tolerance?



:penguin:

94cobra69ss396
11-08-2013, 08:42 AM
What did the plastigage show for clearance?

Damian
11-08-2013, 09:06 AM
I didn't check the ones I just pulled out but the 0.01" underbore ones I just put in are right around 0.002", which is within spec.

Damian
11-08-2013, 10:37 PM
Engine back in and running. No more knocking! About fucking time. I just drove it down the street and back and it runs really smooth now. Right bearings and I ended up replacing all of the pulleys and harmonic balancer, nice and quiet too. Not so much quiet, but much much better than when I took possession of it.

Vettezuki
11-09-2013, 01:02 AM
:thumbs_up:

94cobra69ss396
11-09-2013, 09:55 AM
I'm with Ben, congrats.