HELP---Strange Engine Noise is very puzzling

[raythomas]

As you can see the clutch has little to no wear. In fact on the first picture you can still see the factory white company logo showing on the clutch plate itself. If anyone sees anything out of the ordinary please let me know.

Thx

Ray

[datzenmike]

If this makes that sound while driving then can't be the pilot bushing as it and the transmission input shaft are spinning but locked together by the pressure plate. This is true of the release bearing also as it's not in use with the clutch engaged.

[Stoffregen Motorsports]

That does sound like a rod knock, but kind of hard to tell with all the other noises.

 

Mechanics use a stethoscope of sorts to find noises -

 

[paradime]

It does have a synchronized knock with engine rotation suggesting a rod bearing, but it only happening at specific load/rpm does not compute. That leads me off into thinking elsewhere, but what would gap only at a specific resonance frequency like that and continue for 2 months? The timing of the knock does sound to be happening every 2 rotations of the engine. Could it be a single cylinder knocking due to an intermittent injector/timing issue? Did you try pulling individual plugs while run it under load to see if it stops with one cylinder disabled and not the others? 

 

I'm with Soffregen. If you can make it happen while parked, the stethoscope will at least get you in the right neighborhood trans vs engine, and at $17 it's money well spent.  

 

 

 

 

Edited January 5, 2023 by paradime

[datzenmike]

25 minutes ago, paradime said:

.... Could it be a single cylinder knocking due to an intermittent injector/timing issue?

 

 

The Z24i was throttle body injection. (two injectors)

[raythomas]

5 hours ago, datzenmike said:

 

The Z24i was throttle body injection. (two injectors)

Yep, and 2 spark plugs per cylinder with 2 coils. 1 coil for each side.

Do you think I should still pull the oil pan while I got it where I can get to it? I mean I've got it tore down this far, might as well keep going.

Actually now I'm really super curious to know whats going on under that oil pan.

Thx

Ray

Edited January 6, 2023 by raythomas

[Stoffregen Motorsports]

Yes, take the pa off now. Please be careful to number the rod caps and keep them in order. Note that rod caps can be installed backward on accident. The two "tangs" of the upper and lower bearing shells should both be on the same side. You'll see what I mean when you get in there.

 

If you find bad bearings, it doesn't necessarily mean rebuilding the engine. If the crank looks good and there are no metal shavings, and the bearing hasn't spun in the rod, just replace them and hit the road. You can polish the crank while still in the truck. Use 320 grit emery cloth and pull it back and forth over the journal. You can buy it in rolls on Amazon. https://www.amazon.com/gp/product/B07D5KSHF8/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&th=1

 

Rod bolt torque should be 38 lb/ft.

[Stoffregen Motorsports]

Let us know if you need guidance replacing the bearings in the truck.

[datzenmike]

The rod and cap are matching stamped 1/1 2/2 3/3 and 4/4 on one side. If new bearings grease or assembly lube them.

[raythomas]

UPDATE: 1-6-2023

 

Well I drained the oil, took off the cross member and removed the oil pan. And found absolutely nothing other than this tiny bent spring. And I know that little thing wasn't making noise.

All the cylinder walls looked good so wrist pins haven't moved. All the cap and rod bolts were tight, so nothing loose there. There was no play in any of the rods. There was no slack in the pistons fitting the bore. Oil pick up tube bolts were tight and the screen and oil pick up tube looked fine. And I could see no scaring or rub marks anywhere in the crankcase. If you thought I was stumped before, well multiply that by a gazillion!!

[EDM620]

I'm thinking that might be the oil pressure bypass/relief spring. Have a close look at your oil pump for an open hole.

[raythomas]

28 minutes ago, EDM620 said:

I'm thinking that might be the oil pressure bypass/relief spring. Have a close look at your oil pump for an open hole.

 

Can this falling out cause a noise? Low oil pressure? High oil pressure? No oil pressure?!!!!

Thx

Ray

Edited January 7, 2023 by raythomas

[EDM620]

Check the outside of the pump, the bypass is the brass screw in this pic.

This is the exploded parts view - verify that the parts are all in as shown and in the correct order as highlighted. There is not a ball, but a valve and shims.

 

Oil pressure would likely be low, possibly erratic depending on what's happening inside. Datzenmike may have better insight to that.

[EDM620]

Also a reminder that the drive gear shaft is directly connected to the distributor, and the upper end has a slight offset to the flat where it fits into the distributor. You won't disturb this by removing or opening up the pump.

[Stoffregen Motorsports]

7 hours ago, datzenmike said:

The rod and cap are matching stamped 1/1 2/2 3/3 and 4/4 on one side. If new bearings grease or assembly lube them.

They're not always stamped.

[Stoffregen Motorsports]

That does look like an oil pressure relief valve spring, but what the hell is it doing in the oil pan?

[thisismatt]

What about the pressure bypass at the oil filter? I can't remember what that one looks like

[raythomas]

22 minutes ago, Stoffregen Motorsports said:

That does look like an oil pressure relief valve spring, but what the hell is it doing in the oil pan?

My thoughts exactly! If its located in the oil pump on the outside bottom of the front of the engine, there is no way for it to get into the crankcase I wouldn't think.

Thx

Ray

Edited January 7, 2023 by raythomas

[datzenmike]

Looks like the timing chain tensioner spring to me. Looks short so possibly it's broken. Would explain the noise and a direct access down the front and into the oil  pan. The shoe and possibly another piece of spring is still up there in the bottom of the timing cover.

 

 

 

 

 

Someone may have had the head off in the past and never knew to block the tensioner. Or the timing chain and tensioner were replaced and the old spring got away and everything is fine up front.

 

 

[raythomas]

If the tensioner has slack in it now cause the spring may have fallen out, wouldn't that mean the timing chain would have noticeable "slack" in it pretty much all the time? It is odd that the spring in the picture you posted is pretty much bent in the same angle as the one I posted above.

Reason I ask is I've checked my chain and its tight as new pair of boots. Maybe its like you said and its the spring from a previous one. And the plot thickens!

Thx

Ray

Edited January 7, 2023 by raythomas

[datzenmike]

It would have slack only on the right hand side if the tensioner was out.

 

 

Pulled a KA24E apart and everything looked fine, and was. However in the pan were...

 

Several pieces of the original chain guide coverings. They had been replaced.

[EDM620]

I think Datzenmike has nailed that one, chain tensioner spring. You never indicated what sounds you were hearing, I'll bet there is grinding sounds from the chain eating away at the guide (assuming the spring isn't a leftover).

 

An excellent way to hear what is going on inside an engine and pinpoint where a sound is coming from, is to use a solid rod (pry bar, shortened broomstick will work ok) placing one end against the engine and the other against your head right behind your ear. It's amazing the sounds you can hear that way. Poke around and listen to the different sounds components make.

[raythomas]

1 hour ago, EDM620 said:

I think Datzenmike has nailed that one, chain tensioner spring. You never indicated what sounds you were hearing, I'll bet there is grinding sounds from the chain eating away at the guide (assuming the spring isn't a leftover).

 

An excellent way to hear what is going on inside an engine and pinpoint where a sound is coming from, is to use a solid rod (pry bar, shortened broomstick will work ok) placing one end against the engine and the other against your head right behind your ear. It's amazing the sounds you can hear that way. Poke around and listen to the different sounds components make.

Sir, already tried that with a rod. And my chain is tight down both sides, plus I can see both guide plates still mounted to the front of engine with the black pad slide material still on each one. I'm gonna go out on a limb and say that's the spring from a previous chain tensioner and not the one on the truck now.

I had a guy around here say it could be "universal joint" in the driveshaft making a sound. Mine feel tight and smooth and I find it hard to believe I would be hearing it at the back of the engine if it was actually a joint underneath the rear of the truck. But at this point who knows!

Thx

Ray

[Stoffregen Motorsports]

Mike beat me to it. Tensioner plunger spring.

 

It would make a noise, but not the noise I heard in your sound clip.

[raythomas]

14 minutes ago, Stoffregen Motorsports said:

Mike beat me to it. Tensioner plunger spring.

 

It would make a noise, but not the noise I heard in your sound clip.

That's what I was thinking. I've heard a loose torque converter on an automatic before and this sounds a lot like this. But mine is 5 speed manual so there's that.

Thx

Ray

Edited January 7, 2023 by raythomas