HELP---Strange Engine Noise is very puzzling

[raythomas]

8 minutes ago, EDM620 said:

If it is something more serious, and just a noise now, it will make itself more apparent (and easier to diagnose). 

If you still feel the need to find it, do the stethoscope/stick method and listen to the engine as it runs. If internal issue you'll know for certain.

I actually looked at stethoscopes the other day wit that thought in mind. I just might give that a try.

Thx

Ray

[EDM620]

a stick or broom handle is free...

[bilzbobaggins]

was randomly thinking of this recently, any updates?

On 3/17/2023 at 7:06 PM, raythomas said:

I actually looked at stethoscopes the other day wit that thought in mind. I just might give that a try.

Thx

Ray

 

[datzenmike]

The hamster wheel just needed some 3 in one.

[EDM620]

Like the cat, we're curious...

[bilzbobaggins]

we may never know

[raythomas]

My apologizes fellows. I've been terribly busy with things at work and around the farm. Haven't had much time to devote to the D21. 

I've been driving my old silverado. I'm hoping now that works slowed and the temps have dropped some that I'll get a chance to look at it again.

I sure do appreciate ALL the info and help you guys gave me these past months. It's been a huge help so far.  

I'll try to post back when I get some updated news. 

I purchased a stethescope so I can't wait to try it out.

 

Thanks
Ray

[EDM620]

18 hours ago, raythomas said:

purchased a stethescope so I can't wait to try it out.

👍

[raythomas]

Well I got a little time to spend on the truck. The battery needed charging cause it was to low to crank. I figured that was gonna happen. Charged it  and It cranked right up and idles fine. Sitting there purring like a kitten, a 36 year old kitten mind you, but a kitten none the less.  Probed all over the engine with it running with the stethoscope and heard not one sound that sounded out of the ordinary. Bummer. Took it for a test drive and the noise is still there. When taking off and shifting through the gears it has that stupid rattle / pinging sound. If I clutch it and remove the load from the engine but leave my foot on the throttle the sound goes away.  To say this is beyond depressing is an understatement. I'm so tired of worrying if it's gonna blow up or leave me stranded that I haven't drove it in months.  My father-in-law had a crazy idea that we should take off the hood and let me hang over the motor and let him drive it up the road (slowly) to see if I can pinpoint where the noise is. After all this work and worry I'm inclined to throw caution to the wind and give that a shot. I mean dang. Sorry for the rant. Thanks for listening and all the help so far. 

 

Ray

[datzenmike]

Exhaust pipe rattling from engine torque under load.

 

Timing too advanced? pinging?

 

Small exhaust leak. Crack in manifold or gasket on pipe end? Crack or hole in the EGR pipe from manifold to EGR valve? Noisiest under load.

[EDM620]

27 minutes ago, raythomas said:

Took it for a test drive and the noise is still there.

That narrows the problem to the drivetrain and not an engine issue. Score 1 there.

 

A much safer method is to put the truck up on jack stands (not driving as a hood ornament) and while someone operates the clutch and gears, listen & probe for the noises. Narrow the problem sounds further: Clutch - engaged/disengaged? Varies during clutch engagement? Difference between Neutral, Forward or Reverse gears? Is there any slop in the driveshaft? U-joints? Middle support bearing? Rear axle pinion (again Fwd/Rev).

 

You should be able to pinpoint the problem much easier & safer.

[raythomas]

Just a question for you fellows. What brand and type of motor oil do you suggest I use in this Z engine? Can you use a heavier weight without issues?

Thanks
Ray

[raythomas]

I've had the trans and driveshaft out already. The driveshaft and swing bearing are in great shape with no slop. EGR someone said. This truck had all the smog stuff deleted off of it years ago.  Where and or how would I check the EGR? 

Thanks
Ray

[datzenmike]

There will be a small metal pipe connecting the block vent, behind the exhaust manifold, traveling around the back side of the head to the EGR valve mounted on the rear of the intake manifold. It may be leaking or badly removed and not sealed.

[raythomas]

1 hour ago, datzenmike said:

There will be a small metal pipe connecting the block vent, behind the exhaust manifold, traveling around the back side of the head to the EGR valve mounted on the rear of the intake manifold. It may be leaking or badly removed and not sealed.

Gotcha. I've seen where they cut those pipes and bent the ends of them shut. I'll check that.

Is there any way to get the exhaust header off without breaking those stupid bolts off in the head? Mine are all rusty looking and i really dont want to have to deal with broken bolts in an aluminum head.Thanks

Ray

Edited September 22, 2023 by raythomas

[Crashtd420]

18 minutes ago, raythomas said:

Gotcha. I've seen where they cut those pipes and bent the ends of them shut. I'll check that.

Is there any way to get the exhaust header off without breaking those stupid bolts off in the head? Mine are all rusty looking and i really dont want to have to deal with broken bolts in an aluminum head.Thanks

Ray

Heat is my go to when things are rusty and stuck..... 

Try running the truck up to temperature and then shut It down... while the engine is still hot try to remove the bolts.... 

You can swap for studs after if you want... 

[raythomas]

1 hour ago, Crashtd420 said:

Heat is my go to when things are rusty and stuck..... 

Try running the truck up to temperature and then shut It down... while the engine is still hot try to remove the bolts.... 

You can swap for studs after if you want... 

Never thought of that. I'll give it a shot. Wonder if a small propane torch would help if they need "more" heat that just a warm engine?

Anybody see my post asking about using a heavier weight oil? Like going from 30 to 40 weight, or 40 to 50 weight?

Thanks
Ray

[620slodat]

Ten pounds more oil weight will help the oil pressure, but unless you are having problems with keeping oil in somewhere (mains or rods?) it will result in not enough oil getting somewhere important. More oil pressure might result in oil getting somewhere important slower, unless the clearances are more open than should be. If oil pressure is going down with standard weigh oil then heavier weight oil might be needed. Usually a larger oil pump will do the trick.

 

Don 

Edited September 22, 2023 by 620slodat

[datzenmike]

Oils are all about the same 'weight' or viscosity when hot. The W is for ease of winter starting. Too thick doesn't really lube the bearings very well on cold starts. Select your W depending on the coldest weather you expect before the next oil change. 20w and 30w anything shouldn't be used below freezing. 15w40 and 10w30 and 10w40 is good to zero F.

 

As to your oil, after '92? all oils makers began to lower the zinc anti scuff additive ZDDP in their oil formulas. Newer engines don't need it, and it's bad for today's catalytic converters. Before that ZDDP was above 1,000PPM now it's 500-600ppm and in my opinion may not protect out valuable, even irreplaceable valve trains. The wear is accumulative and adds up over time. You can add ZDDP to your oil or simply go down the aisle to the diesel oil section. I use Shell Rotella T4 in 10w30 and 15w40 is also available in much warmer climates. T4 has 1,200ppm of ZDDP in it. Diesel oils are also much more detergent so don't be surprised if it darkens quickly after a change. This is the oil cleaning your engine. By the third of forth oil change this will go away.

[Stoffregen Motorsports]

1 hour ago, raythomas said:

Never thought of that. I'll give it a shot. Wonder if a small propane torch would help if they need "more" heat that just a warm engine?

Anybody see my post asking about using a heavier weight oil? Like going from 30 to 40 weight, or 40 to 50 weight?

Thanks
Ray

Engine heat usually works great. If you plan ahead, squirt it down with WD40 every once in a while days or ever weeks before you attempt to loosen things.

[Crashtd420]

2 hours ago, raythomas said:

Never thought of that. I'll give it a shot. Wonder if a small propane torch would help if they need "more" heat that just a warm engine?

Ray

Yes the small propane torches work but if you can, grab a small cylinder of map gas.... it's a yellow bottle... I believe you can get both at homedepot or Lowe's... it's a little hotter than propane....

[datzenmike]

6 hours ago, raythomas said:

Gotcha. I've seen where they cut those pipes and bent the ends of them shut. I'll check that.

Is there any way to get the exhaust header off without breaking those stupid bolts off in the head? Mine are all rusty looking and i really dont want to have to deal with broken bolts in an aluminum head.Thanks

Ray

 

Why take it off??? Check for cracks/leaks? Wait till cold then have someone start it while you quickly run your hands all over the back sides of the manifold. Probably 10 seconds or maybe more till too hot. Did this on a Buick V6 with blown head gasket. It whistled on start up but was quiet once warmed. You could feel the pulses.

[raythomas]

I think  we have a break-through!!!

I'm crossing my fingers, but after work I changed the oil and filter. 

Used 10w-40 conventional oil. 

After the oil change I drove it down the road and back.

No change to the clatter sound, but the engine sounded quieter overall I guess in part to the new oil.

Anyway, after the third trip down the road I noticed that when I took off from a stop sign and shifted through the gears it clattered between each gear, but in each gear if I did nothing but mash on the gas pedal or increase throttle, the clatter all but went away. My thought was, if its something drastic, like blowing up the engine drastic that the sound should get louder and increase with more throttle added. Well it doesn't, it goes away.

Which led me back to my thoughts about valve knock. Well long story short I loosened the distributor bolts and moved the timing a smidge CCW, locked it down and drove it and the clatter all but disappeared !  I lugged the engine between each gear and if it made the clatter, it was so faint you could hardly detect it.

Now I haven't touched those distributor bolts since I've owned the truck until tonight. So I'm thinking what if anything could have moved or got out of adjustment in the timing to cause such bad valve knock?  I'm including a picture of the mark I made on the distributor before I moved it CCW just a fudge. The two marks in the picture were aligned before I moved it. I'm curious as to what you guys think about all this.

 

Thanks
Ray

Edited September 23, 2023 by raythomas

[datzenmike]

23 hours ago, datzenmike said:

Exhaust pipe rattling from engine torque under load.

 

Timing too advanced? pinging?

 

Small exhaust leak. Crack in manifold or gasket on pipe end? Crack or hole in the EGR pipe from manifold to EGR valve? Noisiest under load.

 

I'll take door number 2 Bob.

 

The Z24i uses a CAS crank angle sensor to supply crank position to the ECU and it calculates and fine tunes the ignition timing. CCW is in the retard direction. So it can be assumed that it's too advanced. I would get a timing light and be sure it's correct.

[raythomas]

1 hour ago, datzenmike said:

 

 CCW is in the retard direction. So it can be assumed that it's too advanced.

Yes sir, I understand that. But is there any reason for the timing to be out or "moved"? I mean this truck has been fine for years. Can a crank sensor that's failing cause the timing to change enough to make this happen? 

Thanks
Ray