Help Wanted with Engine Knock

[Pak Meul]

Well, I've read about a hundred or so posts I've found after searching variations of "Knock", "Ping", "Tick", and "Slap" and still haven't found anything that seems to describe my engine noise.

My 95 FZJ80 has 171K well maintained miles. The PO had the maintenance records and I confirmed it when I took the head off to replace the head gasket as a PM item so I could tow with peace of mind. There wasn't even much discoloration inside the valve cover compared to pics of others I've seen posted here, and the cross hatching was still visible inside the cylinder bore.

A machinist used by the local Toyota dealer milled .006 off the head to clean up the fire ring grooves, replaced the valve seals, and ensured the valve seats were still sealing. I also had the fuel injectors reconditioned. My miss has disappeared and it runs smooth as a baby's butt.

I've put about 500 miles on it since the work and now notice, what I initially thought was valves ticking, under certain conditions. It seems to be getting more noticeable. It sounds like metal tapping metal. I can hear it constantly when driving at high rpm's (3500-4000) so I'm afraid to do any towing. I can also hear it when I rev it when parked. If I rev the engine to 2500-3000 RPM's, let off and then hit the gas again the tapping noise starts as the RPM's change from dropping to rising.

Using my $5.00 Harbor Freight mechanics stethescope I've been able to determine that the sound is heard mostly in the block. I can hardly hear anything in the head.

When listening from the exhaust side it seems like it is coming more from the top of the block. It's hard to tell, but I hear it more from the front of the engine, but I can also hear it pretty well by the #4 cylinder area. I might be able to hear it all across the top of the block, but I haven't had much chance to put the rod from the stethescope all over without interference from other parts deadening the sound.

I did have some issues with the timing chain when I put the head back on, but I don't hear the noise on the tensioner cover at all.

Is is possible that by shaving .006 off the head that the valves are intermittently hitting the tops of the pistons?

Is is possible the chain is hitting something, could valve/piston conflict only occurr under certain rpm conditions?

I'm at a loss and wanting to get this cleared up before pulling my trailer on vacation. Any help is appreciated.

Thanks

Steve

 

[cruiserman]

Out of curiosity, did you check your valve clearances?

 

[Pak Meul]

I did check my valve clearances in accordance with the FSM. This was the first time I've checked it so I'm hoping my feel for the feeler guage was right. The guage for the tight end of the scale, .006 In. for intake and .010 for exhaust was very snug. The guage for the maximum looseness wouldn't go, so I'm hoping I was correct in using the guages as a go/no-go. The other thing I was relying on was that the PO had the valve adjustment checked at the dealership about 60K ago and I had returned all of the parts to their original locations when reassembling. I didn't think it should be too out of whack.

 

[CERES2]

Just did a head gasket replacement and had the head rebuilt. I would pose that every time you remove the rocker assembly you need to adjust the valves and do it again when the engine has warmed up. See the FSM.

 

[Pak Meul]

Am I mistaken, or would misadjusted valve noise be heard best on the valvecover or head? My noise is best heard in the block, definately well below the cam, down in the area of the pistons.

For clarification this is a 1FZ (no pushrods or rocker arms)

 

[CERES2]

Yeah. I have 3FE on the mind at all times............

 

[Pak Meul]

So, I'm not feeling real good about the tapping sound. If I don't get any ideas soon I'll probably opt to run it till whetever is wrong with it works itself out. Kinda like walking it off, but more expensive.

Any ideas out there?

 

[IdahoDoug]

I've noticed a couple of noises the 1FZ makes that most people will never notice. I'm blessed/cursed with hearing that has been tested and is literally off the scale. I protect my hearing to a fault with a range of earplugs and such I wear even while bike riding (wind noise is annoying). You must be similarly blessed.

One noise happens when you park nose down a hill and leave the truck idling in Park. It can be heard outside the vehicle as a low frequency grumbling deep metallic klokking sound and I think it's the heavy crank journals.

Another noise is what you describe in Park revving the engine up and down. Right at the point where it goes from RPM dropping to rising and also vice versa under certain RPM/temp conditions it will make a metallic pinging sound. From listening to this over the years, I've decided that it is from the brief moment where the piston/crank/wrist pin/crank journal slack all changes direction and the engine is unladen. This is a truck engine and these components are unusually heavy for folks like us who are used to finely balanced modern high revving engines. A truck driver hears all manner of mechanical whirring, clacking and pinging because his engine was designed for durability and not to minimize consumer complaints.

There is an RPM point on my 93 where I can bounce the revs up and down a few hundred and make it give off a sound you'd think associated with imminent destruction (to my ears, grant you). I think it's around 1700-1900 or so if I recall. Since discovering it, I haven't done it again after that few minutes of wondering/listening except once. After the HG was replaced and the head/valves were completely stripped, measured and adjusted I checked and it still does it exactly the same. It's the moment where the slack in the crank/journals/wrist pins all go from end to end with no load and sounds like hell. That fits with your feeling it's in the block - I agree. That's in a vehicle I bought new and it has had nothing but synthetic oil in it an average of 6100 miles per change over its 190k life. I noticed that noise around 90k miles a decade ago. I think there's a good chance this is what you're hearing and I will speculate a bit that the under load sounds while driving are from you listening too closely and hearing something that's normal.

So. Here's what I'd do if you're still worried. I'd change your oil since with only 500 miles you still have crud in it from the head work. Then I'd put a quality synth in it and run it to the full 7500 mile interval and send a sample in to Blackstone Labs. For $25 you'll find out if something's wearing fast because they can tell if there's excessive bearing molecules, excessive block molecules, excessive piston ring material, etc in the oil. They're that good and they know exactly what materials are used in every major part in the 1FZ. They will tell you if something's banging on something else and removing material because it will end up in their world - your oil - where spectrometry will reveal everything.

I think they'll find nothing amiss with your engine, but I'd do it for peace of mind. In the meantime, just drive it normally and even tow the heck out of it.

DougM

 

[dodgefate]

well i was a mecanic for 7 years and saw alot of blown engins (Also blew a few my self). If the tapping noise is irregular like tap tap .....tap, it could be a bad bearing. if it its a consistant tap could be a wrist pin. If the valves were tuching the pistons, even the slightes bit, it would bend them and most likely run horrible. I had a problem when I fist got mine where I heard a small tap and it turned out the plug wires were bad and arching whic suprizingly sounded like a tap...... Are you hearing the noise inside the vehicle while driving? If so prob not what i just said. Firs ting I wold do is drain the oil. Whne you drain it use some sort of cheese cloth or coffie filter or even a rag to filter the oil. If there is little shiny peices of metal that look like gold or brass this is most likley from a bearing. If it is clean then id say your problem lies up in the top end. I had a minivan that the engine started knocking and i drove it until a rod came through the block (It was under warranty). Started off small and kind of quit but at about 100 miles since the noise it blew right through. Another good way to tell is if you can hear it while driving, put it in drive 2 or one. On deceloration the knock shoud get louder and more inconsistant if it is a rod knock. I also had many of problems with putting headgaskets on cars with himg milage usaly short after it blew the bottom end out. Oil pressure is also made not from the pump but by being forced threw all the tiny holes on the crank jurnals. If oil pressure has dropped could be a rod bearing.... Let me knwo what you find out

 

[Pak Meul]

That's what I'm talkin' about! Thank you, both Doug and Dodgefate, for your input. Both are realistic possibilities.

I can certainly eliminate spark jumping to ground as the culprit, and the noise is too consistent, and limited to the conditions I specified to be a rod bearing I think. When it is parked the description of my sound seems to be identical to what Doug described. The only concern I have now is when I hear it under hard accelleration from 3K to 4K RPMs (Specifically after it downshifts when I'm trying to accellerate up a grade. (I first noticed it at about 4K feet and higher, but I haven't had the opportunity to try it at a lower altitude than that.)

Of course when the truck is moving there are lots of other sounds to clutter the noise I'm listening to, like wind, so what I'm hearing under high rpm accelleration may be something slightly different than what I am able to induce when it is parked.

I need to double check the timing this weekend. I don't know if the computer will let it get so out of what that it could be predetonation, but I need to eliminate that I suppose.

Doug, the pinging sound you have when switching from dropping to rising rpms, are you able to induce the pinging sounds best when stabbing the throttle as the engine switches from dropping for the first couple hundred RPMs of increase (maybe 10 or 20 quick pings) or is it only 1 or 2?

Also, I'll be sure to change out and filter the oil to check for anything visible. (Seems like a waste to dump 7 quarts of Mobil 1 0-40W, I did a quick dino oil and filter change 20 miles after the head gasket, but I guess it's cheaper than driving around in ignorance tearing up stuff if there is a problem). Then I'll have the oil analysis done.