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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #1
Good Morning,

I am staying up late looking for information regarding an engine noise on my 1996 Toyota Tacoma 2RZ-FE with manual transmission.

I bought the vehicle about a month ago with only 63,000 miles. According to the CarFax report it was driven normally for the first 3-4 years and then must have sat a lot.
When I received it, it was freshly tuned up, had new belts, plugs, wires. It still needed new tires (dry rot), shocks, all fluids changed, etc., basically all routine maintenance appeared to have been more or less neglected.

Now to the noise:
At idle fully warmed up, it sounds like a diesel engine. It's not a ticking like a valve and it's not a pinging like ignition. It's a typical diesel chatter sound but quieter, somewhere between a knock and a rattle. An engine stethescope pinpoints it to the bell housing of the manual transmission, but it could be the rear lower part of the engine as well.

When the RPM's are increased slightly, the knock seems to go away.
The engine runs great, no smoke, gas mileage is perfect, plenty of power... The oil was changed recently after a 1500 mile trip at relatively high speed (80-85) and although I wasn't specifically looking for shavings, did not see any and the end of the drain plug was clean.

I would really appreciate some help from you guys. I have read a lot of posts but it doesn't seem to be a rod knock (not loud enough), but nothing seems to be particularly encouraging...

THANKS!!! :)
 

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750 Posts
It could be a fuel supply problem. If you didn't change the filter during the tune-up, it is probably due. The injectors may require a cleaning as well. Try a fuel additive first. Gumming up, from sitting around, can often cause this.
 

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2000 Tacoma 4x4
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28 Posts
Does the noise persist when you depress the clutch? Some of these manual trans' have sloppy clearances and they tend to make some noise when the clutch is engaged (clutch pedal out). It's not a problem, just a characteristic of the trans. Also your throw out bearing could be making the noise. Make sure your clutch is properly adjusted.



chipsndukes said:
Good Morning,

I am staying up late looking for information regarding an engine noise on my 1996 Toyota Tacoma 2RZ-FE with manual transmission.

I bought the vehicle about a month ago with only 63,000 miles. According to the CarFax report it was driven normally for the first 3-4 years and then must have sat a lot.
When I received it, it was freshly tuned up, had new belts, plugs, wires. It still needed new tires (dry rot), shocks, all fluids changed, etc., basically all routine maintenance appeared to have been more or less neglected.

Now to the noise:
At idle fully warmed up, it sounds like a diesel engine. It's not a ticking like a valve and it's not a pinging like ignition. It's a typical diesel chatter sound but quieter, somewhere between a knock and a rattle. An engine stethescope pinpoints it to the bell housing of the manual transmission, but it could be the rear lower part of the engine as well.

When the RPM's are increased slightly, the knock seems to go away.
The engine runs great, no smoke, gas mileage is perfect, plenty of power... The oil was changed recently after a 1500 mile trip at relatively high speed (80-85) and although I wasn't specifically looking for shavings, did not see any and the end of the drain plug was clean.

I would really appreciate some help from you guys. I have read a lot of posts but it doesn't seem to be a rod knock (not loud enough), but nothing seems to be particularly encouraging...

THANKS!!! :)
 

·
Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #4
Good morning karazy and jeffmazz, thanks for the suggestions:

I changed the fuel filter during the tune-up, it looked original. The fuel that spilled out of the inlet side was cloudy and brown. :eek:

Is there a way to check out the fuel injector theory, maybe pulling a spark plug wire, looking at a plug?
What additive would you all recommend, I used to use Techron but that was a long time ago.

I like the clutch idea because when I first got the truck, the throwout bearing was squeaking at idle with the clutch out, like the release fork was grazing it. Slight touch to the clutch pedal and the noise stopped, but it hasn't done that for a while. I honestly haven't messed with the pedal adjustment.
Pushing the clutch in or releasing it doesn't seem make a difference, I thought maybe the throwout bearing was "stuck on" and was destroying itself, the sound is really loud just underneath the front of the bell housing, maybe it's echoing from the bell and is in reality the engine, don't know. If you idle the truck down the street in first gear with the clutch out, the noise is still there, in fact it does kind of sound like detonation.
Either way, if you raise the engine speed a little bit, the sound seems to almost completely disappear. I'm surprised at how low the truck idles, I know spec. is 650, I need to check it with an engine tach that I have, will do that still today. I think it may be even lower than that. For example when the A/C compressor turns on (yes, it's supposed to be 85F today), the noise disappears, idles bumps up to about 300 RPM would say. I will check this and write back.

Also thought there may be an oil pressure/sludge problem from sitting. Oil pressure indicator light works and is not on, bought a $6 tiny oil pressure gauge off e-bay reads somewhere about 1/3 between 0-25PSI for what it's worth.

Thanks for your suggestions, seems like there's some progress... :)
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #5
OK, I went back to the engine with the stethescope and a little logic.

I can definitely rule out the injector theory. With the stethoscope directly on the injector and the cylinder head next to the injector there was no evidence of the diesel knocking sound, only the sewing machine sound of the valves and the steady tap-tap-tap of the injector opening and closing.

And now, and unfortunately, I can rule out the clutch. I opened up the little boot where the fork enters the transmission and listened with my ear, only whirring of the clutch assembly, no diesel knock. Yes, on the bell housing the diesel tapping sound is loud, but I found a place where it is even louder--directly on the bottom back of the oil pan.
And to me and unfortunately that can only mean one thing, that a main bearing/bearings is going bad.
I put the stethescope (is a rod type) carefully along the length of the mating surface between the oil pan and the block from front to back. The diesel knocking noise is audible along this line from front to back, suppose it is more audible in the back on the bottom of the pan because the it is closer to the bearings, there is also not 3-4 inches of oil to muffle the sound.

I have never heard a main bearing sound before, can only guess by elimination and where the noise is coming from that that is what it is.

The truck sounds like a diesel at idle, oh yes, and I increased the idle speed to about 1500 RPM with a carefully placed screwdriver and the noise is still the same from the oil pan, in fact louder, just that it was muffled by fan noise, accessory drive noise, etc., before, made it seem only like it went away, in fact was just drowned out.

So do I have a bad main bearing/bearings?

What would cause that problem?

If I pulled the crankshaft, had it machined and reinstalled oversized bearings, would that fix the problem, or would it happen again because somewhere an oil passage is plugged?

HELP!!!

Thanks guys, I am just a little worried now. I hope this little engine can be saved, I really like this truck, it's in perfect shape otherwise.

Chipsndukes
 

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2000 Tacoma 4x4
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28 Posts
Very Very Very Very unlikely that it is a bad main bearing!!! First of all you would have very low oil pressure if it were a main bearing. Second of all they rarely fail.

You have a pilot bearing in the end of the crankshaft that the input shaft of the trans slides into. This is usually replaced along with the clutch when the time comes but many people fail to replace it. It is a roller type bearing so it could very well be the source of your noise. Unfortunately you need to pull the trans to check/replace it.

This noise could also be coming from the oil pump. How about the timing chain and related components even though the sound seems to be coming from the rear of the motor. It could resonate from front to rear. Just a thought.

I would look real hard at that pilot bearing. But before doing that I would make sure that throw out bearing isn't the true culprit. Adjust your clutch and make sure the throw out bearing isn't spinning with the clutch pedal at rest. I know you mentioned you didn't hear anything when you removed the rubber boot....I have seen stranger things.

Jeff
chipsndukes said:
OK, I went back to the engine with the stethescope and a little logic.

I can definitely rule out the injector theory. With the stethoscope directly on the injector and the cylinder head next to the injector there was no evidence of the diesel knocking sound, only the sewing machine sound of the valves and the steady tap-tap-tap of the injector opening and closing.

And now, and unfortunately, I can rule out the clutch. I opened up the little boot where the fork enters the transmission and listened with my ear, only whirring of the clutch assembly, no diesel knock. Yes, on the bell housing the diesel tapping sound is loud, but I found a place where it is even louder--directly on the bottom back of the oil pan.
And to me and unfortunately that can only mean one thing, that a main bearing/bearings is going bad.
I put the stethescope (is a rod type) carefully along the length of the mating surface between the oil pan and the block from front to back. The diesel knocking noise is audible along this line from front to back, suppose it is more audible in the back on the bottom of the pan because the it is closer to the bearings, there is also not 3-4 inches of oil to muffle the sound.

I have never heard a main bearing sound before, can only guess by elimination and where the noise is coming from that that is what it is.

The truck sounds like a diesel at idle, oh yes, and I increased the idle speed to about 1500 RPM with a carefully placed screwdriver and the noise is still the same from the oil pan, in fact louder, just that it was muffled by fan noise, accessory drive noise, etc., before, made it seem only like it went away, in fact was just drowned out.

So do I have a bad main bearing/bearings?

What would cause that problem?

If I pulled the crankshaft, had it machined and reinstalled oversized bearings, would that fix the problem, or would it happen again because somewhere an oil passage is plugged?

HELP!!!

Thanks guys, I am just a little worried now. I hope this little engine can be saved, I really like this truck, it's in perfect shape otherwise.

Chipsndukes
 

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2000 Tacoma 4x4
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28 Posts
I just noticed you only have 63,000 miles on this truck. It is unlikely, although not impossible, that this noise is coming from any major component failure ie. bearings, oil pump, etc. at that mileage. Throwout bearing is a definite suspect due to the fact that the previous owner may not have driven the thing correctly.....riding the clutch and sitting at lights with the clutch to the floor will ruin a good TO bearing in fairly short order. The pilot bearing as I mentioned before or maybe the clutch assy. itself are possibilities but unlikely.

Adjust the clutch as mentioned in my last post.... make sure the TO bearing is not spinning with the clutch pedal at rest. At least this will eliminate the TO bearing as the source and this is the easiest step to take in your quest to find a solution.

Good Luck,
Jeff
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #8
Thanks Jeff.

I'll have a week to think about it, in fact I also thought (hoped) it would be the clutch/throwout/pilot, anything but serious engine damage, the truck seems to run perfect otherwise...
When I get back from my trip next weekend (maybe in two weeks) I will start working on pulling the clutch and then write back.
Really don't think it's an oil pressure problem, but don't know these engines well enough to aay (it's a Toyota, what could go wrong, right?).
I will throw in a pint of fuel injector cleaner as well, always a good idea. A quick search of this site should come up with a good brand to use, just in case, anybody have any recommendations straight off?
Never had this sound before on any cars, but I swear, it sounds like a diesel, knocking, chatter at idle, but when the engine speeds up, the noise is pretty much drowned out, would say more like a quiet diesel.
Hopefully I'm exagerrating and will find another cause...

Either way thanks to all. All other opinions/comfort are welcome, will get back to all after I get a chance to get into it.

Thanks again, have a good week.
Chipndukes
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #9
Jeff, just saw your post, thanks.

Will do, when I get back in a week. It's an easy adjustment, although I did try manually pushing back on the fork while under the car. I pushed the slave cylinder back in the bore and then quickly pressed on the fork towards the front of the car, no luck. Still dieseling, but I haven't lost hope.
I know that the previous owner was very heavy, the seat was collapsed and the back rest was broken at the supporting tube on the bottom (bench seat). Maybe he had a heavy foot resting on the clutch, could be.
The reason I think maybe main bearing is because the CarFax history of the truck shows the first about 33000 miles driven in 3 years, the remaining 30000 in 7 years, not a lot of use, and the maintenance, at least for the last while appeared to be totally neglected. In fact, to my knowledge (I'd guess I'm right on this one), the only things that were changed were the front brake pads, battery and the tires. The windshield is all hazed from using wipers way past their expiration date. I think the guy thought that it was a turn the key and go car, but every car needs oil, even Toyotas.
Either way, the clutch will get done, if nothing else just to see the throwout bearing and to know that it's taken care of.
After that we'll see if there's a change.

Is replacing the main bearings a big deal? Have read a lot about it, doesn't look too bad, but it could be worse than i think?

Thanks again.
 

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2000 Tacoma 4x4
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Replacing the main bearings would require you removing the engine and totally disassembling it. It is a major undertaking. If you have the tools and experience in rebuilding engines it is certainly do-able. I just don't think you need to do it. As I said before it is very unlikely that the main bearings are bad even if maintenence was neglected (to a point). One way to see if the oil wasn't changed on a regular basis is to pull the valve cover and see what it looks like inside. If it is packed with sludge then you know the oil wasn't changed and you might have problems. If it looks clean under the cover than you will most likely be wasting your time looking at main bearings as a source of your problem. It is very difficult, if not impossible, to diagnose something like this without actually being there to hear the noise in person. Before spending any money (especially big $$$$) I would take it to a good dealer and get their opinion as to what this noise may be. This could save you a lot of time and $$$$.

chipsndukes said:
Jeff, just saw your post, thanks.

Will do, when I get back in a week. It's an easy adjustment, although I did try manually pushing back on the fork while under the car. I pushed the slave cylinder back in the bore and then quickly pressed on the fork towards the front of the car, no luck. Still dieseling, but I haven't lost hope.
I know that the previous owner was very heavy, the seat was collapsed and the back rest was broken at the supporting tube on the bottom (bench seat). Maybe he had a heavy foot resting on the clutch, could be.
The reason I think maybe main bearing is because the CarFax history of the truck shows the first about 33000 miles driven in 3 years, the remaining 30000 in 7 years, not a lot of use, and the maintenance, at least for the last while appeared to be totally neglected. In fact, to my knowledge (I'd guess I'm right on this one), the only things that were changed were the front brake pads, battery and the tires. The windshield is all hazed from using wipers way past their expiration date. I think the guy thought that it was a turn the key and go car, but every car needs oil, even Toyotas.
Either way, the clutch will get done, if nothing else just to see the throwout bearing and to know that it's taken care of.
After that we'll see if there's a change.

Is replacing the main bearings a big deal? Have read a lot about it, doesn't look too bad, but it could be worse than i think?

Thanks again.
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #11
back from trip, good tip Jeff.
I will take it to the dealership and have it listened to. You're right, I could spend a lot of time talking about it and at the end it's something they can easily diagnose for me. Now I hope that the (only) dealership in this area is any good, I don't have any experience with them.

Thanks again!!!
 

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/

"What additive would you all recommend, I used to use Techron but that was a long time ago."


I'm a fan of the Barryman's B-12

good stuff...IMHO
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #13
Thanks Andyf80 for the tip on the fuel injection cleaner, any response is appreciated.
I'll keep an eye out for Barryman's B-12.

Today I took the truck to the Toyota dealership. The assistant service manager went with me to listen to the truck at idle, agreed that it was making a noise and that it came from underneath the truck, said they would have to pull the oil pan to tell me what it is, though.

For now I think I am going to keep driving it as is. The noise itself is not loud, even though it is very distinctive. As the service person from Toyota and I approached the truck to listen to it, it definitely sounds like the light knocking of a diesel engine, sound is in fact coming from underneath the engine.

Thanks to all who have replied, I will keep you posted on any new developments.
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #14
I pulled the clutch, the throwout bearing was bad, made most of the noise, but the engine is still knocking slightly.
I plan on pulling the engine next and doing an overhaul, will have to download the manuals from techinfo.com, Haynes is not detailed enough.

Now the throwout bearing scrapes slightly when the engine is at idle. Moving the fork by hand towards the front (away from engagement direction) stops the scraping. I think this is why the first throwout bearing went bad in the first place, was always engaged/scraping on the pressure plate. The fingers of the old plate were all scraped up...

If anyone has an idea on why the throwout bearing is touching the pressure plate fingers when the clutch pedal is up, I would appreciate knowing. I plan on rebuilding the slave cylinder and bleeding it well, it seems to creep forward and apply ever so slightly pressure to the fork, pushing the throwout bearing ever so slightly into the pressure plate fingers. Doesn't quite spin, more scrapes and spins....

Thanks!
Chipsndukes
 

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Before you pull the engine put a stethoscope on the front timing cover.You could have a bad tensioner, loose chain or those stupid plastic chain guides could be worn.Check your oil press with a mechanical gauge also.I wouldnt be so fast about pulling the engine with that little miles on it.Check you engine mounts if they are loose or the rubber is dry rotted could be letting the engine move just enough to smack something causing your knocking sound.Its one of the better engines toyota made.I put over 200,000 on one with nothing major replaced.Up to you.
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #16
Thanks rugerm44.

I put the stethoscope everywhere possible--timing cover, valve cover, exhaust manifold, all bearings and moving parts (belt tensioners, A/C compressor, alternator...) and nowhere else is this diesel like knocking to be heard.
It is especially loud/noticeable when the engine is hot and at the very lowest idle, barely running (600 rpm). Most people would probably laugh when they here it, but I have a sensitive ear and I know it is not normal.
Putting the stethoscope square on the back of the oil pan where it is thinnest is where I can here the ticking/knocking on the stethoscope and at the same time with the naked ear correspond it to the knocking sound I am hearing when I stand next to the vehicle.
It sounds like a little diesel engine and is driving me crazy.

My theory is that the old owner ran it low on oil and damaged a rod bearing, now it is loose.

My next step was to do some diagnostics like pulling each spark plug wire off and see if I could isolate the sound to any particular cylinder.
In my humble opinion it is definitely lower engine and it is definitely some kind of knock, like a diesel engine rattles.

Any ideas?
 

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Dose the engine use oil?I hate to say it but it may very well be a main bearing,rod bearing or piston pin.Like you said yank a spark plug wire and see if it quits or quiets down a bit.I had a tundra witha bad number one main bearing with just 13,000 miles on it.I ran synthetic oil in it and drove it easy since day one.It was noisy right where the oil pan meets the block.
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #18
yeah, I kind of think so too, but it's not so tragic.
I've never rebuilt or torn down an engine before, Harbor freight has a sale on engine hoists and stands, I'll have to go tomorrow.
Oh yeah, and I have the manuals downloaded from the Toyota website and my Ford Ranger (sorry) will get me to work until things are back together.

No, there is no oil usage whatsover. I think maybe one drop in 3000 miles, really, the quantity doesn't even move on the dipstick between changes.

Would you recommend any particular place to get engine parts (cheap and good) for the Toyota? I was tipped off to engnbldr.com, seems like a good outfit.
I think only a gasket set with bearings will be necessary depending on what I find when I tear the engine down.

thanks again rugerm44.

Duane
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #19
the scraping noise in the clutch was fixed temporarily by rebuilding and bleeding the clutch slave cylinder. I don't know if the problem will come back but will report further.

The old cylinder I think was more slippery in the bore/pushed out more and caused the fork to drive the face of the throwout bearing ever so slightly into the pressure plate fingers causing a scraping noise (very slight but audible) when the TO bearing was brushing up against them. The bearing didn't actually turn (who knows), more just scraped.
Pushing the clutch pedal all the way in where the TO bearing could spin, noise was eliminated.

So for now it is OK, a tip for anyone else out there who may have experienced this, maybe this helps you.

BTW the engine will probably wait until the fall until the sun stops shining so hard and the temperatures go down. It is 98+ every day in South Texas. You can only work until about 12PM and then after 8PM. It's really even dangerous, you can get heat stroke. October, November things will cool down into the 80's, hope the engine holds till then, there is definitely a noise there, am thinking rod bearing.
 

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Hmmm...
1996 Tacoma
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544 Posts
Discussion Starter #20
FWIW I finally got around to diagnosing and repairing the problem--TIMING CHAIN

Rattles transmit throughout the engine, just because the noise was loudest at the back of the pan with a stethoscope, doesn't mean it didn't come from the front.

So...FWIW, it was the timing chain.

Thanks to all and this great community!!!!

Chipsndukes
 
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