Please advise…Timing belt tensioner go bang. (4 Viewers)

[JungleMunkee]

Yesterday cylinder 1 got 86/100. That was lower than the rest so I rechecked it today after finishing alol the cylinders and it’s way worse now. I smell fuel by the engine but that’s near the fuel filter but also smell it from exhaust pipe. No hissing from exhaust tip though. Hissing noise is coming from the cylinder area. I’m thinking all that crud near valve is the culprit. It’s noticeably drier in #1 than the rest and there’s a bubbled up spot on the piston face.

 

[JungleMunkee]

I think it is leaking through the exhaust valve. Must have dried overnight and leaks more now. Sounds like it is hissing from the exhaust manifold below the spark plug hole and I can feel air coming from cylinder 3. Cylinder 3 tested fine at 94/100. If cylinder 3 has valves open when #1 is closed, it could come in through the exhaust manifold.

 

[Nardulli]

That’s a lot of ring wash - and that one cylinder makes me think valve seals. You seem to Know your way around an engine, why not pull it, tear it down, and check tolerances? Send it out to be baked and cleaned, honed, and reassemble - it might be the only way to ensure you’ve got to the root cause.

 

[2001LC]

It's likely tensioner bolts where not torque to 25ft-lbf. Likely loose, and over time vibration weaken the bolts.

I also see a lot of oil. This may be from tension pulley bolt. Those thread need sealing. If not sealed, we get an oil leak.
Additionally, a large thick spacer, goes on tension bolt. Between tensioner pulley housing and oil pump .

Check timing marks. Are they dead on?

The one piston top, looks a bit to clean. Which could be sign of coolant steam cleaning. Coolant/water in cylinder, cleans out all carbon.

One valve need closer look.

If borescope of cylinder walls okay, and No burnt/cracked valves. I re-due time belt service. See how it runs.

 

[2001LC]

I just notice, the clean piston top. Has what looks like a rough shaped hole in center. Could be a sign of pre ignition.

Pre-ignition is the premature ignition of the air-fuel mixture in an internal combustion engine, caused by a hot spot in the cylinder, such as an overheated spark plug or carbon deposit, rather than the timed spark. This event occurs before the proper moment for combustion and can lead to severe engine damage by creating extreme cylinder pressures that work against the piston's upward movement. Symptoms can include loud engine knocking, loss of power, and rough engine operation, with causes ranging from hot spark plugs and glowing carbon deposits to engine overheating and low-octane fuel.

Pre-ignition vs. detonation
While both are abnormal combustion events that can cause engine knock, they are distinct phenomena with different causes and effects.

[th]

Feature​

[/th][th]

Pre-ignition​

[/th][th]

Detonation (Engine Knock)​

[/th]​

[td]When it occurs[/td][td]Before the timed spark event, when the piston is still compressing the air-fuel mixture.[/td][td]After the normal spark event, when pockets of unburned fuel explode rather than burn smoothly.[/td] [td]Causes[/td][td]A hot spot in the combustion chamber ignites the fuel. Common sources include:
• Glowing carbon deposits
• An overheated spark plug
• A burned or glowing exhaust valve[/td][td]Anything that makes the last part of the fuel-air charge ignite spontaneously, such as:
• Low octane fuel
• Over-advanced ignition timing
• High engine temperatures
• High-pressure turbocharged engines[/td] [td]Damage[/td][td]More severe and instantaneous. The extreme pressure and heat can melt holes in the piston and electrodes off the spark plugs.[/td][td]Can cause sandblasted-looking pistons and bearing damage over time, but is less immediately catastrophic than pre-ignition.[/td]

 

[JungleMunkee]

I just notice, the clean piston top. Has what looks like a rough shaped hole in center. Could be a sign of pre ignition.

Pre-ignition is the premature ignition of the air-fuel mixture in an internal combustion engine, caused by a hot spot in the cylinder, such as an overheated spark plug or carbon deposit, rather than the timed spark. This event occurs before the proper moment for combustion and can lead to severe engine damage by creating extreme cylinder pressures that work against the piston's upward movement. Symptoms can include loud engine knocking, loss of power, and rough engine operation, with causes ranging from hot spark plugs and glowing carbon deposits to engine overheating and low-octane fuel.

Pre-ignition vs. detonation
While both are abnormal combustion events that can cause engine knock, they are distinct phenomena with different causes and effects.

[th]
Feature

[/th][th]
Pre-ignition

[/th][th]
Detonation (Engine Knock)

[/th]​

[td]When it occurs[/td][td]Before the timed spark event, when the piston is still compressing the air-fuel mixture.[/td][td]After the normal spark event, when pockets of unburned fuel explode rather than burn smoothly.[/td] [td]Causes[/td][td]A hot spot in the combustion chamber ignites the fuel. Common sources include:
• Glowing carbon deposits
• An overheated spark plug
• A burned or glowing exhaust valve[/td][td]Anything that makes the last part of the fuel-air charge ignite spontaneously, such as:
• Low octane fuel
• Over-advanced ignition timing
• High engine temperatures
• High-pressure turbocharged engines[/td] [td]Damage[/td][td]More severe and instantaneous. The extreme pressure and heat can melt holes in the piston and electrodes off the spark plugs.[/td][td]Can cause sandblasted-looking pistons and bearing damage over time, but is less immediately catastrophic than pre-ignition.[/td]

Ok so a glowing exhaust valve could have caused the preignition “rod knock” the mechanic heard. Burnt carbon deposits around/on exhaust valve and the cleaned and dry cylinder from possible coolant wash combined with leaky valve seals. Could that have kicked the belt hard enough to jostle the tensioner that was possibly missing a spacer and break the bolts off caused the timing belt to slip? #6 Spark plug just happened to be loose as separate issue? I need a board with red line indicating the sequence of events to solve this mystery like Sherlock Holmes. Should I just stop now and get another engine, eventually? I don’t really want to do all this just to end up at the same place I started.

 

[JungleMunkee]

It's likely tensioner bolts where not torque to 25ft-lbf. Likely loose, and over time vibration weaken the bolts.

I also see a lot of oil. This may be from tension pulley bolt. Those thread need sealing. If not sealed, we get an oil leak.
Additionally, a large thick spacer, goes on tension bolt. Between tensioner pulley housing and oil pump .

Check timing marks. Are they dead on?

The one piston top, looks a bit to clean. Which could be sign of coolant steam cleaning. Coolant/water in cylinder, cleans out all carbon.

One valve need closer look.

If borescope of cylinder walls okay, and No burnt/cracked valves. I re-due time belt service. See how it runs.

I just confirmed there was a large washer/spacer on the back of tensioner pulley. I don’t think I used any thread sealer on the bolt so that checks out for the oil.

No, the timing wasn’t on.

All the walls look similar with good cross hatch and no vertical scoring. A lot of oil and build up inside. Tiny bit of rust on 2 of the walls, I think.

I don’t think there are any cracked valves. One of the exhaust valves for cylinder 1 has a bunch of white and black carbon at the edge of seat and on the rim of valve but unsure if it’s a chip on the edge also. Is that considered burned?

 

[JungleMunkee]

That’s a lot of ring wash - and that one cylinder makes me think valve seals. You seem to Know your way around an engine, why not pull it, tear it down, and check tolerances? Send it out to be baked and cleaned, honed, and reassemble - it might be the only way to ensure you’ve got to the root cause.

lol fooled you. This the first time messing with an engine. Money is a little tight for all that but it is an option. From what I gathered that would cost just as much or more as another engine. Thank goodness for mud members, YouTube, and FSM for getting me this far.

 

[nissanh]

Which picture shows the valve you are talking about?

Why not throw a new timing belt kit, set timing and run until you come across a good used engine? If you waste any money that will be the kit. An Aisin kit is like $300. I know we live in the USA, but in 3rd world nations, they run these 100's almost everywhere and their maintenance is 1/100 of ours.

The 2UZFE got knock sensors which can a advance or retard timing if pre ignition occurs. If in doubt, roll the window down, with AC on check sudden accelerations... Pre-ignition occurs with a heavy load after like 3000 rpm. I am dealing with it in my 4afe Prizm which got no knock sensors. It ruined the head gasket making a hole between cylinders 3 and 4. Now, I pump 93 octane and the frequency of occurrence is quite less.

 

[JungleMunkee]

Which picture shows the valve you are talking about?

Why not throw a new timing belt kit, set timing and run until you come across a good used engine? If you waste any money that will be the kit. An Aisin kit is like $300. I know we live in the USA, but in 3rd world nations, they run these 100's almost everywhere and their maintenance is 1/100 of ours.

The 2UZFE got knock sensors which can a advance or retard timing if pre ignition occurs. If in doubt, roll the window down, with AC on check sudden accelerations... Pre-ignition occurs with a heavy load after like 3000 rpm. I am dealing with it in my 4afe Prizm which got no knock sensors. It ruined the head gasket making a hole between cylinders 3 and 4. Now, I pump 93 octane and the frequency of occurrence is quite less.

Sorry I couldn’t get good focus. I already have the new kit. I was just trying to verify no damage with bore scope and leak test. Also just piqued my interest once I started. I’m not sure I can just let this stuff go, though. I think it would bother me knowing there’s problems. Plus the mechanic said he heard rod knock, so I’m trying to see what that’s about. I already have another vehicle now but registration is due on this or I have to turn in the plates (NC).

 

[Bisho]

View attachment 4008669View attachment 4008670View attachment 4008671
Sorry I couldn’t get good focus. I already have the new kit. I was just trying to verify no damage with bore scope and leak test. Also just piqued my interest once I started. I’m not sure I can just let this stuff go, though. I think it would bother me knowing there’s problems. Plus the mechanic said he heard rod knock, so I’m trying to see what that’s about. I already have another vehicle now but registration is due on this or I have to turn in the plates (NC).

Whatever the mechanic said means nothing knowing it was running with jumped timing belt. I recommend not to over think it. Get the new kit on there and see how it runs. I’ll bet it will be just fine. When you start down this rabbit hole, you’re not only opening your wallet, but risking you break something else and create more issues. If fixing the belt doesn’t result in a smooth running 2UZ, you can dive down the hole.

I’d also replace the fan bracket if you didn’t the last time.

 

[3_puppies]

Yeah I pressed firmly on the concrete and it didn’t budge. I’ll see how much force it takes today. I think the kit said 100 lbs or so but I don’t have it in front of me, right now.

being it was an aftermarket kit, I was wondering if for some reason the spring tensioner seized up and won't move then all the forces were applied to the bolts versus the spring taking the movement, thus breaking the bolts.

just a theory of mine

not really sure how much movement there is when it is running????

 

[2001LC]

Blurry, but looks like a V notch, in valve.
Different patterns in area around head gasket. Unsure if lower area, cylinder wall or piston top.

I'd pressurize coolant system, to about 17PSI. Inspect each cylinder for drips of coolant. Best done in cold engine.
Leak-down test on each cylinder. Best done with engine at op temp. But it and compression test, can be done in cold engine. Comparing cylinders, which should be within about 10% of each other.