timing belt broke

[MrMoon]

Any idea when the last time the belt was changed?

I doubt it went 275 on an original belt, it was likely swapped out once if not twice already.

 

[waterrunner]

Timing

So here is my related issue, I was changing my timing belt on my 99 and during the course of getting the new belt on (so much tighter than the one I did on my old Frontier), the left cam (passenger side) turned 1/3 of a turn. Didn't panic, just called a buddy who has rebuilt a few engines in his day. He just told me to turn the cam back to where the mark was realigned. Turned it back to TDC, since putting it back together it has run fine except for going up hills. There is some hesitation and power loss. What is the best course of action for determining if my timing is a hair off in the pre or post ignition? I want to do things right and screwing up is part of learning, especially when you don't have mentors. Can anyone give me an idea on this without a "take it to a mechanic" as that really doesn't teach me anything in the long run.:noidea:

 

[4everun22]

I went 201k miles before I did mine. Could have went 100k more it didn't look bad. It's hard to break one els something causes it they are pretty durable.

 

[SpidermanGeek]

275,000 miles. No way I'm changing it at 90k intervals now. Glad things worked out!

Yeah, my Timing Belt has 115K miles on it (was replaced at 66K). Coupled with the fact that other than needing a tow if it snaps (yay non-interference!), I'm in no real rush to do this maintenance again. I'd rather wait a little longer and change everything out when I get in there anyway (water pump, tensioner pulley, etc. etc.)

 

[Rock_Rat]

So here is my related issue, I was changing my timing belt on my 99 and during the course of getting the new belt on (so much tighter than the one I did on my old Frontier), the left cam (passenger side) turned 1/3 of a turn. Didn't panic, just called a buddy who has rebuilt a few engines in his day. He just told me to turn the cam back to where the mark was realigned. Turned it back to TDC, since putting it back together it has run fine except for going up hills. There is some hesitation and power loss. What is the best course of action for determining if my timing is a hair off in the pre or post ignition? I want to do things right and screwing up is part of learning, especially when you don't have mentors. Can anyone give me an idea on this without a "take it to a mechanic" as that really doesn't teach me anything in the long run.:noidea:

If you installed it correctly you would have lined up the marks on your cam gears exactly with the arrows on the belt with your harmonic balancer pulley at tdc. When complete, with the tensioner pin pulled you would have hand rotated the pulley at least one to two revolutions.

When you brought it around to tdc again the belt would have been off by one tooth to the right (facing the front of the vehicle) on each cam gear. If you did that you're timing should be spot on.

EDIT: Are you hearing any pinging or knocking at higher RPMs? Are you monitoring your TPS to see if your timing is advancing/retarding as needed? What year? Have you disconnected and reconnected your negative terminal.

 

[TheDurk]

So here is my related issue, I was changing my timing belt on my 99 and during the course of getting the new belt on (so much tighter than the one I did on my old Frontier), the left cam (passenger side) turned 1/3 of a turn. Didn't panic, just called a buddy who has rebuilt a few engines in his day. He just told me to turn the cam back to where the mark was realigned. Turned it back to TDC, since putting it back together it has run fine except for going up hills. There is some hesitation and power loss. What is the best course of action for determining if my timing is a hair off in the pre or post ignition? I want to do things right and screwing up is part of learning, especially when you don't have mentors. Can anyone give me an idea on this without a "take it to a mechanic" as that really doesn't teach me anything in the long run.:noidea:

First, you need to realize that the timing belt has nothing to do with ignition timing. That is set by the ECU and varies continuously as various sensor inputs change.

Second, if you want to verify your VALVE timing, which IS controlled by the timing belt, you can do that. First, use a wrench on the crank bolt to rotate the crank and set the pointer on the crank pulley to 0° (TDC). Loosen the clamp ring on the top radiator hose and slide it forward. Remove the bolts from the top timing cover and pull it forward so that you can see the cam pulleys. Verify that the marks on the cam pulleys are at top center lined up with the marks on the block. If the pulley marks are at 6 o'clock, turn the crank another 360°. Disregard any marks on the belt itself.

 

[98OzarksRunner]

I went 201k miles before I did mine. Could have went 100k more it didn't look bad. It's hard to break one els something causes it they are pretty durable.

I helped a friend change one in a 4th gen a while back. It had 180K on the original belt and it looked good, and you could still read the labels. I think Toyota says change them at their 'half-life' just to be safe.

 

[jhfleet]

First, you need to realize that the timing belt has nothing to do with ignition timing. That is set by the ECU and varies continuously as various sensor inputs change.

Second, if you want to verify your VALVE timing, which IS controlled by the timing belt, you can do that. First, use a wrench on the crank bolt to rotate the crank and set the pointer on the crank pulley to 0° (TDC). Loosen the clamp ring on the top radiator hose and slide it forward. Remove the bolts from the top timing cover and pull it forward so that you can see the cam pulleys. Verify that the marks on the cam pulleys are at top center lined up with the marks on the block. Disregard any marks on the belt itself.

You might want to mention that the camshaft timing marks only line up every other time the crankshaft pulley marker is at TDC.

 

[TheDurk]

You might want to mention that the camshaft timing marks only line up every other time the crankshaft pulley marker is at TDC.

Good point. Done.

 

[Joe Z]

Second, if you want to verify your VALVE timing, which IS controlled by the timing belt, you can do that. First, use a wrench on the crank bolt to rotate the crank and set the pointer on the crank pulley to 0° (TDC). Loosen the clamp ring on the top radiator hose and slide it forward. Remove the bolts from the top timing cover and pull it forward so that you can see the cam pulleys. Verify that the marks on the cam pulleys are at top center lined up with the marks on the block. If the pulley marks are at 6 o'clock, turn the crank another 360°. Disregard any marks on the belt itself.

Now that is a good piece of information as the guy i bought my 4Runner from wasn't exactly sure when it was changed and just said 100k I now have 170k on the engine and to get a peak down in there would be a big help.
Thank you so much

 

[stir_fry_boy]

I honestly don't think anyone can determine the age of a timing belt just by looking at it. If it's fraying or cracking, then replace it.

Keep in mind that if you do break a timing belt, you loose power steering and power brakes. I changed mine 5,000 miles early because the idlers were making quite a bit of noise.

Ive seen VW timing belts break before the recommended replacement interval, those have an interference motor. Good thing I've never seen that on a Toyota or Honda.

 

[nobb]

I really think these OEM parts have a huge safety factor to them. I did a full change out of my belt, idlers, water pump, and all associated parts (of which the previous owner used OEM) at 150,000 kms (100,000 miles) since the last change. The belt still looked like new and all the idlers felt smooth.

On my previous 4Runner when I bought it, there was roughly the same amount mileage since the last belt change, but the parts were not OEM and you could see the belt rubber completely splitting such that the belt was almost all held only by the threads. The idlers were also starting to get rough. Everything still was functioning though.

Also an interesting note, the camshaft and crankshaft have different ratios so the initial line up of the timing belt marks are for install only. Once you've rotated, they won't line up anymore relative to the pulleys. It's important to do a few test rotations to make sure the actual markings of the cam and crank still line up with TDC.

 

[WallyWest]

Gotta do mine soon, got a loud squeal for the first 30 seconds or so when I fire it up, and a slow coolant leak probably from the water pump. The belt itself looks fine. 162k miles, belt and pump have never been done.

Good info in here, I'll be referring back to those videos.

 

[Joe Z]

Also an interesting note, the camshaft and crankshaft have different ratios so the initial line up of the timing belt marks are for install only. Once you've rotated, they won't line up anymore relative to the pulleys. It's important to do a few test rotations to make sure the actual markings of the cam and crank still line up with TDC.

Question: So after a few revolutions the timing marks on the 2 cams will not be lines up in relation to the crankshaft marking?
Or is it every other revolution they will line up?

 

[turbo8]

Question: So after a few revolutions the timing marks on the 2 cams will not be lines up in relation to the crankshaft marking?
Or is it every other revolution they will line up?

the timing marks should always line up, but the lines on the timing belt won't line up.

 

[Joe Z]

the timing marks should always line up, but the lines on the timing belt won't line up.

That makes plenty of sense.....
Thanks

 

[TheDurk]

That makes plenty of sense.....
Thanks

Well, actually it IS every other revolution of the crank. On the second turn of the crank the cam marks will be at 6 o'clock and then come back to 12 on the following turn. Then 6, then 12, and so on. The crank turns twice for every single turn of the camshafts. The belt marks will realign eventually, but only after a ridiculously large number of turns, and then only once until another ridiculously large number of turns. So, after initial installation, you just ignore the marks on the belt.

 

[Joe Z]

Well, actually it IS every other revolution of the crank. On the second turn of the crank the cam marks will be at 6 o'clock and then come back to 12 on the following turn. Then 6, then 12, and so on. The crank turns twice for every single turn of the camshafts. The belt marks will realign eventually, but only after a ridiculously large number of turns, and then only once until another ridiculously large number of turns. So, after initial installation, you just ignore the marks on the belt.

Durk.... I was thinking about this last night.....
Timing belt off.... Every one revolution of the crankshaft the #1 piston would be TDC.
Then line up the cams timing marks?_____

 

[stir_fry_boy]

Question: So after a few revolutions the timing marks on the 2 cams will not be lines up in relation to the crankshaft marking?
Or is it every other revolution they will line up?

Are you asking if you need to turn the crank after installing the timing belt to recheck your timing marks?

 

[stir_fry_boy]

Durk.... I was thinking about this last night.....
So if and when i do the timing belt the crank mark lined up, I would imagine i have to get the proper revolution. so would that would mean on the proper revolution the #1 cylinder should be TDC (top dead center)?? on the crank then line up the cam marks?
Or does it make no difference because that piston will always be up and then time the cams from there?_________

As long as the belt marks are correct on the cams and crank, the marks on the block (oil pump housing) for the crank and black backing plate for the cams are irrelevant. Just put the belt on with the timing marks lined up with the pulleys, and pull the tensioner and you are done.