Timing Belt Alignment question
#1
Driver School Candidate
Thread Starter
Timing Belt Alignment question
Crappy picture I know but it shows that the R-CAM mark on the belt no longer lines up with the marks on the pulley - after rotating the crankshaft two revolutions clockwise. The timing marks on the crankshaft aligned at "0" and the marks on the cam pulley's align with the marks on the head - but the LH and RH marks on the belt are now way off - is this right? Guess this is different because the initial belt alignment was with the crank mark at the 6:00 position - can't seem to process this.
Wish I there was an easy way to check TDC on the #1 piston but I don't want to pull that cam cover to look at the cam.
Waiting on my replacement fan bracket so have time to wait for a comment. Thanks,
Wish I there was an easy way to check TDC on the #1 piston but I don't want to pull that cam cover to look at the cam.
Waiting on my replacement fan bracket so have time to wait for a comment. Thanks,
#2
Crappy picture I know but it shows that the R-CAM mark on the belt no longer lines up with the marks on the pulley - after rotating the crankshaft two revolutions clockwise. The timing marks on the crankshaft aligned at "0" and the marks on the cam pulley's align with the marks on the head - but the LH and RH marks on the belt are now way off - is this right? Guess this is different because the initial belt alignment was with the crank mark at the 6:00 position - can't seem to process this.
Wish I there was an easy way to check TDC on the #1 piston but I don't want to pull that cam cover to look at the cam.
Waiting on my replacement fan bracket so have time to wait for a comment. Thanks,
Wish I there was an easy way to check TDC on the #1 piston but I don't want to pull that cam cover to look at the cam.
Waiting on my replacement fan bracket so have time to wait for a comment. Thanks,
the belt will not be lined up anymore
the belt doesn't matter, all that matters is that the cams and crank are lined up
if you have time why take not off the cover?
#4
Its a ratio thing, after so many turns they will again line up, and then will not be, its a hunting design so all the cogs in the belt get used and not just a few of them. Like mentioned above all that matters is if the sprocket to the engine marks line up again.
Last edited by dicer; 01-16-16 at 03:43 PM.
#5
the RH cam will jump when the belt gets old - Code 13 tell tale sign. Time for a timing service. And you dont have to pull a cam cover - straighten out a metal hanger and put in spark plug hole and make sure its at its high point while the line is marked up
#6
That scared the heck out of me first time I did a timing belt with transferring the marks to the new belt and having the marks on the belt not line up after two rotations. Sure wish my procedure had had a warning. Sure would have saved me a lot of panic time. I think after so many revolutions the marks would line themselves up again. 12, 16, 18?
#7
Driver School Candidate
Thread Starter
Engine started right up after timing belt and water pump replacement. Idles smooth as ever. AC, etc all works ok. No noises or leaks.. Warmed right up and idle slowed to normal. No obvious oil leaks at the crank or cam seals replaced during job.
Car had a slight misfire before starting job above about 2000-2500 rpm - seemed to smooth out above about 3500 rpm - but that was hard to tell as this engine is so smooth. So, the only thing I had not replaced in the last year or two was the drivers side coil.
Now the car misfires badly above about 2000 rpm under load - and is clearly running rich under load. Seems to rev up ok in park (no load) but is clearly running rich - I think the cats were getting hot.
Now to start searching these forums for something I can check. Sure hope it's not another computer going bad.
Car had a slight misfire before starting job above about 2000-2500 rpm - seemed to smooth out above about 3500 rpm - but that was hard to tell as this engine is so smooth. So, the only thing I had not replaced in the last year or two was the drivers side coil.
Now the car misfires badly above about 2000 rpm under load - and is clearly running rich under load. Seems to rev up ok in park (no load) but is clearly running rich - I think the cats were getting hot.
Now to start searching these forums for something I can check. Sure hope it's not another computer going bad.
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#8
Racer
TDIGREEN1,what was the fix on this?
#10
Lexus Test Driver
iTrader: (1)
yes, where X (crankshaft revolutions) is the least common multiple of the number of teeth on the crank pulley and the number of ribs on the belt, divided by the number of teeth on the crank pulley, times 2. Anyone got those numbers?
Last edited by oldskewel; 02-08-18 at 06:16 PM.
#12
Moderator
iTrader: (7)
please check me on this but from my limited memory the cam marks should line up again after two (2) revolutions of the crank pulley.
and by marks i mean the marks on the gears themselves NOT the belt markings (which OneJay said as well)!
i did this hand rotation on the belt before i put everything back together as a double check.
and by marks i mean the marks on the gears themselves NOT the belt markings (which OneJay said as well)!
i did this hand rotation on the belt before i put everything back together as a double check.
#13
please check me on this but from my limited memory the cam marks should line up again after two (2) revolutions of the crank pulley.
and by marks i mean the marks on the gears themselves NOT the belt markings (which OneJay said as well)!
i did this hand rotation on the belt before i put everything back together as a double check.
and by marks i mean the marks on the gears themselves NOT the belt markings (which OneJay said as well)!
i did this hand rotation on the belt before i put everything back together as a double check.
#14
Lexus Test Driver
iTrader: (1)
please check me on this but from my limited memory the cam marks should line up again after two (2) revolutions of the crank pulley.
and by marks i mean the marks on the gears themselves NOT the belt markings (which OneJay said as well)!
i did this hand rotation on the belt before i put everything back together as a double check.
and by marks i mean the marks on the gears themselves NOT the belt markings (which OneJay said as well)!
i did this hand rotation on the belt before i put everything back together as a double check.
I don't know the numbers, but let's take OneJay's numbers (which I did a quick google of and seem correct) ... crank pulley = 24 teeth, so cam pulleys = 48 teeth (half the rotation speed, so 2x the teeth). For non-VVTI, say the belt is 209 teeth (not confirmed, that was OneJay's guess).
So the number of crank revolutions will be LCM(48,209) / 48 * 2. Wow, in this case it would take a while. The factors of 209 are 11 and 19, nothing common at all with 48. So it would take 209 full cam rotations to get the belt back where it started. And 2x that for the crank. 211 is a prime number, so that's not any better (no common factors with 48). So if those numbers are correct, you can basically forget about having the belt marks ever lining up again. But with better numbers, it would be a different story.
For example, if it was 50 teeth on the cam pulleys instead of 48, and 225 teeth on the belt, instead of 211. LCM(50,225) = 450. 450 is 9x 50 and 2x 225. So it is a multiple of both numbers. LCM. So in this case, the belt marks would come into alignment again after 9 cam pulley revolutions, or 18 crank pulley revolutions. In this time, the belt would have made 2 full rotations.
So you can see, it depends on how the numbers share common factors.
Last edited by oldskewel; 02-08-18 at 06:19 PM.
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OneJay (02-09-18)