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Skyvisions
Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 14500
Experience:  Toyota Master Diagnostic
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I replaced the timing belt on my 06 Sienna, which I've done

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I replaced the timing belt on my 06 Sienna, which I've done a couple times before with no issue. This time, when complete, the belt does not track correctly. It comes off the cam sprocket nearest the front of the van by about 1/8"+/-, off the crank sprocket about 1/16" and off the tensioner pulley about an eighth, maybe little more. On rear cam sprocket, belt is seated all the way back. What could cause this? Only thing I can think of is I didn't install the washer behind the tensioner pulley mechanism, so it is seated too far back and sending the rest of the belt off. I would appreciate your insights. Thank you.

Can you send me some pictures of the belt and where is running off and the tensioners and the idler bearing and water pump?

Customer: replied 1 month ago.
I'll give it a go here . . .
Edge of the belt is now frayed -- I have a new one.
You can see it is also off the idler. Hope these pictures are OK -- don't have a cell phone (!) so I took these with my SLR, which isn't as slim. Thanks for the help.

Just got the info I have to step out for and hour or so. I will review this evening and get back to you.

The pictures not quite crystal-clear but it looks like your problem stems from the fact that that front cam gear on the front bank by the radiator is on backwards you need to take a cam gear often flip it around so that the outer ring keeps the belt from walking off the back camshaft drive gear ring is on the back side towards the plate or the engine.

If that is the case you should be fine once you flip the gear around or you can post clearer pictures if I'm not seeing it correctly.

Customer: replied 1 month ago.
I don't know if those went through . . . .
Customer: replied 1 month ago.
I'll look at that, and also try to give you better pictures. Sorry about the clarity.

No worries I am about 90% certain I am seeing it correctly. Front pulley has to be taken off in order to loosen up the backing plate if the water pump is ever replaced and it looks like someone just put it on backwards.

On second thought I was replaying a timing belt I just did over the weekend in my head it's the back cam gear that keeps the belt from walking off the front of the engine that gear appears to be on backwards.

Customer: replied 1 month ago.
If you're right, I think a Homer D'oh headslap is in order. Let me get better pictures to be sure.
Customer: replied 1 month ago.
Let's try these:
I'm curious, however. How can I have the cam sprocket/gear on backwards when you can see the timing mark (at about 8:00), and I can see the key on the end of the cam engaged in the keyway on the gear?

Okay those pictures work fine. It is 100% certain that that back camshaft sprocket is on backwards. The flange on that sprocket keeps the belt from walking off the front of the gear and the bank two or front bank sprocket on the camshaft keeps it from walking off the back of the pulley. the timing marks are stamped on both sides of the gears because the gear is the same for front and back you just flip them around, it doesn't change the timing..

Here's a picture you can basically make the outline of the land on the back bank and none on the front bank

Here's a picture you can basically make the outline of the land on the back bank and none on the front bank

Also just as an FYI if that belt still has the original timing marks or paint marks make sure that when you put the belt back on that the arrows on the belt are facing away from the engine that will throw the cam timing out if you put the belt on backwards.

Customer: replied 1 month ago.
OK, I'll give that a try. I have to admit a bit of doubt, however, so we'll see. Belt was on correctly -- all three lines were on their marks. But, just to be crystal, arrows on belt should point to the passenger wheel (what I interpret as away from engine)? I won't get at this until tomorrow, but I'll check in with the result.
Customer: replied 1 month ago.
Thanks for your help! Sorry, I've had a day . . . .
Customer: replied 1 month ago.
One more thing -- what's your trick to keep that back cam from snapping back about 60 degrees when the belt is off (esp when the pulley bolt is removed and can use a wrench on that pinned against the firewall)?

Once you get that pulley swapped around on the back put a 17 mm wrench on it and once that ***** *****nes up on the backing plate or you have the paint marks still on the original belt will be a sweet spot where it will actually line up with the mark and should stay in place. I use a pair of needle nose vise grips to clamp very lightly over the pulley so the belt can't come loose then I take the belt under the upper bearing and over the front camshaft down to the crank I put it on the crank and over the lower tensioner bearing last. I keep all the slack on the downward or forward side of the belt until I get line on the crank then slowly put pressure on it to bring all the slack up on the tensioner side. And yes the arrows should be pointed away from the engine on the belt towards the passenger will well.

Customer: replied 1 month ago.
Sorry for the delay -- I finally got to it and the swap went fine. I have found that sweet spot you talk about through experience as well, but boy is it small. I also found I had neglected to install the 3mm washer behind the tensioner pulley. I think that was key as well. I can't say I'm completely thrilled with the result -- it still seems to make more noise than before, but it tracks right where it should as far as I can tell. So, for now, I'll consider the matter closed, and thank you for your help. I'll add a positive rating.The thing that made me skeptical was that each time I've replaced this belt the pulleys have both been flange-in (toward the block), so I've never seen it any other way, and never had an issue until now.As a final note, just to satisfy my curiosity, what is it about that back bank that makes it so susceptible to snapping either way? Is it where the cam lobes end up, or ???? Is there any way to mitigate this procedure wise, and make it more stable (like the front seems to be), such as something other than the 60 degree clockwise rotation spelled out in the Alldata procedures? Thank you again. Blessings.

The cam snapping back is due to the lobe location on the valves. I don't recommend turning it one way or the other I suppose you could as long as the marks on a brand-new belt line up. to get the sweet spot it'll stay where it's supposed to and then you know for sure that you have it in time. If you have not done so please do not forget to rate the assistance I provided to you at three or higher.

Customer: replied 27 days ago.
Thank you. To clarify, procedure in Alldata says to rotate the crank to 60 degrees BTDC before removing the belt. When you do this job, you leave it at 0? Also, the belt is whining. Is this due to what I see as common Gates whining, or ? The only thing I am a bit worried about is that when installed and after running for several revolutions, the belt was is place except for being just a smidge pround on the crank sprocket -- just a fingernails worth. Is this a concern? This is not my daily driver, so it has not been driven since the belt change, other than idling. Thank you.

I set everything at 0°. Once you install the timing belt and all the marks are lined up and you 100% certain you are good to go. Once you crank it over the marks will not line up again for about 32 revolutions. I'm not a real big fan of Gates drive belts or timing belts. If there is any debris or glazing worn into the pullys you might get some noise from them.

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