Timing belt question

Question for anyone who knows timing belts well -

I’m deep in the process of replacing mine and I’ve run into a problem that I just can’t figure out..

I’ve gotten everything taken out, and the new belt back in. Everything lined up perfectly TDC.. hydraulic tensioner pin is pulled and tensioner pulley is taught as much as i can figure. I’ve done this three times now with slight variation.

The problem is when I go to check my work - when I manually rotate the engine a few times using the crankshaft pulley bolt, and get the belt back around I’ve moved a tooth forwa. And if I do a full rotation of the belt again then I’ve moved another tooth on the belt. And so everytime the belt rotates fully it’s moved ahead a tooth.

My only thought is that the belt doesn’t have enough tension, but I can’t figure out how to get anymore tension on there.

I’m pretty frustrated. Like I said, this is my forth time taking out the belt and re-pinning this damn tensioner.

Any constructive thoughts would be appreciated.

 

Ive never done a t belt on a toyota, but have done thousands...
start with putting belt on at crank sprocket & always go up to the cam making 100% certain you have zero slack in that side of the belt.
If you have to rotate the cam some to get the belt on & then take the slack out, so be it...
All the slack extra needs to be on the tensioner side...

If you tension everything & all your marks are lined up, I wouldnt be terribly concerned where they sit after rotation, but thats only if youre 100 certain you did it right.
That only comes with experience though, not trying to be condescending here at all!!!
I know you only want to do it once & do it right.
Kind of hard to know if you are or are not w/o seeing it in person...

As I stated, sometimes you need to turn the cam to the right some, out of time, to get the right part of the belt cogs on the gear & then rotate it back to "in time" to get all the slack out...
If you have ANY slack on the non tensioned side, theres your issue.

 

(saw your post on reddit; adding my answer here, too) My answer matches up pretty well with @slater, just said in a slightly different way

OK, so there are two things here:

1. Alignment of the belt marks.
2. Alignment of the actual cam/crank pulleys. (what you seemed to mention in your initial post)

#1 - After rotating the cam/crank pulleys, the belt marks will no longer align at top dead center (TDC), as rotations of the belt do not coincide to rotations of the pulleys.

#2 - For the actual cam/crank pulleys, you definitely need to be sure that they are aligned TDC at the same time. If you rotate the belt, and the pulleys are off by a tooth after one rotation, and a second tooth on the next rotation, then you're timing is off (because after a certain number of rotations, you'll be 45, 90, 180 degrees, etc out of timing). No good.

My guess is that you're asking about #2, because the belt marks are off by *way more* than a single tooth after a rotation.

Assuming that's the case, the "issue" is *most likely* that you aren't getting the belt tight enough prior to pulling the pin on the tensioner. It is *very* important to get the belt *very* tight on the driver side of the 5VZFE.

1. Start by getting the cam/crank pulleys set to TDC.
2. Align the belt mark with the passenger cam and be sure to hold it very securely in place.
3. Be sure that you're pulling the belt really tight and get it onto the driver cam (and the mark aligned with the TDC mark). Hold that one securely in place, too.
4. Now, being sure to keep a lot of tension on the belt, get the crank mark onto the TDC of the crank pulley. Secure that one, too.
5. Only at this point can you tension the system. The key, really, is that the tensioner only really tensions the passenger side of the system; the tension for the driver side is done by you, at the time of installation.
6. At this point, rotate the cam pulley's clockwise until the crank pulley gear completes two full rotations and then ensure that all marks on the crank pulley and cam pulleys are aligned top-dead-center. Note that the belt marks will no longer be aligned.

Sounds like you've got most of the process under control, but here's a good writeup if you have other questions:

Step by Step Toyota Tacoma Timing Belt Replacement for 3.4L V6 5VZFE (also 4runner, Tundra, and T100) – AdventureTaco

 

@slater

Yea I think that my inexperience is making me weary here. I think a lot of people would just put the belt back on and forget about it, but when I checked I maybe found a “problem” that isn’t really a problem.

I can’t be 100% sure I did this right because this is the first time I’ve ever done it, but I’ve had my father in law check it a bunch and he can’t seem to see anything that’s “wrong”.

 

I also cram something under the timing belt at the crank pulley so the belt stays tight against the gear while im messing with the belt on the other gears...
Just makes things easier & not worried about the belt dropping down off the gear.

 

I get it, you really need to pay attention to details...
Its the guys that have all the confidence in the world & slap it together wrong, off just 1 tooth will get you in a pickle, wont run right, could surge, etc....
Cant be careful enough.

As a professional ive seen many techs do things on auto pilot & thats when mistakes happen...

 

@turbodb @slater

okay guys thanks for the reply’s. I think I found my answer in this YouTube video. If you care to see you can start the vid at 50:50.

https://youtu.be/BnrEcRAemMo?si=dRPs-OzulcOU-oRI

lmk any thoughts

 

Is your answer that the markings on the belt didn't line up after rotation?

 

YES!!!!
The white marks on the belt will NEVER line up again to the timing marks on the gear or engine after you rotate the engine...
Dont care how many revolutions you make.
If they do, stop what youre doing & go buy a lottery ticket...

Get it back together...

 

@koco

yea… sorry this was probably a stupid question, but I was stuck for about 6 hours trying to figure it out..

 

Not a stupid question, especially if you dont do this on a regular basis...
Good on you for paying attention to detail...

I have techs ask me the same question...
I timed it & rotated my the engine but cant get the colored timing chain links to line back up on the cam gear.....

 

It is called a "hunting pattern", if the belt didnt "hunt" and the same tooth hit the same spot on all pulleys every time the belt wouldnt last too long.

https://patents.google.com/patent/US3738187A/en

 

The crankshaft rotates twice for each camshaft rotation, so the timing marks won't line up again until a few hundred rotations later.

You can use dollar store plastic clamps to hold the belt on the sprockets before you release the tensioner. Subaru example shown:

 

I did know about this since I have performed that job and that info is in the FSM. I used some tire crayon on the timing marks.

The last belt I did was tight going on and it was a "toyota" belt. There is a nice time-saver trick for the tensioner that eliminates the need to remove the AC compressor. It involves using tape to stick the tensioner bolt into a socket with a swivel to install it.