After hearing a chirping from my serpentine belt area, I decided to replace the tensioner pulley/bearings and the 3 idler pulley/bearings. I have a 2005 SE V6 4x4. All my pulleys were original OEM.

Well, after ordering the proper parts online according to the common parts diagram that most parts sites use I installed the new idlers. I noticed the top right idler (idler # 2) was oriented in a way such that the belt was nearly riding off the side of the pulley. Additionally, I noticed that both top idlers (# 2) both had some wobble after driving a total of about 15 miles.

It turns out that the OEM idlers have been superceded and now require a small washer-like "plate" that fits between the pulley and the block. The cute part is that these plates are not shown on most parts schematics.

So after burning up the top # 2 idlers, I order two more. All is well now.

If you have a 4th gen V6 and plan on updating your #2 idlers the parts you will need are:

IDLER #2 (TOYOTA #16604-0P011)
INSIDE PLATE (#16649-31020)

Hopefully this will save a few people some pain and cash.

Cool thanks for the heads up. I too starting to hear some chirp on my 2005 and just started looking into some new idlers.

I wanted to bump this for some additional thoughts as I'm getting ready to tackle this on our 2007 v6 4x4. Could the lack of installing this additional plate be the reason for so many oem idlers prematurely failing?

good post, bookmarked

Thank you. I'm getting a chirp on my 2008 V6

What do you consider "premature" failure.

I just hit 183k on my oem pullys so I'm very impressed with their lifespan but unfortunately they are starting to whine. I want to stay oem but the #2 pullys on my '07 v6 #16604-31020 have been superceded to #16604-0P011, confirmed by my local dealer.

After research on this board and fj cruiser & tacoma boards, many have chosen to go aftermarket due to experiencing failures of self installed or dealer installed toyota pullys and maybe falsely believing these toyota oem pullys have unsealed bearings?

I'm wondering if it's just the failure to install this second rear mounted pully plate that has been the cause for others to experience issues? It is very easily overlooked when ordering as the OP has stated.

I wouldn't worry about the quality of the new Toyota bearings. I did a side-by-side and both appeared very similar. Both original and replacement bearings were made in Japan.

I haven't played with the idler pulley on my 4Runner but have replaced just the sealed bearings in other Toyota and Subaru vehicles. Can't we just replace the actual sealed bearing in our idler pulleys? Just curious.

Bumping an old thread. I have a 2008 4.0 V6. I replaced the two #2 idlers. I used the parts listed in the OP. At first I did not install the back plates because the pulley looked lined up well. I put the belt on and ran it a while, the belt seemed just a bit close to the front of the pulley. So I reinstalled with the backing plates, now the belt seems like it rides toward the back of the pulley with about 1/16” of pulley showing between the belt and back lip of the pulley. I’m going to leave it this way, hopefully won’t shread the belt on the way to work tomorrow. I have all the old parts in a box in case I do.

I also replaced the #1 pulley, without using the backing plate, the belt is very well centered.

Anyway if you have replaced the #2 idlers with OEM and back plates does the belt ride closer to the back (engine) side of the pulley?

Thanks

I don’t have a V6, nor have I changed the idlers (yet) on this vehicle, but what you describe makes sense to me because the belt will be more on the flat area with the spacer, preventing possible side loading of the bearing. It does seem awfully close to the edge though from what you described. I’d probably try to find a slightly thinner spacer washer if it were mine.

Necromancing an old thread, again.

A word of caution when doing this:

In the garage swapping out all idlers and belt on my 07, 195k on it now. Went to install the right #2 with the spacer plate indicated by OP (thanks for the heads up on that btw) and it seems the current koyo pulley didn't like it very much. I noticed after the bolt was tight, the pulley will not spin. This is bad. Taking it back our for a second look, it seems, at least with my setup here and now, when the bolt is tight, the spacer and the washer on the OEM bolt are pinching the pulley to where it can't spin on the bearing. I solved this by going into my trusty bin of random hardware and finding a small washer that fit only the bearing and sits flush with the pulley mounting surface. Plugged it back in, torqued it down, now it spins just fine. Looked to be a 3/8 flat washer. So be sure you check to make sure that your pulley spins after install, that is it's point and purpose after all.

So I've had the engine running for about 40 minutes. All looks well. The belt does ride a little further back on the pulley, but I checked it with a straight edge and it appears to be flush with the edge of the pulleys. That's fine in my book, the grooved pulleys will keep it in line, and I've seen that type of tolerance on other engines in the past, so it's all good in my book. Enjoy!

Thanks for posting this warning. I changed these a few days ago and they just want to sell the “plate” but do not mention the spacers for 16604 that go between the engine block and the pulley. I went the fastener store and hardware store. Ended up using the 3/8th inch washers between the pulley and the block. Not a huge offset when I look at where the belt rides. I will post any failures if and when they occur. Also, if anyone uses thread locker, beware as it climbs the bolt’s thread and may bind the bearing.

It’s been very confusing to keep track of all the part numbers in regards to replacement of the idler pulleys. I’m planning on replacing all of them soon. Can someone post the latest OEM part numbers I need to have all the correct parts required for this job. I know that sounds kind of lame and being lazy but reading posts from years back has made it difficult to understand what the latest and right parts are including ordering these washers. I’m sure others would appreciate it and simplify what are the part numbers of this very popular issue with the 4L .
Thanks in advance.