3.4 Harmonic Bal Bolt Article - Must read for timing belt replacement!
 

This article is a must-read for those of you doing a timing belt replacement...


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Also, if you navigate through the www.motor.com site to the article by Dan Marinucci, you can view it as a pdf with lots of pictures....

I tried to upload the PDF file, but it's too big... Anyone know how to reduce the file size or increase upload limit ??


S.

I had a new short motor paid for by the stealer after the tech did not tighten the bolt corrctly and the pulley came off while driving and trashed the crank.

E

Seen that many a time on here but very good article!

Just to make sure it gets saved for posterity later....

Foreign Service
by Dan Marinucci

January 2007. An improperly tightened harmonic balancer bolt can have expensive consequences on many engines. Here's how to do the job right on Toyota's 5VZFE powerplant.

"We often see the instruction ?torque to specification? in this business. Unfortunately, many technicians don't take that directive too seriously. Instead, they guess at the spec by using a breaker bar or big impact gun. Sometimes they get away with it.

Experience has taught us that guesswork is a bad gamble when tightening the harmonic balancer bolt on Toyota 's 5VZFE powerplant. This 3.4L V6, which debuted in 1995, is commonly found in such vehicles as the 4Runner, T100, Tacoma and Tundra. An improperly tightened crank bolt on this engine has unpleasant consequences?comebacks, misfiring, confusing trouble codes and possible engine damage.

The spec for the harmonic balancer bolt on this 3.4L V6 ranges from 184 ft.-lbs. to 217 ft.-lbs. That's a considerable amount of torque in anyone's book. You have to hold the crankshaft steady in order to achieve this and the ?holding? step is one many technicians skip. Let's look at this task and see how little effort it takes to do it correctly.

The timing belt on the 5VZFE engine drives the water pump and the belt's replacement interval is 90,000 miles. But as I explained in a previous Foreign Service column, it's not uncommon for the pump to leak long before the engine is due for a new belt. Therefore, you may end up replacing both parts sooner than you think. As long as you have the front of the engine apart, don't forget to check for camshaft seal seepage and for slop in the timing belt tensioner. Check the tensioner by pushing down on it with your hands; Toyota specialists have told us that you should replace it if its plunger moves as little as 1 /8 to 1 /4 in. Several specialists have said the best way to sell this job is as a package containing a new water pump, t-belt, cam seals and a tensioner.

Usually a tired tensioner causes a telltale rattling sound in the front of the engine right after start-up. Also, revving the engine may diminish this rattling, but the noise never goes away completely. By the time this rattle appears, there's probably 1 /4 in. of movement in that tensioner plunger. If you decide to reuse the existing tensioner, you can retract it quickly and safely with Schley Products' compressing tool Part No. 97300 (or equivalent).

Way back in days of yore, a Toyota crank sprocket usually was pressed in place and the engine had one woodruff key for this sprocket and another for the harmonic balancer. But on the 5VZFE, the crank sprocket and harmonic balancer share the same woodruff key. Plus, the crank sprocket just slips onto the end of the crankshaft. Some techs believe that this arrangement of slip-fit sprocket and single woodruff key make it extra important to cinch that harmonic balancer securely in place.

Before you button up this job, be sure the harmonic balancer bolt threads are clean and in good condition. Treat the bolt with a good thread-locking sealer such as blue Loctite or its equivalent. Then hold the harmonic balancer steady while you torque this bolt to spec. One way to do the job quickly and safely is with Matco's No. MST6440 holding tool (photo 1 on page 14). This tool, which accepts a 1 /2-in. drive ratchet or breaker bar, has a pair of sturdy pins that engage the holes in the front of the harmonic balancer hub.

Motor readers who service lots of Toyotas also may want to check out OTC's tool kit Part No. 09213-54015-01 (photo 2 above left). This OEM setup, which requires tool handle Part No. 09330-00021, fits a broad range of Toyota harmonic balancers. Also, a product such as Matco's or OTC's makes this task a one-man job.

Some guys grip the outside of the harmonic balancer with a chain wrench or a giant pair of Channellock pliers while another tech torques the bolt. Here, remember that there's always the risk?however small?of separating the outer part of the harmonic balancer from its inner hub. What's more, those who use this technique should grasp the smooth, meaty area of the balancer between the drive belt grooves. More than one tech has caused premature drive belt failure by carelessly gouging the drive belt grooves with some kind of gripping device.

Several years ago, I said that our sources were seeing various symptoms that they ultimately traced to an improperly tightened crank bolt on the 5VZFE. We're still encountering these problems, so it's worth reviewing them here. Photo 3 shows the crank sensor on the right, the crank sprocket and the reluctor teeth on the inner end of the sprocket. To generate a clean, consistent crank sensor signal (CKP), those reluctor teeth must be aligned with the crank sensor.

If the crank bolt loosens up, it allows the harmonic balancer and crank sprocket to shake back and forth. First, this unwanted movement usually causes an rpm-sensitive noise and vibration in the front of the engine. You can watch the harmonic balancer wobbling while the engine is idling. Beyond a point, those drive belts are the only things keeping the balancer on the crank snout. It's anyone's guess as to how long a driver will ignore this noise and vibration.

Second, although the loose crank sprocket causes an erratic CKP signal, experience shows that it rarely triggers a crank sensor trouble code. However, the unstable signal creates an assortment of driveability problems. For instance, the engine often idles okay but misfires during acceleration and the ECM sets one or more misfire codes. Eventually, the engine may misfire all the time and become hard to start. Before you dive into a diagnosis, always get the vehicle history and watch for a wobbling harmonic balancer.

When in doubt, thoroughly test the crank sensor with your oscilloscope. Look for the familiar, cyclical, sine wave-like pattern at idle and higher rpm. (Note that a flat spot among the reluctor teeth creates a crisp, repeatable pattern ?blip? representing piston position.) Sprocket movement causes an ugly, erratic crank sensor pattern.

A driver may ignore the noise, vibration and misfiring symptoms until it's way too late. By that point, the loose parts may allow the woodruff key to wear or wallow out the keyways in the crankshaft and/or crank sprocket! The unwanted movement also may distort the woodruff key itself. Sometimes the wear and looseness allows the crank sprocket to twist or shift far enough to alter timing; then overall performance suffers. So if you discover a wobbling harmonic balancer and a loose crank bolt on one of these Toyota engines, a tear-down and thorough visual inspection is the best way to know what's damaged and how badly."

Yep, good article. I've seen some cases around on these forums of this problem. I made a holding tool to check mine to see if it was tight before I put the engine in.

http://thumb7.webshots.net/t/36/36/4...7RzBiok_th.jpg

http://thumb7.webshots.net/t/59/59/5...7lojkbc_th.jpg

http://thumb7.webshots.net/t/53/453/...7jktBjX_th.jpg

I was told that the new Toyota spec for it is the 217 ft-lb figure and that the 184 ft-lb was an old spec that Toyota had some problems with.

That's the reason why I got my truck for free. The motor that was in the truck when I got it, they balancer pulley spun off cause the shop that did the timing belt last didn't torque it right and the water pump was leaking. A friend of mine works for Toyota and he told me this happens because you are supposed to use a paper gasket on the water pump, not the black sealer stuff. On another note, the replacement motor I got was the same way just with 60,000 miles on it.....the shop I bought the motor from paid for a reman crank with all new bearings.....not a bad deal, huh?

might as well put a urd lightened 5vz crank pulley when before your torque it down ;)

That's what I did!!!!

gangster i wanna see pics. Hey are you running that lightened pulley on a na 5vz or is it boosted im contemplating on getting the pulley for a NA setup.

Wow, This article is about a week late for me.. My Mechanic just replaced this on my truck after another mechanic screwed up my timing belt replacement. I have the sprocket, I get a pic up of what mine looked like.

http://www.therolphierun.com/joe/truck01.JPG
http://www.therolphierun.com/joe/truck03.JPG

Let's try this link:
http://www.motor.com/MAGAZINE/Pdf/012007_04.pdf

Awesome informnation. I'm finally getting ready to order all of the required parts to do the timing belt. Figures I pick wintertime to do this....

Andreas

Has this ever happened to anyone not related to work performed - meaning the crank pulley just loosened up a bit for whatever reason (defective bolt, pulley or other) and began causing the issues referenced in the article.

All the cases of failure that I am aware of were related to timing belt changes.

Wish I'd seen this a year ago! I took a shortcut (no one to blame but myself!) after a timing belt replacement, and didn't torque the bolt correctly. One year later (almost to the day), it began making a little noise, and the next day threw the PS belt. The pulley's inside bore had worn, but crankshaft was ok. I put a used pulley on it ($130), new woodruf key and torqued the bolt, holding the pulley with a chain wrench.

I was told that Toyota had a problem with this on trucks from the factory with the early 5VZFE (like 96-97) and that's when they changed the torque spec from 184 to 217.

And even at the 217 torque he still recommends using Loctite!

Yeah, Mike @ ORS told me to use RED loctite.

If I was going to pay someone to replace my timing belt, the first question I'd have is what are you planning to torque the crank pulley bolt to. He better say 217 ft-lbs or at least agree to that spec. The second would be do you have a SST to hold the crank? If he says he can just use an impact wrench on it I'd run for the door.

BTW my 2001 Tacoma FSM lists the crank pulley bolt as a "Non-reuseable part"

Yup.... I think the timing belt replacement, if you're not going to do it yourself, is one of those instances I'd wait for a dealer special, then go! From the above postings, there's no guarantee the stealer will do it right, but at least most have gotten the motor fixed!

:horse:

Incidentally, the tools he lists are very expensive (200+), and primarily for pro mechanics. I did the job with an OTC Universal Pulley holder (No. OTC-4754), had for about $40 on ebay.

My FSM for '99 4Runner said the same thing. However, I checked at three different dealers, and none had it in stock. Evidently, they don't replace them either, or they'd keep it in stock.