Join Date: Aug 2018
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Thanked 109 Times in 85 Posts
demoder, I hope the yard has the harmonic balancer.
I think I have recommended to around six people already that, in advance, they either purchase or construct all the tools you (demoder) suggest in the rav4.1world timing belt DIY thread. Gosh knows it cost me a lot of time and energy making or buying the tools on the fly.
Here's my tedious amateur's chatter on these pulley bolt situations: Some folks apply upwards of 500 ft-lbs of torque to break these pulley bolts free. Of course the pulley bolt is not actually tensioned to this amount: If one torques a 14mm bolt (like the typical pulley bolt) to 500 ft-lbs, the shear stress (tau = T c / J yada) in it would be around 182,000 psi. The shear strength of grade 10.9 is only around 75,000 psi. Grade 12.9 is stronger at around 88,000 psi, but this still would not prevent a failure by shear. So if the pulley bolts are not actually tensioned to say 500 ft-lbs, why is it often so difficult to free them? Years ago some Civic folks and I speculated that these crankshaft pulley bolts are heat cycled. They are also a fine thread. The bolts never seem to be noticeably corroded, as in rusted in place. We speculated a bit of galling, and maybe just a touch of corrosion, were going on. We figured this often caused the need for massive amounts of torque to free them. So was our guess.
One thing I learned is that it seems better to apply impulses of force, either with an impact gun or manually when putting the, say, five-foot pipe over one's 1/2-inch drive, 1.5 foot long breaker bar. The vibrations of the impulse help break free the galling (or sometimes, a bit of rust)?
As for the 8mm x 1.25 bolts the Rav4.1 pulley holder tools require: Demoder posted in the timing belt DIY thread that she used metric Grade 10.9 bolts. Which of course is wise and what the experienced DIY folks elsewhere use. This past year in my sophomoric design efforts, I demonstrated several times that two 8mm metric Grade 8.8 bolts failed (several times) not from shear stress but from bending stress. As in sigma = M c / I yada. Grade 8.8 has a yield strength of around 120,000 psi. When re-installing the pulley bolt and torquing to the required 80 ft-lbs., on my tool (which is similar to to demoder's), each of the two bolts will see around 147,000 psi of bending stress. Grade 10.9 is good up to about 151,000 psi. Using Grade 10.9 bolts, and for tightening the pulley bolt to 80 ft-lbs., the tool should work.
For removing the pulley bolt, either a heftier tool is recommended, or one has to use the bump-start method. Demoder does have a heftier pulley holding tool than mine, but it appears it has its limits when we are talking about upwards of 450 ft-lbs of torque ultimately being applied to the tool. By my calculations, this 450 ft-lbs of torque subjects each 8mm bolt to around 900,000 psi of stress on my (less hefty) tool. Crash.
I confess I may end up buying some Grade 12.9, 8mmx1.25 bolts from the net for my homemade pulley holder tool. eBay seems to have them for around $1 each. Still, my tool is only for re-installing and torquing the pulley bolt in place.
1998 Rav4, Manual Transmission, 2WD, JDM engine with 85k miles in early 2019