Since it was so nice this weekend, and I had some spare time, and was putting new spark plugs in the other car, I thought I'd just pop the plugs in the Prius out and put some anti-sieze on them. A few questions: I usually don't worry about torque settings as much as I should perhaps, but I'd read here they needed to be torqued to 13 ft/lbs, my torque wrench (one of those two foot or so jobs with the twistable ring for setting torque, clicks when you tighten to the specific torque) starts at 40 ft/lbs, assuming I could have maneuvered it under the hood there to reach the plugs. What do you other DIYers use to get a specific torque like that, or do you just kind of wing it like I usually would? Also, those clips on the wires to the relay box, how to you release them? I ended up leaving them attached and just swing the box a little out of the way, but it would have been easier to take them loose and move the whole bit out of the way.
Back in the "good ol days" we never worried about torque values for spark plugs, just crank on them till they feel OK. But with aluminum heads and as long as we leave them in now I think I would torque them. I haven't changed mine yet, not enough miles. I think they rent torque wrenches at rental places for not to much. I have a torque wrench that goes down to 100 inch pounds but I'm to far away to help you.
Thanks. I never worried about this before either, but 13 ft/lbs sounded awfully loose, so I thought I might try to be a little more precise as to avoid strippping them etc. Time for a new torque wrench, maybe at the after Christmas sales.
Just take the bolts off the relay box and swing it aside, you won't hurt anything. I finally checked my plugs this fall and they were TIGHT. Most 1/2 inch torque wrenches don't go that low, like you discovered most start at 30-50 lb/ft, which is way too high for that application. Consider investing in a 3/8 inch torque wrench, most can go down to 5 lb/ft. Proper torque was never really considered or needed for cast iron heads, you just went another 1/4 to 1/2 turn once the plug seated, for tapered plugs. For plugs with gaskets, which needed a "crush" value, maybe 1 1/2 turns at most. For aluminum heads you absolutely must torque to the correct value, and you really should use an antiseize like Loctite Nickel Anti Seize. I don’t have the shop manual for my Prius, but I did the same procedure on my 2000 GMC Sierra, which had an aluminum head 5.3 litre V8. The shop manual for that motor recommended around 12 lb/ft, and that is the value I used on my Prius.
