torquing spark plugs hot or cold???

Hey everyone,

Kind of a silly paranoid question but I decided to check the torque on my spark plugs a few weeks ago to make sure they were still at the fsm spec'd 13 ft lbs (I have the 5VZ-FE 3.4). All I did was just set the torque wrench to 13 ft lbs and apply the torque to each of the plugs. The engine was cold when I checked the torque probably about 35 degrees F. Main question is, does anyone know if Toyota wants the plugs torqued on a hot or cold engine? NGK seems to want them installed on a cold engine which is the brand of the plugs installed (

$6 BKR5EKB-11 NGK Spark Plug Stock # 3967

BKR5EKB-11). Installing (or torqueing them) on a cold engine seems to make the most sense to me as the plugs and heads will be at the same temp and will then expand accordingly. I honestly might be making mountains out of molehills but I like to do things right.

 

I thought the aluminum was slightly weaker when it's hot, so you risk damaging the threads (stripping them) when torquing hot. I don't know if it's really significantly weaker at 200°F compared to 35°F, but I've always played it safe and waited about an hour after the engine is turned off.

If the torque wrench clicked then you should be good. If you kept turning and turning and it never clicked then you've got a problem!

 

Cold or at least cool. Metal expands when hot. Torque it hot and you're over as it contracts.

However doing what you did doesn't mean they're torqued correctly, it only tells you they are at least as torqued as they're supposed to be. If you really want them to be at xxx pounds you have to loosen below that amount and then correctly torque up.

 

When I did the initial install I torqued them to the proper spec. Doing the re torque was just ensuring the bolts didn't loosen over the span of time from the initial install.