Don’t overtighten your water pump pulley bolts

[jgilber0]

Total boneheaded mistake – I misread the shop manual and tried to tighten my water pump pulley bolts to 80 foot pounds!

In the Bentley manual, nearly all the force specifications for bolts are in foot pounds, but for some reason the water pump pulley bolts are in inch pounds.

Same thing here:

http://www.e30zone.net/e30zonewiki/index.php/M20_Timing_Belt_Change

I read it three times, and ignored my gut which kept saying “that’s awfully tight for such a skinny little bolt!” Sure enough, one of the little bastards broke off.

Thank goodness I was able to unscrew the remaining hunk of bolt from the water pump. If that hadn’t happened, I might’ve had to tear down my entire front again.

Don’t make this mistake!

[digger]

I tighten stuff like that by feel lol

[kronus]

That bolt size is definitely in the category of a very light grunt

[e30davie]

yah, i don't put the torque wrench near anything other than a head bolt and a caliper bolt these days. Learnt my lesson good and proper a few times.

However breaking stuff is how you learn mechanical sympathy. Its very difficult to describe "tight enough" to someone. You really have to take some heads off bolts to really get an idea:)

[jgilber0]

...breaking stuff is how you learn mechanical sympathy. Its very difficult to describe "tight enough" to someone. You really have to take some heads off bolts to really get an idea:)

I’m just glad that was a simple error to fix. Lesson learned!