The manual says to use new bolts when working with the subframe. Is that really necessary? These are awfully long (and probably expensive) bolts. I would think they would be good for more than one use.

Peter

I've removed and reinstalled subframe bolts before and I've never had a problem. You should definitely torque them, but I wouldn't go as tight as the spec for a brand new bolt. If the book says to torque them to a certain value and then go X number of degrees, it is because the bolts are torque-to-yield and you're putting a stretch on each bolt. If it was a head bolt, yes I would change it without a question. But, since it's a subframe bolt it doesn't experience the same repeated pounding and torque is not as critical. If it's going to fail, one bolt will break at a time. It's not likely that's going to happen until you whack a curb really hard. If it were mine, I'd torque them and inspect them at each oil change when you're under the car. Since you're the driver of this car (are you?), you're going to notice a change in alignment if a bolt breaks and the subframe shifts because it will change the caster of one wheel and pull to one side.

If you're at all concerned, just go pick up some new bolts and forget about it.

Steve

All bolts that get torqued to a reasonably high value and then tightened an additional number of degrees stretch the bolt. These bolts are designed for one time use, not multiple stretches. You might get lucky and save some money, but having an engine sit on the ground is not what you want to happen.

Klaus
--
Always willing to listen, just not able to take direction.

really necessary? probably not. Would I? Yes.

I think the bolts are about $4-5 each. You have to put 105 Nm on each, then torque an additional 120 degrees. I can't remember what grade they are (8.8 or 10.9) if its 10.9 (stronger steel...) they should be able to handle twice the torque you put on BEFORE you spin it an additional 120. Once you spin them you're getting close to failure with it, and the last thing I'd want is to shear off the bolt head. One broken bolt would really make you wish you had spent the $20..

--
If you're not driving it "like its stolen," are you really driving?