stuck bolts

have you watched any of the battery replacement video's?

 

Maybe: see page HB-89 in the attachment. Try an impact wrench, either an electric one, or even the kind you hammer?

 

These bolts are tight, but they've always come loose for me with a 3/8 ratchet and socket. Sometimes my impact driver will not budge them. Check to make sure you're going lefty loosey and don't be afraid to put some ummmph into it.. They're also very easy to cross thread, so the possibility does exist that a previous user did that. I've seen people cross thread them and then say the heck with it and drive them all the way in.

 

Try taking the battery out without seat removal first. You may reach an impasse, at least you tried.

I get the sense the Repair Manual goes overboard, sometimes.

 

Use some type of extension bar to add to your socket wrench for extra torque. Ideally you should have a breaker bar to do the job. Remember after you loosen them, you'll have to torque them just as tight to secure them when you're done.

 

If they were originally installed with the specified torque, and then they rusted to the car, the torque you need to apply to break them loose will be waay more than they should be tightened to when you put them back in.

If they are badly stuck, then the approach of just exerting tons of torque hoping to loosen them will run a nonzero risk of breaking them off (which solves your removal problem, but creates a devil of a headache for reinstallation). If you try to apply the same torque when tightening, you run the same risk of breakage again, to no purpose.

If you get them out, run a thread chaser up and down the threads to clean out the rust, add a touch of anti-seize, and tighten them with a torque wrench to the specification, no more.

Lisle and Thexton both sell interesting tools for rusted fastener removal that work in conjunction with an air hammer (not an impact wrench).

They work by recognizing that repeated blows really do help to break up the rust and let the fastener move, but they don't have to be repeated twisting blows like you get from an impact wrench (which, again, could just twist the bolt head off). They let the air hammer rain down lots of fast blows straight onto the head of the fastener, shaking it up and down to loosen the rust, while you turn the tool with an ordinary wrench and only an ordinary amount of torque.

P.S. over the years, I've become very wary of rusty bolts that want to break. If you overcome the initial stuck-ness and it starts to turn, you're not necessarily out of the woods yet. You might relax and start unscrewing it with the ratchet and it comes out a few turns, then starts to feel a bit bindy again, you keep twisting and snap.

If one is on the way out and then starts to feel bindy again, I usually stop, spray some more penetrant on any threads that might now be accessible because it came out a few turns, reverse the ratchet and drive it a couple turns back in, then back-and-forth it a little before trying again to unscrew it further. I've been known to do this several times for one especially cantankerous bolt.

 

If you're in the USA, then Kroil is your friend.

Amazon.com: kroil penetrating oil

If in the UK, then use PlusGas!

Amazon.com: plus gas penetrating oil

 

I've removed these bolts many times and they are torqued really tight. They cannot be removed with a short socket wrench (unless you're really strong), need a proper breaker bar. It's not rust that is keeping it tight. Those bolts have no way of getting rusted.....unless of course the car has been flooded before.

 

Still, maybe OP should try battery removal first?

 

Well, as it happens, a closer look at the manual excerpt Mendel posted doesn't show any instruction to remove the rear seat backs at all ... only the bottom cushion, which just pulls out. So if that's to be believed, there's no reason to fuss with the seat-back bolts.

The torque spec for the bolts from the seat-back hinges to the seat frame is 27 foot pounds. Shouldn't feel any different from the (properly tightened) oil pan drain plug when changing the oil.

(The spec for the seat back hinges to the body is even lower, 13 foot pounds. But I think normally you'd leave the hinges attached to the body if just removing the seat backs.)

 

Don’t know about with the Prius, but the seat bolts on BMWs have Lock-tite on them and are supposed to be one time use. Not sure if that is also the problem here....

 

pipe = breaker bar

 

Apologies for the necro, but I have a similar problem but in reverse. I am trying to reinstall my seats after changing the hybrid battery, and the two middle bolts only screw in part way before seizing up. The two outer bolts closest to the doors easily go down all the way, so I'm not sure why the middle two bolts are stuck. I don't recall having this much trouble removing them. Could the bolt hole have been cross-threaded somehow, and if so is there a way to fix it?

 

That's always a possibility to be alert for. I would carefully back them back out, and equally carefully run a thread chaser or tap of the proper size and thread down through the hole to make sure it is clean, and maybe also run a good nut or die of the proper size up and down the bolts to make sure no defects on those.

 

I suppose they could have been cross-threaded. Or maybe there's rust or some other debris in there. Your best bet is probably to get a thread tap the right size and chase out the threads with that. Use some oil on it as you run in the tap and if the tap gets tight, back it off a turn or two and then resume.