Weld a larger nut over the broken bolt and let it cool. It will turn out for you.
To remove the tensioner, you will have to remove the belt as well as unbolt the motor from the motor mounts and lift the engine. Be cautious to block up the engine before removing the mounts. The wheel well side cover and timing cover will also need to be removed. At this point you will have access to remove the tensioner.
there should be a bolt that holds it on to the engine block, just take of thee belt and remove the tensioner.
Remove the Right wheel and inner plastic fender which will allow you access to the tensioner side of the motor. There will be a few bolts holding into place on the block. Remove the bolts and remove the entire tensioner assembly. Reverse for replacement.
After you have released the tension from the belt, remove the 2 obvious bolts that hold it to the engine block.
The procedure for changing the tensioner is to first remove the belt. Remove the two bolts holding the tensioner to the engine block. This may require you to remove the bolts through the wheel well, via the access hole in the firewall. Once the bolts are removed, change out the new tensioner for the old one, and repeat the process in reverse.
You have to remove the tensioner assembly, not just the tensioner pulley, but the whole assembly, in order to access the plastic bypass hose. Be very careful, as these pipes get old, the plastic becomes brittle, and possibly the flange end will break off and remain in the block when you remove the pipe, check the block opening carefully to remove all of the remaining flange. Also, be very careful when removing the lover pipe nipple into the engine block, if you try to pry the tensioner assembly off the block, you will probably snap off the machined nipple that locates into the block, Ask me how I know!!! Good Luck, it can be done but you need to move carefully and deliberately. (by the way, a rebuilt tensioner assembly costs about $80 US, the pipe is about $6. New tensioner assembly comes with the pipe)
the belt tensioner is mounted to the block if you are trying to change the tensioner tou have to remove the alternator.if you are trying to change the belt it is the pulley to the left of the alternator it takes a 15mm wrench which you have to pull upwards to release tension
Move the tensioner to release belt (use bolt in center of pulley and move with socket) Then simply remove bolts from block. Reverse to put on new one.
The easist thing to do is replace the tensioner. A new one will set you back around $40 and should take you well under an hour to change. Just release the belt and remove off the tensioner, undo the single bolt that holds the tensioner in place, remove, and replace. The hardest part is there isn't a lot of room to get your hand in there so you might have to remove the idler wheel to get more room, but again, this is only held on with one central bolt. Hope this helps.
1. Place a three-eighths-inch ratchet driver into the square hole on the face of the tensioner pulley. The idler pulley is bolted onto the side of the engine block and does not attach to any other accessories. 2. Pull up on the ratchet handle to release tension on the Cadillac's serpentine belt. Pull the belt off the tensioner pulley. Don't remove the belt from any of the other pulleys. 3. Remove the two bolts that secure the tensioner arm to the engine block using a socket and ratchet. The pulley permanently mounts to the tensioner arm. 4. Remove the tensioner arm and pulley from the engine bay.
To change the tensioner you will need to support the oil pan with a floor jack and block of wood, Remove the upper engine mount 15mm nuts (5), then jack engine up a bit Remove the serp belt Remove the upper tensioner bolt. Lower engine down to normal position, remove the r/f wheel Remove the splash guard Remove the lower tensioner bolt. Jack engine back up and remove the tensioner. To install install in the top and LOOSLY put in uppwer bolt Lower engine and install lower bolt Tight then reassemble wheeel etc jack engine tighten upper bolt and fiish reassembly
The dodge 400 is a big block.