How do you replace the alternator on a 1991 Honda Civic Si?

to replace the alternator there is 2 bolts.. one that lets you adjust the belt to take it off and tighten it and one at the bottom of the alternator and it come right off. Now the hard part is removing it from the engine compartment. I removed the brake booster to gain enough room to remove the alternator from the top. remove the 2 bolts holdind it on to the firewall and gently pull it back, there is a shaft with a spring attached to it on the inside of the booster along with a rubber O-ring, KEEP ALL THESE PARTS TOGETHER and DO NOT remove the shaft and spring from the booster housing!! JUST PUSH THE BOOSTER ASSEMBLY GENTLY TO THE SIDE ENSURING YOU DON"T BEND OR BREAK THE BRAKE LINES!! Once you removed the booster you can now remove the alternator through the top. To install just go in reverse order. Make sure and re-attach all the hoses and electrical wiring that you removed. Caution: DO NOT overighten the nuts on the brake booster when re-installing!!!!!

There is an easier way:

'89 Civic si 3dr: Alternator removal

Note: if it's been a while, best to use 6 point sockets / wrenches on all

A tiny drop of penistraining oil on fasteners where steel meets alum helps

But DO NOT soak em! - probably would be better to just leave em dry

Jack up & remove LF wheel

Disconnect + battery cable (10mm)

Depress pry tab & disconnect larger round multi connector

Remove (10mm nut under boot) alternator + cable

Loosen top alt adjust bolt (12mm?)

Loosen (14mm) nut from lower alt sleeve bolt (easier from below)

Push alt toward timing cover & remove belt

Remove lower (14) nut & upper (12) bolt loosened above

Tap sleeve bolt (w/wood or plastic) thru & remove (other end welded square flange)

Wiggle and/or gently pry alt off (place on frame behind oil filt for now)

Can remove upper bracket (14mm) to get outaa way

Remove lower sleeve mount bracket (2X14mm)

Remove 3 plastic (Phillips) snap nuts from crank splash shield in front of LF axle

Pull shield down & leave hanging (leave 4th snap nut underneath in)

Can now slide alternator along frame and remove past crank pulley thru wheel well

Reasm notes: A little auntie seize lube on all (non electric) threads will go a long way next time you go to loosen ( if you have a car this old you probably already know this).

Square flange on lower sleeve bolt is not perfectly square, (rotate 90 deg. if necessary).