This write up is for the 4.3l V6 "W" engine as found in a 1999 Blazer ZR2.

So in the process of changing my timing chain I decided I would need to change my Harmonic Balancer as the old one was destroyed by using a 3 claw puller instead of the proper tool that has bolts that thread in to the balancer. I wish I still had my original balancer so I could compare the measurements.

Removal:

Harmonic Balancer Removal tools are available form all auto parts stores for either purchase or as a rental. These range from $15-$30. Autozone carries OEM 27019 for $20, which you buy for full price and return it when your done for a refund of your "deposit".

Start by loosening the fan. There are special tools available for doing this, but I found it was possible to use a 12" crescent wrench on the fan nut and tap the wrench with a hammer to shock it loose. Tap the hammer from the drivers side so the nut is turned counter clock wise. I understand this is a 36mm nut if you have a wrench that big.

Remove the serpentine belt. This is done by placing a 3/8" drive ratchet or breaker bar in the spring tensioner and turning counter clock wise.

Then unbolt the A/C compressor and lay it on the top of the front grill so you can remove the fan shroud. These are 4, 13mm bolts and the front right bolt will stay with the compressor so you don't loose the refrigerant, You should use ratcheting box wrench on that one. Also there is a electrical connector on the back that comes off.

Remove the fan shroud. 3, 10mm bolts along the top and 2 on either side half way down to connect it to the lower half. The bottom half is held on to the radiator with a couple of plastic tabs, pop those with a straight screw driver.

At this point in time you can remove the water pump and alternator mounting bracket to give you more room to work with, I'll detail that in a separate thread because it isn't necessary unless changing the timing cover.

Remove the center bolt from the harmonic balancer. This is a 16mm bolt and generally requires an impact gun to shock the bolt to turn without rotating the engine. There is just enough room between the engine and the radiator to use an impact gun with a standard 16mm, 1/2" drive socket.

Remove the belt pully from the balancer, These are 3, 14mm bolts. To use the impact gun requires a 3/8" to 1/2" drive adapter to fit a 14mm socket. Room is tight to the radiator so just tap the gun to crack the seals and finish backing the bolts out with an air or hand ratchet.

Install the harmonic balancer removal tool. Make sure you install the cone at the end of the center screw so you minimize damage to the crank shaft. Turn the center bolt until the harmonic balancer comes off the crank shaft. If needed place a breaker bar between the bolts of the tool to prevent the crank from turning. The balancer will come out from the timing cover about 1.25".

Installation:

Squealing belts are attributable to getting a balancer that is machined wrong and of course this usually doesn't show up until everything is back together. At this point in time you should use a micrometer and measure your original balancer to avoid tears later.

Avoid the Precision Parts balancers that are available from CSK Auto. Apparently these are made in Australia and the companies website is a single page filled with broken links. More to the point, the one I got was 0.13" too long and the ID was undersized 0.06" making it extra tough to get on and off and destroys the serpentine belt. Autozone carries the Dorman 594-181 balancer, which fits almost perfectly. But none the less, compare the measurements to your original.

Apparently CSK Auto doesn't sell or rent a proper installation tool. The clerks at the local store recommended banging it on with a sledge hammer. Do not do this. Autozone carries OEM 27144 for $45.00 which is a good tool for this job. I've also used a Mr. Gasket 6291 installation tool which is built a little more better in my opinion and available on eBay in the $25 dollar range. Prepare the installation tool acording to the instructions. You will want to use the 7/16-20 shaft with the OEM tool and the side of the thrust bearing with writing is the one that goes towards the balancer.

Heat the new harmonic balancer in the oven. 250 degrees for 30 minutes. Apply oil to the threads of the install tool and the crankshaft. I used some new 5W-30. Also put some on the balancer inner collar when it gets out of the oven.

Using oven mitts, put the balancer on the crank shaft and rock it back and forth a bit to get it started on the crank shaft. Thread in the installation tool and start cranking the large nut with a crescent wrench. Work quickly as the 2 metals surfaces will come to equilibrium whiten a few minutes.

There has been alot of debate as to how far to turn it without destroying the tool or threads. As long as the balancer is hot it should turn down fairly easily. With a caliper I was able to measure 1.01" between the top deck of the balancer and the top surface of the crank shaft. So I would assume that 1" is the ideal measurement.

Install the pully on the harmonic balancer, take care not to cross thread the bolts as they are all fine thread. Using a straight edge make sure the pully aligns with the gooves in the pully on the power steering pump.

If all is well install the center bolt and torque it to 70 ft. lbs. I used a new Mr. Gasket part 945 because the threads on my original bolts were damaged.

Reinstall the rest of the components in the reverse order they came off the engine.