Harmonic Balancer seal

So along with my VC and RMS, the Harmonic balancer seal leaks too.

I've been reading posts about how to replace the HB (it requires puller/installer). From what I can tell, the balancer is not wobbling and turns straight; it just leaks like a sieve.

However, I'm not exactly sure how the whole thing is set up ... how does the HB attach, and how does it seal?

Can I just replace the seal or do I need to replace everything?

It takes a puller to get the dampener off the crank. It is held on with a bolt and a large washer into the end of the crank. I normally ends up being a lot less work if you go ahead and pull the radiator. If the rubber in the harmonic dampener is fine, just make sure the surface where the seal runs is smooth and not pitted or scratched. They do make a jiffy sleeve that can be put over the HD if the surface is bad, but I would just replace the HD if that is the case.

You have to pull the timing cover IIRC to replace the seal. When you have it apart, check that the timing chain isn't stretched.

Year/engine?

There is a bolt holding the HB to the crank, you will need a longer bolt, some washers, and some grease to start the new HB--the original bolt is too short to get the HB started.

Grease between the washers (for ease of operation), use the longer bolt with washers to start the HB without destroying the threads in the crank. Draw the new HB onto the crank, remove long bolt, remove a washer, draw the HB some more, remove bolt, remove another washer, draw the HB some more, remove bolt, remove another washer, keep repeating until you can use the original bolt and make sure to torque it down to specs.

As far as the seal, and whether or not there is an oil slinger in there will depend on the engine and year.

I have a 1988 MJ.

So how is this whole she-bang set up? The HB is just the big flywheel, right? It dampens vibrations from the crank. The end of the crank is threaded, and the bolt from runs through the middle of the HB and into the crank. Does all that sound right?

Yep, but the flywheel/flexplate is at the other end of the crank.

Oops, my term of flywheel was misleading. I meant to say 'pulley'.

crap, so you need a longer bolt to get the HB back on??? I thought you could just use the HB "Puller" to kind of push it back on......

no, what i did was went to auto zone and had to rent a HB installer. basicaally a long threaded rod with a large ball bearing ring on the end to help push the HB back on evenly

So the puller and the installer are two separate tools then - ya?

yeah they are. i know it sucks. when i was swapping in my stroker, people were telling me just to use a block of wood and a hammer to get it to sit on there right. but i didnt want to take the chance of it not seating properly so i just ran to the auto parts store and rented one. It only took ten minutes to get it in there. hardest part was finding the right piece of threaded rod to fit in the HB

Depends on which store. The Autozone is two separate tool kits.. the ones I get from Advance are one tool kit.

So how does an HB actually go bad?

Can the seal go bad w/o the HB being bad?

bigalpha said:

So how does an HB actually go bad?

Click to expand...

The outer metal ring separates from thew inner mounting part

Can the seal go bad w/o the HB being bad?

Click to expand...

Yes, just like any other seal.

Depending on how many miles you have on it you may just want to replace the HB while you are doing the seal.

So the HB is actually two parts that are connected? Then there is a bolt that goes through the middle and holds it in place on the crank.

So, what type of seal is it that keeps it from leaking? Is it an o-ring or what?

Yes, its two pieces with a rubber ring connecting them. Then there is a bolt and larger washer that holds it to the crank, torqued to 80ft lbs.

The seal is just like an o-ring, similar to seals found on axle/transfercase yokes.

So it's really just a matter of unbolting the HB and installing the new seal/HB.

Remove bolt, pull off balancer, remove seal, reinstall seal, reinstall balancer and bolt.

Fabulous. I'll have some time to get on that soon, I hope. I'll report back on whether I caught the truck on fire or if it went ok.

The HB is just a specialized pulley and has nothing to do with the seal as such. It just happens to be in front of the engine's "front main seal" and therefore has to be removed to get at the seal. The seal itself is mounted in the timing chain cover. I believe it is possible to change out this seal without removing the cover but if you are going to the trouble to remove the balancer anyway, it usually makes sense to go ahead and remove the cover and inspect the timing chain and tensioner. Replacing the seal with the cover off is an easy job.

The HB has two steel parts joined by a rubber ring. Over time, this ring will deteriorate and begin to bulge out. As this happens the rubber may contact the timing cover and wear a groove eventually cutting completely through the metal. It may also begin to wobble shredding the drive belt. For these reasons it usually makes sense to go ahead and replace the HB when going to the trouble to remove it to work on the seal and/or chain but it is not necessary if the HB is in good condition.

There is mention of a special tool to reinstall the HB. Fine if available but all you really need is a common bolt from the hardware store that is a bit longer than the original bolt along with some washers. When reinstalling, make sure the key in in place and the balancer should go on the shaft easily.

Finally, a common inexpensive strap wrench can be useful to keep the HB from turning while loosening the center bolt. The book will tell you to put a big screwdriver or similar through the puller bolts but all this accomplished for me was to bend the bolts and send me off to the hardware store for replacement. It usually makes sense to rent these specialty tools but these pullers are inexpensive and have other uses in and about the shop.

Thanks for the detailed response, Pelican. This process seems straight-forward enough. I assumed the seal was a part of the HB process. As long as the HB is in good condition, it is reusable?

To tackle this job, I need a removal/installer tool, new HB, seal, and timing chain cover gasket.