Crankshaft Sprocket and Seal

Andrew Sarangan

My Kia has had a persisient oil leak for years, which I finally traced down to the crankshaft seal. It is a $5 part, but to get to the seal, all of the following items have to be removed: accessory belts, water pump pulley, timing belt cover (three pieces), timing belt rollers, timing belt tensioner, the timing belt itself, and crankshaft pulley/harmonic balancer. Then the crankshaft sprocket that drives the timing belt has to be removed. It is a fairly big job to get to the small seal.

Prior to removing the timing belt, the camshaft and crankshaft positions have to be moved to their respective alignment marks. The Kia is an interference engine, which means that the valves can contact the piston if the alignment is incorrect.

Once all the accessories, timing belt rollers and tensioners are removed, the timing belt can be slid off the crankshaft sprocket. There is an alignment mark for the crankshaft sprocket as well, which must be preserved.

The crankshaft sprocket is locked in place with a Woodruff key, which was easily removed by pulling it with locking pliers. Once that’s done, the sprocket should slide off the crankshaft. However, years of corrosion had fused the sprocket to the crankshaft. I made the mistake of trying to push it out with a prybar, and that broke off the back flange of the sprocket wheel. Heating it with a torch and soaking it in PB Blaster had no effect. The standard gear pullers did not work either because there wasn’t enough room behind the sprocket to grab on to. I drilled and tapped two 6mm holes (while breaking off the drill bit and having drill a third hole). In the end, I didn’t need to use these holes. An armature bearing puller from Amazon did the trick. It had a very thin lip that I was able to slide behind the sprocket and pull the whole thing out.

Pulling the old seal out also requires some care to avoid damage to the underlying surfaces, but I was able to pry it out carefully with a flat edged screwdriver. Then the whole area was sprayed and cleaned.

To ensure that the new seal goes in parallel to the face, I used a sawed off PVC pipe and a bearing installer puck, and hit it with a soft mallet.

New seal is installed.

Since the old sprocket was destroyed, I had to buy a new one. However, none of the standard places like rockauto carried this item. I called the Kia parts dealer, and they said it is not available anywhere in the whole country. Luckily I found one on Ebay.

Installing the timing belt requires some careful thought because the belt is under significant tension, and its alignment is critical. The trick is to use zip ties to hold the belt against the cam sprockets at the correct positions. This way the cams can be allowed to rotate without losing their belt position. Then tie one of the cam sprockets to the frame to prevent movement. This allows the second cam sprocket to be turned with a wrench to stretch the belt and allow the tensioning rollers to be installed.

In addition to the timing belt, all of the accessory belts should also be replaced with new ones when we are this far into the process. Before starting the engine, it would be wise to rotate the crankshaft by hand a couple of revolutions to make sure that the cams are moving correctly, and that the valves and pistons are not interfering. Everything came back to life, and the engine oil leak was gone.

Leave a Reply

Your email address will not be published. Required fields are marked *