Motor and transmission oils differ in smell, so with a certain amount of skill you can determine which of the seals has failed.
To replace the crankshaft seals on a vehicle, you will need: all the tools needed to remove the timing drive (see "Replacing the timing belt of the camshaft drive and the tension roller"), the rear cover of the timing drive (see "Removal and installation the oil pump"), cylinder head covers (see "Replacing the cylinder head cover gasket"), gearboxes (see "Removal and installation the gearbox"), clutches (see "Removal and installation the clutch"), flywheel (see "Removal, inspection and installation of the flywheel"), as well as a screwdriver and a hammer.
To replace the front crankshaft oil seal on a vehicle, perform the following work.
1. Disconnect the wire from the negative terminal of the battery.
2. Set the piston of the 1st cylinder to the TDC position of the compression stroke (see "Setting the piston of the first cylinder to the TDC position of the compression stroke").
3. Remove the timing belt (see "Timing Belt Replacement (camshaft drive) and tension roller").
4. Using two screwdrivers, remove the crankshaft toothed pulley.
5. Using a screwdriver, remove the crankshaft oil seal from the oil pump cover.
6. Lubricate the working edge of the new oil seal with engine oil, install it in the oil pump cover, orienting the working edge inside the engine, and press the oil seal into the oil pump cover until it stops using a mandrel. As a mandrel, you can use a head from a tool kit of a suitable size or an old oil seal.
7. Install all removed parts and assemblies of the timing mechanism on the vehicle in the reverse order of removal.
8. Adjust the tension of the camshaft drive belts (see "Timing Belt Tension Adjustment (camshaft drive)") and generator (see "Checking the alternator drive belt tension and replacing it").
For replacement rear oil seal crankshaft, perform the following work.
1. Remove the gearbox from the vehicle (see "Removal and installation the gearbox").
2. Remove the clutch (see "Removal and installation the clutch").
3. Remove the flywheel (see "Removal, inspection and installation of the flywheel").
4. Using a screwdriver, remove the rear crankshaft oil seal.
5. Lubricate the working edge of the new crankshaft oil seal with engine oil...
6. ...install the crankshaft oil seal into the cylinder block socket, orienting the working edge of the oil seal towards the inside of the engine, and carefully tuck the working edge of the oil seal onto the crankshaft journal.
7. Press the rear crankshaft oil seal into the socket until it stops, using the old oil seal as a mandrel.
8. Install the removed components on the vehicle in the reverse order of removal.
Note: When installing the flywheel, lubricate the threaded portion of the flywheel mounting bolts with Loctite thread locking compound or any similar anaerobic thread locking compound.