What are the classic signs of a blown rear main seal? I know oil leak, but where? I honestly can't find anything when I searched on here.

The rear main seal is the crank seal on the transmission side, but you have a crank seal on the passenger side as well you can see if you take the timing belt inspection covers off. (12mm bolt for the upper one) That one is much cheaper to replace than the other one.

I you pop your hood and look on the passenger side of the motor at the plastic timing cover and go about 1/4 way down you will see the bolt that holds the inspection cover on. 12mm bolt. You unbolt it and lift the cover straight up. You can then shine a flashlight in there towards the bottom. If you see the oil around the bottom, that's the crank seal. If you have oil dripping or running down from the timing sprockets, those are the cam seals, and again, cheap (relative) to replace.

There is a small weep hole close to the bell housing of the tranny. When the RMS fails, engine oil will start dripping out of the hole.

Klaus
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Proud owner of a 220S. If I had more room, I would have more Volvos.

I bought this car and the previous owner told me the rear main seal was blown. When the car gets to operating temperature and the oil heats up a bit, it starts dripping (fast) from the passenger's side.

And the engine seals begin to leak when the crank case presure gets too high. You need to find out where the source of the oil leak is, the tranny is on the driver's side.

Usually, oil leaks on the driver's side are from the oil cooler lines at the radiator or the bottom of the engine. Remove the Tbelt cover to verify the location of the leak - you will need a flashlight.

If the crankcase pressure is too high, check the PTC nipple (do a 'search') and check for positive pressure at the oil dipstick.

Klaus
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Proud owner of a 220S. If I had more room, I would have more Volvos.

I thought I should update this on my findings.
I popped the timing belt cover off and found that the exhaust camshaft seal had unseated, and that looks like the source of the oil leak. I am ordering a new one and having it shipped over, along with a new timing belt.
This means the crankcase pressure was too much, and I also found that two of the vacuum lines from the PCV box were cut, so the PCV system must be completely clogged and caused that seal to leak and unseat.

You are in luck, it's a 95. Much easier to work on than a 99+. Suggestions from the peanut gallery:

Loosen the cam gear bolts, use a pencil or awl and scribe the washer/bolt location on to the cam gear. You need this to put it back in the same spot.
Remove the 5 spark plugs. Line up all 3 timing marks, the crank mark is a real pain to see.
Remove the bottom shield for the belt next to the crank pully.
Cut off the old Tbelt.
Take off the exhaust cam gear.
Dig out the old seal, tap the new seal in place after wiping it clean.
Check the tensioner rollers for smoothness.
Put on a new Sbelt?
Put it all together. Slowly.
Turn the engine 720 degrees by HAND to make sure it is all together correctly.
Put the plugs in and start the engine. Let it run for at least 3-5 minutes.

Replace the separator box and all of the lines. Clean out the hole through the block, you can use a flat screwdriver if needed. It gets pretty crusty down there.
Clean out the PTC nipple before putting the vacuum line on it. Be careful, the old plastic gets brittle. Use a flashlight to see properly.

Use synthetic oil only! Unless you want to try AutoRx in the engine oil for 1,000 miles to clean out any and all passages in the block.
Then get a new oil cap seal and start running it. Keep the revs up and heads up for law enforcement :)

Klaus

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Proud owner of a 220S. If I had more room, I would have more Volvos.