Saturn L100 coolant leak

It sound's like your describing the water pump weep hole without a picture it's hard to say. But if there is a large pipe going into it from the other side of the engine where a housing is then your taking about the water pump it need's to be changed. To change it you need a holding tool to hold the chain inside the timing cover while you replace the pump. Let me know.

Yeah the water pump is chain drive on that engine that small cover on the opposite side is where you install the chain sprocket holding tool. That hold's the gear on the water pump when you change it so the chain doesn't drop down. That would be the water pump.

I have never removed the exhaust manifold when i replaced them the directions i have it say's to remove the exhaust manifold heat shield not the exhaust manifold itself.As far as renting the tool i would say no but you can call around to see if you can find one.I found one on amazon for 31 free shipping made by otc which is a good one.I posted a the link to the tool for you plus the directions on replacing the water pump.
http://www.amazon.com/OTC-6616-Water-Pump-Holding/dp/B001C6P0NS/ref=sr_1_1?ie=UTF8&s=automotive&qid=1298840584&sr=8-1

Water Pump Replacement (L61)

* Tools Required
* J 43651 Water Pump Holding Tool

Removal Procedure

1. Drain the coolant.
2. Remove the thermostat housing pipe-to-cylinder bolt near the front of the engine.
3. Remove the exhaust manifold heat shield and bolts.

4. Remove the water pump access plate from the front cover.
5. Remove the right hand wheel nuts and wheel assembly.
6. Remove the right hand inner push-pins and splash shield.

7. Disconnect the engine coolant temperature sensor electrical connector.

Important: A drain plug has been provided at the bottom of the water pump assembly for additional coolant drainage from the engine block and water pump.

8. Drain the coolant from the plug at the bottom of the water pump.

9. Remove the thermostat housing bolts.
10. Move the thermostat housing toward the left hand side of the vehicle while twisting the water feed pipe from the rear of the water pump assembly. Leave the coolant hoses and thermostat housing cover connected.
11. Remove the water feed pipe.
12. Discard the water pipe seals.

Important: The water pump holding tool supports the sprocket and chain during water pump service. The tool must be used or the balance shaft must be re-timed.

13. Install the J 43651 into position.
14. Tighten the bolts on the water pump holding tool into the threads on the water pump sprocket.
15. Install the access cover bolts that were removed earlier to secure the water pump holding tool to the front cover assembly.
16. Remove the 3 inner water pump sprocket to water pump blots.

Important: Be sure to remove both water pump retaining bolts from the front of the engine block.

17. Remove the 2 water pump assembly bolts.

18. Remove the rear 2 water pump assembly bolts.
19. Remove the water pump assembly and water pump O-Ring seal.

Installation Procedure

Important: Prior to installing the water pump assembly, read the entire procedure. This will help avoid balance shaft chain re-timing and ensure proper sealing.

1. Install a new water pump assembly seal.

Important: A guide pin can be created to aid in water pump alignment. Use a M6 m x 6 mm stud. Thread the pin into the water pump sprocket.

2. Using the guide pin, align the pin with the water pump holding tool.
3. Position the water pump assembly against the engine block and hand tighten the water pump bolts.

Notice: Refer to Fastener Notice in Service Precautions.

4. Install the inner water pump sprocket bolts. After 2 are snug, remove the guide pin and install the 3rd bolt.

o Tighten the water pump bolts to 25 Nm (18 ft. lbs.) .

5. Tighten the water pump bolts.

o Tighten the water pump sprocket-to-water pump bolts to 10 Nm (89 inch lbs.) .

6. Remove the J43651.
7. Install the water pump access plate and bolts.

o Tighten the water pump acce********-to-front cover to 10 Nm (89 inch lbs.) .

Important: The water feed pipe seals can be lightly lubricated with silicone gel to aid in assembly.

8. Install a new O-ring seal on the water feed pipe.

9. Install the thermostat housing to block seal onto the thermostat housing, if damaged.
10. Install the water feed pipe into the water pump assembly.
11. Align the water feed pipe to the thermostat housing assembly.
12. Seat the water feed O-ring seal by pushing and twisting toward the water pump. Take care not to tear or damage the O-ring.
13. The water feed pipe has a locating tab to assure proper alignment.
14. Position the thermostat housing against the engine. Be sure that the thermostat housing pipe is properly positioned against the support bracket near the front of the engine.
15. Install the thermostat housing to block bolts.

o Tighten the thermostat housing-to-block bolts to 10 Nm (89 inch lbs.) .

16. Connect the electrical connector to coolant temperature sensor.
17. Install the right hand inner splash shield and push pins.
18. Install the right hand tire assembly and wheel nuts.

o Tighten the wheel nuts to 125 Nm (92 ft. lbs.) .

19. Lower the vehicle.
20. Install the thermostat pipe bracket to cylinder head bolt.

o Tighten the thermostat pipe bracket-to-cylinder head bolt to 8 Nm (71 inch lbs.) .

21. Install the exhaust manifold heat shield.
22. Install the exhaust manifold heat shield bolts.

o Tighten the exhaust manifold heat shield bolts to 23 Nm (17 ft. lbs.) .

Important: The vehicle must be level when filling the cooling system.

23. Verify the drain valves at the radiator and water pump are closed.
24. Fill the engine coolant.
25. Verify the repair and inspect for any leaks.

Let me know how it turns out.