My old Bunn coffee maker started boiling water out the resorvoir rather than pour out the sprinkler head. I unscrewed the head and ran the delimer spring through it, and it is totally clear. Now what?

Water discharge tube from heated tank is likely caked with mineral deposits. Bunn makes a de-liming tool for just such a problem.
Google "bunn deliming tool", or buy it on Amazon.
Bunn Deliming Cleaning Spring 01193 0000

To clean the vpr you will need to take the lid off the machine. Be sure to unplug while doing this. First clean the water tray. You can unscrew the nut holding this tray and clean the tray in your sink. Put the tray back in and put the lid back on. Plug coffee maker in. Fill one coffee pot with vinegar and pour it in machine. After the water finishes coming out let the coffee maker sit overnight. Before you start filling the maker with water at least 6 times, be sure to clean the spray head. Make sure the 5 or 6 holes are free and clear of any build up. Then start with fresh water. Fill the coffee pot with fresh clean water and pour into machine. Let it finish and do this at least 6 times. If you can still taste or smell the vinegar repeat until you cant.

turn the water main off, unscrew the spigot base just below the handle, and pull out the silicon cup. delime spigot and inlet with a deliming spring or a screwdriver. make sure the cup is pushed all the way onto the handle post and reassemble.

Try using a bunn deliming spring.Remove sprayhead and run thru the brew tube all the way into the tank.If the water is hot the brew tube is partially blocked going into tank.

First thing to check is that there is no blockage in the funnel. Next thing is check the spray head and make sure that it is not limed up. After removing the funnel there will be a round silver head that screws in above the funnel, it can be removed by hand but usually you need a pair of channel locks. If so you can clean the spray head with a wire brush. Also if that is not an issue you can purchase a deliming spring from http://www.google.com/imgres?imgurl=http://ecx.images-amazon.com/images/I/21IeXJoqjnL._SL500_AA300_.jpg&imgrefurl=http://www.amazon.com/Bunn-Commercial-Deliming-Spring/dp/B0032QNRH2&usg=__mJkJExy1qExfrZEEbtxW6EAQGSw=&h=300&w=300&sz=5&hl=en&start=4&zoom=1&itbs=1&tbnid=tHf1BPtEJIafsM:&tbnh=116&tbnw=116&prev=/images%3Fq%3Ddeliming%2Bspring%26hl%3Den%26gbv%3D2%26tbs%3Disch:1
WIth the deliming spring you need to remove the spray head and simply run the spring through the hole til you hit the water in the tank and pull it back and forth about 4 or 5 times. Also something siple make sure there is only one coffee filter it is easy to put two in. Hope this helps.
www.midstatebeverage.com

It sounds like the thermostat might be allowing the water to boil and cause the grounds to be scorched and making your coffee bitter. It also could be caused by the machine needing to be cleaned and delimed. I would recommend you do this first-and if you don't have the use and care manual, you may call Customer Service to have one sent out or access one at www.bunn.com @ home, then products.

The pressure stat is defective and needs to be replaced.

You might try this first. Remove the entire top lid and remove the clear suction cup located near the back of the brewer. Clean this cup with white vinegar and also take your deliming tool and place it in the hole where the suction cup was and clean out. If this does not correct the problem, please call customer service with the model and code date. If your machine is 3 years old or less, we can replace it at no cost. If it is over 3 years old, we will replace it at a reduced price.

You can go to Bunn.com and print one out or I think buy one. To clean you need a deliming spring and white vinegar. You put the spring up into the hole where your water comes out of to empty into your carafe. Remove the grounds basket. then remove the spray head by twisting off. Then you are ready to put the spring into the hole. Insert all but a couple of inches into it. If it has been awhile you may have to force it by twisting and pushing. Work the spring up and down and it will eventually go in and out with no problem. Check the holes in the spray head to make sure they are clean and free of any build up. As you know Bunn has a reservoir where water is kept hot. You put in and what is in the reservoir comes out. Pour 1 quart of white vinegar into the pot. Let it sit for two or three hours or longer is OK. After your wait pour water in 8 to 10 times to flush all vinegar or you can unplug the pot and turn upside down over the sink. If you do this while the water is still hot be careful. Most of the water will come out of the hole where you put the deliming spring into. Some will come out of the top possibly. If you do it this way make sure you fill back with water before you turn it back on. Repeat vinegar flushes again if you water isin't running clear yet.

Use the de-liming spring to clean the copper tube behind the spray head. Pour several pots of clear white vinegar through the unit to further remove lime and scale from the interior of your coffee maker. My Bunn is 24 years old, and the only replacement parts I've ever required are new carafes and the 4041 silicone washer repair kit.