Thanks, lots of great information, should be of value to many readers of this thread. Just for discussion, I decided to drain the rear differential with the car on the garage floor, I didn't even raise it on low ramps, so I had more difficulty developing much torque with my outreached arm I just looked up the torque, surprised to find it is 30 ft-lbs. I carefully watch all fluid changes, oil included, by putting a clean piece of cardboard under the drain plug area and coming back in a couple of hours and look for any drips - of course I wipe the plug area well before putting starting the drip test. This was my first rear differential change and the only other person to have their "hands" on my Forester is the dealer, and never for service. But when they get the car in they do a general check over and come up with $500 + recommendations for fluid/grease change. I always figured that was a good deal, they are looking for more profitable work and should be good at finding real problems too. Now here's one for you, given what I just said, I yesterday pulled the glove box to gain access to the cabin air filter. I figured it would be time to change as it is recommended at 30K and the car has 55K miles. Wow, open the filter housing, no filter! Now where did it go? Anyone's guess, but the only two I can come up with is 1) factory error, 2) dealer took it out and forgot (?) to put it back during one of their look for work efforts. The car has been to the dealer twice, once for tires and once for a recall. The '04 Forester has a "crush" washer on the oil drain plug, and when not changed/replaced at least for a few (I wasn't counting) drains it may start to drip very slightly. I was in Advance Auto yesterday to buy ATF to drain/fill the auto transmission (just the pan, no power flush)and asked after purchasing some new crush washers. They had some, per their computer, but had trouble finding them. They must not be a big seller. I have never replaced an oil drain plug washer in any other car and I've kept one of those to 200,000 miles. There may be an oil drain plug replacement with a better washer arrangement. I suppose the auto transmission drain plug is the same. But as this is the first time it is off, I'll just reuse it.

A dirty engine air filter will indeed cause a car to run poorly, lack power, burn too much gas. The car "breathes" through the air filter and a clogged one restricts the air coming in. But a dirty engine air filter has nothing to do with the car's heater. The heater runs off the warmed coolant (yea, sounds backwards). As the car warms up, the warmed coolant supplies warmth to the interior heater. Some cars have cabin air filters and maybe that's what they were referring to. But if the fan blew out air that wasn't warmed, the no-heat problem was unlikely to have been caused by a filter.

Timely topic! We live in a wooded area with lots of oaks and maples and stone walls and gardens. Consequently there are many chipmunks. They have nested in my car's cabin air filter and have even hung out in the cabin. Their scat resembles that of other small rodents, but the acorns in the nest is sort of a giveaway. I have cleaned the vehicle and replaced the air filter on more than one occasion. I recently did that, and the chipmunk/s is back again. I had saved a dead, dried out, cool, large benign insect (to photograph) in a small cup that I set in the center cup holder bin. It was very DEAD. A few days later when using my car, GONE! Mr. Chippy took it. So, once again I must go through the cleaning, sanitizing and replacement of the cabin air filter. Grrr. It goes without saying that rodent poop, like the scat of most wild animals, is nothing to mess around with. Rodents can harbor parasites and diseases. I spent a while perusing online for solutions to this common problem. I read about a lot of purported solutions, most of which are ineffective or problematic (dryer tissues, scents, gizmos and gadgets, and, heaven forbid, poisons -- NO!). There is no way to "exterminate" every chipmunk, even if I wanted to. Our home is in a conservation area, for one, and there are hundred of nut and seed producing trees. One year a small weasel showed up and had a talk with a lot of the chipmunks. Weasel was t seen this year. I am going to have to clean out the garage from inherited furniture, replace the rodent chewed garage door gasket, and keep the car or cars in the concrete bunker garage. Meanwhile, I will try to remember not to have any snacks, even food, taco wrappers in the car. No eating and no crumbs. No ketchup packets in the glove compartment. I will look into installing some wire mesh physical barrier around the air intake and the cabin air filter. Not as easy as it might sound. Here, below, is the only promising approach I can across online. It is from a viewer's comment on a YouTube video and I will include it here for the purpose of discussion. Seems like a lot of effort. (Note: anyone trying to install a mesh barrier wants to be sure that they don't end up choking off outside air supplie to their engine of something important.) ~~~~ The only way you can stop the mice from getting into the Cabin air filter in a Toyota Corolla is to place 1/4" square wire mesh (buy from Home Depot), in a small roll, ( its called "1/4 x 1/4 Welded Hardware Mesh" ) over the openings where the air goes into the car's cabin. I own a 2008 Corolla and I raised up the front hood, then removed the passenger side plastic cover that is at the base of the window, and that gave me access to the air intake holes. Guess what: Toyota made it all but impossible to actually get your hands into that space where the air intake is. They put another beam in front of the intake, about 1.5" in front of it. I cut 2 strips of mesh, each one 2.5" wide, (one set 5" long, another one 6.5" long), and I used 1/2' dia SUPER-MAGNETS to hold the wire mesh strips into place while I used 'Goop' glue (from Walmart) to glue those mesh strips securely into place. The magnets 'PUSH' the mesh onto the metal of the car itself, so the mesh has to be placed between the car and the magnets. I just left the magnets behind on the 2.5" wide mesh strips. For the 2 mesh strips on the left hole; I had to glue the magnets onto the strips first, then let the glue dry, and then push the strips in with the magnets securely fastened to the strips, because the magnet at the far end is so far into the body work of the car that its impossible to actually get your finger into that space to place the magnets once the screens are pushed into the proper place. As if this was not hard enough, Toyota placed a bar in the middle of the air intake hole, so you have to cut the screen covers into 2 halves, one half for the left hole (using 2 6.5" long strips) and one half for the right hole (using 2 5" long strips). Because the holes in the beam covering the air intake are only 2.5" high, that means the strips of mesh you insert cannot be more than 2.5" high. But what you REALLY need is a screen 4.5" high, the only problem is you cannot actually get a screen that wide into that space because the holes in the beam in front of the intake are smaller in size, that's why you have to insert 2 strips of screen, each 2.5" high. Yes, Toyota has really fu*ked up big time with this design ! First you place one 2.5" mesh strip over the hole, so it covers the lower half of the air intake hole. Then you take the second 2.5" mesh strip and place it over the hole, raising it upwards so it covers the upper half of the air intake hole. When you push it up it is pushed up and almost out of sight, so you have to do everything by feel, and using a small mirror to see what's happening. Doing all of this is an all-day job. But once you are finished there is no way in Hell any mouse is going to get through that wire mesh. The problem is that there are so many OTHER places around the car for those mice to build nests in, so just covering up the access to the ventilation system will just push them to build a nest somewhere else instead. But at least the insides of your car won't smell bad anymore. ---- Was a comment on the video below. https://m.youtube.com/watch?v=O9JruyHm89g

I found how to fix a late model clothes dryer that needed a new heater element; and more recently how to fix my electric corded lawn mower (a $5 part that took 5 minutes to install), repair shop would have charged over $70. I learned how to disassemble, clean and reassemble various vacuum cleaners also. BTW in the process of learning to repair the lawnmower, I learned that it is important to to open the cover and clean out accumulated grass clippings - I was shocked to see all that were in mine - because they can actually get into the motor eventually and ruin it.