How does a screen door closer work?

 My screen/storm door started slamming a lot when the weather got cold. I adjusted the screw and it got better for a bit, but then would close really slowly, or start slamming again. I replaced it, and being curious, cut the old one open to see how it worked. (Google searches turned up nothing, so I'm posting here.) 

The first lesson is that it was all air operated--there's no fluid like in a car's shock absorber. The bulk of the thing is a cylinder and a piston and the screw adjusts how quickly the air is released as the piston compresses air in the cylinder, thus determining how quickly the door closes. The cylinder contains a big spring that gets compressed when the door is opened and pushes it closed when you let go. The piston part has a rubber O-ring around it as a seal.  

The O-ring rests in a groove that is a bit wider than the rubber ring, so that the ring can slide a bit. When the door is opened the O-ring slides, letting air go past the piston through four passages in the piston (see photo) and the door opens easily. When the door closes, the O-ring slides to cover up the passages and the piston compresses the air in the cylinder. It works similar to a bicycle tire pump, where the piston compresses air in one direction and then pulls back easily in the other direction. These parts were lubricated with grease. I suspect this is where the door closer was giving me trouble--the O-ring may have been failing to seal properly when the rubber or grease was affected by cold temperature.

It was not obvious how the adjustment screw works. A close look showed that the threads in the female part had 2 or 3 grooves cut into them along their length, creating small passages for the air. When the screw is turned outward, these passages get shorter, the air can get out of the cylinder faster, and the door will close more quickly. I suppose if some debris was getting into this area the door could operate erratically. 

Inside the large spring, which was about 1 inch in diameter, was the piston rod which eventually connects to the door frame. Sliding along that rod was another spring, about 1/2 inch in diameter and 3 or 4 inches long, and very stiff because it was made of heavier wire. (See first photo--look carefully.) This appears to have two functions: when the door approaches the maximum-open position, this short spring starts getting compressed to reduce any shock as the door reaches its maximum open position (possibly when caught by the wind); and second, when you let go of the door from the fully-open position, the short spring will give a push to start the door closing quickly.

Finally, there is a very subtle thing I almost missed. When the piston reaches the almost-closed position, about 3/4 inch from the end of its travel, it reaches two small depressions in the cylinder wall. (They are visible, as bumps, if you look carefully at the outside of the cylinder. See orange arrow in the first photo above.) When the piston gets there, some of the compressed air will leak past these depressions and the door will suddenly close a little faster. The end result is that the door accelerates a bit just before finally closing so that there is enough force to get the latch to work.  I have seen this advertised as "two phase" closing.

Fixing a Shimano 10-speed road shifter that won't shift to smaller cogs

My 10-speed Shimano Dura Ace "aero" shifter was getting stuck on the large cassette cog. When I swung the shift lever that is closer to the handlebar, nothing at all would happen. Occasionally it would work for a few shifts but then revert to the failure mode. Lubrication did not help. Actually I've had this happen on two different shifters, the other one Ultegra, which appears to be identical.

I decided to take the shifter apart to see what was happening. In both cases, a tiny spring was broken and causing the problem. 

This video tells how to see if the spring is broken without taking the shifter apart:
https://www.youtube.com/watch?v=-1r9CESluVQ

Here's how I replaced the spring.

The older non-aero shifters were close to impossible to disassemble, but the aero shifters, with the shift cable under the bar tape, are much easier, though they are still difficult. This YouTube video shows how to take one apart.

https://www.youtube.com/watch?v=wJj6dASBMN0

You will see the problematic spring at 2:40 in the video. It's one of the

first parts that come out, so you can skip the following steps.

The broken "spiral" spring is made of 0.025 square wire. I found a coil

spring with round wire about that size, straightened it out, and bent it

into a spiral. I did not need to anneal the wire to bend it. Perhaps some

springs would require annealing and then properly re-hardening them.

When I first tried the spring it was not working smoothly. I had to straighten the spring so the spiral was very flat. Otherwise it was dragging where it was "pinched" by the mechanism.

A few notes on things that are not clear from the video: 

1) At 1:18 a 1.5 mm hex wrench is used to loosen a set screw that 

locks the main shaft. It is not explained in the video.
2) Shimano tool Y6RT6800 can be used to remove the C-clip from the brake lever pivot. (http://si.shimano.com/pdfs/dm/DM-ST0002-05-ENG.pdf )

3) Note the exact order of the pieces as you slide off the main shaft 

4) When you are replacing the two parts that have swiveling pawls on them, make sure the pawls are properly positioned. Once the piece is on the main shaft the pawls cannot be adjusted. 

5) When you install the brake lever, make sure the shifting lever is placed into its hole before you press in the pivot pin. (9:40 in video)

Bicycle Saddle Sore Turned Out to be a Pressure Ulcer

In May 2010 I was commuting 38 miles per day, and also mixing in some high-intensity efforts. I wore the same pair of shorts both ways, to and from work. At one point I started feeling a “saddle sore” but ignored it as I had done many times in the past, assuming it would go away. After several weeks, I finally took a look with a mirror and was shocked to find a cavity almost an inch long, ¼ inch wide, and about ⅛ inch deep, ugly red color at the bottom, off to one side of my crotch. I looked things up and decided it was a pressure ulcer, also known as a bedsore, at least Stage II, probably Stage III.

I stayed off the bike for about a week and it healed over some. It broke open again after a small amount of riding. Then I tried waiting several weeks, but the healing was again short lived. There was very little pain: this contributed to my original negligence and made it easy to re-injure myself. Surprisingly, the wound never got infected. I went to see a physician, a “wound specialist”, and he did not have much to help. I don’t think he had seen my problem before. The dressings that he would normally use would probably not be suitable in the crotch area. He suggested an anti-fungal powder named Zeasorb-AF (I find that baby powder works better at keeping things dry), waiting several weeks, and then resume riding at 15 minutes per day.

The rest of the summer I took things very easy: riding on alternate days, using Chamois Butt’r, standing up every few minutes, and wearing two pairs of padded shorts. I think the two pairs of shorts idea was the most help. It is also a good idea when commuting, since you can put the clean pair on first when going home.

Along the way, I have received lots of suggestions about what to do: different saddles, creams, shorts, bike fit etc. It’s difficult to empirically test such suggestions since failure means several months of recovery time.

In November the wound looked mostly healed but I took things easy for the winter. I changed to Brooks saddles which seemed to help. (See Sheldon Brown’s procedure for breaking them in.) In May of 2011 I started interval training again, getting ready for the Mt. Washington Hill Climb, but I rode just 12 days and generally not two days in a row. On May 30 I did a 1.5 hour hard effort, and when I was done the wound had torn open again. Very disappointing.

I saw the wound specialist again on June 3, 2011. He said the scar is 60-80% as strong as the original skin. There is no way to “toughen up” skin that has healed. Plastic surgery would make a bigger wound, will have stitching on both sides of the graft, and will probably be weaker than the original wound.

I tried various saddles. I found that wearing two pairs of padded bike shorts really helped. Over the summer of 2011, things seemed to be getting better while limiting riding to about 3 times per week. The spot was still tender to the touch.

On Apr 30, 2012, after about an hour of intense riding, the wound opened up again, about ¼ inch long. I took time off.

By Spring 2013, the wound was mostly healed, but still tender to moderate finger pressure. I trained carefully and was able to do the Mt. Washington Hill Climb. All in all, the wound took 3 years to heal. It never got noticeably infected.

Edit: In Spring 2014, the wound opened up twice, even while treating it pretty carefully. I am limiting riding to twice a week.

I have found very little information about pressure ulcers and cycling--nothing in the ultra-distance cycling sites that I have looked at. I suspect that skin gets weaker as we age, and it might be much less likely to happen in younger people. (I was 60 years old when this started.)

Lessons for dealing with pressure ulcers in the crotch:

• Don’t ignore crotch trouble
• Use a mirror frequently to look at the area (pain is not a reliable measure)
• Take time off if bruising appears
• Keep shorts clean, take them off right away. Replace them when the pads get old.
• Chamois Buttr probably helps.
• Use double shorts, especially for commuting (swap them for the ride home)
• The Pearl Izumi short liners with an orange pad are the best I have found
• Hard efforts like intervals cause extra stress
• Stand up frequently, especially on long rides
• Take days off
• A pressure ulcer will heal, but it could take 2-3 years
• NEW 2016: stick Dr. Scholl's Callus Cushions over the tender spot. Helps a lot.

VW GTI VR6 exhaust leak caused code 16804 - Catalyst System; Bank 1: Efficiency Below Threshold.

On my 2000 Volkswagen GTI VR6 the engine light was coming on and when diagnosing it with VAG-COM I saw code 16804 - Catalyst System; Bank 1: Efficiency Below Threshold.

The Cat and O2 sensors were replaced 5 months ago.

It turned out the problem was an exhaust leak at the rear of the Catalytic Converter. Tightening the clamp fixed the code and let me pass the readiness test. The catalytic converter is apparently very sensitive to back pressure.

[VAG-COM Basic Settings Block 46 (catalytic converter efficiency) improved from 0.71 to 0.46 (< 0.50 is passing). Block 34 (O2 sensor aging) improved from 1.75 to 1.91 (1.99 is new)]

Shimano Ultegra Shifter Jamming After Broken Cable

Last year the cable broke inside my Shimano Ultegra 10-speed rear shifter. The cable was just 6 months old with less than 3000 miles. I rode home and found that I could not remove the nipple end fragment of cable. I could shift back about 5 gears by creating some torque on the shifter drum with the sharp end of a small screwdriver, but I could not get all the way to the "small cog" end of the shifting range. I finally removed the unit from the handlebars in preparation for taking it apart. I made one more try, and found that the loose cable end had apparently moved, no longer jamming the mechanism, and I could rotate the drum back to home position and remove the nipple and cable fragment. The nipple was still in its socket.

Well it just happened again, this time after 13 months and about 3000 miles. This time the unit was totally jammed. I removed it from the handlebars and rapped it a bunch while holding it in various positions. It finally started to "shift" but this time the cable fragment was no longer seated in its socket and was badly jammed way underneath. It took about an hour of shaking, shifting and probing with tweezers and wires to get it out.

Unlike older shifters which had a drilled hole where the cable sits in its socket, this 10-speed shifter has a notch. This makes it much easier for the broken end to fall out and jam the mechanism. Thanks, Shimano.

Both cables were genuine Shimano. Perhaps some other brand will last longer.

(In the process, I tried to remove the combined main shift lever and outer shell to get at the loose end. I got as far as a small Phillips head screw underneath the lever with a locking plate. Even with the locking plate disabled I was not able to loosen the screw.)

Lessons learned:

• Replace the rear shift cable every 2000 miles and the front every 4000.
• If the cable breaks, try to resist repeated clicking of the shift lever, which just rotates the loose end to the bottom where it will fall out.
• If the cable breaks, try to get the loose piece (cable end and nipple) out of the shift lever immediately. Riding the bike is likely to jar it loose.
• If the shifter is jammed after a broken cable, try inverting the bike and then shaking it or tapping the shifter with something like a screwdriver handle.
  

New Fairfield Petition (a genealogy query)

I am trying to find the source of the following pre-Revolutionary petition from Fairfield, Connecticut. If you have found this page by Search Engine, please contact me at mark at markdionne dot com. (I am interested in the name Coffman that appears in the list of signers.)

---

New Fairfield Petition

Dated 24 Dec. 1747 - Signed 23 April 1748

We the subscribers, inhabitants of New Fairfield and loyal
subjects of King George by virtue of the laws of this
government, have a right to vote for town officers. We
do hear (sic) complain and say that we have been denied
that privilege this year by not being lawfully warned.
For we never heard of a meeting till after it was over
and we do denigh (sic) the legitimacy of such a town
meeting. For either the town men we believe did not
set up the warning or trusted to such men as did not
set it up so that the people might see it. So that its
evident to us that they were employed to set up the
warning. We believe that in the North Society but three
or four men knew of it. Therefore we think such meeting
to be unlawfully held and that the officers chosen at
it are not lawfully chosen. Therefore we humbly desire
the townsmen forthwith to warn a town meeting according
to law. For we think if such present doings are winked
at which according to law should be most publick our town
stands on a presipis (sic) ready to fall into confusion.
Which is the complaint of us whose names are hereunto
subscribed.

James Tryon   Samuel Wright   Abel Wright

Azariah Coffman   Ezek Hubbell   John Pepper

Benjamin Eastman   Lyddel Buck   Joseph Congar

Thomas Barns   John Barns   John Pepper Jr.

Benjamin Seelye   Benjamin Elliott   Jefferson Commings

John Commings   Samuel Waters   Daniel Commings

Jonathan Page   Peter Eastman   Samuel Commings

William Barns   Nathan ?   Latham Clark

Benjamin Benedict   Samuel Tryon   Caleb Morgan

Joseph Coffman (illegible)

Elnathan Commings   Azahel Harding

Jonathan Hill   Zeth Tryon

Peter Eastman

Hazardous waste

I'm cleaning out the basement of my parents' house, which is soon to be sold. Above is a picture of one of the things I found. It's a roll of asbestos paper, about 50 feet long.

Our town's recycling center accepts hazardous waste, but they won't take asbestos because they don't want people doing do-it-yourself asbestos cleanup. They directed me to a commercial outfit that charges something like $50 per trunk load.

So I put it on eBay. I got $33 for it, and somebody came in late and offered $100!

Fun with chemistry

I just found this box in my parents' basement.

My 7th grade science teacher let me order some chemicals from a scientific supply house. He said everything was OK as long as I didn't order sodium nitrate, since that could be used to make gunpowder. Here's what I got:
nitric acid
sulfuric acid
potassium chlorate
magnesium ribbon
sodium peroxide

I had a lot of fun with that stuff!

Worcestershire wasabi

For this project, I translated this passage into Old English, Middle English imitating Chaucer one in a Shakespearian spirit and one in a moron’s spirit. -- Sam Dionne

Several days ago, my beloved wife of 15 years left me due to her cheating ways and I’ll tell you straightforwardly, I can not believe it. We met while on a hike. We talked for a while about the chilly weather and then hiked together. It was a beautiful afternoon.

And ever since then, I’ve hated mountains.

One insane woman had to get involved in my life and send me into a downward spiral of alcoholism and depression and drug abuse. Seven years later, we wed and fought viciously in the hotel about who gets the sole room key. It could have fallen apart a hundred times, every single day.

In all honesty, she disgusts me. She eats sushi with Worcestershire Sauce and bathes three times a day. She steals all of my beer and I confront her about it and she coos me into submission. No more! I looked at her cellphone text messages last week and found a rather ghastly correspondence that has sent me over the edge. Thank God for saving me from any more despair.

So now I sit at the office playing shooter games on the computer, then I do my work at home to keep me occupied, because I want to die. I must stay busy with useless tasks and mind-numbing activities to stave off the violence.





Chaucerian Spirit

O these woeful days. Naught but three days past,
my wyf of years hast cheated her last.
Straightcometh I say, I cannot believe
She had been off and asking to leave.
If that when we walke, up heigh on the mound
Twas nary a gentle note voiced in the sound
That bodeth to future days speaketh good fates
We ghouls desiren awfulest mates.
She long been assaileth me, keeping me chepe
What eyleth me now I see is my keep
We could hev split, and thanne we wod know
Her lavours of person, in sickness she go.
To steal my beer’s grave illness to me
Of women yblessed moot she not be
Wyf, go wher thee liste, Taak youre disport,
She wol nat dwelle in house a single day forth.



Old English

Feower þrio dagashæfde, æþeling bryd to me fyftynera læf side sibbene,ac ic forsceal, ic hit sare. ic ðæt mæl geman we niosað, on fyrgenholt. Wit cwæð gecwædon sy wedera cealdostc, þanon giong. ðæt wæs ond sceaw dogra.

Us wæs a syððan, ic hatod fyrgenholts.

Et wæs geomuru ides on helle drihten linnan ond eowic me to weal bregdan to beore ond sarlic ond meselfes hrusan. Syfonera æfter wit cwæð, wit æste geworhte ond wit ðam wange on husa þæt he heoguide. Wræc meahtan gefetan oþer ahund mæla, ǽghwilc he dogore.

Anfaldlíce, sy ádlig. Sy ellenrof gódléas ond sy áwascans þrio tíma adagore. Sy ætniman beore ond ic nebbian on sy loccia innan álote. Astyntan! Ic lóca cranica ond infindan ymbsprǽc yfele. Hit þe worna fela. Gode ic þanc secge þæs sy scacen.

Nú ic ymbsittan ond plegan ac ic nyllan nága min geþanc.



Shakespearian Spirit


Functionario: Rosicrucio! Old, dear friend, well met!

Rosicrucio: O! for days my heart hath bled.
For fifteen years my loyal wife she'd been.
Another man hath shorn my love from me.
From the forest I once took delight;
Woodland eaves are now a dreadful sight.
Woman-tired was I, but enamored still—
Her love, this drink, that drink, this pill—
A thousand times each day the gods I begged
For mercy, for disaster, for another wooden leg,
For mine she would hide when drenched in drink!

Functionario: O! a lamentable fate, I must think.

Rosicrucio: A foul sight to me has she become,
Too often hath my ales wet her tongue.
Experience may make the best of men,
But Worcestershire wasabi was my end.
My desk is cold, but the cold I prefer—
False weapons hath more life and fire than her.
Into idleness must I now retreat,
Lest real weapons offer me release.


Moron’s Spirit


It was maybe a long time ago that I went on walk up in Maine on a mountain hike and had a good time. I met a woman fifteen years ago there and she talked together and walked along the hill and we spoke with to each other about weather. It was a nice time but I hate mountains.

I like computer games at work because work is boring and I get hungry too often so I pretend to kill things.

That woman left home last week because she cheats. I wonder if she steals my beer and steals my food and lies to everyone. It’s not so terribly awful.

My wife left me cause of fighting and things. It happens a lot.

Bicycle Helmet Wind Noise

About ten years back, the bike catalogs like Performance were selling gadgets that you placed over your ears to cut down on the wind noise while riding your bike. They didn't stay in the catalogs for long.

Recently I was thinking about them, after becoming aware of the wind noise in my ears. Then I tried a few experiments:

-If you turn your head 90 degrees to one side, the noise goes way down. This is not practical for very long...

-Covering the ears with ear warmers doesn't help noticeably

-Cupping your hand in the vicinity of the ear helps a bit in certain positions.

-Removing your helmet helps A LOT! It's almost as effective as turning the head 90 degrees.

-Using a fabric helmet cover did not make a noticeable difference.

The reduction in wind noise when not wearing a helmet was surprising. It appears that there must be quite a bit of turbulence around the edge of the helmet. It would be interesting to try a time-trial helmet to see if it is any quieter.

Mark Dionne

PS: the ear cover gadgets have been re-invented. They look very much like what I remember seeing years ago:
http://www.nytimes.com/2006/11/02/technology/02headphones.html?ex=1320123600&en=d60b435da49ba4b0&ei=5088&partner=rssnyt&emc=rss

2000 VW GTI clicking noise behind instrument panel

For the last year or so I have noticed a clicking sound coming from the area of the instrument panel (behind the speedometer). The clicks were pretty random, but averaged about one per second, and sounded like a relay--a bit like the click that you get when using the turn signal, but not as loud. Oh, this is a 2000 VW GTI/VR6 (Golf). I tried to locate this noise, but there's no obvious easy way to access that area.

I recently brought the car to the dealer for two minor recall items (a fuel line, and flasher switch.) They also did a third recall, which appeared on the work order like this:

B VS RECALL
CAUSE: RECALL
    VS EMISSION SERVICE ACTION ( VS ) 2000 GOLF/JETTA
        VR6, JETTA/GTI 1.8T, AND GOLF 1.9L TDI:
        REPROGRAM INSTRUMENT CLUSTER SWITCHING RELAY
        SOFTWARE.
            455 WV2 0.20

I have not heard the noise in the last week!

Kenmore Elite Dryer Stopping Mid-cycle

My Kenmore Elite gas dryer was occasionally stopping in mid cycle, especially when using the hot setting. I found that the thermal cutout was being triggered. (You can check this by putting a volt meter across the terminals of the cutout switch. If it reads anything other than zero volts, the cutout has opened up, indicating overheating.) I replaced the cutout switch which did NOT fix the problem. Conclusion: the dryer really WAS overheating.

I replaced the electronic contoller board (due to a different problem) and there was no change in this problem.

I figured that the thermistor must be bad. I took out the old one and I found that it was coated with lint! The lint was sort of greasy and difficult to remove. I cleaned it off and put the thermistor back in, and the problem was fixed.

Clearly the coating of lint was insulating the thermistor enough that it was not registering the temperature of the exhaust air properly. Since the temperature never appeared to reach the threshold expected by the controller, the flame was never turned off and the dryer was overheating.

Yes, we have been using Bounce fabric softener sheets. No more! They apparently cause the sticky coating that attracts a film of lint.

2000 GTI VR6 Engine Knock at 2800 RPM

After about a year, my 2000 GTI VR6 started knocking between 2700-3000 RPM when accelerating moderately hard. (Using premium gas.) It was under warranty, the dealer replaced the coil, and the problem went away.

Some months later, it happened again. I found that cleaning the ignition wires with alcohol made the problem go away. After a couple of rounds of this, I bought some "Blue Injector" aftermarket wires, hoping they would last. After about 9 months, the knock is back. (The original wires are better. It's hard to remove the aftermarket wires from the plugs without pulling the wire right out of the connector. The original wires have plastic "handles" that help to get them out.)

New wires from the dealer did the trick. Not only is the knock gone, but acceleration above 3000 RPM seems improved. parts4vws.com had factory wires for $114. The factory wires are preferable to the Blue Igniters because they have the built-in "handles" that allow you to remove the wires without risking pulling the wire out of the connector. I also think they lasted longer.

I first cleaned both old sets and tried them, with no luck. Spraying with a mist in the dark showed leakage in the wires near the coil area. I suspect that cleaning the wires may sometimes help, but once the spark has caused microscopic holes in the insulation then the wires are toast.

Adding an LED indicator for heated mirror on VW Golf or GTI

It it very easy to leave the heated mirror on when it is not needed, and then it will eventually burn out.

I added an LED indicator that will light when the mirror heater is ON. Here are a few notes.

I put the LED in a hole near the bottom of the small speaker that is just inboard of the driver mirror.

The whole door panel has to come off (section 70-13 in my book). You do NOT have to disassemble the mirror shell.

There is one Torx screw on the bottom of the speaker enclosure. Next to it is a snap-in connector, and another is near the top. Pry carefully. There is foam behind the speaker that tends to be sticky. You will want to trim some of it to make room for the LED and wires.

I found an old LED and put a 400 ohm resistor in series. (The long lead was the positive lead.) Test it with the battery before installing it. I think some LEDs have a built-in resistor and others MUST have a resistor in series. Ideally you will adjust the resistor to the best value, checking in both day and night conditions.

On my 2000 GTI, the positive side of the LED goes to the white wire that goes to the mirror assembly, and the negative side goes to the brown wire. The relevant wiring diagram in my book is No. 27.5 on P 97-216.

One more thing: BEFORE you remove the door panel, mark where you want the LED on the speaker housing. The panel covers quite a bit of the bottom of the housing, so you will need to drill the hole about 1/4 inch below the "grill" part of the speaker housing.

Coolant temperature sender on my 2000 VW GTI

Here is how I replaced the coolant temperature sender on my 2000 VW GTI VR6. I wrote this up because I could not find anything about it on the web. Then I found Arthur's useful post here, but since I have some additional info, I thought I'd post it, even though it repeats much of what Arthur says.

I was getting this DTC on VAGCOM:
17704 - Error in Mapped Cooling System (usually temp sensor or thermostat)
35-10 - - - Intermittent
Also, about one time in ten, when I tried to start a hot (190 degree) engine I had significant difficulty, but eventually got it started after perhaps a minute of cranking. (Usually a second try at starting would be successful.) These episodes were accompanied by a smell of gas.

I planned to change the "G62" temp sensor and went to a VW dealer. They could not tell me which part to get! I bought the "standard" part, 059-919-501A, green plastic for about $6 just as a guess. I also ordered another part on-line (P4036-84658 from VolkswagenPartsStore.com, color blue. The part itself is unmarked, but the box is marked 078-919-501B ) The wiring connector for this part is obviously very different from the 501A part, though the sensor end looks the same as the green one.

I put things off until I got another hard hot start when the car then ran horribly and hobbled home stalling repeatedly. The same 17704 showed, but this time not intermittent.

Replacing the part is NOT easy. It is on the left (driver side) of the engine, pointing forward, a bit in front of the spark coil, surrounded by lots of plumbing and other mysterious parts. Very hard to get at or even see it.

I removed the battery. I removed the left front portion of the plastic manifold cover (one Torx screw.) I also removed one end of a large coolant hose, but that didn't help much because the nipple for the hose was still in the way. (To the outside of the sender unit is a rubber plug in a hole apparently the same size, held in with the same U clip as the sender.) Don't drop anything in this area because it will land on a plastic tray at the bottom and be a pain to retrieve.

I pulled up on the U clip for the sender, and HALF of it pulled out (shaped like a J). Then I noticed that the leg of the clip on the right side of the car is held captive by part of a mounting bracket that would be VERY difficult to remove. It's hard to even see it.

Then luck was with me--I was able to wiggle the sensor out even with half the retaining clip in place. It was still very difficult to disconnect the wiring connector. The old part was colored black and numbered 078-919-501C. I replaced it with the green 501A part. Several places on the web mention that the A part is an improved version of the C part. (The blue "B" part is obviously wrong). I measured the ohms of the two parts, and they were close (Green: 779 ohms A to B, 1749 ohms C to D. Black: 836 ohms A to B, 1700 ohms C to D). I'm not sure the old sensor was even bad.

I was able to get the new sensor back in place, even with the broken clip. If I had to do this again, I would consider LEAVING the old sensor in place and putting the replacement in the hole where the dummy rubber plug is sitting. (This is much easier to reach.) There would still be the difficulty of getting the wiring connector off the old unit though.

Needed about a gallon of coolant to refill.

After all this, I noticed the following DCT in the Instrument section on my VAGCOM:
01039 - ECT Sensor (G2)
30-10 - Open or Short to B+ - Intermittent
where ECT stands for Engine Coolant Temperature. I had not looked under "instrument" before. I suppose this was an old code from before the fix.

Six weeks later, no more DTC codes and no leaks. I guess the old part was bad, even though the resistance seemed OK. Probably intermittent.

This is a test to see if Google can find this. Search for Mark Stephen Dionne.