Brigitte,
As somebody else has mentioned, Heet works well to improve the anti-freezing capability of your windshield washer fluid (WWF). Heet is really intended as a gasoline additive, but that doesn't matter since Heet is pure alcohol - methyl alcohol or isopropyl alcohol - and it works well for your windshield washer fluid (WWF) since the main ingredient in that WWF is methyl alcohol.
There are common warnings about Heet and WWF damaging painted surfaces, but I don't know how true these are. I'm pretty certain that both will remove the protective wax that most of us put on our car finishes. I also know that in the past I have observed auto paint finishes which "blushed" (lightly dulled) when they came in contact with alcohols. Modern paints are much more resilient, but I'd still feel very uncomfortable getting pure Heet onto auto paint.
Heet costs about $2 for a 12 ounce container. I'm guessing that there are other sources of alcohol which might work as well and be less expensive and more common around the house. Common rubbing alcohols are generally 70% isopropyl alcohol or 70% ethyl alcohol. They cost about $0.50 to $1.00 per 16 ounce bottle and you are likely to already have some around the house. The better grades are 90% alcohol and are about twice as expensive. Some homeowers also have gallon containers of pure methanol solvent for working with shellac. Obviously the pure methanol solvent will work fine, and I am guessing that the rubbing alcohols should also work.
I don't know why the manufacturers always use methanol as the alcohol in their WWF. Possibly because it is the cheapest alcohol or possibly because it works best. Still, I'm certain that any alcohol will function to improve the antifreeze properties of your WWF.
Different brands of WWF will vary in how much methanol they contain (this is the most expensive ingredient) and how well they will resist freezing. WWF is mostly water, then some alcohol and finally some trace amounts of detergent and pretty blue tint (so that you don't feel that you are paying $2 for a gallon of water).
The definition of freezing is also a bit vague - these solutions will begin to turn slushy before they "freeze" according to the manufacturer's definition of freezing. That slush won't move through the thin hoses very well. Often, you can pinch the rubber WWF hoses in cold weather and fell the ice crystals in the lines. Also, the nozzle exits will freeze - either from snow or from the water that is left behind when the alcohol in the WWF evaporates at the nozzle exit and leaves pure water behind. It is ALWAYS the lines and nozzles which have freezing problems first.
Pouring warm water over the lines and over the washer nozzles will sometimes provide a temporary fix when your windshield washers aren't working. Don't use hot water - getting it on your windshield can crack the glass and getting it on your painted surfaces can damage the paint or damage the bonding of the underlying primer. Water at body temperature (about 100 degrees F) is sufficiently warm to unfreeze WWF, even if the WWF is at zero degrees. (I'd still avoid getting the water on glass or paint).
I've used a garden sprinkler can full of warm water to very successfully help folks with doors that are frozen shut, windshield washer lines which are frozen, gas compartments doors which are frozen, etc.
I'd suggest experimenting with Heet or another source of alcohol to determine the minimum amount that you need to add to get the antifreeze level that you want. If I were buying Heet, then I'd probably buy the "standard" Heet which contains methanol, although either version should work.
My bit of pragmatic advice: You may be able to avoid a lot of hassle and experimenting by simply quizzing your friends, neighbors and family who live near you. Find out who has extremely good luck avoiding WWF freeze-ups, check to see what brand of WWF they are buying, and buy some for yourself. Other T&C owners would be optimal.
Try to identify folks who have situations similar to yours - garaged vehicle vs vehicle parked out in the open, driving distance to work, driving speed to work, etc. Obviously, a garaged vehicle will be warmer than one sitting outside. Also, a garaged vehicle will stay warmer if it is driven slowly and a shorter distance to work or school in the morning. A warmer vehicle and components are less likely to have freezing problems.
I can't recommend any particular brand since I've had very good luck with a variety of brands of WWF while living in a Northern state. This includes my '89 Grand Voyager and my '02 Town and Country. Obviously my situations must be different from yours.
You may also want to do a bit of experimenting with your current WWF. Get two containers with screw on lids and put some WWF in each. Put one outside and put the other in the garage. Observe fluids each morning to determine if they look even slightly slushy. You must have lids on the containers - otherwise alcohol will slowly evaporate and ruin the experiment. This experiment will help you to determine if the manufacturer has fibbed about the antifreeze level of their product. If so, then you can experiment by adding various percents of auxillary alcohol.
Also, I know that this seems obvious, but please insure that your windshield washer nozzles are not blocked by snow or ice. Also insure that the methyl alcohol in your WWF isn't evaporating - this means a good lid and seal on your WWF gallon bottle and a good lid and seal on your WWF reservoir in the engine compartment. Also, are the folks who do your oil change providing a free top-off of fluids, including WWF? Possibly they are using the cheapest WWF they can provide.
Wind chill factors: Wind chill factors normally apply only to living creatures. If you are standing outside in 20 degree weather with a strong breeze, then you are going to feel as if it is much colder than 20 degrees. The main reason for this is the fact that we always have a bit of moisture on our skin and the wind evaporates that moisture. The evaporation steals heat from our skin and can cause our skin to cool below the 20 degree ambient temperature. Normally, an inanimate object such as a car does not experience this effect. BUT, the nozzles and lines for your windshield washers may be impacted by a wind chill factor (either from wind or from the perceived wind cause by driving). WWF will be present on the tips of the windshield wiper nozzles and some WWF may also splash onto the lines. Air movement over this WWF may cause the alcohol content to evaporate. This can drop the temperature below the ambient (air) temperature. On the nozzle tips, the alcohol will evaporate and cool the remaining water component of the WWF below freezing. This could produce a thin layer of ice over the nozzle tip. (Any liquid which evaporates will cool the surface that it is upon. This is why we cool down when we have a liquid on our skin - water, sweat, rubbing alcohol - and it is evaporated.)
There are urban legends about various solutions to WWF freeze-up. The most common is adding copper tubing to the windshield washer lines and routing the tubing over the exhaust manifold so that the WWF is warmed by the engine heat. I have no knowledge of anybody who has successfully done this. Plus, there are many '99 T&C's out there which are performing well without such extreme measures. There definitely must be a SIMPLE solution to your problem.
On the lighter side, I can tell you about the good old days when we had to roll down our window while driving down the road, scoop snow off the roof of the vehicle, and toss the snow onto the windshied to clean it with the wipers. We also kept spray bottle of water/alcohol mix in the passanger compartment so that we could stick our arm out of the window and spray the windshield while driving. (We were young and poor and we used the cheapest isopropyl rubbing alcohol that we could buy). Some of us also remember the early after-market windshield washer systems which had a small rubber bulb on the floor on the vehicle, generally to the left of the gas, brake and clutch pedals. If you wanted to squirt WWF onto your windshield, then you rapidly pumped the rubber bulb with your left foot.
I hope all of this rambling helps you solve your problem.
Gideon
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The reservoir has never had water in it. I always use washer fluid rated for sub zero temps. Any idea what could be causing this?
Any and all input is appreciated.
Thanks, Brigitte