Destilled Water for Coolant? Removing Thermostat?

[jderrick]

Hey folks,
Getting ready to do my first coolant drain (& flush?) and I've got a couple questions:
When I'm flushing or mixing the coolant with water, is there any use to using distilled water so's I'm sure there's not a bunch on minerals in there?
Also, I've read from some sources not to remove the thermostat unless I've had problems or am doing other work. Is it an option just to leave the thermostat well enough alone?
The manual says to drain and fill the coolant -- does that imply flushing as well?

Thanks,
JD

[Jimnist]

Yeah, you're supposed to use distilled water as there are no minerals or other crap that can deposit in the cooling system. In the real world, your mechanic wouldn't bother and would just use normal tap water.

A flush would be good to get any corrosion out and the old coolant out. May as well if you're going to drain it.

As for the thermostat, i'm not sure. When people have cooling problems they always say check the thermostat. If you're draining, flushing and re-filling, you can take the thermostat out and test it. Your service manual should tell you how. But basically, but it in hot water with a thermometer and make sure it opens the valve at the correct temp with the thermostat suspended in the water or on little bit of wood. Direct contact with the glass or whatever you're heating the water in will increase the temperature it's exposed to.

[Stillrunning]

Doing a complete drain and flush in your driveway is a huge pain. Requires large amounts of water and 5 gallon pails to catch and dispose of old fluid properly. I used to do it but have gone to one drain and flush at auto shop using their flush machine(about $60-$70). From then on I drain rad once per year and fill with new pre-mix. That keeps the sytem Ph level proper and after 3 years or so all old coolant is replaced.

[Venom_5]

distilled water is the only water id feel safe putting in my radiator ... however, its still gonna evaporate just like any other water at high temps

no reason not to just use coolant, really - also no reason to remove the tstat

but like the post above, id just bring it in and let someone do it with a flush machine .... quicker and easier, and if you have the money then its worth it

[bcp477]

If one wishes to split hairs, then yes, technically, it is better to use distilled water. In the REAL world, however, it will never make any difference - so just use tap water and don't worry about it. Or, you could purchase the already-mixed (50/50) coolant - which is what I do. As someone else mentioned, a complete drain and flush is a PITA. Draining the radiator is easy. However, to drain the engine block, there is a drain plug on the back side of the engine, which can only be reached from underneath. What usually ends happening is that you spill lots of coolant when pulling this plug - or get a face full of it. Many people will drain the radiator, then try to flush the system with a hose - without removing the engine drain plug. So, they end up with the engine block full of plain water, as the engine block can't be drained this way, and which dilutes the new coolant mixture they put in the radiator. Do NOT do this - it is a recipe for corrosion in the system. I use a "hybrid" system, so to speak, like one of the other posters. I drain the radiator, about once a year - which removes about 1/2 of the total coolant in the system. Then, I refill with proper 50/50 mix. Since I do this about twice as often as the book recommends, the coolant never has a chance to get old and ineffective. The "old" coolant left in the system (since I only drain and replace about 1/2 of the total)...mixed with the new stuff....will be removed and replaced approximately on schedule (that is, about every 2 or 3 times I do the service). This procedure is MUCH quicker and easier (and less messy) than a full flush/ replacement, works just as well at the end of the day (as long as the coolant already in the system is not old and neglected)....and costs nothing, except for the cost of the replacement coolant. There is NO possible harm in doing it this way, as long as you are starting with coolant in good condition.

As for the thermostat - there is no reason to replace it, if it is not malfunctioning - that is just a waste of time and money.