[flash]

if you have a restricted system, it's hot outside, or something else going on, they might do that.  here where i am, the almost never came on during normal operation.  also, tiptronic cars run hotter than 6 speeds, as the trans cooler is involved.

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[Bulti]

FWIW, I replaced my fan switch, not because it was broken, but because it was off. My fans came on too late. They should have come on at 92°, but instead the switch activated them at about 99°. High speed was the same. The new switch was surprisingly accurate.


Is your switch still functioning the way it should?

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[flash]

those things are notorious for failing too.

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[wildcat]

if you have a restricted system, it's hot outside, or something else going on, they might do that.  here where i am, the almost never came on during normal operation.  also, tiptronic cars run hotter than 6 speeds, as the trans cooler is involved.

How do you mean "restricted system" ? The temp gauge on the night in question was running a hair below the line and at a moderate 2500 rpms. I would conclude there is no restriction in the radiator. But the car was moving which means it was getting outside air.  Sitting, warming it up the fans would come on. Most of daytime driving is stop and go, and I would frequently hear the high speed fans come on at a stop light on a hot day.  Black is not a great pigment for sunny warm climes especially in the city. Once driving (with the relay installed) it never occurred to me they might shut off.  I couldn't hear them at all on low.  When the one motor started crunching, I turned it off and ran the other on low to see how much difference it made, on a 70's day down here its not a problem.  But 80+ weather and that black paint really retains the heat, the car runs hotter and on a steep incline like leaving La Jolla for the free-way in bumper to bumper traffic it could get to mid way between normal and the next line.  When I get on it, it can heat up, typically just above the line or quarter way to the next line. Having viewed some of your previous posts on the subject I'm inclined to think this is well within limits. Watching that needle climb can be a little disconcerting if it gets to mid-way, I'm not accustom to such wide deviation, but it has always settled down once the car got some air.  My last car the needle never moved unless there was a problem, like no water. B)  

Don't know about the switch Bulti but at this point its moot, I've gone to manual control of the fans. It is something I may look into just out of curiousity. 

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[flash]

you would be amazed at how easily these radiators get clogged.  i've seen a ridiculous amount due entirely to running tap water, which is a huge mistake, instead of running deionized or distilled water.  the capillaries are very small.  mineral deposits cling easily.

 

my blue car would run in 90 degree weather and not engage the fans as long as the car was moving.

 

most people fail to flush their systems every 3 years max too.  that causes all sorts of problems.

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[wildcat]

I'm confident the radiator is in good shape. The temp outside maybe 80 degrees but the internal temp gauge on the dash will be reading 105 plus and that black hood is hot enough to burn.  The engine bay is retaining that heat. But I can't explain why the fans come on if yours don't.

 

As for Bulti and the fan switch (thermostat switch) there are two switches actually, and I would suspect that the switch wasn't activating till it reached the second trigger point. Which means that you were wise to replace it.  That switch activates the relays which close the circuit to the fans. The manual switches are independent of that switch.  Having thought about it, I've decided to put a red light next to my manual switches and wire it in series after the thermostat switch so that when it closes, the light will come on. I have to determine whether there are three wires or two from the switch. I could wire it so that the red light only comes on when it hits the higher temperature setting. 

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[flash]

why not just change the thermoswitch?  why rig that up like that?  it's a $20 part.  fix it right.  no ghetto rigging.

 

a black car will run hotter than a lighter colored one

 

a tip will run hotter than a manual

 

these radiators are already too small.  any blockage reduces thermal efficiency.  tap water will kill them in a hurry.  so will the wrong coolant.  not flushing them will reduce the effectiveness of the coolant.  deionized water and a 50/50 blend of phosphate free coolant.  change every 3 years max.

 

water wetter works wonders too

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[Bulti]

About my switch: both low and high speeds still got activated, but no longer at the correct temperature. Maybe not surprising after 24 years of service.


I don't know if there are actually two switches in one casing, or there is only one switch activating both low and high speeds. If that is even possible.


Re coolant: you can measure the conductivity with a multimeter, but I don't know if this is enough to base your decision on to change it or not.

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[flash]

one thing to remember is that the head gasket is deteriorating in every one of these cars.  we've seen it countless times.  a large component in determining the timing of this is the frequency of coolant change.  engines who did not change their coolant have shown a higher rate of failure than those who followed the industry standard of a max of 3 years

 

also, porsche will void warranties if other than a phosphate free coolant is used.

 

you have to be pretty much a bonehead to not know about the problems with tap water, so i'll leave that one alone.

 

i have found water wetter to lower operating temps and stabilize them.  it may be purely because it prevents deposits from clinging to the capillaries.

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[williamoss]

OK I'll be a bone head Flash. There was a mention on some sort of topic that one should use Distilled Water and not tap water, with no explanation. All My life I used tap water, and changed coolant on a shorter time list as I call it over maintained schedule. So WHY DISTILLED WATER?

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[MLB]

Williamoss,

Well, lets avoid speculation were possible: what does the car manual say? What type of coolant are you using, and what does its label recommend?

A lot of problems can be avoided by simply following the directions.

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[flash]

tap water contains minerals and deposits.  that's bad for the cooling system. the key is to maintain the lowest TDS (total dissolved solids) measurement.  reverse osmosis is best at about 2.  distilled water is generally 11.  bottled water will be a bit under 50.  tap water is usually over 200.

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[Bulti]

Indeed, calcium deposits in tapwater will eventually block anything. Take a look at your shower head or the fosset in your kitchen. It will get clogged eventually, unless you got an installation to filter the minerals before they get into your in-house water pipes.


I use pre-mixed long-life phosphate-free anti-freeze (G12+). Like Flash indicated, it is (according to VW standard) to be changed every 3 to 4 years). My car came with blue coolant, which is obsolete now, but can still be bought. It doesn't mix with the modern coolant!


More about coolant in this article, because apparently colours do not tell the whole story :-)


And William -if I may- stay away from the tapwater. Distilled water is very cheap. Why risk anything?


http://www.caranddriver.com/columns/top-...antifreeze

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[wildcat]

Minerals attach themselves to the metal, in this case aluminum through electrolysis. The catalyst is static electricity running all through the body of your car, and they bond to the radiator as a result. These radiators are rather small with small capillaries as Flash mentioned, so the potential for clogging is greater.

 

The issues I mentioned were experiences I'd had but were within tolerance. None passed the second line. But that is a wide variation. The car never has had an over heat condition since I've owned it. Cleaning the motors has dramatically improved the car's operating temperature, which I neglected to preface when I mentioned them.  Currently the needle barely rises above the normal operating temp line under heavy load, ie: hard driving. I read in a post a year or so ago a comment that the line below the red one wasn't all that hot. Flash had mentioned a temperature I've forgotten. Maybe so, but it is disconcerting to see such a wide variance. It only happened under some circumstances so I wasn't all that concerned.  Now, it is not an issue. I bring this up because while it was within tolerance, I just thought it was a Porsche thing, and didn't take it all that seriously per comments on previous posts. But it is an indication that something is a miss. In my case it was the fan motors filled with road dust and grime, which is why I posted my experience. 

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[Bulti]

I think the temperature of any car engine varies more than most meters will show. Aren't most gauges dampened so people won't worry too much? Maybe ours is a bit more realistic?

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[flash]

the first thing to do is remember that these gauges are frequently not at all accurate.  check with a laser thermometer

 

while it is correct, that the second (or 10 o'clock) line is only 212, i have never seen a car go there when the system was stock and clean, other than on the track.  when the system is using the low temp fan switch, and water wetter, i have never seen it go there even on the track.  my blue car has never gone past 9:30, even in 100 degree weather

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[Bulti]

When checking the temp with the Durametric, would that be accurate? My coolant temp sensor is brand new.

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[wildcat]

 I would suspect considering the variable temperature rate the 968 can display, that the gauges are better than most and after Flash's comment about the 9:30 position, a fair amount of consistency between them. So my system was in better shape than I thought even with the motors clogged.  I did see that variation from time to time, more frequently than I should, where it went to 9:30 but it didn't go beyond that except in one case when one of the motors didn't kick in due to a malfunction in the relay. I just concluded that that was normal.  And taking the load off cooled it right down albeit more slowly on a really hot day.  With an older car its a live and learn proposition. I'm still impressed with how robust the car is overall. The engine obviously doesn't need a lot of water cooling but it does need some. The old Porsche philosophy of "air cooled" would appear to have been a factor in its design. Quite remarkable really.

 

There are 3 wires on the thermostat switch, two switches with a common ground, one for each temperature. I agree that being an electro-mechanical switch it is age that resulted in the higher temperature.  The only other factor I need to discover is if its a closed circuit or a jumper needs to bridge where the relay would close the circuit.  

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[MLB]

While I'm thinking of the cooling system here, I realize I've got my radiator out of the car and sitting protected in the garage but open on both ends.i'm starting to think I should be concerned about that and either washing it out thoroughly or capping it. Any comments on that?


Williamoss, I checked my bottle of Pentofrost NF coolant and found that it says nothing about the quality of water, likewise the workshop manual, the spiral-bound owners manual and the maintenance booklet, so you are right in that it's not always easy to just look up the best recommendation. Only clear statement is to replace the coolant every two years.

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[968Syncro]

I'd say that the water in WI has gotta be fantastic and excellent with few minerals -- at least compared to the "questionable who knows where it came from Cali water which might be from the Colorado river, some oddly sun-drenched areas in the central valley that the PC call "Sierra snow melt" before it picks up all kind of pollutants, or some already mineral saturated ground water.  Ok fine, this is my best advertisement about water in Cali -- although really good news.  Here in San Diego we have the first RO plant ($1B to build) converting ocean water into wonderfully clean and pure H2O.  Not sure how that will affect the mineral content, it will certainly be diluted with our imported water which for all I know may be runoff with salts and poisons from the massive irrigation in the Imperial Valley. And the CA government will now spend $100B on some oddball high speed train that nobody will use, instead of building 100 desal plant at $1B each which would secure water for the whole state forever.  I think I should run for office.

 

OK, back on topic. If my radiator was out, I would find a nice big tub that holds the whole thing, create a solution of vinegar and water, maybe 1..3 and let it soak overnight.  Amazing what a good acid wash will do for minerals.  Or even better, got some Muriatic Acid (pool acid), dilute about 1..8 and let it soak for 2 hours, shake every 15 mins.  Drain, check, repeat the soak maybe only one more time.  Then get a box of baking soda, or soda ash from your pool store, let it soak as long as you like -- only to remove the acid.  Rinse with hose.

 

Flash?   Does this sound reasonable?

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