Wally,

Thanks for clarifying. I usually know how the stuff works, but don't know where it all is.

err, the temp gauge is a little *ammeter*, no?

The fans are controlled by the coolant temp & the freon temp, right? Can the ECU turn them on also?

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Old & New:
<strong>Wally,

Thanks for clarifying. I usually know how the stuff works, but don't know where it all is.

err, the temp gauge is a little *ammeter*, no?

The fans are controlled by the coolant temp & the freon temp, right? Can the ECU turn them on also?</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">The temp gauge is indeed a little ammeter, but calling it an ammeter causes more confusion than it cures. Voltmeters are really little ammeters anyway, right? And ammeters are really little voltmeters. It all depends on how the movement is wired and where the other side of the dropping resistor is plumbed. <img border="0" title="" alt="[Wink]" src="wink.gif" /> There's currently a series of parallel exercises on this if you want to continue the discussion offline.

Fan controls vary by year. I have recent intimate experience with the S4 system, and offer the following:

Fans operate based on any of the following.

1) A temp switch (labeled a 'sensor') that lives at the top of the intake manifold. Green wire switched to ground causes the fans to run after a second or three.

2) A Temp sensor (labeled as a 'switch') in the water manifold front of the engine. The controller adjusts the speed of the fans (and the flap position) based on the reading from that sensor. It's a thermistor with resistance rising as the temp rises, so in theory one could add a small resistor in series to get the fans to come on sooner if one desired, especially when used with a 75C thermostat. More on this later.

3) Freon pressure (normally an indirect way to read high-side temperature) causes the controller to work the fan speeds and the flap positions.

4) Auto trans fluid temp, as determined by a temp switch in the rear somewhere. FSM syas it's at the torque converter. This is appropriate only on M249 optioned cars... That would be Auto trans cars if I remember correctly, unless the rowing team has figured out how to add a torque converter.

The hood switch is an interlock with the fan controls, blocking fan run when the engine is off and the intake temp switch says hot.

HTH!

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Old & New:
<strong>The use of phosphate free antifreeze is not critical if distilled water is used!

<a href="http://www.peakantifreeze.com/tech/tech_b.html" target="_blank">Antifreeze with Phosphate Inhibitors</a>



I'm trouble tonight.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Be advised. All German car manufacturers recommend that coolants which contain phosphates should not be used in their aluminum engines. Also, using distilled water doesn't protect the aluminum from damage caused by phosphate under pressure.

Likewise, avoid coolants with silicates. They tend to act like tiny sand particles. YMMV.

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by dr bob:
The temp gauge is indeed a little ammeter, but calling it an ammeter causes more confusion than it cures. Voltmeters are really little ammeters anyway, right? And ammeters are really little voltmeters. It all depends on how the movement is wired and where the other side of the dropping resistor is plumbed.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">bob, that sounds suspiciously like the thermostat discussion <img border="0" title="" alt="[Wink]" src="wink.gif" />
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</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">
1) A temp switch (labeled a 'sensor')...
2) A Temp sensor (labeled as a 'switch')...
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Who's on first?
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Ed, I thought the antifreeze manufacturer in the link was clear that phosphates are not a problem in themselves. Can you substantiate that this is not true? Agreed on the silicates - mostly... If you happen to have a car with silicate antifreeze in it, it might not be the wisest thing to change it to the non-silicate type:

<a href="http://www.lt5registry.net/pub/antifreeze%20options.htm" target="_blank">Antifreeze discussion</a>

 

By a little reasoning and deduction, if phosphates are not a problem then why would Audi, BMW, Mercedes, Porsche, and VW make a point of requiring the use of Phosphate free coolant in their engines? Moreover, why would they go through the trouble of making phosphate free coolant, if any coolant will work just fine?

Lastly, I think (but don't know for sure) there is a Porsche service bulletin on the matter. YMMV.

BTW, There are several (inexpensive) versions of phosphate free coolants. I have used Quaker State, but currently use Prestone. To be sure it's phosphate free, you'll have to read the information on the bottle, including the list of ingredients. ;^)

 

Ed,

I agree that the policies of the aforementioned companies are good, in that they cover all regions and situations. However, I merely want to bring to light that there are some caveats. For instance, the use of purified water in the mix negates the need for phosphate free antifreeze, and there might be some risks associated with changing from silicate based coolant to another variety. I have substantiated my position in both of my previous posts. Your reasoning and deduction have me floored!

Now the real issue is determining which type of antifreeze exists in a vehicle so as not to mix them...

 

Years ago, I watched a segment presented by Pat Goss (a MD automotive repair guru) on MotorWeek (back when they were only on MD Public TV) on the subject of coolants. In it he categorically said coolants with phosphates should not be used in aluminum engines. He also recommended the use of distilled water, in addition to phosphate free coolant. Moreover, he said to steer clear of coolants with silicates. No mention was made about problems with mixing one type with another.

I had the pleasure of meeting Mr. Goss (when I invited him as the guest speaker for our local PCA monthly meeting). I saw why he was/is highly regarded as an expert in all-things automotive. The subject of coolants came up at the meeting, and again he was very forceful in his opinion about avoiding coolants which contain phosphates and silicates. He claimed he'd seen direct evidence of damage to aluminum engines caused by coolants containing phosphate.

Then as now, I consider his opinion on automotive matters to be GOSPEL. YMMV.

 

Ed, I can't criticize you for following the GOSPEL; I just don't accept everything at face value and like to make up my own mind based on the facts available.

Just to be difficult, I'll sign off on this note: There are good reasons to use one of the newer phosphate free mixtures (longer change interval, for instance).

 

I'm pretty sure that silicates and phosphates are actually GOOD for our engines - they help to keep the insides all shiny and clean!

Ducking...

 

Considering that all the German car manufacturers, and at least one prominent automotive expert say "coolants containing phosphates and silicates should not be used in aluminum engines" - then that advice is good enough for me. YMMV.

I have not seen the statistical data or the evidence on which the car manufacturers and at least one expert base their recommendations. However, considering what the consequences may be if they are right compared to the cost savings if they are not, it seems prudent to err toward their recommendation. Again, YMMV.

BTW, another 928 friend who was a manager at a automotive parts supply store/(chain) said that he was told by a Prestone chemical engineer that any car that originally came without the long-life coolant would get no benefit from switching to long-life coolant. Basically, the drain interval should be the same as before, regardless of the type of coolant in the system.

Please - Don't shoot the messenger. ;^)

 

Just for fun, here's official Prestone info which disagrees with that heresay:

<a href="http://www.prestone.com/products/14.htm" target="_blank">getting full benefits of the longer-lasting formula</a>

 

Old & New:
The reference you mentioned states, "If you decide to replace your existing antifreeze/coolant with Prestone Extended Life 5/150 Antifreeze/Coolant, make sure you completely drain and flush the cooling system first in order to gain the full benefits of the longer-lasting formula."

When was the last time you "completely drained and flushed the cooling system"? And just how completely flushed was it? Was there even one drop of the old fluid still hiding in there, somewhere? ;^)

In my case, I change the coolant in all my cars every two years anyway, so it doesn't really matter. YMMV.

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Mark:
<strong>&lt;&lt;...&gt;&gt;

Dr Bob - in the FAQ section, it talks of a cooling system diagnostic guide you wrote - but I cannot find it (The link to someone's web page you gave is no longer valid). Can you send to me or re-post.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">It took me a bit to run it down. Here's a link to John Pirtle's new website, where he has archived some of his favorite Rennlist posts.

<a href="http://members.rennlist.com/pirtle/zcool_overview.txt" target="_blank">http://members.rennlist.com/pirtle/zcool_overview.txt</a>

Fortunately, that discussion doesn't delve deeply into the intricacies of the thermostat itself, but only touches on the effects of poor thermostat performance and overheating issues when it's stuck in the closed/bypass position (stay away from this, O&N... ).

Unfortunately, I also recommend no-phosphate, no-silicate anti-freeze in low dosages (not appropriate for anybody east of San Bernardino, Ca or north of Buttonwillow Raceway this week...), distilled water, and a dose of Redline Water Wetter. Appreciate that this was written from the perspective of an owner who lives in the L.A. area, with an occasional freezing nigh during the winter, but who otherwise thinks that a day that doesn't make it to 65 is damn cold. Our summer cooling loads are comparable to most any location in the lower 48, however.

Enjoy!

 

The distilled Water argument is interesting. I do believe that I have read this Distilled Water is IONIZED which makes the water more electrically corrosive to the aluminum engine. I have spoken to a gentleman here in San Diego that suggests simple drinking water for aluminum engines. NOt tap water - drinking water.

Whaddayall think?

I am spefically thinking of the ionization process and its effect on the water.

 

Distilled water is free of disolved minerals. It's no more ionized than tap or drinking water. ;^) YMMV.