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Feral Cat
 
bill d cat's Avatar
 
Join Date: Jul 2003
Posts: 21
Late 944 Temperature Gauge Calibration

On Saturday I was stuck in some awful awful awful beach traffic and "noticed" my climbing temperature gauge. Never overheated, not much past the second white line at all but scary, since on the highway the needle is usually lined up in it's Prussian best with all the other needles, exactly 1/2 way up the gauge. So Sunday I spent a delightful day losing nuts and bolts into the nooks and crannies of the 944 motor, breaking washers and going through the Clarks Garage cooling fan diagnostics. It passed, at least I think. I was actually SHOCKED by how much air is moved by the cooling fans on "high", I'm sure the fans have gone to high speed only rarely while I've owned the car.

I attempted to research what, exactly the various markings on the 944 temperature gauge actually MEAN, and exactly when stuff is supposed to happen.

Here's what I came up with:

Bottom of broad white line (40C)
Top of broad white line (60C)
Low temp 160F Thermostat opens, if so equipped (70C)
First thin white line (80C)
OE Thermostat opens (86-89C)
Thermo-Switch (92C) ON cooling fan low speed operation
Second thin white line (100C)
Thermo-Switch (102C) ON cooling fan high speed operation
Bottom of red zone (115C)
Top of red zone (call AAA and tell them flatbed needed)

What I'm concluding from this information is that my car is operating, more or less, as designed.

I'm also concluding that about 3/4 of the range on the temp gauge is devoted to absolutely useless information, ie. "it's not warmed up yet" and "the engine is melting".

Only 1/8 of the range of the gauge is devoted to the span between normal operation (cooling fans advance to high speed at 102C) and imminent disaster (the red zone at 115C).

So my question, the answer to which is probably lost in the Porsche factory records from the 1970s is: "Who's idea was THAT?????" and "WHY?"
Old 09-01-2003, 05:24 PM
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Location: Viera FL
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You are correct - you car is functioning normally.

On some (emphasis on some) of the gauges, if you remove them from the gauge from the cluster, the temp markings are on the side.

"why did they do that" - couldn't tell you. Probably the same guy that made the oil pressure gauge in "bar" (1 bar = 14.7 PSI @ sea level) rather than put numbers on that gauge too.

AFJuvat
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Old 09-01-2003, 05:37 PM
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Feral Cat
 
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Well, put another way - I can understand that it's useful when driving a race car to be able to obtain information at a glance. So I can see why Porsche's engineers might have calibrated the gauges so that the small gauge needles - temperature, oil pressure and voltage - are horizontal during normal operation, say driving on the highway. But considering that a large share of Porsche sales is always to the US which suffers from temperature extremes and often massive traffic jams they might have made some more concessions to this market. Searching out the number of "overheating" and "temperature" threads here it must account for a fairly large proportion of the total, particularly during the summer months. There have probably been countless hours and dollars spent correcting overheating problems on 944s that aren't overheating. Or not quite overheating. Had I been a Porsche engineer I would have expanded the "critical zone" between 102C and 115C to a larger portion of the gauge, and shrunken the "non-critical" 40-90C range to much less than 1/2 of the gauge face. This is mostly a rant.
Old 09-01-2003, 07:18 PM
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vott does ziss do?
 
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Join Date: May 2003
Location: Seattle
Posts: 6,676
Quote:
Originally posted by AFJuvat
Probably the same guy that made the oil pressure gauge in "bar" (1 bar = 14.7 PSI @ sea level) rather than put numbers on that gauge too.
hmm, there are numbers on my oil pressure gauge. 1 thru 5 bar
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Old 09-01-2003, 09:59 PM
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Location: seattle
Posts: 307
when I get into the middle of seattle traffic...

my temp gauge will start to climb up, but go back down when I start moving again

my temp gauge when warmed up always stayed at half way too
until I removed my license plate (cut it down to fit inbetween the air inlets for the radiator and intercooler) and now my temp guage when fully warmed up stays at below the half way mark.
I don't know the exact temperature it lowered it to but it really helps (especially at freeway speeds)


they haven't had a problem with it (like they have a chance to see the front!)
Old 09-01-2003, 10:57 PM
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i HAD a similar problem.

I drove car, then it went past the red and eventually the needle dropped off, so I thought I better stop.

on poping the hood up, I noticed that the engine was glowing red hot, and white molten gobs of metal were pouring onto the road.

so I opened the radiator cap, waited for the hot presuurised gush of super heated steam to clear and filled it up again.

she made a bit of a clanking but I got her home.

now the engine wont start, I wonder if it is related ?????
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Old 09-02-2003, 02:24 AM
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Old 09-03-2003, 11:50 PM
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