Still overheating

[Ssj7blade]

Okay, so I have a 2002 2.7 tiptronic. For a while now I've had issues with my car overheating. It'll sit around 180-185 degrees. The car only really heats up when I sit still though. In really heavy traffic I've gotten up to 190, but only once. I've replaced the water pump and thermostat and cleaned the radiators of all dirt and debris. Does anyone have recommendations of where I should go next? I'm considering the possibility that one of my radiator fans might not be running perhaps? Now if I turn the A/C on both fans work fine, but I'm not sure if they're coming on when I'm driving, and without the A/C running. Thanks.

[logray]

Overheating is much much hotter than 180-185F, or even 190F. If the engine hasn't seen higher temps than that, you aren't driving it hard enough. ;)

Overheating would be water temp probably over 240 F and oil temp over 260 F ish.

Spend some time with search here, there is a wealth of great info about how to read your temp gauge and also how to get the "real" temperatures from your engine, for example using a tool such as Durametric.

Edited February 7, 2012 by logray

[Ssj7blade]

Haha thanks. I know I'm still in the safe zone but it irks me that the temperature isn't hovering right at 180 like it used to before my first water pump failed. I'll do some further searching.

[1schoir]

If you think that your low speed fans may not be coming on when needed, you have to diagnose the cause:

1. the low-speed fan relay (located in the bottom row of the relay tray in the kick panel);

2. the ballast resistor (located aft of the fan housing, clipped on to the lower rail of the housing);

3. the fan motor itself.

Since you are certain that the fans work when you turn on the A/C, it's not #3.

To eliminate the relay, you can swap each of the two high-speed relays (left and right) with the two low-speed relays. If both fans kick on after you turn on the A/C (after swapping the relays), then it's not #1.

If you have determined that it is the ballast resistor (cause #2), you have to replace it. These fail often because of their location. They heat up and then can get splashed with cold water if you go through a puddle, etc, which causes them to crack and fail. You will have to remove the front wheel well liners to access them.

Here is a photo of the low-speed relays and their location in the relay tray by the kick-panel:

Here is a photo of the right side ballast resistor (it's the bullet-shaped part):

Regards, Maurice.

[Ssj7blade]

Hey thanks a lot man that helps big time. I'm going to check the relays this weekend and then consider checking the transistors. I don't want to sound stupid, but before I do that, I understand that when the car is running hot the fans should kick on. Where exactly can I feel if they are actually on? I read to put my hand under the bumper. I know where they're located, which makes this seem like a dumb question. Maybe I'm missing it but it feels like neither are on. I have the car in park, does it need to be in neutral or should I have a second person be outside the car while my foot is on the brake? Is it suppose to be as loud a when they come on from the A/C?

I just struggle to believe I have two radiator fans not running and the car is only a few degrees hot.

[1schoir]

Hey thanks a lot man that helps big time. I'm going to check the relays this weekend and then consider checking the transistors. I don't want to sound stupid, but before I do that, I understand that when the car is running hot the fans should kick on. Where exactly can I feel if they are actually on? I read to put my hand under the bumper. I know where they're located, which makes this seem like a dumb question. Maybe I'm missing it but it feels like neither are on. I have the car in park, does it need to be in neutral or should I have a second person be outside the car while my foot is on the brake? Is it suppose to be as loud a when they come on from the A/C?

I just struggle to believe I have two radiator fans not running and the car is only a few degrees hot.

The car can just be in park....if the water temp gets high enough, the fans (both left and right) should kick on to run at the low speed at the same time. The ballast resistors are what causes the fans to run at the low speed, unless the resistors are fried, in which case they will not run at all when the low speed is called for.

The fans are supposed to run at the low speed when the coolant temp is higher than 206°F or the A/C is on. The fans switch to high speed when the coolant temperature is higher than 215°F or the A/C freon pressure is higher than 16 bar.

You can also get a clue about whether the resistor is bad by "feeling" the relay with your finger. With the car cold, you can start the engine (leave it in "park") and put your index finger directly on the first of the two low-speed relays shown in the photograph above (IIRC, it's relay in position #19). With your finger on the relay, press the "snowflake" button on the dash (to turn on the A/C). When you do that, you should feel (and possibly hear) the relay click. If it clicks and the fan does not turn on, the resistor is bad. Repeat with your finger on relay #21.

If you stick your hand below the front bumper, immediately ahead of each front tire, you should feel each one blowing air.

They definitely don't sound as loud at the low speed as they do at the high speed.

The part number for the ballast resistors is 996.616.101.00. Same part for either left side or right side. The last time I checked, they listed for about $90 each and could be had for about $65 at sunsetimports.com.

Regards, Maurice.

[Ronald Breeze]

Want to know if your fans are working drive your car into a dusty parking area or field when it is up to the temp they should be on and you'll see dust flying up from both front sides if the fans are working. Learned that the hard way just after I washed and detailed my car then went on a wine tour where we had to park in a dirt lot. When I first got my '99 with 74K miles on it it also ran right at the 180 deg. mark but around 82K mi. it kicked up to as high as 199 deg. on hot days. It generally stays at 189-190 deg. and both fans are working, radiators clear, new water pump and it's a tip. After trying to figure out what changed I read the owners manual one day and it states the temp gauge should be at the halfway mark in normal running conditions. Halfway on my gauge is around 190 deg. As long as it doesn't start creeping up into the 200+ range I don't worry about it anymore.

[Rapewta]

I am curious to know what the line (graduation) between 180 and 250 is in degrees.

My 996 has never gotten to the middle line. I don't think anything to the left of that line would be

considered "over heating." Water boils at 212 deg f and under pressure even higher.

[JFP in PA]

I am curious to know what the line (graduation) between 180 and 250 is in degrees.

My 996 has never gotten to the middle line. I don't think anything to the left of that line would be

considered "over heating." Water boils at 212 deg f and under pressure even higher.

You need to remember that the dash gauge in these cars is both non-linear as well as grossly inaccurate to begin with. Rather than trying to finely increment what is known to be questionable to begin with, plug an OBD II scanner with PID catalog capability into the port under the dash and read the real temperatures……

[logray]

The gauge accuracy has been covered many many times here before.

But I'll entertain with a perfect example.

Out today on some hard drives to get it hot and help break in my rebuilt engine while logging with Durametric.

With the dash gauge just a hair right of straight up. Coolant temp was about 92-95C (197F-203F), Oil Temp about 100-105C (212F-221F). The oil temp takes longer to respond in changes than the coolant temp, and you can sorta read the oil temp from the oil pressure gauge.

Gauge over the middle of the 0 in the 180, Coolant temp 100C (212F), oil temp 107-109C (224F-228F).

I didn't even bother with the AC hack since it is just an extraploation of the real OBDII data.

But yes, the dash temp gauge is a farse.

Edited February 10, 2012 by logray

[GOALIE31]

If your Fans are working,you might try bleeding the coolant system again you could have an air pocket.

[Ronald Breeze]

The gauge accuracy has been covered many many times here before.

But I'll entertain with a perfect example.

Out today on some hard drives to get it hot and help break in my rebuilt engine while logging with Durametric.

With the dash gauge just a hair right of straight up. Coolant temp was about 92-95C (197F-203F), Oil Temp about 100-105C (212F-221F). The oil temp takes longer to respond in changes than the coolant temp, and you can sorta read the oil temp from the oil pressure gauge.

Gauge over the middle of the 0 in the 180, Coolant temp 100C (212F), oil temp 107-109C (224F-228F).

I didn't even bother with the AC hack since it is just an extraploation of the real OBDII data.

But yes, the dash temp gauge is a farse.

Wow! That's quite a difference. Where does the Durametric reading come from, is it the same sensor as the gauge? I know the gas gauge is really off but didn't realize the temp gauges where that bad. Makes me wonder how accurate the tach and mph gauges are.

[JFP in PA]

Not very................. The sensor section in these car are fine in terms of accuracy, it is the dash displays that are questionable. OBD II/Durametric/PIWIS/PST II all read the sensor.

Edited February 11, 2012 by JFP in PA

[logray]

This is what I've found...

Speedo is generally about 4mph too fast.

Tach is spot on.

Rest of the gauges are pretty good, voltage is a little off too, towards the low side.

[JFP in PA]

How bad they are, and which ones are the worst often vary from car to car, but I am yet to see a coolant temp unit that was anywhere near correct...............

[Ronald Breeze]

Yeah but you can't go around with a Durametric hooked up to read your temp all the time can you?

[logray]

There is an aftermarket head unit upgrade I'm looking at for my old Pioneer AVIC-Z3. If I remember right it has the capability to display OBD2 values on screen.

[JFP in PA]

If you really wanted to get cute, you can heliarc a fitting into the top of your oil cooler and get temperature and/or pressure readings; or as shown use it to feed an Accusump unit...........

[Ronald Breeze]

Ok, so I get the readouts on my climate control unit which are these:

To access diagnostics:

Hold down the Recirculating & Air up buttons for 5 seconds. The + - buttons go up and down through the list of "c" codes. The center vent button switches the left display between the "c" code and its actual value. Press the Auto button to exit.

0c - ERL

1c - Oil Temp?

2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash.

3c - Outside temp. Sensor located inside the air inlet of the A/C unit.

4c - Outside temp. Sensor located in front grill of the radiator. The data is fed to the Climatronic from the instrument cluster. When not moving, the instrument cluster OBC temp display retains it's last setting until moving. This is to prevent heat emanating from the radiator affecting the temp. sensor. The A/C unit uses the lower of the two outside air temp values in determining fresh-air temp.

5c - Outside temp. (matches with OBC outside temp display)

6c - Coolant temp.

7c - Foot well discharge temp.

8c - Sun sensor (dash top)

9c - Sun sensor.

10c - Passenger compartment fan speed.

11c - Passenger compartment fan voltage.

12c - Temperature mix Flap command 1=COLD, 100=HOT

13c - Temperature mix Flap position

14c - Central Flap command

15c - Central Flap position

16c - Foot well/Defrost Flap command

17c - Foot well/Defrost Flap position

18c - Recirculation Valve command 1=OFF, 100=RECIRC

19c - Recirculation Valve position (feedback)

20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer)

21c - Engine RPM in hundreds. This too only updates once per second.

22c - ?

23c - ?

24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illumination.

25c - ?

26c - ?

27c - ?

28c - Fan speed?

29c - ?

30c - Engine run time in seconds (255 max.)(=0xff)

31c - Timing counter

32c - Displays test

33c - Software version? (Some say 3.4, what does your say?)

34c - ?

35c - Outside temp. from inlet sensor (filtered?)

36c - temp?

So if I look at 1c and 6c that will give me an accurate oil and coolant temp? What then is a "normal" operating temp for both? Or is there a normal?

[logray]

This has been covered many many times here.

The figures from the AC hack are simply not accurate, they are an extrapolation of the real figures.

In other words, you can use them to get a ballpark, but to get the real temps you need to read the OBD2 data directly.

[Ronald Breeze]

Since my car's prior life was a lease car I doubt anyone "hacked" the AC reading in and I did not as I wouldn't know how. My understanding is that the information was a programmable feature that could be activated by the dealer. I'm surprised that Porsche would provide two readings that are so inaccurate and I'm disappointed that my fan speed reading is not accurate. I'm also sorry that these posts seem to annoy you logray but rather this topic has been covered before or not it appears to have relevance once again.

[Loren]

Since my car's prior life was a lease car I doubt anyone "hacked" the AC reading in and I did not as I wouldn't know how. My understanding is that the information was a programmable feature that could be activated by the dealer. I'm surprised that Porsche would provide two readings that are so inaccurate and I'm disappointed that my fan speed reading is not accurate. I'm also sorry that these posts seem to annoy you logray but rather this topic has been covered before or not it appears to have relevance once again.

Sorry, but your understanding is wrong. Dealers can not and do not program that in.

The only Porsche approved way to read the sensors is with a Porsche PST2 or Porsche PIWIS tester. Durametric has tapped into those same values with their software and cable.

Compared readings have proven that the "AC Hack" (as it is called) is grossly inaccurate. I have verified that myself as we have both a Porsche PST2 and Porsche PIWIS testers. The two Porsche testers agree but the AC Hack readings are many times are not even close.

So please -- lets get back to solving the original posters issue.

[logray]

No it doesn't bother me at all. I should have added more smileys. :) :) :) Just sayin.

AC hack otherwise known as "climate control diagnostics".

Porsche eliminated the AC hack in 2001 if I remember right.

The information is not programmable.

Yes it is a little frustrating that it's not accurate, but that's what we have to live with.

It turns out the only thing that is accurate is reading the sensor data directly from the DME using an OBD2 diagnostics reader.

[Ronald Breeze]

Since my car's prior life was a lease car I doubt anyone "hacked" the AC reading in and I did not as I wouldn't know how. My understanding is that the information was a programmable feature that could be activated by the dealer. I'm surprised that Porsche would provide two readings that are so inaccurate and I'm disappointed that my fan speed reading is not accurate. I'm also sorry that these posts seem to annoy you logray but rather this topic has been covered before or not it appears to have relevance once again.

Sorry, but your understanding is wrong. Dealers can not and do not program that in.

The only Porsche approved way to read the sensors is with a Porsche PST2 or Porsche PIWIS tester. Durametric has tapped into those same values with their software and cable.

Compared readings have proven that the "AC Hack" (as it is called) is grossly inaccurate. I have verified that myself as we have both a Porsche PST2 and Porsche PIWIS testers. The two Porsche testers agree but the AC Hack readings are many times are not even close.

So please -- lets get back to solving the original posters issue.

I think the original posters issue is also mine as his car is similar to mine and we are running the same temps so if we solve the issue he and I have both been helped (the point of these forums). I've discussed the temp issue on other forums and have come away without clear answers as to the cause. Unless I'm wrong it is not feasible or safe to drive around with an OBD2 hooked up and refer to it regarding the cars temp unless there is a way to mount it where it is visible? After using an OBD2 to get operating temp readings at idle how would you extrapolate those to temp when in traffic or on a track at a DE? And I guess the fundamental question is what is overheating range on his car that would cause damage?

[logray]

The original poster states he has observed a temp of 190 F degrees. The question is, where did he get that temp reading from? The dash? A/C hack? OBD2? External sensor? There's not any real way to tell from the dash gauge what 190F is unless he knows where his needle must point in order to reach this temp. Also what temp was that, coolant? oil?

190 F degrees coolant temp is just about perfect for most cars. Not even close to over heating.

The 986 and 996 like to run hotter than 190F, more like 200-212 F for coolant is considered normal. Oil can be anywhere from 0 to 20 degrees hotter than the coolant depending on how it's driven. So I'm not quite sure what the issue is here, since there doesn't seem to be a problem - what was described in the original post is perfectly normal and there isn't a problem to solve that I can tell.

Overheating on this car is going to be coolant temp over 245 F and oil over 265 F ish.

The best thing to do to get a feel of how hot your specific car is running is to plug in an OBD2 reader and observe what the actual oil and coolant temp is and compare that with the reading on your own dash gauge. Then you'll have an idea of what the coolant temp dash gauge is really telling you.

There are plenty of aftermarket solutions for reading and displaying data from the OBD2 port in a driver friendly format and in real time (not just sitting at idle), from things that mount to your dash, to software that connects to your iphone, even aftermarket stereos are starting to display this data.

Hope this helps!

Edited February 14, 2012 by logray