Water Pump

[Blue-S]

I had some time this evening to drive a bit and collect some data from the HVAC control panel's diagnostic mode as explained above. The car was a 2000 Boxster S 6-speed, with a new Porsche water pump and a 1-year-old standard replacement thermostat (presumed to be 80 deg C). The A/C compressor was off throughout the testing.

* During warmup, with the temp gauge needle exactly on the "tic" mark above the "8" in the "180" label, the HVAC panel (in 6c display) read 79 degrees C coolant temp. That converts to 174 degrees F.

* After allowing coolant temp to stabilize by driving approximately 10 miles with cruise set at 71 mph indicated in the digital speedometer display, I saw the following in the HVAC panel diagnostic mode:

Outside Temp Average (5c display) = 30 deg C (converts to 86 deg F)

Coolant Temp (6c display) = 91 deg C (converts to 196 deg F)

Vehicle Speed (20c display) = 111 km/h (converts to 69 mph)

RPM (21c display) = 2700

The coolant temp gauge needle in the instrument cluster was pointing straight up between the "8" and the "0" of the "180" label.

Oil temp was unavailable in the HVAC control panel diagnostic mode, because (I think) the 986 Boxster does not have an oil temp sensor in stock form.

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When I returned home, I idled the engine for a while and gathered some more data:

* at 100 deg C (6c display on the HVAC) the gauge needle was approximately in the middle of the "0" in the "180" label.

* at 102 deg C (6c display on the HVAC) the right side radiator fan came on. This correlates with the specification in the Bentley manual for HIGH speed (stage 2) fan. The coolant temp crept up to 104 deg C (219 deg F) and stayed there for at least 5 more minutes with the right side radiator fan running. The gauge needle was at the right edge of the "0" of the "180" label when the HVAC was displaying 104 deg C coolant temp.

It is apparent that I have a radiator fan problem on my car. According to the wiring diagrams, both left and right side fans should be controlled at the same speed (stage 1 or stage 2) at the same time. It should be pretty simple to begin testing at the relay locations under the dash, since the relays seem to follow the standard ISO terminal definitions. I'll start with my Fluke 88 meter and a fused jumper wire...

So, what's going on here? These coolant temperatures do not match what JFP in PA, cnavarro and Jake Raby have posted on multiple occasions. Is the DME lying to the cluster and/or the HVAC control panel? Is the cluster lying to the HVAC control panel? Is the HVAC control panel lying to me? Or is the HVAC panel diagnostic mode accurately reporting the coolant temp as the DME reads it from the ECT sensor? None of the scan tools I have access to will read DME data, so this might be the push I need to buy the Durametric package...

[pk2]

Blue s,

Great work. So what has been said appears to be true. Have to ponder a bit...Think I'll see if I can get the same in my car... maybe I can even get the oil temp.

Let ya know whhat I come up with.

Regards, PK

[JFP in PA]

Originally Posted by Blue-S

I had some time this evening to drive a bit and collect some data from the HVAC control panel's diagnostic mode as explained above. The car was a 2000 Boxster S 6-speed, with a new Porsche water pump and a 1-year-old standard replacement thermostat (presumed to be 80 deg C). The A/C compressor was off throughout the testing.

* During warmup, with the temp gauge needle exactly on the "tic" mark above the "8" in the "180" label, the HVAC panel (in 6c display) read 79 degrees C coolant temp. That converts to 174 degrees F.

* After allowing coolant temp to stabilize by driving approximately 10 miles with cruise set at 71 mph indicated in the digital speedometer display, I saw the following in the HVAC panel diagnostic mode:

Outside Temp Average (5c display) = 30 deg C (converts to 86 deg F)

Coolant Temp (6c display) = 91 deg C (converts to 196 deg F)

Vehicle Speed (20c display) = 111 km/h (converts to 69 mph)

RPM (21c display) = 2700

The coolant temp gauge needle in the instrument cluster was pointing straight up between the "8" and the "0" of the "180" label.

Oil temp was unavailable in the HVAC control panel diagnostic mode, because (I think) the 986 Boxster does not have an oil temp sensor in stock form.

------------------------------------------------------

When I returned home, I idled the engine for a while and gathered some more data:

* at 100 deg C (6c display on the HVAC) the gauge needle was approximately in the middle of the "0" in the "180" label.

* at 102 deg C (6c display on the HVAC) the right side radiator fan came on. This correlates with the specification in the Bentley manual for HIGH speed (stage 2) fan. The coolant temp crept up to 104 deg C (219 deg F) and stayed there for at least 5 more minutes with the right side radiator fan running. The gauge needle was at the right edge of the "0" of the "180" label when the HVAC was displaying 104 deg C coolant temp.

It is apparent that I have a radiator fan problem on my car. According to the wiring diagrams, both left and right side fans should be controlled at the same speed (stage 1 or stage 2) at the same time. It should be pretty simple to begin testing at the relay locations under the dash, since the relays seem to follow the standard ISO terminal definitions. I'll start with my Fluke 88 meter and a fused jumper wire...

So, what's going on here? These coolant temperatures do not match what JFP in PA, cnavarro and Jake Raby have posted on multiple occasions. Is the DME lying to the cluster and/or the HVAC control panel? Is the cluster lying to the HVAC control panel? Is the HVAC control panel lying to me? Or is the HVAC panel diagnostic mode accurately reporting the coolant temp as the DME reads it from the ECT sensor? None of the scan tools I have access to will read DME data, so this might be the push I need to buy the Durametric package...

I have never used the climate control panel, so I cannot vouch for its level of accuracy, or how it compares to those seen on a scanner. You also need to recognize that these cars do vary somewhat in the temperatures they run at, even with the LN stat, due to differences in the cooling system (debris in the radiators, condition of the pump, non linearity of the dash unit, etc). I do know that the water temperature senders, at least those I have had the chance to evaluate, are pretty accurate. When using an OBD II scanner to monitor coolant temps, you are seeing the actual sensor data being relayed to the DME, so the numbers are also pretty reliable, and have correlated well with aftermarket gauge setups in the same cars.

On the Boxster, you cannot see the M96’s oil temperatures with out adding an oil temperature sensor to the engine, and while it can be done a couple of ways for testing, it is not a practical setup for day to day driving; so we only have used it for test purposes.

[pk2]

Originally Posted by JFP in PA

I have never used the climate control panel, so I cannot vouch for its level of accuracy, or how it compares to those seen on a scanner.... I do know that the water temperature senders, at least those I have had the chance to evaluate, are pretty accurate. When using an OBD II scanner to monitor coolant temps, you are seeing the actual sensor data being relayed to the DME, so the numbers are also pretty reliable, and have correlated well with aftermarket gauge setups in the same cars.

JFP IN PA

Very interesting information. You inadvertanly answered 2 sticky questions I was trying diplomatically compose. so moot now. At this quick moment I have, I can recall two comparatively softball questions.

1) As I understand from you and maybe others on this thread, Porsche concocted this whole charade so they could burn up more oil with the extra heat. I thought it was for emission issues but, if it blows out the pipe it's going to hurt not help in this arena(No?) is it blow-by?

Or, Could it be just to mitigate that early morning start-up cloud syndrome that some people have and freak out about? In which case, no matter for me, it would be long gone by the time you get to the smog station.

Tell me they did not do this to try to keep the outside the motor cleaner> avoid build up to...keep the motor running cool? (To ironic)

Thanks as always, gotta run...

PK

Is blow by that going to become aprent or

[JFP in PA]

Originally Posted by pk2

JFP IN PA

Very interesting information. You inadvertanly answered 2 sticky questions I was trying diplomatically compose. so moot now. At this quick moment I have, I can recall two comparatively softball questions.

1) As I understand from you and maybe others on this thread, Porsche concocted this whole charade so they could burn up more oil with the extra heat. I thought it was for emission issues but, if it blows out the pipe it's going to hurt not help in this arena(No?) is it blow-by?

Or, Could it be just to mitigate that early morning start-up cloud syndrome that some people have and freak out about? In which case, no matter for me, it would be long gone by the time you get to the smog station.

Tell me they did not do this to try to keep the outside the motor cleaner> avoid build up to...keep the motor running cool? (To ironic)

Thanks as always, gotta run...

PK

Is blow by that going to become aprent or

The use of higher coolant temperatures is done purely for emissions purposes. Running the cooling system at very high temps has been a crutch used by the OEM’s since the late 1960’s when everyone ran carburetors. Running hot helps nearly any engine reduce emissions with the poorly controlled fuel delivery systems that existed at the time. Unfortunately, even though modern injected and ECU controlled systems do not need to run that hot, the band aid has persisted because it also helps extend the cat converter life, and as the cat is covered by the federally mandated 80,000 mile operational life warranty, they will do anything to prevent having to replace the cats.

Interestingly, jacking up the coolant temperatures also lowers the volumetric efficiency and increases the chances for fuel flame front propagation issues (knock, detonation, etc.), so decreases in ignition timing are needed when the engine runs hotter. Net result is poorer performance, worse fuel economy and shortened oil life.

As for coolant temps allowing the oil to “bun off” contaminants; that rationale has always been somewhat suspect as the oil always runs hotter than the coolant anyway, plus the two main contaminants (water and fuel) would still flash off at lower temperatures as well, so lowering the coolant temp 20-30 F should not be a factor.

[Blue-S]

I realized that I do have a scan tool that is capable of communicating with the DME in SAE J1978 "Generic scan tool" mode. One of the data lines available in the Generic scan tool mode is ECT, so off I went to compare temp gauge readings, HVAC diagnostic mode coolant temp readings and scan tool ECT readings.

Key on, engine off:
HVAC = 31 deg C (88 deg F), Scan Tool = 91 deg F

Gauge needle exactly on the "tic" above the "8" in "180':
HVAC = 78 deg C (172 deg F), Tool = 181 deg F

10 miles on highway at 75 mph indicated, 83 deg F ambient temp & gauge needle straight up between "8" and "0":
HVAC = 91 deg C (196 deg F), Tool = 194 deg F

Idling:
HVAC = 100 deg C (212 deg F), Tool = 208 deg F
HVAC = 101 deg C (214 deg F), Tool = 210 deg F
HVAC = 102 deg C (216 deg F), Tool = 212 deg F (gauge needle near right edge of "0" in the "180" label)

Given these results, I can only conclude that (on my car, anyway) the HVAC panel diagnostic mode is reasonably accurate at typical cruise temps, and that when the gauge needle is "straight up" between the "8" and the "0" my coolant temp is 190 - 195 deg F. It is a bit odd that the HVAC diagnostic display ECT is cooler than the scan tool displayed ECT until approximately 190 degrees F coolant temp, then the situation reverses -- the HVAC display reads slightly higher than the scan tool reported ECT. The Bentley manual hints that the HVAC panel receives engine coolant temp from the instrument cluster, so maybe the cluster is re-scaling the ECT data to effect a slight change...or maybe not.

These results make a lot of sense to me, because a 10-11 degree C (18-20 deg F) coolant temperature gain through the engine is quite plausible under the conditions noted above. If the inlet side thermostat is 80 deg C, and the coolant exiting the engine is 90-91 deg C, then I'm quite happy with that.

BTW -- I noticed an anomaly: at highway speed, my cluster was showing 83 deg F ambient air temp but my Intake Air Temp (on the scan tool) was showing 66 deg F! Maybe this gives me a wee bit more spark advance than I otherwise would have...

[JFP in PA]

Originally Posted by Blue-S

The Bentley manual hints that the HVAC panel receives engine coolant temp from the instrument cluster, so maybe the cluster is re-scaling the ECT data to effect a slight change...or maybe not.

Based upon the 986/987 wiring schematics, I would have suspected that would be the case, which unfortunately means that the inaccuracy and non linearity of the dash gauge is transposed onto the HVAC display. Standard diagnostics for faulty dash displays always start with measuring the same data via the OBD II port, which is an indication that the port sees the sensors directly without the influence of the dash display. This is why I tend to trust my diagnostic instrumentation over what the dash is telling me…………….

"BTW -- I noticed an anomaly: at highway speed, my cluster was showing 83 deg F ambient air temp but my Intake Air Temp (on the scan tool) was showing 66 deg F! Maybe this gives me a wee bit more spark advance than I otherwise would have..."

Be aware that these measurements come from two different places, one is in the front grill, the other is inside the MAF; so cooling effects of the relative air movement as well as exposure to ambient sunlight are different…….

[Blue-S]

Yeah, I knew that the cluster's ambient temp sensor was in the grille area and I was pretty sure that the IAT was built into the MAF sensor. I was doing my test driving at 10:30 at night, so sunlight wouldn't have been a factor. I had the top down for my test drive (why not?) and the air temp definitely felt a lot more like 83 deg F than 66 deg F. I'm not particularly worried about the low IAT reading, though. Everything else that I could see looked good -- LTFT on both banks was +1 to +3% and STFT was bouncing +/- 2 around zero. I even found that my radiator fans DO work on high speed with the A/C on, so my only fan issue appears to be an inoperative left low speed fan. It was a good test drive...

[pk2]

Originally Posted by JFP in PA

Based upon the 986/987 wiring schematics, I would have suspected that would be the case, which unfortunately means that the inaccuracy and non linearity of the dash gauge is transposed onto the HVAC display. Standard diagnostics for faulty dash displays always start with measuring the same data via the OBD II port, which is an indication that the port sees the sensors directly without the influence of the dash display. This is why I tend to trust my diagnostic instrumentation over what the dash is telling me…………….

"BTW -- I noticed an anomaly: at highway speed, my cluster was showing 83 deg F ambient air temp but my Intake Air Temp (on the scan tool) was showing 66 deg F! Maybe this gives me a wee bit more spark advance than I otherwise would have..."

Be aware that these measurements come from two different places, one is in the front grill, the other is inside the MAF; so cooling effects of the relative air movement as well as exposure to ambient sunlight are different…….

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JPF and Blue_ s ("s"for "sleuth"?)

Good job. What a plot twist, What a surprise! (not).

Aren't all these sensors O to5 v? and gauges the same? If so, with schematics, pretty simple measurement; sensor to tach and from tach to hvac, although it might easier said than done, that instrument cluster is just about every but, mainly one big circuit board is more like it

Anyways, if you wanted, it would seem like an easy hack to jump your way around the gauge.

Anyways, with an obcII reader, it makes all of this moot I, but it would be nice to accurate look at the dash and get an accurate read, and worst fumble with the hvac.