Jonathan C

[edit. I originally wrote a long, rambling note about my higher oil temps, neurotic oil level readings, et cetera, et cetera, but "breuitas delectat", so here is the highly abridged and unannotated (except for this bit here!) version]

On the tiptronic-equipped car, there is an ATF cooler right next to the oil cooler. Basically, the oil cooler is sandwiched between the fan on the right and the transmission cooler on the left. Surely this could affect oil cooling, relative to a vehicle without an ATF cooler? The ATF cooler could both affect/restrict the flow of air through the oil cooler and also transfer heat to the oil cooler if the transmission were running warmer (e.g. being used in manual mode).

Thanks for your thoughts! Jonathan, 1997 Carrera

johnfm

Jonathan

not significant IMHO.

With the fan on high speed, my oil temp doesn't get over the 8 o'clock mark. I agree that in theory, the proximity of a second cooler may have some impact on deltaT of the first cooler, but it also depends whether the fan suckes air from teh ATF cooler side, or blows air across the cooler TO teh ATF cooler side.

If you have an oil temp problem, I suggest you look at your thermostat (to see if any oil is getting to your oil cooler) and check the operation of your fan at both high & low speed.

The archives have a good guide to oil temp problems.

Jonathan C

John F-

I was trying to avoid writing up a recap of my entire oil temp situation, but since you asked! here is the original, unabridged version, which refers to my past research in the archives, P-Car.com, and a couple of prior posts on this forum:

****unabridged version****

“hypothesis: tiptronic may cause higher motor oil temps?”
(or, “flogging a dead horse”)

In my attempts to analyse my slightly higher oil temps, I have noted the following:

1. Almost everyone has written that his “normal” oil temp when fully warmed up tends towards the 8 o’clock = 194 deg. F reading. Readings of 9 o’clock = 220 deg. F are not unusual, but are usually indicative of high ambient temps, spirited/track driving, and bumper-to-bumper city traffic.

2. I think it is safe to say that the vast majority of these people have manual transmissions (but this may also include most tiptronic owners....survery?)

3. My motor oil temperature (given enough time, say 20 minutes or more) tends toward the 9 o’clock = 220 deg. F reading. This happens whether in “auto” or “manual”; this happens whether the ambient temperature is 50 deg. F or 95 deg. F. It will not go over 9 o’clock, but this seems to be the temperature it naturally “seeks”. Of course, this is also the upper limit, and any higher temp will cause the fan to turn on, which keeps the temp down at the 9 o’clock = 220 deg. F reading. For that reason, I do believe my cooling system is functioning properly (as indicated in a prior post, my oil thermostat does open around 190 deg. F).

4. Highway driving in top gear (4th for the tip.) will eventually bring the 9 o’clock = 220 deg. F reading down to an 8 o’clock = 194 deg. F. Also, if I force the oil cooler fan to run (I did the “permanently on” experiment, followed by a manual switch) I get the same, dramatic results others have reported: the temperature stays near 8 o’clock = 194 deg. F in almost all circumstances.

So my question is still: why is my “natural” running temperature 9 o’clock when almost everyone else’s is 8 o’clock? The reason I’m so curious is two-fold:

A. This may be indicative of some short-coming or potential impending failure on my particular vehicle (continuously excessive heat is usually not good!); and

B. my neurotic tendency wants to grasp my proper oil level, as read on the gauge; i.e. due to oil expansion, my oil level reads higher when the temp is at 9 o’clock then when the gauge is at 8 o’clock, but most accounts of how to read the oil level require that the car be both “fully warmed up” and “in the area of the [194 deg. F] marker”; in my case I can either be fully warmed up OR at the 194 deg. F marker, but not both – unless my fan is permanently running. (I fully understand that point B. is not a dire question, but rather a neurotic desire, and that my dipstick reading should be the final arbiter if I’m really concerned about current oil level, but the same expansion that applies to the gauge should apply to the dipstick, right?)

So finally, on to my hypothesis. On the tiptronic-equipped car, there is an ATF cooler right next to the oil cooler. Basically, the oil cooler is sandwiched between the fan on the right and the transmission cooler on the left. Surely this could affect oil cooling, relative to a vehicle without an ATF cooler? The ATF cooler could both affect/restrict the flow of air through the oil cooler and also transfer heat to the oil cooler if the transmission were running warmer (e.g. being used in manual mode).

Please excuse this long, babbling post, but I am trying to lay this all out as concisely and logically as possible. I realize that I do not really seem to have a major problem, but I’ve only had this car for a few months, and I am trying to get my mind around this conundrum.

Thanks for your thoughts! Jonathan, 1997 Carrera

johnfm

Er, you may find that your fan isn't automatically switching to low speed mode. Th epermanent on switch, as found in Randall's posts in the archives, sets the fan on at full speed. I suggest that the 'normal running at 9' is because, like my car, the fan isn't coming on at low speed.

THe only real way to check this is to get the car warm & idling & listen for the fan. If you need to check what low speed sounds lik eyou will need to 'jumper' the low speed fan connection on the relay - I cannot remember whether this is a bad thing to do with the engine running or not??

Either way, this is what I suggest your problem may be, as I don't think the presence of the ATF cooler will make a 25-30 degree difference in oil temp.

Jonathan C

John -

I did replace the oil cooler resistor several weeks ago, and with the ignition off, both high and low now work. I'd certainly defer to you as to whether it is safe/sound to jumper that connection with the car running! What *sounds like* the low-speed fan comes on at ~9:15, but I've also rigged a spare relay with a jumper (as described in a post a few weeks ago) so that the low speed is superceded by the high speed.

As to your response to my main question, I'll grant that you're probably right - the ATF cooler is unlikely to raise the oil temps by 30 deg. F - but having reviewed my situation I thought I'd at least pose the question. Thanks again for your input.

Regards, Jonathan

Jonathan C

actually, let me add that, for the purposes of my question, I don't think it should matter whether the low-speed fan comes on, because the fan (low or high) comes on *above* 9 o'clock, so the fan will not prevent the car from running at 220F, but rather higher than 220F. My question has more to do with the increase from 194F to 220F, a range of temperatures which precludes automatic fan operation at any speed, if I understand everything that's been written about it already.

johnfm

So, your low speed fan works automatically. But, you think it odd that the car still settles at 9 rather than 8 o'clock.

HAve you taken ambient humidity & temp into account in your 'survey' conclusions. I find that on humid days, though not particulalry hot (say 23 to 25 deg C), the car can easily get to 10 o'clock in traffic - I keep the fan on constant now on hot days!

Jonathan C

John - (un)fortunately, ambient temperature seems to have little effect (touch wood!). As I said earlier, it might be 50F or 95F, the car still settles in at 9 o'clock/220F. So far, on hot and humid days (it's rather hot & humid here in the summer), the cooling system has worked well at keeping the temperature at 9 o'clock.

So, at this point, my concern isn't that the car is going to overheat, but rather that the car should "normally" be running at 8 o'clock, but instead "normally" runs at 9 o'clock. Thus I was trying to find some element of the car (as in the ATF cooler) that might contribute to warmer running. If all tip owners said, "sure,once warmed up, my car regularly runs at 9 o'clock, except when on the highway", I'd be reassured.

An example of how regularly warmer temperatures can be annoying is: today (ambient temp = 75 deg F) when the temp. gauge was approaching the 9 o'clock point (say 8:30) the oil level gauge went over 3:00. But after I switched on the fan, and the oil temp. fell back to 8 o'clock, the oil level gauge now read just above "red". I could watch the oil level gauge fall as the temp. fell! I'd always based my oil level checks on a fully warmed-up engine, which for me meant 9 o'clock = 220F. If I need to be checking at a lower temp., ~200F, then perhaps I've been keeping the car a little too low on oil? The difference of 20 deg. F. oil temp. seems to expand or contract the oil by a reading of possibly .25 to .33 litres?

--Jonathan

STLPCA

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Jonathan C:
<strong>Almost everyone has written that his “normal” oil temp when fully warmed up tends towards the 8 o’clock = 194 deg. F reading. Readings of 9 o’clock = 220 deg. F are not unusual, but are usually indicative of high ambient temps, spirited/track driving, and bumper-to-bumper city traffic.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Jonathan
As you know, our cars live blocks apart in the same environment & mine responds as described above, ruling out several variables.
2 thoughts:
- I know you've checked oil level, but have you changed the oil since buying your car? I wonder if your higher running temp may be related to differences in oil viscosity, brand or type.
- It is also possible there are variances in gauge readings so your 9:00 may be lower than my 9:00. A thermometer should resolve that issue.

Glad you're getting to know your car so well.

Jonathan C

Hi Dan! re: oil -- The car is filled with Mobil One 15W50. Had it changed at Reid Vann about two months ago. Since then, I've had to top it up a bit, and by my calculations, they car is burning approx. one litre every 1,250 miles, which I realise in on the high side, but still less than Porsche's "panic" level (600 mi/litre?) (n.b. the car had sat with little mileage for a while before I bought it; perhaps a DE or two would help reduce the burning)

re: gauge -- since I can see the effects of the thermostat opening quite clearly between circa 180 deg. F and 195 deg. F on the gauge - and after it opens it settles back down to about 185 for a little while before it begins its ascent to 220! - I assumed that the gauge reads fairly accurately. Likewise, when the fan kicks in at about 230 deg F, it reads at the 9:15 position much like the photos at P-Car.com. For those reasons I have trusted the gauges readings. I do have a IR thermometer, but I'm unsure of the best place(s) to take readings that would reflect oil temp as indicated on the gauge. I guess perhaps the lines into the cooler, but I'd rather be able to do the test with the car intact and driving.

As Dan reiterated, and as did BradB when I saw him at the Jaguar/Aston dealer last week, their temps. don't normally get up to 9:00 tootling (is that the right spelling?) around Clayton on Sunday afternoon. Mine does. I was hoping the difference was my Tiptronic, and that these temp ranges were "normal" for the tip., perhaps because of the ATF cooler.

--Jonathan

johnfm

JOnathan

1 litre per 1250 miles isn't on the high side of oil consumption. Specified consumption in the hanbook is 1 litre/1000 km (625 miles), so your are consuming HALF the expected amount.

STLPCA

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Jonathan C:
<strong>...perhaps a DE or two would help reduce the burning</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Now that's an easily corrected problem - <a href="http://vista.pca.org/stl/0309CCRegistform.doc" target="_blank">Download Driver Education Registration Form </a> for upcoming STL PCA Summer Carrera Classic DE August 16 & 17 at GIR.

Jonathan C

Dan - depending on family commitments, I may try to attend a session. Also, an ex-vintage Jaguar saloon racer (among other things), Philip Wicks, has started a DE "academy" in town, so I may enroll in that too. He actually has an advert. up at Reid Vann.

JohnF - oil consumption is another big topic! From my reading in the archives, I recall (perhaps hazily!) that someone conducted an informal survey here, and the results ranged from 1 litre/,1000 mi to 1 litre/5,000 mi or less. I think the average was around 1 litre/2,500 miles maybe? My *understanding* is that the upper limit per Porsche is 1 litre/600 miles: this is not the expectation, but rather the "worst" possible case without cause for alarm. But, as the addage goes, your mileage may vary! I think you'll find more people on the 993 list who say "close to no oil consumed" than you will who say "close to 1 litre per 600 miles", but that's just a guess on my part...I may be totally off on that one! --Jonathan