Jonathan C

I am trying to determine if my vehicle is running too hot, and I have done a lot of reading in the archives to see what is “acceptable” and what is “too hot”. Data:

1. 1997 Carrera coupe, 32,000 miles. Ambient temperature this time of year in the 60s and 70s deg. F – not even hot here yet.

2. I just replaced a faulty Oil Cooler Resistor - with a big thanks to Dan 96C2 St. Louis for an emergency house call after I failed to loosen the oil cooler – he’s a truly generous person! - and the fan now passes the test for low and high function.

3. Upon cold start-up I usually hear a gurgling on the right side, which indicates to me that the thermostat may be stuck partially open.

4. After about 10 minutes of “gentle” driving, <3,000 RPMs, the temperature gauge reaches the 3rd marker = 8 o’clock = 194 deg. F. It then drops down a bit, indicating to me that the thermostat has opened more.

5. After a total of 20-30 minutes, including the 10 minutes above, of normal driving, cruising at around at an average of 3,000-3,500 RPMs - mostly suburban - the temperature slowly rises to the 9 o’clock mark = 220 deg. F.

6. The needle will then hover between 220 and 235 deg. F. The fan will switch to high during these fluctuations, pushing the temperature back down to 9 o’clock/220 deg. F.

7. The needle has NEVER yet reached the 4th mark = 10 o’clock? = 248 deg. F.

My concern is: all my research in the archives seems to indicate that during “normal” driving in “pleasant” temperatures - two slightly subjective measures, I know - the oil temperature should stay close to the 3rd mark/8 o’clock/194 deg. F marker. The archival search also indicated that 9 o’clock/220 deg. F, whilst not unusual, was a bit high, usually corrected by a new Oil Fan Resistor, and potentially detrimental to both engine performance and engine life.

So my questions are, finally!:

A. are these temperature readings normal, high, or somewhere inbetween?

B. is the oil thermostat - about which little I could find in the archives - the likely culprit? It seems to me it might be stuck partially open all the time, never closed and never fully open.

C. are these thermostats normal-wear items as on a water-cooled engine, and what is the cost/difficulty to replace?

I come from a Jaguar background where overheating was a constant worry...I hope that the problem has not followed me to this car! Thanks for any assistance,

Jonathan

Edward

Jonathan,

All that you describe sounds normal to me. Point #3 is normal, as well, on start up and not an indication that the thermostat is stuck partially open; your point #4 indicates that it's working as it should. It seems like you're getting to 9:00 pretty quickly, but that may be due to slow traffic or your climate (I no nothing about the latter ). If you're cruising steadily at freeway speeds, your temp should drop to around 8:00 + or - a bit.

I've heard of many replacing the resistor; don't know if many here have replaced the thermostat (don't recall seeing it as a posted issue).

I'd say, relax, and enjoy the car

FWIW, I personally like the oil temp lower than 9:00. Do an archive search on a manual oil-fan switch. It's an easy DIY, and I find it a great benefit, especially if caught in stop-and-go traffic, and really helpful on the track. Hope this helps

Edward

Ray Calvo

Hate to go against Dan, but for street driving/cruising (not stop & go, and I assume country/rural road driving) in 60/70-ish temperature, your numbers seem high. I don't remember 9:00+ needle position unless it's a hot day, slow traffic, and AC is on with my '95.

tom_993

I agree with Ray, Jonathan’s temperatures seem high to me. My typical temperature reading, as long as there is reasonable air flow, is between the 122 and 194 marks. On cold mornings, at freeway speed, it’s closer to the 122. On warmer days, in slower city driving, it’s closer to 194. It doesn’t get above 194 unless it’s really hot and/or I’m stuck in traffic (no air flow), or during track driving.

Tom
’95 993

(Picture credit: Robin’s 993 web page)

<img src="http://p-car.com/diy/fan/1.jpg" alt=" - " />

Jonathan C

Thanks for the responses. The majority opinion so far is that the oil is getting too hot for normal usage. I would imagine that there is some variation in temperature from car to car and gauge to gauge, and that could account for the difference, but likely my oil temp. is excessive for my non-track, moderate weather use.

So, I assume that the oil thermostat begs closer attention in this case? As I surmised before, it seems perhaps to be neither closing fully nor opening fully (assuming its operation is similar to that of a water/coolant thermostat). Lack of information in the archives leads me to believe that this is a very unusual thing to have happen, however.

What other alternative causes are there? Otherwise, as they say, the remaining solution, however unlikely, is my answer. --Jonathan

STLPCA

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Ray Calvo:
<strong>Hate to go against Dan ...</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Hey Ray - I agree w/you. Jonathan's temps are a bit higher than I see in the exact same climate.

It was Edward who opined the temps as normal. As a former New Yorker, I understand your confusing us since we're both West of your coast somewhere in "the rest of the country."

Regards.

Jonathan - as an afterthought - have you checked your oil level w/the dipstick?

Randall G.

Hey Johnathan,

Sounds okay to me, with the crux being how much of your suburban driving was stop, and how much was go. If primarily stop, then your observed temperature sounds normal.

With respect to your oil cooler fan, that's mostly good news. It's starting at about the right temperature and staying on long enough to actually cool the oil. What's odd is your describing the fan running in fast-speed. It should first run in slow-speed, only kicking into fast-speed if slow-speed is inadequate or inoperable. Are you sure it's not running in slow-speed?

The 964 guys are starting to see thermostat failures, but (as you suggest) I can't recall ever hearing of one that partially failed. When they break, they seem to break completely = no flow to the cooler. You obviously have flow to the cooler, since the fan running cools the oil.

I've never heard a good explanation for the gurgling sound coming from the engine when cold. A thermostat that leaks by a bit--with the sound stopping when it opens--is the best explanation I've heard so far. Regardless of source, the gurlging sound appears to be common and harmless.

bet

Jonathan,

I hate to ask the obvious, but have you check to make sure there isn't an obstruction in the area of the oil cooler up front? What about oil levels?

With either improper an improper oil level or an obstructed cooler you would still notice a temporary drop in the oil temp when the thermostat opened all the way and allowed the oil that was in the cooler lines to mix with the oil in the tank.

Have you followed all of Randall's diagnosis help at <a href="http://p-car.com/diy/fan/" target="_blank">http://p-car.com/diy/fan/</a> ? To rule out things such as a temp. sensor? You might try using E.J’s trick of running the fan on high all the time and see where your temperatures are (http://www.pcarracing.homestead.com/fantrick.html). Maybe your cooling fan is still not working properly. Of course you could always install a manual fan override switch.

TamiyaGuy

Johnathan,

It sounds like your weather is similar to what I'm experiencing here in Seattle. The rpm range is about the same as well. I've never had it go to 9pm on the gauge before. It typically hovers around the 8pm position as far as I've seen.

Thanks,
Peter

Jonathan C

The majority consensus here continues to be that the car runs too hot. The oil cooler is not physically obstructed (e.g. leaves, dirt). I shall test the temperature sensor per p-car.com during my next free time.

Oil level *might* be a bit low, perhaps 1/4 litre if measured when temperature is at 8 o'clock. When gauge is at 9 o'clock level is higher due to expansion. Dipstick corresponds to gauge readings. But I must say that during the regular oil consumption cycle (top off, burn, top off, burn) I see no difference in temperatures at the low and high points of oil content.

Edward has been the one dissenting voice so far, but I did stop by the mechanic's shop yesterday, and his reply to the situation was: 220 deg. F. = 9 o'clock on the gauge is an appropriate operating temperature both for performance efficiency and fuel efficiency. He believed that the fact that the fan kept the temperature from ever going above 9:30 was a sign of a properly operating system (a 95 deg. F day will put that fan to the test though!). My gauge indeed corresponds to the photos on the P-Car DIY oil cooler page, where 9:30 represents the fan onset and 9:00 represents the fan shut-off. Were the system to require lower temps, wouldn't the high fan stay on 'til the temp was pushed down much lower?

What is *not* reassuring is that almost everyone else seems to run around the 8 o'clock mark. So either I have a hot car by nature, a failure in the cooling system, or a error in my gauge. Using a IR thermometer, where is the best spot(s) to gauge the engine/oil temps? (I used to try to "heat map" my Jaguars when I had these problems).

--Jonathan

Edward

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> Edward has been the one dissenting voice so far, </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Wait a minute...not exactly a dissenting voice here. Did you miss this part:

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> but that may be due to slow traffic or your climate (I know nothing about the latter). If you're cruising steadily at freeway speeds, your temp should drop to around 8:00 + or - a bit. .</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Your temp may or may not be getting hot too soon, but that depends largely on whether you car is moving, and at what speed, ambient temperature, etc....just to keep my original post in perspective.

Edward

Jonathan C

Another thought to consider, though not at all scientific nor proof: on the temperature gauges, dead-centre on the scale is the usual "sweet spot" for every other car I've owned. Dead centre here being ~221 deg. F at 9 o'clock. (Dead centre on those non Porsche, water-cooled cars usually being ~190 deg. F.) Or am I now grasping at straws here?

Jonathan C

Edward - sorry to take your comments out of context; that's a big problem with e-communication these days. My point in mentioning you was more that a local, well-respected Porsche expert had a similar attitude to the one you expressed, i.e. "I'd say, relax, and enjoy the car".

To answer your "questions", my routes rarely include highway driving (unless I go out of my way, which I try to do at least 1 or 2 times a week), but the city driving is hardly bumper-to-bumper, so it's moderate stop-and-go, suburban driving mostly.