How hot is *too* hot?

[widebody911]

I got stuck in traffic today, and my oil temp got up over 250 for a about 20 minutes. How worried should I be? Once I got moving again, it quickly dropped to below 200.

I can't think of anything I can check for damage, and there are no funny noises. The oil still looks good.

It has never been this hot. The OEM oil cooler fan finally gave up the ghost yesterday; I bought a new one months ago, but never installed it. I guess we know what my next project will be...

[KobaltBlau]

depends on who you talk to. I think it's definitely fine if it didn't beat 260. how hot did it get?

[Jack Olsen]

With a 3.6 and Mobile One? I think you'll be fine. 3.6's seals are better than in early motors, and synthetic oil can take pretty much all the heat you can throw at it.

[pgsandiego]

I was driving hard the other week in my new (to me) 82' 911SC and hit above 250 for an extended (30 min?) time. I found out later that 250 is way too hot! No problems with the car though. Still drives great! Now, I need to find a carrera cooler to upgrade...

I wouldnt worry about your short time at high temp.

Patrick

[cantdrv55]

If it's possible to reach 250 in an SC during regular driving, why didn't Porsche issue a recall if that situation posed a danger to the engine? Or did they? Does anyone know what the official word was from Porsche back then? I can't believe they recognized it to be a serious problem and did nothing about it.

[klaucke]

I think my 74 2.7 gets up to about 230 in this summer heat, is this too hot? Normally I don't like it to pass 210 but I don't have any type of external oil cooler. Lately I've been thinking I don't want the engine getting this hot as I risk pulling head studs (2.7 has never been rebuilt). I plan on making a finned aluminum "cooler" tube like pelican sells that goes between the engine and oil tank and installing on my next oil change, think this is enough to beat the heat? I'm a pretty conservative driver especially when I see the temps start to rise. Guess I could try a cool collar...

[911pcars]

It's not the oil that's in danger at 250 although synthetics usually remain more stable at elevated temperatures. As the temperature increases, parts continue to expand. In the case of a piston, there's only 0.002-0.003" cylinder clearance. Once this is taken up by heat expansion (cylinder and piston), there is metal-to-metal contact and bad things happen.

Use good quality oil (petroleum or synthetic) and keep the oil temperature below around 220ºF.

Germany doesn't have the extremes in temperatue we do here, and only a few selected early 911s needed an oil cooler (S models). Nowadays, most manufacturers send their prototypes to extreme climates (Minnesota in winter and Arizona in summer) to test vehicle heating, cooling and A/C systems.

Porsche still thought the early SCs were fine with the minimal trombone cooler. We know better. In general, any engine 2.7 or larger needs an external cooler if the ambient temperatures are +80ºF.

Sherwood

[Bill Verburg]

In the 3.6s 250&degF isn't considered excessive. The worst thing may be a slight acceleration in guide wear, but nothing to worry about.

[tsuter]

Anything under 300 is no big deal. Most current technology vehicle temperature management systems use 300F as the point to initially richen the mixture by first lengthening the pulse width, then lowering the idle and then if that still doesn't result in temperature drops, skipping cycles. And as a last resort shutting down your ignition to save the motor.

All you peeps with the yellow mystery gunk aren't getting your motors hot enough. Sustained 220+ is excellent operating temp.

Under 200??? And you're wondering what that gunk is????

[widebody911]

I have 2 front coolers - the Carrera cooler in the fender, and a Setrab in the nose. Under normal driving conditions, this is enough . Even on the track in 100+ tems it's fine. But the combo of getting stuck in traffic and the dead fan weren't workin' in my favor.

I think I'll change the oil to be on the safe side.

[BGCarrera32]

So...for those of us that don't have numerals on the oil temp gauge...which lines correlate to what temperatures? I've wondered at the track if I'm running too hot...

[masraum]

The fan in the late year 3.2's didn't kick on until 245. That considered I don't think it's a huge problem. You are more likely to run into a problem if you are at elevated temperatures when you are pushing the car really hard than if the temp goes up while you are sitting still. The important thing in my eyes is that you weren't at redline when the thing was that hot and then once you got moving it cooled down.

[SC-targa]

Originally posted by widebody911
I have 2 front coolers - the Carrera cooler in the fender, and a Setrab in the nose.

You need to dump those inefficient coolers and replace them with a "trombone" cooler I happen to have.



My SC with a stock loop cooler was up to 220 - 240 F yesterday in 100 F traffic here in DFW. Last week it briefly topped 120 C (248 F).

Regards,

Jerry Kroeger

[Wil Ferch]

BGCarrera32:

See here....

Oil temp gauge

--Wil

[Chuck Moreland]

Originally posted by tsuter
Anything under 300 is no big deal. Most current technology vehicle temperature management systems use 300F as the point to initially richen the mixture by first lengthening the pulse width, then lowering the idle and then if that still doesn't result in temperature drops, skipping cycles. And as a last resort shutting down your ignition to save the motor.

You are comparing apples and oranges.

Oil is not the same temp throughout the system, it varies a great deal in different locations. The oil temp sending unit samples temp in exactly 1 spot, and it is not the hottest. In the case of a 911, oil in the heads will be hottest - the sending unit is in the case.

Further, the difference between hottest spot and coolest spot will be greater in our air / oil cooled motors than a typical water pumper.

The typical Audi, Vette, Honda, etc also samples one location (completely different) and has a more stable oil temp throughout the system.

[chrisp]

FWIW, before I swapped my trombone for a radiator my I used to see 250 on the track. This happen only in the summer months (3-4 track days a year) for three years. Most of the run groups I would hit 250 for between 10-15 minutes each time. With the fender radiator cooler I am in the 220-230 range.

My motor was rebuilt this winter and once apart the builder said that it was very clean with no visible heat damage.

I run Mobil 1 as I think it's the best protection against heat available.

[RarlyL8]

911 engines don't get into "failure" zone unless temps are crazy high for extended periods. What happens at "elevated" temps (like 220-260F) is a direct correlation between temperature/time/and engine life. You cut years off your motor's life if it often runs hot. This was part of the 2.7L legacy.

[safe]

What about oilpressure at higher tempratures?
At 176 degrees I have more than 1 bar / 1000 rpm, but when I hit 210-230 the pressure drops. Then I maybe only have 2bar at 3000 rpm (20-50 mobil dino). Is that something to mind?

[aigel]

Originally posted by safe
What about oilpressure at higher tempratures?
At 176 degrees I have more than 1 bar / 1000 rpm, but when I hit 210-230 the pressure drops. Then I maybe only have 2bar at 3000 rpm (20-50 mobil dino). Is that something to mind?

I wouldn't like that. I'd put the cam oil restrictors, that'll fix it. Did it for me.

On a separate note, I am still wondering, why Porsche made 250 degrees F the center (!) of my SC gauge along with >300F being the red zone. Temp range on SC gauge After ducting air on my SC I don't get to 250 any more, unless I run an hour straight in 105F heat at the track, but if I do, I quit worrying.

The engine has 155k miles and has no signs of valve guide wear. If it has to come apart some day it will likely be at 200+k miles. I am not going to fool myself that I won't need new pistons. It's beyond that point. A few hours a year at the track at 250 won't make a difference.

Just my two cents. I think most people are too paranoid about their temperatures. 250 isn't great, but it is fine. I trust Porsche not to put it in the center of their gauge on the 3.0 if it wouldn't be.

George

[KobaltBlau]

Magnus, that is simply what happens as the oil gets thinner at higher temps, it does not create as much pressure when the positive displacement pump turns the same amount. As long as your pressure numbers are still high enough (perhaps another discussion), don't worry.