Oil Temp too high?

[lespaul]

Last summer when I bought my 1973.5T, the oil temp held steady at about 185 F. Once in traffic on a hot day it went to 215-220F.

Over the winter, I adjusted the valves. I have now started to run it again, however, the oil temp is running at between 210-235F.

Besides the valve adjust, the only difference is my driving. Last year, I was running it between 3000-4000 RPM. I am now more aggressively driving and keeping it between 4000-5000 RPM, with an occasional move to 5500, and sometimes to 6000. On Vermont's back roads, I can hardly get out of 3rd because at 4000 RPM I am going 65 mph flat.

Anyway - is an oil temp that hovers around 225F normal? The owners manual says don't let it get over 265F.

Appreciate any insights.

[javadog]

I'd wager you are just spinning the engine too fast. Before you get contrary replies from the peanut gallery, let me explain. There's nothing wrong with revving the engine high while accelerating. If however, you are running in a low gear while cruising at a constant speed, to keep the revs up, you may be better off shifting to a higher gear. Although you get more airflow from the cooling fan at higher engine speeds, the oil temp is usually higher than it would be if you cruised at a lower speed.

You never want to run a 911 engine at a low rpm range where it doesn't respond readily to changes in throttle input. Likewise, it's pointless to spin the engine fast, when you don't need much power. Somewhere in between the two extremes is best and you'll learn what this is for your car if you experiment a little.

JR

[rfn026]

I'm willing to bet that you're running a heavy weight oil. That old fashioned heavy weight oils create a lot of friction - which means a lot of heat. I dropped my temps below 180 degrees by switching to a 5W-30.

Richard

[lespaul]

Not sure the oil is making a difference. I was running 10w/40 last year and, just did an oil change to a new batch of 10w/40.

It does seem the heat is more related to the higher revs. I will eventually find my sweet spot on revs, but -- my question is whether running the engine at 215-235F on a steady basis is harmful to it?

[javadog]

I don't think anybody gets too excited about oil temps around 215. You want to get the oil hot enough to keep water condensation out of it. If it runs closer to 235 all the time, you might get an oil cooler if you don't have one, or a better one if you do.

If you run a good synthetic oil, I think you have less to worry about.

JR

[KNS]

Take a look at some of the BMW boards and the new 335i (E90-92). These cars are running 250-270 as *normal* temps - Yikes! When the Oil Temp reaches 300 degrees the car goes to limp-home mode. Can synthetic oils really handle these kind of temps? The BMW fill is 5W/30 synthetic.

[kach22i]

When I reindexed my distributor and set my ignition timing last year I lowered my average operating tempeture 30 degrees.

[barney911rs]

Brad,

You never said if the oil temp come back down after the car sits and idles for a few minutes. If it does, I think you are fine with the temps you are running. 250 is the start of the real danger zone. If your car does not have any additional oil cooling other then the engine mounted cooler, you may want to look into that as a future mod.

Sounds like you are starting to have more fun with the car. I agree that cruising at higher RPMs is not necessary, but zipping up there while under acceleration is fine.

[lespaul]

John, yes, the temp does come back down to the 210-215F range on idle and also when I run at lower revs - 3000--4000 range.

Thanks to all for the input.

Sounds like I need to upshift more often when cruising.

I am also going to double check my distributor dwell and timing. I did not check it after I did the valve adjust - could adjusting the valves impact distributor timing?

[javadog]

Originally posted by lespaul
I am also going to double check my distributor dwell and timing. I did not check it after I did the valve adjust - could adjusting the valves impact distributor timing?

No.

JR

[kach22i]

Maybe you are running "lean", that could be a serious problem you want to catch early.

[azasadny]

Brad,

Just for reference, my '74 with Webers runs consistently at 190 degrees and has not gone over that in over 4000 miles, but the hot summer is approaching. I run AMSOIL 20W50 full synthetic and I have the Carrera-style oil cooler. My temps dropped about 10 degrees when I replaced the CIS with Webers and it dropped another 10 degrees with the switch to AMSOIL.

I replaced the engine too, so I have a hard time with an "apples to apples" comparison, though I'm comparing 2 2.7L '74 engines. Hope this helps...

[lespaul]

What is the best way to catch it if I am running too lean?

After the valve adjust, my idle after warm up dropped to a steady 800 RPM - and sounds even and nice (except for one ticking valve I will catch on the next oil change). Before valve adjust, idle was 950 per the book. I plan to adjust it back up to 950 but does the drop in idle indicate anything about whether I am too rich or lean?

[lespaul]

For what it is worth, I have the Behr Turbo oil cooler.

911-107-041-00-M6

Is there an upgrade for my 73.5T beyond that?

[Chuck Moreland]

Why not take a drive using your old style of 3000-4000? See if the temps return to the old temp. You'll very quickly be able to see if that is the cause of the change.

911s like to be in the 180-210 range. Safe oil temps on a BMW are meaningless, very much an apples and oranges comparison. For instance - Air cooled engines are much more reliant on oil to cool the heads and critical areas than are water cooled engines. Oil temp depends on the location it is measure, etc.

[javadog]

Originally posted by lespaul
For what it is worth, I have the Behr Turbo oil cooler.

911-107-041-00-M6

Is there an upgrade for my 73.5T beyond that?

The cooler you have mentioned above is the one at the engine. We were referring to an auxiliary cooler, usually mounted in front of the right front wheel. My personal favorite, for the typical driving conditions seen in the US, is the factory 28 tube brass cooler.

JR

[lespaul]

Thanks again guys. Tonight I will run it more gently and see what happens.

Brad

[barney911rs]

To check for lean/rich, you either need an EGT (Exhaust Gas Temp) or an O2 sensor. A shop with an analyzer should be check for that.

[Paulporsche]

lespaul,

As a general rule, if nothing else changes, if you richen your mixture, the revs @ idle will lower, and if you lean it, the revs will rise. In you example, what would cause the enrichment? If you retarded your timing, that might do it. I don't know if the valve adjustment would do it. Someone else may know.

Also, in general, if you are running richer, usually that lowers engine temps, while running lean can raise them.

[jmcn3rd]

I am loving this post. I have a 72 911t targa and have been driving it for about a year now as well. I too finally have it sorted out enough that I can start hammering on it a little and am finding that sustained higher rpms make the engine temp hotter than I am used to seeing. Everyone says to shift at 4500-5000 but I am finding that is fine for accelerating but not for cruising. Seems better to cruise at 3000. I guess the problem is that I am usually accelerating. I cruise in my other cars!