2.7 Too hot, or is my gauge off?

[RetroSC]

Was pretty warm today, 92, so had the A/C running in stop and go and the gauge got uncomfortably high, see pic, showing just under 250. Surprised at this because it's a stock 2.7 with a Carerra fender cooler w/fan. I'm new to this car, so just learning it's ins and outs..

Got home and took some infrared readings. The oil tank was 202, pressure fed tensioner oil lines were 208, cam housings 195, and oil line running up front to cooler was 155, then 135 coming out of cooler. Those cooler lines seem kinda low, but maybe that's right?

Anyhow, I'm feeling like my gauge is high, the only place I got a high reading was the bottom of the engine case, 240, but that's right by the exhaust and probably not reflective of actual oil temps.

[manbridge 74]

The lines should be close to the same temp as the oil tank, I think your thermostat controlling flow to front cooler is not opening fully.

[manbridge 74]

Correction: the line flowing TO the oil tank should be roughly the same temp as tank.

[dwelle]

i shoot the lower valve covers for temp, i'd trust that number for now until you dig deeper.

you can test the oil temp sender, but i'd agree with jeff, check out your thermostat first...

[RetroSC]

Originally Posted by manbridge 74

Correction: the line flowing TO the oil tank should be roughly the same temp as tank.

That's kinda what I was thinking too, but is that just because my oil isn't hot enough to keep the thermostat open? If the tank is reading 200 degrees, maybe the thermostat is just kicking on and off, and all is well with the car and oil system, just my gauge is way off?

[manbridge 74]

Extremely doubtful the gauge is off by more than 5 degrees. Your oil line coming from oil tank to t-stat and then leading to front cooler should be heating to around 180 to open t-stat.

The good news is even at elevated temps it appears (can’t see rpm) you have 40psi oil pressure around idle.

[RetroSC]

So is my IR gauge off, or is the IR method not a good test of actual oil temps? Doesn't jive why I'm reading 200 on my tank and engine oil lines while dash gauge shows 245.

[manbridge 74]

I meant your cars gauge. The IR gun only reads the cooler surface temps not internal oil temp which are higher. I would concentrate on making sure your t-stat is working correctly, etc.

[Flat6pac]

The 2.7 temp sender is a brass unit. If it is chrome, you’ll get bogus numbers as the sender and gauge are matched.
Bruce

[spyerx]

Seems a bit high. I don’t have ac on my 71 with a 77 2.7 w carbs, it has a carrera cooler with no fan. I have on my seen it a needle width above 180 it’s usually parked on 180, and i was driving the crap out of it in the hills on a 90 degree day....

I’m with others you want to ensure your front cooler thermostat is opening all the way.

[930cabman]

I would be very careful as 250 degrees of oil temp is close to the temp where the oil will begin to breakdown. What temp does your IR gauge when pointed at boiling water? What type of oil are you running?

Hope your temp sender is not working correctly, this would be the simplest route

[Jack Stands]

I’d check the accuracy of the oil temperature sender/gauge by using boiling water, then you’ll be confident in your readings.

[fanaudical]

Originally Posted by RetroSC

So is my IR gauge off, or is the IR method not a good test of actual oil temps? Doesn't jive why I'm reading 200 on my tank and engine oil lines while dash gauge shows 245.

My opinion: IR temperature measurement, especially at temps under ~250°C, have accuracy problems if you don't correctly compensate for the emissivity of the emitting body.

Suggestion - Find a long thermometer or thermocouple probe. Stick that into the oil tank via the filler neck while the car is idling and check tank temperature that way. See how it compares to your onboard temp gauge.

[Nick Triesch]

i dont drive my 3.2 on hot days. our air-cooled cars do not like it . on hot days i drive in the morning or the evening. fall is a great time to drive. why put your car through that?

[dwelle]

why not?

it's hot here in central CA during the summer and the 3.2 in my '76 generally won't go above 200˚ with the fan on. i just don't drive the piss out of it when it's hot...

[RetroSC]

Originally Posted by Nick Triesch

i dont drive my 3.2 on hot days. our air-cooled cars do not like it . on hot days i drive in the morning or the evening. fall is a great time to drive. why put your car through that?

90 is a normal day here in the midwest summer, and I've been driving 911's in it for 20 years, they can handle it just fine if things are working right.

[Nick Triesch]

Our cars are tiny little cars . Mine is black on black. It is just not comfortable driving in the stinking hot summer. like riding in a oven. For me, much better later in the day. These cars cost a ton to fix, I know, just had much work done. One of the cars problems was that it developed a large oil leak where the head meets the case. The mechanic said one of the reasons is that it just got too hot at some period. My point is even if they can take it, why put them through it?

[RetroSC]

Originally Posted by Nick Triesch

Our cars are tiny little cars . Mine is black on black. It is just not comfortable driving in the stinking hot summer. like riding in a oven. For me, much better later in the day. These cars cost a ton to fix, I know, just had much work done. One of the cars problems was that it developed a large oil leak where the head meets the case. The mechanic said one of the reasons is that it just got too hot at some period. My point is even if they can take it, why put them through it?

It's a lot of money to have sitting in the garage if I only drove when weather was perfect. My car is not black on black, it's mint on tan, 90 degrees was plenty comfy the other day with the A/C on and I had a nice drive. A 2.7 with carrera cooler and fan should be just fine in those conditions, but something is wrong with my setup, hence this post. New car to me so I'm going to sort it out, and then continue to enjoy my warm summer days driving the old 911.

[Larmo63]

I drove 180 miles yesterday in my car, windows rolled down - no a/c. Temps never got above 200degrees and it was a hot day here.

[spyerx]

Following up on my earlier comment (for clarity my car is a 71 with a carb'd 2.7 from a 77S in it, with the full elephant racing finned lines + carrera cooler in fender, no fan).

Drove the crap out of the car yesterday, it was hot 85+, in the hills, so lots of higher RPM driving up hills and canyons. Over 200 miles of this. The hottest I saw the gauge get was to about 1/2 way between 180 and 210 so call it about 195. Cruising on the highway at 80 in near 90 degree weather later in the day it was sitting at 180 to just a hair above.

Anyway, a stock-ish 2.7 in good tune with a properly working fender cooler shouldn't be that hot. BUT, the AC condenser on the deck lid does pull warm air into the motor + the compressor does place load on the motor.

Definitely get your thermostat (i would check both case and front cooler thermostats) checked out, the line to the front cooler should be really hot. And make sure you don't have any creased lines slowing the flow up there.

As mentioned, you can test the sender and gauge. You could send both to North Hollywood speedometer, or, do a few simple tests, this post has some information:

Oil temp & pressure gauge / sender operation

Its not too hard to use a meter to check the resistance at various temperatures, then you could use a variable potentiometer in that range to check the gauge - use meter to set the potentiometer then jump to the sender and check gauge readings. If you have a little bit of electrical knowledge his is pretty easy to do.

Hope you get it figured out, you definitely do not want to run these mag cased motor hot.

P.S. your oil level may be a bit high, when hot (180) at idle i like the gauge to point at about 4 o'clock. But, make sure your gauge and dip stick match, trust the dipstick! (mine are dead on). My car consumes very little oil but when the gauge is above 1/2 the consumption rate is higher.