New to me 1978 911sc running extremely hot

[lfitzsimon]

Hello all,

I purchased my first 911, a 1978 SC about a month ago and am loving it so far but am having major worries with how hot it's getting. I've searched and can't find any answers, and am hoping that somebody has some insight.

The car runs beautifully, great oil pressure, very strong power, no worrying sounds at idle or acceleration, but in stop and go traffic and in hot weather the needle creeps quite high up the temperature gauge. I asked a few people and was told that this was normal for an SC in LA stop and go traffic, especially paired with 90 degree weather, but it still worried me. I ordered an IR thermostat, and when measuring temps in a few places I got some scary results. The worst I've seen it has been ~238-243 on the oil tank, and a frightening 305 on the large black hose that comes out of the bottom of the oil tank. The 305 especially worries me because at that temp the gauge should be well into the red. I don't know whether I'm measuring the wrong place so hopefully somebody can give some thoughts here. What's also worrying is that when it reaches this temperature, it is all but impossible to get it to cool down, even speed doesn't seem to change anything. I measured the trombone at the front of the car when it's this hot and it measures at about 170-210 depending on the point (wonder whether this means there is a thermostat issue or normal?)


Here are some photos with the IR thermostat for reference (232 is the oil tank, 223 is the oil filter, 305 is that larger black hose on the bottom of the tank)

[lfitzsimon]

Here are the IR thermostat photos:

[timmy2]

Normal to see high oil temps for a car running A/C in traffic with just a trombone oil cooler and high ambient temps. You haven't reached the red zone on the gauge...

A Carrera style oil cooler with fan may be what you would consider going to if it bothers you or you think it is going to get hotter than what you have seen.

[dhanl82]

Here in Tampa Florida it gets very hot! I replaced the trombone cooler on my 82sc with a Carrera style with a fan, it made a very significant reduction in oil temp.

[kjchristopher]

BTW, from these pictures, it looks like you are holding the IR gun too far away. It projects a cone shaped reading area, and at that range, the area is pretty larger. The red dot is just to help you aim. There is probably a diagram on the IR gun that gives the cone demensions.

[gomezoneill]

Even here in the northeast my 82sc ran to hot for me. I added a Elephant oil cooler and the problem was solved.

[RDM]

Originally Posted by sithot

Here is a link showing the numbers at the edge of the gauge.
Replacement oil temperature gauge face with temperature values

Those would be Celsius temperatures.

[Tremelune]

Echoing sentiments. 230°F is common, but still too hot. 210°F is about the max you want anywhere...If your thermostat is in good working order, a Carrera cooler and a fan will make a significant difference. The trombone cooler does very little without air moving through it—the fan is what really helps in traffic.

I believe the Elephant widemouth cooler is about the same price as a used factory Carrera cooler, and I was just about to install their serious fan on my car—it's about the same price as a comparably-sized fan from Spal.

I think the thousand bucks it'll cost you to upgrade will come back to you if you keep the car. The thermostat they provide is adjustable (anyone have thoughts on the optimal temperature?).

[Tremelune]

Originally Posted by lfitzsimon

I measured the trombone at the front of the car when it's this hot and it measures at about 170-210 depending on the point (wonder whether this means there is a thermostat issue or normal?)

I missed this. That seems okay temp-wise up there...If I were you, I'd make very sure your thermostat was working. It's possible that the cool oil up front is simply not returning to oil reservoir. You should be able to determine this by taking temp measurements of the send and return hoses.

The thermostat always sends oil up front to the cooler. When it gets hot and opens, it allows the cool oil to flow into the oil res.

[Superman]

Another thing to consider is oil pressure. If the picture in the opening post was taken at idle, I'd say there could be a pressure issue. My '78 shows considerably higher pressure at idle, and my engine has quite a few miles (well over 300K). There was a service bulletin warning of oil pressure problems if the parts surrounding the oil pump pickup tube are reinstalled incorrectly. That round thing in the middle of the bottom of the engine case. Behind it is an oil screen with an interesting shape. I don't recall all of the details, but if those parts are not installed correctly, the oil pump will have a hard time scavenging oil from the bottom of the sump. According to my hazy recollection, this may have been a problem specific to early SCs.

[lfitzsimon]

Ok, thank you for all of the answers, I’ll look into the thermostat. The fact that the car won’t cool down, even when at speed would make me think something isn’t working properly with the trombone. My dad has a spare Carrera oil cooler that he’s going to fit for me, so hopefully that also helps out majorly (especially here in LA).

Oil pressure seems to be good, I get just over a bar per 1k rpm no matter the temp. It does show that low at idle (~750-800rpm) when extremely hot.

[darrin]

I'd also look at the hard lines leading from the engine up to the front cooler. Easy for somebody that is not familiar with a 911 to crush them while putting a 911 on a lift -- crushed oil cooler lines would reduce flow to the front cooler

[KNS]

On my old SC I swapped out the trombone for a Carrera cooler and it made a difference though I usually try to avoid situations where I might be sitting in grid lock traffic.

Not sure if it was mentioned - are the oil lines in the fender/going to the trombone getting hot?

[Trackrash]

All good suggestions. Here is my $0.02.

What oil are you using? Synthetic 20-50?

You might want to consider installing a 245mm fan. It looks like the one you have is a 226 mm fan.

[pete3799]

Another thing to check would be if a mouse has built a nest in the shroud preventing good air circulation.

[hdrockerroller]

I live in texas, it gets very hot here in the summer, and my 83 911 SC would run hot.

I replaced the trombone cooler with a radiator style oil cooler bought from our host. It does not have a fan. I also added an air scoop that replaces the right front side marker light and directs air directly onto the oil cooler. You also have to make sure that the oil cooler thermostat is working. As long as the oil cooler eventually gets hot, that means that the thermostat is opening and letting oil flow through the cooler. I also swapped out the oil cooler lines with the elephant racing finned oil lines. I figured if it still ran hot, I would add a fan to the oil cooler, but so far the temp gauge doesn't go over 1/2 way. I run AC in the 911 all summer long, and so far no more heating problems.

[Bill Douglas]

An easy way to check if the thermostat is working properly is to feel the oil lines that run up to the cooler. Stating the obvious here; but both should be cold before the engine is really warmed up then when it's hot check that one oil line is HOT and I guess a bit less hot as it comes back from the oil cooler.

[lfitzsimon]

So I took the car to TRE Motorsports in Van Nuys, who were amazing. They made sure there wasn't anything nesting above the cooler or behind the fan, and checked that the thermostats were working properly. They discovered that the mixture was extremely lean, and that my sender was showing about 20-30 degrees above what they were reading with a thermometer.

This was a great weight off my mind, now I'm enjoying the car without worry, and I'm going to fit a carrera oil cooler in the near future.

One thing that has happened is that since they adjusted the mixture, my idle is now about 1200-1300rpm. I've been told that I can adjust the idle down with that hand screw above the throttle body, but I was wondering if this would mess up anything with the mixture?

Also, kjchristopher, you're bang on about the IR thermometer. I thought I was safe because it's 12:1 but I double checked and directly behind that lower line is the exhaust manifold. Once I took the thermometer closer I was getting much more reasonable readings.

[Trackrash]

Originally Posted by lfitzsimon

So I took the car to TRE Motorsports in Van Nuys, who were amazing. They made sure there wasn't anything nesting above the cooler or behind the fan, and checked that the thermostats were working properly. They discovered that the mixture was extremely lean, and that my sender was showing about 20-30 degrees above what they were reading with a thermometer.

This was a great weight off my mind, now I'm enjoying the car without worry, and I'm going to fit a carrera oil cooler in the near future.

One thing that has happened is that since they adjusted the mixture, my idle is now about 1200-1300rpm. I've been told that I can adjust the idle down with that hand screw above the throttle body, but I was wondering if this would mess up anything with the mixture?

Also, kjchristopher, you're bang on about the IR thermometer. I thought I was safe because it's 12:1 but I double checked and directly behind that lower line is the exhaust manifold. Once I took the thermometer closer I was getting much more reasonable readings.

Glad to hear you got it sorted.

FWIW, I found IR thermometers may not work well on shiny metallic surfaces. Once you have one though, you wonder how you did without it.

[lfitzsimon]

Originally Posted by sithot

No

Ok thank you