Mister Quickie

'86 951
Vitesse Stage 3R
Hood scoop
Autometer gauge says temp at 180 most often.
The exception is after I've driven say 30 mins (fully warm) on the highway at roughly 70mph, then I get to a slower area and am travelling in that 40-50mph range, I see the temp gauge gradually creep up to about 185.
Usually after that I come to a light so I turn the fan on and with the fan it comes down to 180.
I've had cars (Normally Aspirated) where the "middle" of the gauge was 190

Thoughts?

Van

I'd say that's about right.

My track car (NA) usually runs in the 180-190 range on the track.

931guru

That sounds like the switch in the radiator is not turning on the fan for you, like it should.

Mister Quickie

I have a manual fan switch and I turn it on whenever the car has warmed up to 180 and is off the highway

Mister Quickie

Ok so it's been cold (not much above freezing) here lately and as long as I'm on the highway the water temp is in the 140 - 150F range ... is the hood scoop (placed right above the turbo charger) working "too good"?

Dougs951S

I doubt those numbers, a hood scoop wouldnt lower your steady state water temps by 40 degrees. Under sustained light load like on public roads, pretty much any properly running internal combustion engine is going to settle right around 175-190 degrees. Anything over about 210 is getting into the danger zone.

Cyril

Same here and IMO the ideal range.

argiopeweb

For what it's worth, the owner's manual describes "normal operating temperature" as 90°C/194°F, with the fans turning on after an additional 3°C. Obviously an upper limit, but still a data point.

The late cars have 150kPa/~22PSI caps, so, from a purely "avoid boiling the coolant" standpoint they should be very capable of handling temperatures well into the 200s (Fahrenheit).

Strictly speaking, the middle line of the pre-85.5 is (according to Clark's Garage) at 89°C, which is 192.2°F. I'm not of the opinion that the late gauge has a middle line, but the specs are here.

VirginiaF1

Welcome Argiopeweb! ^^^^^^^^^

As I grew concerned that either my coolant sensor or dash gauge was failing, I purchased an infrared heat sensor gun thingy.
Turned out my 179F during heat of summer and now 176F in 28F winter were dead nuts accurate.
My gun found the same temps at the coolant sensor location on dozens of tests/situations.
Fresh coolant, belts and replacement oem Behr radiator installed in 1998.

Might suit you to verify your dash readings with a temp gun as well?
Naturally aspirated 2.5L should run 10F cooler than a 951 perhaps?

argiopeweb

Thanks! Don't know how I've been lurking this long without a post...

This doesn't sound right to me... I believe the 951 and 944 use the same thermostat and pump, and the 951 has a slightly larger radiator to make up for the extra heat under boost. If anything, I'd expect the 951 to run slightly cooler under vacuum without a thermostat, and at the same temperature as an NA with the thermostat. Have I missed something here?

On that note, assuming the water pump and radiator function properly (edit: and assuming the engine is running...), the thermostat is the biggest key to coolant temperature. From the initial post, I would assume Mister Quickie is running an 80°C thermostat. I'm habitually suspicious of the mechanical thermostats, so I'd pull and check/replace it. Stuck open is (in my experience) less common than stuck closed, but I wouldn't be surprised to see either...

There's a lot more to say on this, but it'd be difficult to write something that states everything clearly and doesn't blather on excessively. Perhaps I'll write something up somewhere...

Mister Quickie

The water temp gauge is an autometer.
The interior is deleted and the heat comes out into the cabin even if the fans aren't set to 1-4.
The fan is manual.
Most often what I do is get in ,turn it on, and start driving.

Given the above what I did was turn it on, let it warm up until it hit 180F degrees.
After 2.5 miles it went down to 170F, after 5 miles it went down to 160/165F and stayed there.

Is this normal?

I think I could follow this guide, does this smell like a faulty thermostat? I had a new one put it by a shop less than a year ago:

http://944foot2thefloor.blogspot.com...rsche-944.html

argiopeweb

You don't mean that you turn on the fan when you get in the car, right?

160-165°F is 71-74°C. That sounds pretty normal for highway driving in general, particularly if you have the lower-temperature (71°C) thermostat in the car. 180°F is well within the realms of reason for a car sitting still/driving between lights. I wouldn't be concerned about this range.

Mister Quickie

Correct. I only turn the fan on if it's 180F and I'm at a long light to prevent it from getting any hotter.

If I let it warm up to 160-170F before driving it'll settle at around 150F on the highway, if I let it warm up to 170-180F, it'll settle at around 165F on the highway.