RJN025

Seems a little high... Though it's fairly consistent, since I purchased (a little over a year ago).

Can anyone comment?

Details:
8am - after a spirited drive of ~20miles or so.
Morning temp - ~60ish
After the drive the needle is at the very middle...
Slowly climbed but never got past where it is when I captured the video...
I'd say it took less than 5 minutes to get to where it's shown.

Then continued idling for another ~5 minutes to see if it would get hight, but it didn't.

Second fan never kicked in...
Should it?

Dripped a little coolant (2 drops). I do have a hose leak at a connection point some where close to the reservoir.


1985 - 928S

Thanks everyone!

Wisconsin Joe

What are the actual engine temps?
You need to get an IR temp gun and shoot the water bridge or the coolant outlet for an accurate temp reading.

These gauges are not terribly consistent from car to car. Some run at the lower line, some at the middle, some at the upper white line, with the exact same coolant temps.

Once you baseline the normal operating temps and "calibrate" the gauge (where your gauge shows normal temp), then you just keep an eye on it to see if it's running hotter (or colder) than normal.

Randy V

If you have even a small coolant leak that indicates the system is not maintaining correct pressure and thus will overheat.

RJN025

I just realized that I'd posted the youtube video as private...


I'll pick up an IR temp monitor tomorrow.


Thanks.

joejoe

Pretty much exactly where one of my 86.5s' runs. Even in summer heat with air it does not vary.

RJN025

IR sensor readings:
The needle smack dab in the middle of the temp gauge is around 175ish (f).
Temp reading is at the "upper" coolant hose about 2" from the end of the hose going into the engine.
Lower hose is about 7 degrees higher. Temp reading is about 2" from the elbow connector going into the engine.




When the needle is just a hair underneath the "upper" white line (as shown in the video above), the lower hose gets to about 191ish- Second fan never kicks in.
Water pump is about 1 year old.






Any quick insight would be greatly appreciated.

joejoe

Seems real normal to me. Here in the valley temps have been over 100 deg. and there is still no variation with a/c running at idle or on the road. Temp gauge is just below second line.

928NOOBIE

Mine has done that before...but I will say since I put a new radiator cap on (Behr..correct one for our cars...) it runs cooler. With a leak it will run hot because it can't maintain proper pressure...as Randy already mentioned.

My old cap didn't look that bad...but it was several years old...the rubber seal was deformed and my guess is the spring gets fatigued. If you haven't put a cap on in 4 or 5 years I'd start there.

Also.... you need to fix the leak!

Tony

need to tap the coolant bridge and put a real temp sensor in there. Simple and answers all questions of how hot ones (coolant) engine runs. Simple job. Ive done it my oil and transmission.

KenRudd

Tony-
Any pictures or guidance on your additional sensors added to the coolant bridge? I want to add a temp channel to my AIM data system and am pondering best way to do it. If you covered it in in another thread, a link is fine...

FredR

I remain a bit confused about your hose descriptions as they superficially appear to be reading the opposite of what I expect to see but that may just be me.

The temperature of the coolant inside the water bridge is a measure [performance indicator] of how hot your motor is running relative to the design of the engine- too cool can be just as bad as too hot as a general statement in that both can damage your engine. Thus as I am aware the temperature as shown on your dash is a relative marker for how the engine is managing itself cooling wise and thus reflects the hotter of the two temperature points you are trying to measure. I am not entirely familiar with your earlier model engine but on my later motor the temp 2 sensor has two measuring points that supply data to the computers [there are two temperature channels] and the other sensor on the bridge sends a signal to the dash display- hopefully someone will correct me if I have that wrong at all.

When the motor starts and everything is cool, the thermostat channels water from the water pump so that it flows around the cooling jacket only and this circulates taking heat away from the cylinder walls. As the motor warms up the thermostat [if it is the correct item] starts to open at 83C and as it does, water then starts to flow to the radiator and just as importantly, direct circulation is restricted and ultimately is cut off when the thermostat is fully opened. If the rear seal is damaged it can take a long time for the system to heat up as the coolant then goes directly to radiator when the motor is cool- not good.

On your model the mechanical fan has a viscous coupling and if this is working as intended, the hotter the air leaving the radiator the more the coupling firms up until it is direct driven and doing whatever it can to cool your motor. The auxiliary fan presumably is an adjunct to give a bit more cooling if this system is maxxed out such as when the a/c is running.

Thus if the water from the cooling bridge is running at 88C [191F in dynosaur stupid British units] that I would suggest is indicative of a motor that is running just as it should given it is close to the temperature that causes the thermostat to be fully opened. Once the running temperature exceeeds that of when the thermostat is fully open then the system is at its natural limit of control and beyond that the coolant temperature will start to rise. To some extent this is not a problem, Porsche will have allowed for this in the design and is what can and does happen when the motor is run hard in hot climes. At some point the gauge then runs into the red zone as in "red for danger" and on my model at least at some point on the temperature scale the high temperature alarm will trigger and then it is time to shut the motor down quickly or risk damage to the heads or whatever.

With a 50/50 mix of glycol the coolant boiling point temperature at atmospheric pressure will be elevated to something like 108C at sea level whereas pure water boils at 100C. So, if the cooling system cannot hold pressure, no problems will be experienced until the coolant reaches its boiling point. If the coolant does reach boiling point, heat transfer takes a huge dump and the temperature at the cylinder wall will rise rapidly and ultimately, the motor will seize at some point. So to be clear, if the coolant does not boil there is no problem until the boiling point is reached but if this does happen it is game set and match for your motor quite rapidly. Thus why it is important to check that your cooling system does in fact hold pressure and why changing the expansion tank cap every 5 years is a good practice.

Similarly, much as having a 50:50 coolant mix is good in the sense that it increases the system boiling point, it is not so good in that it reduces the specific heat capacity of the coolant [i.e. its ability to carry heat]. If my memory is correct a 50:50 coolant has a heat capacity of about 3.6 kJ/kg whereas a 30% mix is about 4 kJ/Kg and pure water 4.2 kJ/Kg thus why racing engines often run pure water with some anti corrosion chemicals and then drain the cooling water after the event to prevent corrosion. Thus in a hot climate like mine, I run a leaner mix but also add water wetter with its own anti corrosion chemical package and change coolant every two to three years. I also have a bigger radiator and fans that move more air than stock.