Interesting High Altitude 617.950 Behavior:
 

Thought this was interesting so I decided to post it here for all of you. Last month, my wife had the 116.120 down in the high desert visiting relatives. The elevation was between 4000 and 5000 feet (asl) at her destination. She reported that the car was way down on power and even idled roughly. The condition went away when she returned here to the Central Valley at 440 ft/asl.

I don't think I have ever seen one of these cars react to high altitude conditions in such a manner. have any of you????

Thanks....Robert

If the engine is a turbo model I'd suspect that the pressure line on the overboost control system has come loose.

Appears intact and has great power at or near sea level....

The engine runs too cold. It needs an 80c thermostat to function properly.

Runs no different without a thermostat, with a 60°C or with an 80°C, as I have experimented with every configuration.

You must be reading books on theory again....:)

Incorrect. The engine will overheat in the rear two cylinders without a thermostat.

No, I have real-world experience with which I use to earn a living. What has your guessing done besides cause a power loss at altitude?

As previously stated, I have tested every possible combination on this car and the cooling performance/power output never changes significantly, regardless of the engine's operating temperature.

In fact, if you really want to split hairs, the car has better overall throttle response the colder I run it.

Currently, I am running an 80°C Whaler Thermostat, since the dealer in Fresno no longer carries the 60°C unit. And, again, as previously stated, it has no affect on the power output at either sea level or up in Big bear, at about 6700 feet....Robert

Incorrect.


So much for "factory-available". I wonder why they don't make them? :rolleyes:

They still make them, Fresno just doesn't stock them.

There is no opinion involved with factual information.

Yet you openly reject both.

I guess at the end of the day each can do what they like. If you wanted to put square wheels on your car you could. Or running a non diesel rated oil in a diesel ~ a very quick way to void an warranty that may exist.
I am running 85c high flow thermostats in my 602 & jeep as using anything cooler appears to result in them taking too long to warm up in the winter as they are driven at highway speed as soon as they are out the front gate (plenty of air flow).
Maybe its just me, but I like to have a warm heater in the winter.

A 60c thermostat would result in freezing my #### on cold mornings.
Maybe the 60c is a low flow design & for some reason it works. I think it would take too long for the motor to warm up.

Well not knowing what is in mine, it never makes it to 80 on the gauge. Even climbing for 10 minutes straight on a hot day it gets to 70. Most of the time it sits on 45. it's odometer is stuck on 273k miles. It couldn't be that bad for it. Please be absolute and tell me my knock will go away with a 80 degree thermo and it will be out and replaced by midnight!

You guys are great reading though! I can't wait to see what comes next!

Dr. Bert and myself live in the same climate at about the same sea level. I'm running an 80* unit with the manual transmission. I can tell you ditching the autobox dropped my temps to the point that the car runs around 70* at the temp sensor on the coldest of mornings and around 90* on the hottest of days. I think the car is very happy with these temps.

With the autobox it would run between 90* and 110* back when I was still seeing those temps I wanted to install a 60* unit, but never was able to find one in stock when I needed one.

Maybe F.I. up in CO or the engineers back in Germany might have wanted the car to run hotter for their ambient temps. But I can tell you... and sure Dr. Bert can second this, the central valley of California is pretty much a hot plate!

If you temp was 110* with a (presumably) fully open 80* thermostat, what would it have been with a fully open 60* thermostat?

Sorry, no. You simply lack the capacity to understand what either is.

The stock 80*c thermostat is fully open at 94*c and ALL the coolant is forced to flow through the radiator. If your system is passing 100*c, other than in still traffic, you have other problems to address that a cooler thermostat will not alter.

He's right.

The thermostat controls the minimum operating temperature. Once it is open, it is open, so if you are experiencing very high temps, it is possible you have a thermostat that is partially opening or some other abnormality.

We had an 80°C Whaler thermostat on my Dad's 126 (617.952) that would open partially only every now and again. It took extended testing in a pan of hot water to duplicate this!!!!

If the thermostat is wide open, you should not be having an overheat condition, unless you have a restriction of some sort, such as a collapsing lower hose or clogged radiator core.

For example, my 1975 Firebird, with a 380 BHP V8, will run between 140°F and 150°F without a thermostat in 100°F+ weather and less than that (as low as 130°F) when ambient temperatures are around 48°F.

This is indicative of the cooling system's capability to cool the engine. Adding a thermostat will establish the minimum coolant temperature. Of course, this car's cooling system is 100% overkill and designed for my 600 BHP future motor, but I hope this serves as an example of how a properly functioning system (admittedly overkill) will function.

On our 1978 300SD, I have never seen it go over 190°F even idling in hot weather here in California. I have had to block the radiator with cardboard in order to get it to 100°C to test the auxilliary fan switch.

If I run the 617.950 without a thermostat (with just the hollowed out body) it will barely raise the needle above 140°F, as I have done for testing a time or two, so you can see, from this example, the stock cooling system is capable of cooling the motor quite well

The thermostat will set a minimum operating temperature and raise the service temperature to some degree, but it always runs between 180°-190°F with an 80°C thermostat....Robert