1987 300E Thermostat stuck open?

Tube Audio schrieb:
> Hi
>
>
> I have a funny feeling that my thermostat is stuck open and was wondering if
> there is any simple test to determine if it is open>
>
> I just drove home about 35 miles doing 70 mph on the freeway. The gauge
> never got above 60C, the weather here is 52F = 11C
>
>
> I would expect the gauge to go up to at least 80 or 90C
>
> Does the 197 300E run this cold or is the thermostat stuck open and the car
> never heats up?

Switch off heating completely. Start the cold motor and let it run for 5
minutes until gauge is beginning to show more than 40C.

If the radiator top feels like 40C the thermostat is open permanently.
On the other hand if after a quarter hours driving the radiator is too
hot to touch but your temp gauge shows 60C the gauge or the sensor is
defective. May be even both.

To reach working temperature modern diesels need awfully long burning
just the minimum fuel to move. But even in old times the MB six and mor
always needed about one hour full throttle to reach equilibrium temp.

--

Roland Franzius
 >> Stay informed about: 1987 300E Thermostat stuck open? 

I don't see that... I usually see engine at operating temperature in about
15 to 20 minutes of driving.
 >> Stay informed about: 1987 300E Thermostat stuck open? 

You're correct; the motor needs a new thermostat.
--

© 2008 T.G.Lambach. Publication in any form requires prior written
permission.
 >> Stay informed about: 1987 300E Thermostat stuck open? 

Tiger wrote:
> I don't see that... I usually see engine at operating temperature in about
> 15 to 20 minutes of driving.
_____
I confirm this observation about heat up time being about 20 min with
the 5 cyl/3 liter turbo diesel engines in my 300SD and 300D turbo cars.

When i bought the 300D turbo last summer i noticed that the temp gauge
would not rise above 60C. I pulled out the thermostat in the fall and
tested it against a known good one in a pan of water on the stove. Sure
enough, the MB brand stat did _not_ move at all, and the disc showed a
fixed 1mm gap vs the housing; ie it was stuck open! A Bilstein brand
stat is in the 300D turbo engine now, and it controls at a about 88C
after heat up. Since a stat in a car engine is a controller with
proportional action only, the temperature of the coolant at the sensor
location will always vary with load and ambient air temperature; low
load -> 85C, high load -> 100C.
--
Regards / JCH
 >> Stay informed about: 1987 300E Thermostat stuck open?