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- runbiodiesel
December 14, 2010, 9:42 pm
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Here's a real message about a Mercedes as opposed to more offers for
Prada, Rolexes and whatever!
My old 240 has developed an issue where its temperature goes up much
higher than it used to -- not overheating, but up to about 210 degrees
Fahrenheit or so at times, though sometimes it will go back to normal
at about 180. The system holds pressure just fine (no leaks) and the
coolant level is full. I tried replacing the thermostat but there was
no change.
I did discover the electric cooling fan is not working, though I don't
think it ever has (I ran 12V directly to it and no go so I assume the
motor is bad). Also, this happens even in cool weather at constant
speed so I doubt it would be caused by the fan not coming on.
Any thoughts on what to try next or suspicions as to what might be
wrong?
Also, anybody know where I can get just a motor for the cooling fan?
Thanks!
Steve
Re: 1979 240D temperature issue
Merry Xmas!
What do you mean with thermostat? The temperature sensor or the automatic
valve that opens coolant flow once trespassed a temperature limit?
Usually I'd start from one of the two above. You could eventually
disassemble the valve and "boil it" on the kitchen with some water, to
see if it opens correctly, eventually checking with a thermometer the
temperature threshold. It's usually in 70-80° C. Let me say 165-170° F.
--
Hi!
Stefano
Re: 1979 240D temperature issue
It's pretty clear that by thermostat he means the one in the coolant
flow path that every car has between radiator and engine. He said he
already replaced it and it hasn't fixed the problem.
Two? What two? I have yet to see a car with a seperate temperature
sensor
and valve that controls coolant flow between the radiator and engine.
Might exist somewhere in a new car, but in his car, there is only one
thermostat and
it's a self-opening valve that responds to temperature.
I hope by "disassemble" you really mean remove.
Re: 1979 240D temperature issue
Maybe you're overlooking I'm Italian. It's not very easy for me to find
the correct words in a different language, in a semantic space that I only
use here (mechanical English, I'd say mech-american English for the vast
majority of subscribers).
So, pardon me if I'm naive in my choice of words and grammar. I'm just
trying to help. My suggestion was on thermostatic valve, to be REMOVED
(ok...) and tested in a pot of boiling water, visually inspecting if it
opens totally. I can remember here a discussion a couple of years ago on
two different defective valves.
And then to carefully check if the instrument and the sensor of the
instrument work accurately.
--
Ciao!
Stefano
Re: 1979 240D temperature issue
replaced the mechanical thermostat that regulates coolant flow. I did
test the old one after replacement and it wors fine. Oh well, it's a
cheap fix.
Thanks for the advice abou the radiator. That makes sense. I found a
brand new radiator on e-bay for $99 and it just arrived today. When
the weather clears up a bit and I'm not contending with rain and mud
I'll try the swap and see if that does it. It makes sense. I'll repost
when I do and let you know how it goes.
While I'm at it, I'll see if I can find a cooling fan and replace that
too.
Re: 1979 240D temperature issue
Ahye Karumba! $99? Amazing it's even available for a car that old.
Boy did you get lucky!
You should also verify that the circuit that energizes it works. On
my 300SD
there are two temp sensors, one in the engine coolant, other at the
receiver/
dryer for the AC. Either can turn it on via a relay.
Re: 1979 240D temperature issue
I changed the thermostat... no change
Changed the temperature semsor... no change.
Changed the radiator... no change.
Changed the fan clutch to newer type... no change.
Lastly, I had an issue with my odometer so I stuck in a different cluster
and to my shock... the temperature gauge registered normal... The conclusion
is that the temperature gauge does go bad that the reading is off... this is
probably due to some 'extra' resistance... in the circuit... wire
corrosion... etc. or the resistor on the termperature gauge going bad that
it reads higher temperature.
In any case, make sure all your hoses are new... after all the car is over
20 years old by now... so it is time to change all the heater hoses while
you are at it so it will last another 20 years... lol.
Happy holiday.
Re: 1979 240D temperature issue
that since I had something similar happen on my sailboat which has an
old Perkins diesel. I went through all kinds of repairs before finding
out I had a bad gauge head (I had replaced the sender which made me
think the thing was reading correctly). Anyway, to finally test the
gauge theory I got an infrared temperature sensor that you just point
at a surface and click to get temp readings. Turns out when the gauge
was showing in the red the cylinder head temp held consistently at
about 180, just right.
I'll try the same thing on the car and see if I can rule that out.
Thanks again for the suggestion!
Re: 1979 240D temperature issue
at where the sensor is... and that is what the gauge should be reading. 180
degree is perfectly normal.
I remembered helping out another guy with 380SEL long ago... he did
everything like I did... replace this and that... but he had a machanic
suggestiing him to change this and that... costing him a fortune... I told
him to stop and change the cluster I had... and no more after that...
temperature is normal.
Make sure you aux fan is working... it is extremely important when running
AC... it would mean whether you really got AC or not.
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