Hey, I recently bought a 79 240D. Just wondering a few things so I might diagnose why its running hot.

Does the electric fan come on from engine temp or is it just cut on when the A/C is running.
The belt driven fan on it is different than what I'm used to seeing. Seems that out of the 5 blades, its like 2 are grouped on one side and 3 on the other. Like they aren't consistent. But it doesn't look like anything is broken.

Im trying to figure if its not getting enough cooling air or maybe the water pump is getting weak.

I'm assuming the electric fan only runs when the a/c is switched on and wasn't intended to cool the engine. Like the models without factory a/c wouldn't have a electric fan.

Any way to diagnose a failing water pump?

The car likes to overheat when sitting idle in say a drive-thru or long stop light. It takes it a while to start to get up above the 200 degree mark. I haven't had it boiling over hot but a little warmer than I would like.
It also seems to get up towards the 200 mark when on the highway running 55 to 60 mph.

I just put a new fan belt on and am looking to do a thermostat. Hoping the water pump isn't worn out.

Thanks for any advice

Also wondering if this car has a auxiliary water pump? If so Would that be electric motor driven?

I looked at the parts for the cooling system on peachparts.com and didnt see anything about it for this model.

btw the water pump looks pretty tough, if the one in my car is like the ones in the ads I think it might be ok. Unless someone used a plastic impeller or the end fell off.

I'm surprised no one has attacked your questions yet, so I'll take a go and let the true masters check my answers.

The Aux fan as I believe it is run directly through the AC and will only turn on when the air conditioning is running. It is controlled by the Klima relay.

There is an auxiliary water pump located directly under air filter housing near the AC drier. I know on some models that the auxiliary water pump is replaced with just an L shaped pipe. I was under the impression that this pump helps with the climate control system to increase hot coolant to the heater core.

Before pulling the water pump I definitely check the thermostat. Boil a pot of water and see if it opens up fully.

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-Typos courtesy of my mobile phone.

The uneven blade spacing is a design feature intended to reduce noise. It varies the blade passing frequency and prevents harmonic reinforcement.

there's no kilma on a 123.
the fan is controlled by the pressure switch on the receiver/dryer.
it'll run with the ac off or on if the switch is bypassed.

My bad, my 85 is the exception to the group

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-Typos courtesy of my mobile phone.

ARRRGG! I always forget about the ca84 and the 85 models... sorry.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

It's alright they are odd years anyway

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-Typos courtesy of my mobile phone.

And no aux waterpump on a 240D.

Happy Motoring, Mark

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DrDKW

So to get this straight, the lectric fan is not operated by the engine coolant temp or anything to do with the engines cooling system.

It is turned on and off by the swich on the filter/dryer for the a/c.

Is this correct so far?

Also what is the switch at the top of the thermostat housing? Has one wire brown with blue stripe that plugs on there. Is that going to the temp gauge?

My a 78-79 US 240D wiring diagram shows two temperature switches tied into the aux fan relay. A 44F/64C switch on the AC filter-drier, and a second 212F/100C switch, which I presume is on the engine - possiblely the one on the thermostat housing.
The cooling-system section of my factory diesel engine manual has one picture of the switch on the thermostat housing but no further details. That info is probably in the W123 factory heat-AC manual, which I don't have.

Happy Motoring, Mark

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DrDKW

According to my Haynes manual you can check the water pump by squeezing the top coolant tube. You should feel a rush of coolant going through when released (wear gloves!). Also there are weep holes on the water pump that may leak coolant so look out for those.

Another thing to check for - carefully - is to check the radiator for hot or alternatively cold spots. Visually check for dented clogged or distorted fins.

Other than that if it is a new car - well new to you - I would be flushing out the radiator and replacing the coolant anyway.

That is a cut-out switch for the cabin fan. It prevents the fan from operating in the "heat" mode when the engine is cold.

I don't believe the manual 240D heat-AC systems have this feature.
Going out later to test if my switch runs the aux-fan.

Happy Motoring, Mark

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DrDKW

I have read the posts, and did not see any questions about the radiator cap or the water level...have these been checked?

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K