I have a 1984 300 d turbodiesel with 375000 apx. miles on the engine transmission. I am experiencing cooling problems. This is what I have done already. Replaced thermostat, new Behr Radiator. i consider a safe operating temperature to be about lets say 2 mm under the half mark or less. It seems like my car is running around 100 degrees Celsius after getting off the interstate, and for some reason hotter the longer I run the car. I have read things about corrosion being a huge problem in the cooling system but I am scared about doing a citric acid flush (taking out water pump and such). Do you think possibly it is the fan clutch or can a expansion tank cap affect the engine temp to that extent that it would run above normal. I would appreciate some insight on the matter.

What works for me is the 75 degree Wahler thermostat for a 70's 450SL.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1975-Mercedes--Benz-450sl-Cooling--System&yearid=1975%40%401975&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6276%3AMBC%7C1537%3AED%7C10000062%40%40450SL&catid=240909%40%40Cooling+System&subcatid=240978@@Thermostat+Kit&mode=PA

That will take 5 to 10 degrees off the running temperature. You will need the correct thermostat gasket for your 84 diesel. You may need to go back to a normal thermostat for the winter, in order to get enough cabin heat.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

the clutched fan doesnt come into play here since its supposed to be free wheeling at speed and spinning when in idle(or when hot enough). I would replace the expansion tank cap with a proper one anyways since it could be original and or the incorrect cap.

you could also have a pocket of air trapped somewhere in the cooling system.

X2. I went to the 75c thermostat when the new engine with new raidator etc... was running hotter than I felt comfortable with. I even burped the upper hose etc... even in winter (Calif coast) it runs in an optimal temp.

If you changed the radiator, you may have air traped. elevate the front end, disconnect the upper hose at the radiator, and pour in coolant til it full and reconnect. this may help.

being high milage, the engine may have some crudded up water passeges.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Here's a quick way to diagnose the clutch fan:

After an interstate run and the temp is at 100°C., shut the engine off from under the hood and observe the clutch fan. It should stop instantly. If it freewheels for even one second, the clutch is shot.

If you have changed the radiator and thermostat, and the clutch fan is changed, if necessary, I'd strongly suggest shooting the head with an infrared temperature probe...........the 100°C. reading on the gauge sounds suspiciously high after all that work..............

According to the FSM, the valve in the clutch begins to open at 71*C. The working temperature of the clutch is between 90* and 95*C.

The speed of the freewheeling fan is about 1000rpm and the engaged fan about 3300rpm at 5000 rpm engine speed.

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

AS I mentioned above with the new engine running warmer than I fel comfortable.
I changed the temperature sensor on the side of the head, even swaped the 2 wires between temp and glow plug sensor.

changed the temp gauge cluster with a couple good one`s I have.

Then as brian suggested, I bought bought an Infra red temp lazer, and shot different areas around the engine after a hard run. there was no place I could find any high heat problem areas. so I put my fears some what to rest. still keep my eye on the gauge cluster.

charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Ever since I installed a new motor in my 1977 240D I had problems with thermostat, several shops tried everything to make the darn thermostats to open when the engine reached operating temperature, no luck.
I finally removed the thermostat and have been driving without one for about 8 years with no problems.
I know that there is a reason for the thermostat, but try your luck without one and see what happens to your cooling issues.

Vahe
240D 1977 350K

You may want to verify the accuracy of the temperature sender. Immerse it, your thermostat, and an accurate mercury thermometer in a coffee can full of water and heat it on a portable stove. Ground the threaded portion of the sender to the car, and connect the terminal portion to its connector with a jumper wire. Observe when the thermostat starts to open, and compare that temperature with your instrument panel. I went through three senders on my '83 until I found one that was accurate.