I have always wondered what sort of danger of overheating could occur if a MB 5 cyl turbodiesel engine, or any other MB diesel for that matter, has run hot before shutting it off. On very hot days while driving home with the A/C on especially on the last 2 mile stretch which is all uphill, my 300D was at or near the 100°C mark by the time I get home. It seems to still climb a bit more by the time I have parked it in my driveway. I've always been worried that it may reach the overheated range after it has been shut down though I've never checked. About a year ago my old coolant overflow tank burst from sitting after one of those hot drives. It had sounded like a coffee maker before it happened. I fortunenatley still have an intact head gasket. Now I just shut the A/C off on the last 2 miles to avoid any problems but the nagging question remains.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

100 deg after a hot summer run with A/C is ok. anything near the 120 mark is NOT.
Flush and fill cooling system, change thermostat and clean the radiator fins of debris.

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1982 300SD (214 k, excellent shape) kidmobile running mostly biodiesel, gets 31 mpg hwy with 2.82 rear from a euro 500SEL



1976 115 body 240D 4-speed (traded for Jeep parts) - Engine lives on in my CJ7

I only reached the hot temps with the A/C on while driving up steep hills like the one up to where I live. It also got a little hot with the A/C on when I got stuck in some bad traffic. It otherwise runs around 85°C with the A/C on normal grades.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

I would let it idle for a minute before shut down for the turbos sake.........

William Rogers........

Shut the a/c off as you have been doing AND let it idle for a minute or two prior to shutting down. Its not just the engine coolant you are trying to keep at a reasonable temperature but also the turbo. A hot turbo will cook the oil pretty quickly and cause oil breakdown. I run my 84 300DT up a hill going home but usually down shift to take advantage of the gearing (the engine will rev higher but you can watch the temp gauge drop.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)

When you get home and it is hot let it idle.....and mist water from the garden hose on the radiator... from the front... cooling it with the radiator is the way it is designed to function...

DJ,

What you're describing is completely normal.

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Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

How odd is it that this topic should right now?

Coming to school from my home (15 minute drive) yesterday, 7-13-04, my gauge went to 100*c. It was about 98*f and I was in stop-go traffic so I did not think too much of it until it kept kreeping up. I finaly got to school as the gauge read 115*c. I opened the hood to find the main electric cooling fan (In the place of a stock engine fan) was not on. The fan motor was blistering hot and the 25A fuse, fuse holder, 3" of wire insulation, and the relay were MELTED. (Fan from a Caddie V8 had fused inside.)

I was able to make it home last night and to work this mourning without reaching 100*c. I put on the stock metal fan and shroud in place today.

She still runs well. No noises, power issues, extra blowby, or fluid damage. Any points I should check to be sure? An oil or coolant change to be on the safe side?

I noticed one day while tinkering on the 240 (checking vacuum fitting's) that my oil cooler was dark black at the bottom and slowly turned to aluminum color at the top. After looking closer I discovered the cooler was completely blocked, so I headed up the street to the car wash and cleaned the cooler. My oil pressure started stay higher and coolant temps drop some.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

I did this recently and it seemed to get a bit hotter, the coolant temp gauge continued to climb a bit more.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Yes engine temp rises when air flow stops, the idle period allows the turbo to spin down under oil pressure. Usaly your ele fan comes on when stopping and the engine is running or the key is on...............

William Rogers...........