Keeping cool after parking

If I happen to park my '86 300E when the temp gauge reads above 100 and the auxilary fan is running, I see that the aux fan shuts off after the key is removed - which, of course, causes the temp to reach dangerously high levels despite the fact that the engine is turned off. Should the aux fan continue to run after the engine is shut off? - it does run while the key is in the ON position even if the engine is off. Thanks for any and all insight...

[Tobias MB]

Nick,
It is running and hopes that after a short period you would take out the key bacause
all you are doing is cooling the radiator and the water in it. Because the engine is not running, the water pump is not active, hence no water movement. The radiator water is cooled in a relatively short time compared to the engine block and the temperature sensor for the aux, fan is in the engine, not in the radiator. Hope this all makes sense to you.

TobiasMB
300SE
300CE
190/5.0

[Aaron]

The aux fan should shut off after you shut the car off, but when you restart it, the fan should come on before you actually turn the engine over (if it is started not too long after you shut it down) and run until the engine cools down. Some engines are cooler-running than others, so you may not notice the fan running all that much. Hope this helps!

------------------
Rgds,
Aaron Greenberg
MB technician
'67 250SE Cabriolet
'77 450SL
'79 6.9
'79 6.9
'80 300SD
'81 240D
'85 380SE
'89 420SEL
'93 300E 2.8

This to has concerned me over the years, but one thing I do to help out lowering the temp, ( and my concerns ), is that on a really hot day or after a hard run, when heading to my final destination, I will turn off the air, and or drive slower, and or just idle with or without the air on, till I see the temp gauge go down to a point I feel and hopefully the engine does also.

When sitting I always find something to do, make notes, calls, etc...

Stay Cool!

[mbdoc]

Mercedes has recognized this problem & on the W140 chassis installed software in several systems to allow the aux. waterpump to circulate water through engine after shut-off when the engine is "hot".

Thank you all for the info! Chris, I also take the same approach to cooling the engine before parking - but I wasn't sure if the problem was specific to me. It's been a while since this topic was brought up, but a mercedesshop search on redline water wetter doesn't really give a definitive answer. Does this stuff really work? - and is it safe for the cooling system components? It seems that if it does it would certainly alleviate this overheating problem if not solve it entirely. I trust the advice received here and if you guys give it the go-ahead I'll gladly order the product - I intend for this car to last me awhile yet!

Thanks again!

I guess I was late in not inventing this by-pass thermostat as MB DOC is saying benz has, I have thought of this for years!!!

Why not have another pump that circulated water after it shut the engine down?. I am glad benz is doing it, but on what engines?

As to the Red-Line Water treatment, I know and have read where guys whom have re-built some high horsepower engines, (muscle car engines, not benz's ,) like 426 Hemi's whom have had higher than normal temp readings after the re-build, and doing all the tricks possible, like aluminum rads, high flow pumps, have used this product and have seen a decrease in temps.

------------------
Chris Ecklund
98 300 DT

[Steve Guilford]

Two Cents Worth

I have a '76 SLC with Cats mounted under the exhaust manifold. It gets pretty hot under the collar after shutdown. My simple solution for the moment is to pop the hood whenever possible after shutting down.

I also started using Water Wetter and have noticed a favorable drop in temps, good to have here in So. Cal.

[Michael]

Yes, another affirmation...WaterWetter DOES work. I had it in an '88 Accord LXi that I gave to my brother a few months ago with 274k...car still runs as new, the motor's never been apart other than routine valve adjustments, and it's always been on WaterWetter. In that car, I did it primarily for the enhanced corrosion protection that is offered, plus it allowed me to downgrade the gas I was using (from Premium to mid-grade) I figure primarily because it kept the motor's hot spots cooler.

Now I run it in both of my Benzes, and it's brought down the temp about ten degrees C. in both cars. Give it a try, and good luck!

Regards, Michael
'92 500E
'88 300TE

------------------

[Tobias MB]

WaterWetter is more than its cost as I have seen some products as high as $23/pint! I have always used this in my 190/5.0 and it is GREAT

TobiasMB
300SE
300CE
190/5.0

[lkchris]

How is "dangerously high temperature" defined for a motor that is not running? What exactly is it that could cause temperature to rise once engine is stopped? No more fuel is being burned. The coolant may get warmer just where the temp gauge sensor is mounted but it (or the metal in the engine) has to have been that warm somewhere else already. I always thought the most danger as regards heat in a stopped motor was oil and seal damage in a turbocharger--what problems can occur in a 300E? I think that as long as pressure doesn't cause a leak, there may be little problem. Ideas?

------------------
Kent Christensen
'88 300E (wife's)

[Benzmac]

Kent, the heat comes from what is refered to as heat soak. When the engine is producing heat, the water is circulating and cooliing it off. When you turn off the car you turn off the pump as well and the heated cylinders and the water around it do heat soak and increase the temps by as much as 20 degrees Celcius.

------------------
Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I am going to contradict myself here, well actually I am going to challenge ones thinking here...

1. If a thermostat is functioning correctly, what does a product like waterwetter actually have to do with lowering the temperature, would not the thermostat simply close up slightly to get the temp back up again? think about this.......

2. Memory is fading but I seem to remember popping the hood NOT to cool the engine , but to cool down the turbo, ( 1984 vw turbo-diesel 310,000 )

3. I seem to remember that years ago, some turbos where colled with water?, and or not oil.

4. I also remember that some model turbos did not have enough oil passing through them, which made them run very hot, and when the motor was shut down, they actually burned off the oil, and then ruined the turbo. I dont think this was Mercedes-Benz, but some other manufacturer, and most likely a gas engine.



------------------
Chris Ecklund
98 300 DT

[lkchris]

"Heat soak" occurs whether the motor is operating or not because not every part of the engine operates at the same temperature and heat will tend to migrate to cooler areas, which, when the motor is running are areas surrounding coolant passages. "Heat soak is just migration of heat, nothing more. The heat will not be carried away as quickly when the motor is shut off, as the motor then becomes "air cooled" in a different sense. While it is true these same areas of the motor could become hotter than they had been when the engine was running, others are becoming cooler in order for this to happen, because no new heat is being produced since no more fuel is burning and the condition can be only temporary. Clearly this is a "basic" in engine design, occurs in all internal combustion engines, and, given proper design (which I assume with Mercedes) should be of no "dangerous" consequence and nothing to worry about. Should, for example, a way be devised to continue liquid coolant circulation to a fan-cooled radiator after engine shutdown, I would expect only a small increase in engine or component life not justified by the cost and complication of doing this.

Watter Wetter, which I use, is a "can't hurt" product, i.e., it is not needed since plenty of reserve exists in a good engine design. It may add slightly to this reserve. But, since the initial post to this thread dealt with the notion of (dangerous) heat in the engine following shutdown, when the coolant and Water Wetter (when present) no longer circulate, I suggest the effect of Water Wetter is miniscule in this situation.

Here is a truism of automotive design: reliability improvements possible by changes/additions using aftermarket products beyond those recommended by the manufacturer are 95% (if not more) mental, i.e., imagined. The designer sweated the small stuff and if you want to continue the process it's because it's fun and represents "enthusiasm" as opposed to real physical change. Maintenance remains essential, of course, and doing it "by the book" is both critical and at the same time all that is needed.



------------------
Kent Christensen
'88 300E (wife's)

My 1985 audi 5000 had an interesting design in which the electric fan would come on/off once car was off but it would also cycle the water heater pump.


Of course the car is now long gone, but It was an interesting design no less.