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  #1  
Old 09-05-2000, 12:41 PM
Dangeo
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I've got a 92 190E 2.6.

What is considered a hot engine on the temp guage? In downtown Atlanta traffic, I regularly reach/exceed 100 C. Once I get moving again, it drops back down to 82-85 C.

Is it hot?

Also, It's got a new water pump/thermostat (about 2 months ago).


[This message has been edited by Dangeo (edited 09-05-2000).]
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  #2  
Old 09-05-2000, 02:02 PM
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Join Date: Mar 1999
Location: Tucker, Ga USA
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Since MB doesn't turn aux fans on till 107C for engine overheat I'd say it's normal.

------------------
MERCEDES BENZ MASTER GUILD TECHNICIAN (6 TIMES)
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V
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  #3  
Old 09-05-2000, 07:16 PM
Brian16V
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Sounds spot-on. Did a little test in my driveway -- aux fan kicked on at around 105-degrees C, based on interpolation of the temp gauge (100 + 1/4 way to 120).

Brian
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  #4  
Old 09-06-2000, 02:46 AM
Robert W. Roe's Avatar
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Location: Lehigh Valley PA
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Does the 107 deg C apply to my '84 300SD as well? I run 95-100 most of the time but seldom see over 105, if ever.
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  #5  
Old 09-06-2000, 09:09 AM
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On the 1984 300SD there is no overheating switch for aux fans as they didn't overheat unless severe cooling system or engine problems.

------------------
MERCEDES BENZ MASTER GUILD TECHNICIAN (6 TIMES)
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V
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  #6  
Old 09-06-2000, 10:52 AM
Dangeo
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Thanks for the info guys.

After having problems with the water pump, then the heater control valve, I was beginning to question the other parts of the cooling system on this car.

I feel much better.

------------------
'92' 190E 2.6
'89' Dakota Shelby
'96' Chrysler Sebring

[This message has been edited by Dangeo (edited 09-06-2000).]
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  #7  
Old 09-06-2000, 12:16 PM
Geezer
 
Join Date: Aug 2000
Location: Holland, MI
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I was curious too about indicated temperature. My '85SD runs at about 85-90 in MOST circumstances. The exception was when I ran a stretch of freeway at 85-90 mph and it crept up to about 100.

Shall I assume that this is normal, and that the cooling system isn't sized to keep 85-90 at near full power output? In any case, there isn't much opportunity to run high speeds commuting to/from Detroit, where 65 mph is cause for jubilation!


BCingU, Jim

------------------
'96 E300D 58k mi (wife's daily ride)
'95 Audi 90 118k mi
'92 GMC Suburban 138k mi
'85 300SD 230k mi (my daily ride)
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  #8  
Old 09-06-2000, 01:56 PM
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yal yal is offline
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Jim, Yours is a different issue. If your stuck in traffic and the needle creeps up in the heat this is normal but if your flying down the freeway and it creeps up then you have a flow (air/coolant) problem.
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  #9  
Old 09-06-2000, 05:20 PM
makakio
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1993 190 2.6 - regularly sees temps between the 80-105C in traffic here in nor/central Cal. Always hovers just north of 80 degrees when in clean air (read: no traffic and going better than 25mph) regardless of outside temp. I'd say your readings sound normal as well.

Question: any reason why cooling fans DON'T kick in until 107 degrees? It would seem that running a cooler engine would make more sense to an engineer.
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  #10  
Old 09-06-2000, 09:57 PM
mattsuzie
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You could cool the engine / coolant significantly, but that too much would not be good for 2 reasons: 1- For our good Canadien friends, if the coolant was too cool , you would not be able to heat the car in the winter

2- The engine has been tested to operate the most effienciently at its designed temperature. The explosion inside of the cylinder will take place when the heads / block are at its optimum temp, therefore, maximizing power / mileage.

So don't go removing your thermostats now!

------------------
'89 420 SEL
'90 300 SEL
'68 Olds 88 Convertible
'84 300 SD (sold it)
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  #11  
Old 09-08-2000, 12:21 PM
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One curious design feature I have noticed with MB cars since I bought my first one is the way the designers have built the coolant temperature indication system. It will, if working properly, read the actual coolant temperature at the cylinder head and can fluctuate quite substantially during the course of a drive. This can be a little disconcerting if you have just converted from say, a Japanese car that will warm up and then let the temp. needle sit at a 1/4 inch from cold irrespective of the actual temperature in the engine. The MB way actually gives a very accurate state of affairs in the radiator and is realistically a better way to monitor the system. If however, you are not used to this, there is a tendancy to worry somewhat . ." have I got a leak ? " " . .is it running too hot ? ", " Is this the normal temperature ? " and so on. If for your model of car, the needle runs in the range indicated in the handbook as normal, don't worry. Normal precautionary servicing and coolant level checking will keep the system in good shape. It can be a bit more of a concern for those of us living in year round high temperatures and driving expensive, quality cars with nice aluminium engines under the bonnet. Provided you keep an eye on your guage and learn to recognise your own cars characteristics, there really is no cause for concern,,,,

'
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  #12  
Old 09-08-2000, 01:08 PM
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Location: Sunny Florida
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In response to the comment that running an engine cooler is better, to an Engineer:
This Engineer knows that higher block temperatures result in the combustion reaction being closer to "adiabatic", which means the heat from the reaction is not transferred to the engine block, but instead used to push the piston down, and turn the crankshaft.
Also, having high engine temperatures usually results in less build up of crud in the oil. (That is the car mechanic talking, not the Engineer.)
My $.02 worth. Take it for what it is worth.

------------------
1989 560SEL
1971 Cutlass convt. (sold)
1978 Olds Toronado (sold)
the rest are boring
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  #13  
Old 09-08-2000, 01:49 PM
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Location: ajax, ontario, canada
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my 190e2.6 also likes to run hot. That is, during the summer, if you leave the car idling, the fans will kick in when the temp needle gets past that 3rd mark on the gauge. And it will stay there for quite a few minutes.

definitely, there is a sweet spot for the operating temperature of the engine, and it is not only the combustion efficiency that is affected by the temperature.

the effects of temperature on the engine oil are also important. With the engine idling, notice that the oil pressure gauge will show a lower reading when the oil is hot, than when it is cold. This is because the oil viscosity is low at elevated temps, and the effectivity of the oil pump is affected. If the oil viscosity is too low, the oil film that forms in the journal bearings may be too thin, risking metal-to-metal contact at high loads.

if the oil viscosity is too high (e.g. at low temperatures), the oil may not flow freely enough within the engine.

At the extreme, if the oil temp is high enough, the oil can also carbonize (but this will be when other unspeakable things have already happened to your engine ... at which point the oil is the least of your problems ...).

in the winter here in canada, my car wants to be warmed up thoroughly before it can be driven decently. Seems like there are other things upstream of the engine, in the induction and fuel delivery systems that have a sweet spot as well.
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  #14  
Old 09-09-2000, 02:43 PM
mattsuzie
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John's right, It's about the 1st law of thermodynamics,

delta U = Q - W ;

(change internal energy) = heat transfer (positive if comes to the system - work (if work has a negative in front means it is making something move out of the system, i.e., a piston rod).

Let us take a piston in a cylinder. The cylinder is the system and the water and heads are the surroundings. The work extracted from the system is Pressure X Volume final - P X V initial. During expansion, as the piston goes from the top of the cylinder to the bottom, Work is positive.

In the equation, delta U = Q - W

The more work you get out, the better. Solving for W,

W = delta U + Q

If heat is lost to the surroundings, Q will be - and thus will reduce W (work). That is not good. The less work, the less power (horsepower) which is work per time. If no heat is lost, Q = 0 and thus the equations reduces to :

W = delta U.

Some might ask, why not raise Q, make the engine real real hot? Then you can run into other problems, i.e, overheating block, vaporizing liquid, premature ignition, expensive components, etc, etc, etc.

So, you don't want to much Q gain (overheating) or too little Q (heat loss). As John stated, under adiabatic conditions (no heat transfer), Q becomes 0.

Under adiabatic conditions, as John mentioned, the majority of the initial energy of the piston will be transferred to your drive shaft and wheels more than being transferred to additonal unwanted heating of the engine block. Would you rather have more power going to the wheels or a hotter engine?

In a way think of it as you were running a marathon. Would you rather run a marathon in shorts in Vancouver in January, Miami in July, or New York City in October? In Vancouver, your body won't be able to keep up and will freeze, in Miami, you'll pass out, and it NYC, you'll keep chuggin away..... as long as you trained and ate right

------------------
'89 420 SEL
'90 300 SEL
'68 Olds 88 Convertible
'84 300 SD (sold it)
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  #15  
Old 09-11-2000, 04:16 PM
makakio
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WOW. Thanks (I think, MattSuzie) for the lowdown on running too hot or too cool. Nice understanding of how running both these conditions can be disadvantageous and the resulting engineering that allows for a sweet spot. Your technical explanations appreciated (again - I think, MattSuzie).
Makakio
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