Operating Temp for OM617
 

What is the ideal operating temp for a OM617?
The mechanical cooling fan decided that it didn't want to be on the truck.
I'm not sure how it broke off but it was just laying on the cross member of the truck the other day, all 4 bolts sheered off.
So I decided to install an electrical fan.
The flex lite fan I installed pulls 3100 CFM.
I drove into work this morning and low RPM's the temp was a straight 180*F maybe even a little lower.
At high RPM's the engine would go to +- 195*F.
I think that is a bit to hot but any thoughts....

Thanks.

80 to 95 C. Can't help with F.

About 175 to 205 F is the ideal temp.

180 running normal and 195 under load are perfect temps.

Thanks for the replies. Im glad the temps are in range for now. But those water temps are when it was 32*F outside. I am a little nervious for the summer... Being new to this motor, how do they handle heat in the summer?

Mine will reach 110 C in the summer months, under heavy load i.e. climbing through a mountain pass in SoCal on the way to Vegas. It'll usually sit at 80 C under normal driving.

Thats too hot. You probably need your radiator cleaned or replaced. When its 90F out and I run mine hard I can barely get it over 88-90C. With my old radiator it would climb to 110 like yours does.

The deserts and mountains of Southern California might well present challenges not easily duplicated in many parts of the country.

if all 4 bolts sheared, then what is turning the water pump??

Climbing the hills of PA with 1100lbs of stuff in the car, hills so steep that the pedal to the floor in 3rd only gets you to about 35-40mph uphill....outside temp in the low 90's......my car went up to 110C...with a new radiator in similar conditions I can barely come close to 90C, even pulling a trailer on a very hot day.

I run stock thermostat for Fall thru Spring.In summer I have one with 5 holes drilled in it,for mountain high speed driving.Both Benz,and Toyota.

Thats very bad. If you have to mutilate the thermostat just for it to cool better then you definitely need to clean or replace the radiator.

100 degrees C shouldn't be too hot. That's the third has mark, between 80 and 120. My temp gauge will climb slightly higher than the 100 C (110 estimate) mark. It only gets that warm when climbing 3,000ish feet, with three 200lb passengers, luggage, at Hwy speed, in 100 degree desert heat.

My radiator might not be new, but it does fine. The red line is at 120 C and boilover for the coolant is a little higher. Just keep it out of the red I say.

Now that fan that sits in front of the radiator, I have no idea if that works as it should....

Fan Clutch
 

Can a cheap-o fan clutch have anything to do with higher temps? I replaced my thermostat and water pump, both good quality, along with a cheap e-bay fan clutch and temps under normal conditions went from 80 C to 90 - 100 C. Might try replacing the t-stat with a higher quality one, or did I just mess up being cheap?

sorry to jack the thread.....:o

how about lower temps? mine runs a little below 175 most of the time.

I run mine triggered at about 80*C, that's 175*F. Hasn't given me any trouble during the 115* summers in SoCal. Enjoy the extra horsepower!

If anyone wants to convert C to F. Take deg. C times 1.8 then add 32.

If you wanna go from F. to C. Take deg. F minus 32 and divide by 1.8.

Piece of cake!!!

No Both my vehicles will do all year with stock thermos.Its just in Summer I carry more heavy loads,and do not want to tax my heat range.

I know plenty of people that take their thermostats completely out during summer... but thats only on gas engines.

Your diesel will drop in fuel efficiency if you are running too cool. ie.. heavily modifying your thermostat or removing it.

Oh yeah I watch temps.

My OM617 is in a Unimog and has been customized a bit I guess. The fan was extended out with the spacer in the picture. It was mounted straight out of the crank. Here is the broken bolt and spacer picture...

http://img.photobucket.com/albums/v218/stppinz/fan.jpg

I will try to take a picture of what it was mounted on. There was no belt for a water pump so I assume it was moved...I don't know. No you have my interested. I will have to go check it out...

It will also overheat if the thermostat is removed. Unlike most g@ssers, the t-stat in these engines is a mixing valve. When it opens it blocks coolant flow into the engine block and redirects it to the radiator. Without the t-stat, the block and radiator ports will always be uncovered and coolant will take the path of least resistance (back to the engine block).

once the entire system is pressurized (head / block) the pump is not fighting any force other than moving the water

I cannot agree with the overheating w/o t-stat

Its basic hydraulics, every substance on earth flows the path of least resistance. Since both the radiator and block would be unobstructed by the t-stat, water would be flowing through both. But, cooling performance is significantly reduced since some hot water will always be recirculating back. If you want the most heat removal capacity on hot days, the best option is an unmolested and properly functioning thermostat.

Read the attachments. If Mercedes says its a bad idea, its probably a good idea to believe them since their R&D budget is a wee bit bigger than any of ours. ;)

thank you. By reading those attachments I have come to the understanding that the radiator is, indeed, the path of least resistance.

Why else would their R&D staff decide to use a t-stat to LIMIT flow through that region?

If the block and head were less resistant to flow, how would coolant ever circulate through the radiator to cool them under normal circumstances? It is only when there is too much heat, that the flow through the block and head is limited by the bypass valve so that MORE cooling will occur by sending coolant through the radiator in greater proportion.

ie.. IF you begin to overheat the engine w/o your t-stat, you have no chance of cooling it off b/c there is no mechanical means of directing flow based on engine needs. But until then, you are over-cooling the engine due to the nature of the system.

It appears that the t-stat is the dam, and once OT is reached, God opens up the flood gates to nourish the weak under-cooled. But the lord taketh as well, he reduces the flow through the block by proportioning the flood to the areas that need it more.

Clearly you don't understand how it works and are very resistant to learning how it works. I'll drop the argument right here because there is no point wasting my time in drawing it out any firther.

I agree with Forced on that.I built a 351c once in a mustang.We tried running with out a stat.It ran hot,because coolant never had time to cool.

Thanks Forced. Those images set the record straight for me about the role of the thermostat in these fine diesel vehicles... One thing that is appreciated about these cars in colder climates is the warmth they offer the driver (in comparison to modern vehicles) and I can now see one of the reasons how that comes about (as the radiator is only used in cold weather when "need be").

The stat in a benz is not an on off valve like a garden hose. Off on is how a traditional american made car stat works. With an on off valve you can cool fine without it but the car will run too cool under light loading.

A benz stat is a diverter valve. Its more like a switch in a rail line. When the engine is cool the stat diverts all water back to the head without ever going into the rad. When its hot it diverts all water to the rad and none to the head directly. It goes to the head after passing through the rad in that case.

If you remove the benz stat you will allow the water to seek its own course and it will send about half directly to the head and half to the rad. Thus when its really needing cooling its only cooling half the water and the car will run hot.

If its cold outside and the car needs to warm up half the water will continue to go to the rad and it will not warm up.

Drilling holes in the stat will only reduce its effeciency. A good stat working the way the system is designed to be operated cannot be beaten.

If you don't understand look in your repair manual for a diagram of how it works.

Your operating temperature also depends how much rust etc is in your system. A cooling system with rust will make the car run hotter than normal

How did you come to this rate? It is dependent on the restrictions in the head/block vs. radiator. You are saying they are perfectly equal.


this is what I am trying to say.

the natural course of flow w/o the t-stat allows only one rate of cooling. Therefore, until that rate of cooling is matched by an equal rate of heating from combustion, the engine is overcooling itself.

Once the equilibrium of heat production and cooling (w/o t-stat) is breached, you begin overheating and it cannot be controlled.

I have driven well over 200 miles in the summer w/o t-stat and continuously overcooled the entire time. ie..highway 65 mph

only until I climbed a mountain for 15 miles at a very slow speed on a dirt trail did I breach operating temp, and I never hit over 100*c in 85*f weather.

How did you come to this rate? It is dependent on the restrictions in the head/block vs. radiator. You are saying they are perfectly equal.

Not only that...Heat expansion of the coolant (thereby affecting density) would probably play a role in what portion would flow thru the rad at different stages... But...why would you want to run your Benz without the Tstat? The extra cost in fuel (while reaching operating temp) ought to be prohibitive... no?

good point.

I do not wish to run w/o t-stat. I am simply supporting my claim that the engine will OVER-cool until a critical point is reached.

Others have said that it will UNDER-cool.

All b/c a member mentioned that he modified his t-stat to flow more.

All I can add to this depbate is that if your t-stat won't close completely you will run too cool. I just swapped mine out today. Before the swap, with half the radiator blocked with cardboard (a temporary measure to try to raise the temp) it never got above 70*C (160*F) in city traffic, and spent a lot of the time down closer to 50*C (120*F) on city streets.

After putting in the new one it runs right about 85*C - 95*C (185*F - 205*F) on city streets. Haven't had it out on the highway yet. I was getting about 24 mpg around town before. I expect that will go up 1-2 mpg now that it is operating at the more efficient proper temperature.