Motor Temp Guage Indicator - What is the reading
 

Can some one tell me what the motor temp guage is reading?

Is it reading 90C or 100C or?

I've assumed it is 100C and being a 603 #14 head I've been generically worried about running too warm. For example drove accross the AZ /CA desert last week (HWY 10) and with the AC on and 94 to 100 F ambient temps with the needle floating around the mid line mark. Over a tad upgrade and lower down grades.

Thanks

Looks like slightly less than 100 C to me, but due to parallax, the apparent reading may be incorrect. Can you get a photo with the front of the camera lens parallel to the plane of the gauge (as opposed to what you have here, which is at a slight angle)?

How long has it been since you replaced your thermostat? Are you sure you've got a stock 176F / 80C thermostat in there? Some of the ones that are available open at higher temperatures.

Are you using the proper coolant (Zerex G-05) or generic green?

It's 100C. and the temp is not a concern considering your ambients.

If it climbs to 110C. you've got make some provisions to keep it there (shutting down a/c and opening the windows).

The head is only harmed if you lose the belt and/or water pump. Proactive replacement is strongly recommended.

The use of a 140 cap is also strongly recommended. The boiling point is raised to 109C. with that cap with plain water.

Of course you have a 50/50 mix of Zerex G-05 and distilled water in the system............right??

100* C it is then but 110*C is too nearby for me.
 

Thanks guys....I figured so

With the exception of a four year old radiator all the proper goods and maint practices in place. Citrus flushes to new pump, MB Coolant w/ redline, etc. Worked this cooling thing for seven or so years :).

I really don't like to run on the "border" of 110. All winter long with ambient temps < 90*F it runs like a cool cucumber @ 80 - 85C.

I think it just getting older with almost 350k. I'm searching for a 70* "Tropical" thermostat for this summer's desert travel and there will be a lot...twice a month....and its just getting warm out there....and at typical 115 F ambient ya just can't roll down the window or ya overheat ones brain lol.

I think the stock set up just can't handle the extra heat x long distance 75 mph.

Wondering if there is an oversized radiator out there or a custom shop anybody knows. Have more room towards the fan for a deeper radiator. Going with a trans cooler too I think.

Thoughts?

If it never gets above 100, why are you worried? 100 is a long way from 110. Make sure your fan is engaged the next time you reach 100. If it is stop worrying, if it isn't it is time for a new clutch.

You may want to try cleaning the condenser and the exterior of the radiator. If the heat isn't reaching the clutch the fan won't engage.

You ought to see the brain overheat that occurs when the vehicle stops and you're sitting on the side of the road at 115°F.:eek:

............makes the thought of rolling down the windows a positively euphoric experience............

These guys sure hit the nail on the head. I replaced my fan clutch in my 606, as well as a new 85c thermostat and MB coolant with distilled water (60/40 mix currently, I need to dump some and replace it with water to regain the 50/50 mix) and I reached about 95-97c pulling a 5% grade for what seemed like endless miles yesterday. The ambient temps were only about 75f, but I had the ac maxed out in order to test my system and ensure it'll handle the desert heat this summer. I was reading on Jim F.'s site, the Cool Harness guy, that he recommends a 40/60 mix in the summer if you're running a bit warm, but I think given your conditions all seems pretty well.

Not satisfied yet....Aftermarket Rads with Xtra Cooling?
 

I agree with all your notes. All your suggestions have been recently completed. Just was out on the HWY 5 in 75*F and running hills, flats, etc up to 80mph with AC Maxed....no neele deflection off of 85*C.

It is when the ambient temp get over 90F up through 115 F (who knows actual road temp) water temp seems to go up in a linear relationship to ambient air. On long low grades i.e. Phoenix to Tucson it sure looks like it wants to hit 110C on the gauge. Yea it cools down when I slow down to say 65mph when crossing the desert but I should be able to roll at 75, or at least want to.

Bottom line is I suppose its what some may call extreme driving conditions....but I know there are others who travel the south west in summer where 4 - 6 hours at 75 mph with soaring temps is the norm.

Truckers tell me "get a bigger radiator"

So, now that you all have helped me comfirm the 100*C mark, and I think all systems are normal...anybody know of a source for xtra duty radiators?

And once again thanks all.

P.S...I wonder what running without a thermostat would do? Coolant aint going to get below 70*F for a long while now:)

Unless you block the bypass passage, removing a bypass thermostat is quite counterproductive.

Answer
 

The simple answer is to permanently disconnect the transmission cooler hoses from the radiator.

Install an after-market trans cooler, and connect to it.

This removes roughly 1/3 of the thermal load from the cooling system.


.

This is probably what I need to do.

I hope this isn't hijacking a thread, it's relevant after all.

I have recently finished installing my newly assembled 3.0 603 in my '91 350SD. The block's cooling passages are perfectly clean, as is the #22 head. I installed a new Laso water pump, new Behr radiator, correct MB coolant and a new MB 80deg. thermostat. I have driven the car about 500 miles, and the ambient temp has not been above 70deg F. The running temp of the car has consistantly been about 90, and one time off the highway it climbed to 100. Point is, I can't think of anything else I can do to lower the operating temp. Am I missing anything?

Thanks

That engine should be very close to 80 on the highway unless you are driving it at triple digits. You sure you don't have an air bubble trapped in there. How did you top off the coolant?

What you continue to miss is the fact that the engine will run perfectly fine at 110°C. and absolutely will not harm itself at that temperature.

The engine is probably fine all the way up to the boiling point of the coolant which is approx. 138C. with a 50/50 mix of Zerex G-05 and a pressure of 20.6 psi.

Folks make much ado about nothing. The engine will only hurt itself if it runs without coolant flowing.

I know of nobody on the forum, in the last 10 years, who actually overheated a 603 that had the proper concentration of coolant and a proper 140 cap.

Everybody worries constantly, however.

I have been watching the coolant level and adding until the level stabilized.

I suppose if there is ever a time to "worry" it is when putting a new engine into service. Objectively, the cooling system in the car is perfect, and an 80deg thermostat should operate at 80deg. I do have a lot of money and time tied up here, so I would like to understand and protect the investment. I'm still acclimating to the car, and if it is consistant at 90, so be it.

x2

When the system looses pressure, the cooling isn't as effective. Look for leaks, and disappearing coolant. I'll bet it's your radiator/expansion tank cap.

That would be an incorrect conclusion. The figure of "80" indicates that this temperature is the point where the 'stat just begins to open. In reality, depending on many other variables, the system will operate between 80C.and 94C. At the point of 94C., the 'stat is fully open and the cooling system is operating at it's maximum capacity. Of course, as the coolant temperature climbs above 94C., the capacity is also increased, so it's a bit self-regulating once the 'stat is not in equation.

The purpose of the thermostat is to "enforce" a minimum temperature. Considering that an 80 degree thermostat only begins to open at 80 degrees, and does not fully open until 94 degrees, the expectation of an 80 degree operating temperature is completely unreasonable.

I believe this is mostly due to the fact our Mercedes have actual working temperature gauges that, when all is working properly, give quite accurate readings of engine/coolant temperature; whereas just about any newer car you'll drive has nothing more than an idiot light with a needle. I'm glad Mercedes installed a working gauge rather than a dummy, I like to know that my car is running at a given temp under given cirumstances.

Actually, the OP would be better with an idiot light, unfortunately. When that gauge swings up to 110°C., he behaves like a scared rabbit. The engine is fine..........the coolant is fine.............HE is not.

I think this thread should help ease his fears a bit. Your point about cooling system capacities and the thermostat's function is a good one. I have always noticed my 606 can swing between 85c-100c quite easily if it's hot out and the AC is running, but it doesn't seem to surpass 100c no matter what I do or what the ambient temps are. It just goes to show how well Mercedes did infact engineer our cooling systems and engines. 100c is an efficient and safe temp and you really have to try hard to get most of these rigs to exceed 100-110c once that thermostat is fully open. It just tends to freak people out when they see that gauge actually move, rather than sit "harmlessly" in the middle of the temp range as it does on most cars.

Well...I don't accept the 110*C is OK thinking
 

First of all thanks for all the input......

Bottom line though... I agree running at 105 C to 110C or 230F may not kill the motor if incidental and gets to cool off say on a down hill run afterward. However clearly the system is taxed if it is continuously running above 100C – 105C, and sure is not the way it should be running all day. Add some extra hills and yes I’m getting concerned (Please drop the idiot inferences suggesting we play ostrich lol).

See.. my goal in these hot environments is to have the motor running in a manner that when I hit a good grade I have the capacity start well below 100C & to run upwards or over 100C….not start there!

Mercedes did install “Tropical Climate” set ups for other markets needing it to keep these jobs running in the 80C to 95C range…yes even with the AC on. Apparently not in the US Market 603 years.

So in summary what I am searching for is a way to keep the motor cooler during these scorching months here in the South West Desert (as in other regions) where hot and dry is really hot and clearly not incidental (Yea I too have read the “bulletins” that say its ok to run it almost to the Red Zone but not in my car I don’t)

Anyway I have to agree with Hunter here and work to get these temps down by helping the cooling system out with steps like taking the trans cooling function out of the circuit and handling it differently, etc. And that it is important to remember that at high mileage there is more friction / heat being generated by older parts (even rebuilt).

Spoke with the folks at the MB Classic Center in Irvine today who agreed & shared several ideas and suggested I swing by tomorrow. I’ll share their thoughts with y’all asap.

Thanks...Rob

That solution might be a good one for you. I am not aware of anyone else trying it for this vehicle and would be very curious as to what you determine if you implement it.

Please bookmark this thread and return to it if you to make that modification.

Good information, useful to think of the thermostat operation that way.

I agree that those temperatures won't damage your new head, but they are still higher than they should be for an OM603 with a properly sorted cooling system.

I've posted my temperature data here. Hopefully some others will post and we can all learn what "normal" is.

Brian: If my memory serves me correctly you have had 2-3 OM603s. What did your temp gauge read when you were hyper-miling at 62 mph? Yes I know your recent mileage thread was with an OM617, but I'm going to assume you drove the SDLs the same way.

The 80 SL/SLC uses a 75C thermostat. It use to state it in the listing when looking up the part. now doesn`t show it.

Maybe this thermostat will help.

Charlie

A lower-rated thermostat is never the solution to an overheating condition, real or imagined.

A lower rated thermostat will buy time until the engine reaches temperatures that make the driver uncomfortable.

Hey Tango & Mr. Carlton...2 Questions
 

With all due respect....

1) Why the condescending comments...I mean "really". Please give a direct answer why they seem to be required!

2) Why does MB and many other mfgs offer a 80*C & an 85*C thermostat versions for the 603 if it aint gonna mean a hill of beans in the end? Furthermore "Tropical Cooling" systems for arid climate markets with 70*C & 75* thermostats. And ya we understand optimum combustion, smog control, fuel economy etc. Please explain!

P.S. I think it would be safe to say we'd all love a brand spanking new factory motor and cooling system if dropped in our lap at no charge.

Kindly review the three posts that I have made in this thread (while trying to help you at no charge) and let me know what you find to be condescending.

Then help me understand how a fully actuated 75* thermostat promotes cooling any better than a fully actuated 80* thermostat. Presumably, both would allow for the exact same degree of coolant flow to the radiator above 94*. So, if the two thermostats perform exactly the same at the upper end, how is is a lower-rated thermostat going to reduce a 100* coolant temp any better than the higher rated one? 100* is outside the range of regulation for either thermostat.

What is your coolant/water ratio?

I don't think tango was condescending, but Brian Carlton certainly seems to be at times.

That said, around here I think you have to take the good with the bad.

Some of the guys are crusty (and, in fact, are quite proud of it), but they know their stuff.

I think the crustiness must come from a lifetime of keeping old diesel Benzes running. It'll probably happen to me sooner or later.

Hmm
 

It is a well documented FACT that many vehicles benefit from an after-market transmission cooler.

Look at RV and 4x4 forums, not to mention special application vehicles such as Forrest service, ambulance, law enforcement, etc, etc...

Most of our vehicles are high mileage, the thermal load rises from stacked wear factors, and in some cases have exceeded any reasonable factory cooling capacity.

Many owners of RV, 4x4, and special application vehicles have learned why a separate transmission oil cooler is needed the hard way.
transmission oil cooler - Google Search
Transmission Temperature Gauge



For durability.
Removing the thermal load of the transmission from the engine cooling system is a win - win upgrade...
Your source for RV, heavy duty off-road and overdrive transmissions



.

More thoughts from others
 

http://www.peachparts.com/shopforum/diesel-discussion/312501-dedicated-transmission-cooler-1995-e300d.html

http://www.peachparts.com/shopforum/diesel-discussion/146253-buying-installing-transmission-cooler-w123.html

http://www.peachparts.com/shopforum/1103243-post28.html

http://www.peachparts.com/shopforum/diesel-discussion/252462-transmission-cooler.html


.

I like the idea of an external cooler for my 95 E300, I'm sure the transmission would benefit quite a bit in my application as I drive through the mountains regularly in the dog days of summer. I'm hoping he'll be able to rig something up in that thread, or at least figure out a part number for the Mercedes unit. I am not really worried about my engine temps as I have to try really hard to exceed 100c, if I even can that is, but a cooler trans should help improve its life-span. Still, I wonder what my average trans temps are in stop-and-go and mountain driving in the summer, I imagine it can't be too far from 200*...or more.

I'm thinking anybody who drives mountains in the summer in AZ, or CA in a TD or SDL with the 603 would certainly benefit from an external plate style (like the oil cooler) transmission cooler. as a matter of fact, installing one in the same location as the oil cooler, and adding a thermostatically controlled fan would be an interesting project. heck, I bet the 617 would enjoy better life of the transmission with this upgrade...

1) How so? The lower temperature 'stat buys time. That's all it can do. The cooling system has a fixed capability of dumping BTU's. That capability goes up with engine temperature and, the higher engine temperatures make the driver uncomfortable.

I stand by my earlier comments regarding the inability to find a single member who overheated an OM603 with a functioning water pump.


2) They offer the lower temperature 'stat to buy time. Typically, the driver is not going to be climbing a hill for 30 minutes or more. Therefore, if the engine starts at a lower temperature, there is more time available before the engine reaches 110°C., the point at which the driver should be slowing the vehicle and/or dumping the air conditioning.

Thanks for the Tips!
 

Hey guys thanks for the replies. You've helped me understand that what works in one part of the country & in different seasons may not work so well in other geographic climates.

For example here in Southern California I never really have to take the below freezing (or colder) type precautions others have while operating in the north and north east.

Similarly out in the summer Desert South West where afternoon temperatures soar into the stratosphere, night temps never drop below 100*F, < ½ hour hills turn into very, very long grades, dash exterior temps gauges read 125+ at asphalt intersection lights, and travel runs at 75mph+for hours on end, a different set of rules apply.

I’m going to take a couple of extra steps to keep things cooler. To avoid critical review I think I’ll call them “soft mods” where in combination should help. For example window tinting should minimize full blast A/C demand by keeping the interior parts cooler. Some very smart folks in AZ will tell‘ya “it helps the A/C”.:D Another soft mod used to help the A/C is to hard wire the electric cooling fan “on” just because it works and a fair trade off if ya got to buy a new fan now and again. Mine has been hard wired for ages. Additionally, going with a radiator dedicated to the motor and move the trans cooling job over to its own cooler (like some other MB's); put the MB tropical climate thermostat in for the season, and maybe go with a fan other than the stock metal 9 blade...who knows maybe remove the high milage badges to reduce drag...kidding.

Thanks again...rob

Hey it may not help cool your engine, but they definitely help make the car cool.

Do keep this thread updated if you do install an external trans cooler, I'm sure everyone would love to see the pics and results.