Motor Temp Guage Indicator - What is the reading - PeachParts Mercedes-Benz Forum

whunter · #1 05-07-2012, 07:43 PM

Quote:

Originally Posted by 86-300sdl

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?

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.

.

ChiefRider · #2 05-07-2012, 08:28 PM

Quote:

Originally Posted by whunter

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

Bio300TDTdriver · #3 05-07-2012, 08:41 PM

Quote:

Originally Posted by ChiefRider

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?

Brian Carlton · #4 05-07-2012, 08:43 PM

Quote:

Originally Posted by ChiefRider

Am I missing anything?

Thanks

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.

ChiefRider · #5 05-07-2012, 09:09 PM

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.

Brian Carlton · #6 05-07-2012, 09:28 PM

Quote:

Originally Posted by ChiefRider

and an 80deg thermostat should operate at 80deg.

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.

tangofox007 · #7 05-07-2012, 09:34 PM

Quote:

Originally Posted by ChiefRider

Objectively, the cooling system in the car is perfect, and an 80deg thermostat should operate at 80deg.

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.

ChiefRider · #8 05-08-2012, 12:02 PM

Quote:

Originally Posted by tangofox007

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.

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

thatguy · #9 05-07-2012, 09:54 PM

Quote:

Originally Posted by Brian Carlton

.

Everybody worries constantly, however.

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.

Brian Carlton · #10 05-07-2012, 10:02 PM

Quote:

Originally Posted by thatguy

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.

thatguy · #11 05-07-2012, 10:09 PM

Quote:

Originally Posted by Brian Carlton

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.

86-300sdl · #12 05-08-2012, 01:59 AM

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

Bio300TDTdriver · #13 05-08-2012, 01:31 PM

Quote:

Originally Posted by ChiefRider

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

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.

charmalu · #14 05-09-2012, 01:13 PM

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

tangofox007 · #15 05-09-2012, 01:33 PM

Quote:

Originally Posted by charmalu

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.

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