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

86-300sdl · #1 05-07-2012, 09:38 AM

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

flainn · #2 05-07-2012, 11:50 AM

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?

Brian Carlton · #3 05-07-2012, 12:07 PM

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??

86-300sdl · #4 05-07-2012, 01:27 PM

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?

Bio300TDTdriver · #5 05-07-2012, 01:40 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?

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.

Brian Carlton · #6 05-07-2012, 02:17 PM

Quote:

Originally Posted by 86-300sdl

...and at typical 115 F ambient ya just can't roll down the window or ya overheat ones brain lol.

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.

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

thatguy · #7 05-07-2012, 03:01 PM

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.

86-300sdl · #8 05-07-2012, 04:36 PM

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

tangofox007 · #9 05-07-2012, 04:53 PM

Quote:

Originally Posted by 86-300sdl

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.

whunter · #10 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 · #11 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 · #12 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 · #13 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 · #14 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.

anghrist · #15 05-07-2012, 09:22 PM

Quote:

Originally Posted by Brian Carlton

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

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.