yo,

i recently had some work done, as ive mentioned, new cylinder head, turbo works now...

anyway, now my engine runs at about 90-100c and even as high as 110c sometimes, instead of a cool 80-90c like before. i figure that some of this can be attributed to the turbo, but not all of it.

it seems like my car always runs hotter after the shop replaces the coolant, so im thinking that they use too much anti-freeze, which ive been told does not cool as well as water.

my questions:
is it true that too much antifreeze reduces cooling capacity?
what is the ideal mix for summer driving?
whats the best way to drain just some of the coolant?
what is the ideal engine temp?

thanks

__________________
1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

Does the shop use the green coolant? Or the MB or Zerex brand coolant?

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

green, thats what has been in the car as long as ive owned it. when i did a search, i saw alot of people saying the green is no good, and alot of people saying it didnt matter as long as you changed it regularly.

from what i understand, antifreeze is in there just to keep it from freezing and it also increases the boiling point, but does not help cool the engine any better than water. ive noticed that when i add just water alone to top off the coolant it cools better than water plus coolant, but thats not very scientific.

__________________
1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

I believe the type of coolant recommended has to due with additives and formulation to prevent corrosion with several different metals AND prevent embrittlement of plastic tanks on the radiator. You should probably flush and change your coolant, but ask the shop what they used and why - you may learn something interesting.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

The turbo does not have any part in the problem, it doesn't add significant heat forget about that.
What percentage antifreeze is the shop using? Did they burp the system?
MB published a story in the Star about a case where a dealership replaced an engine under warranty after it failed from a warped head. The same owner had the car towed back in a few months later, same problem. At that point they investigated the matter, and asked him what he was using for antifreeze. He said 100% MB antifreeze, he said he figired that if 50% was good, then 100% would be better. WRONG! (no warranty this time, pal! )

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

I thought about the fact you may have been running on a defective turbo, in which case less heat will be developed because the engine is not going to run as fast and use as much fuel (less air less fuel) but I still think the problem may be as you thought, with too much antifreeze. There are small testers that indicate the freezing point by testing coolant. Find someone that has one (they aren't cheap and you don't normally need one of them except for making a point) and have the coolant tested. If its over 50% antifreeze take the car back and demand they rectify the situation and please use MB antifreeze. Order a jug for $14 or so if you don't want to pay the dealer price. Give to them and ask them to replace the green goo before it makes a mess of your engine. I know a mechanic at the local dealership, he told me I should never use anything but MB approved antifreeze, based on the number of head failures he has seen, all aluminum heads BTW, in gassers and diesels, although we know there were a lot of #14 heads that fell into this failure mode, newer heads can also warp if overheated. I am religious about this stuff. Sorry for the rant but I hate to hear about new aluminum heads running hot. Its a time bomb, some hot day the head will warp and you will lose a gasket if your lucky, or worse you can lose an engine. If it's as simple as the antifreeze consider yourself lucky, if it's a bad thermostat (there have been cases where new Behr thermostats are defective) that is another story, something that is hard to prevent, but the coolant thing makes my blood boil, if that is what it turns out to be please don't tell us!

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Replace the thermostat, drain, flush and neutralize the cooling system, then fill with MB coolant.

The new thermostat is cheap insurance.

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
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Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

45% MB coolant mixture, add a bottle of Redline Water Wetter

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

dieseldiehard,

does the redline water wetter work well? my 300D runs at about 100C when running on the highway at 70 with the AC on. I have read other posts and know that the 100C is not terrible hot but was just wondering if the stuff worked.

__________________
1980 300D European
"The Red Fox"
200,000 miles

2003 Chevrolet Silverado

609 Certification

If you are driving slower and/or the weather is hotter than before the repairs, this could explain some or all of the engine running hotter. 90-100C is hotter, but not overheating.
The antifreeze raises the boiling point of the coolant from 100C to 120C or more. (It also adds corrosion protection...) The proportions of the mixture should not make a noticeable difference in engine operating temperature, only the boiling point of the coolant.
The cooling capacity change is negligible. 99 of your cooling capacity is in the radiator surface area. 100% water or 100% antifreeze have a lower boiling point than a proper mixture.
Around a 50/50 mix for summer and winter. See instructions for precise ratio.
You can empty the reservoir... Why drain some?
The engine operating temperature range is at least 80C, so that it is warmed up for proper combustion, and below 120C, where it is beginning to overheat. The 'normal' temp depends on how fast you are driving, ambient air temperature, and the condition of your water pump, radiator and thermostat.

Don't forget the role of the oil cooler in maintaining engine temperature...

Best Regards,
Jim

Okay...here's something...how'd you know the gauge ain't lying to ya ?

Get confirmed temperature readings at the block/thermostat housing/radiator inlet.

Mercedes says 100+ okay as long as no coolant puked out.

Read the temperature with an infra red gun first.


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__________________
[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

Just finished a round trip to Austin; avg. 75 mph. Temp never got above 82C.
I run 45% AntiFreeze mix (not MB but not the green stuff either), along with water wetter.

I tend to agree with W Hunter - replace the thermo & try a 45 to 50 % mix.