Running Hotter on HWY than City - Page 2 - PeachParts Mercedes-Benz Forum

vstech · #16 07-02-2012, 01:47 PM

Quote:

Originally Posted by qwerty

At 80 mph, you don't need a fan to "yank" air through the radiator.

The symptoms of a bad fan clutch are precisely the opposite of the ones described here.

Considering that a new Nissens radiator can be had for under $200, it doesn't make sense to attempt to salvage a (presumably) 30 year-old radiator. But it also doesn't make sense to replace a possibly good radiator without additional investigation.

this is not true for all cars.

above around 65mph, on aerodynamic cars the radiator REALLY needs the fan to get the air to flow through it.
most aerodynamics are designed to move air over and under the car, and at high speeds, the fan is needed to redirect aerodynamic airflow through the radiator.
on a pickup or a 123 with the barn door front grille, sure. but 126 and up, modern cars are going to need a working fan clutch to get air through the radiator.

I also think the problem is in the radiator though. high speeds generate high horsepower loads, and high heat loads. any difficulty with the radiator and it's going to show as high temps.

this said... a cracked head will also perform this way.

MBeige · #17 07-02-2012, 03:10 PM

How old is the condenser and radiator? Do you get cold AC at that speed or just partially cool AC? I ask because it could also be a clogged condenser instead. This heat transfer item is in front the radiator. If this is clogged, then the radiator won't get sufficient cooling and could show as a false high reading.

That, or both condenser and radiator could be bad.

mach0415 · #18 07-02-2012, 03:20 PM

Quote:

Originally Posted by npretnar

Mach,

What was the cost of this procedure? Does anyone think it's more worth it to try this route or just spring for a new radiator?

I think this depends upon a few factors. Mine was running at normal temp, but had a cracked upper hose fitting at the tank. For me, it was more cost effective to have it retanked at $75 rather than buy a new radiator. BUT if it was running on the warmish side and the radiator was the culprit (in my case with a cracked tank in addition) then the obvious choice would be replacement. So there is no real right answer, relatively speaking. There is a lot that weighs in on any decision.

vstech · #19 07-02-2012, 03:28 PM

Quote:

Originally Posted by qwerty

Where did you get your training in aero?

Maybe you could educate me on the specific aerodynamic feature(s) of a W123 front end that prevents air from moving through the radiator.

where did you get your reading skills? I SPECIFICALLY said 126 body and above.

I meant the information to be general, not specific to the car above. in general, MODERN cars NEED the fan to operate at highway speeds.

qwerty · #20 07-02-2012, 03:34 PM

Quote:

Originally Posted by vstech

where did you get your reading skills? I SPECIFICALLY said 126 body and above.

Just one question: Is this thread about a W126 or is it about a W123?

Quote:

Originally Posted by vstech

this is not true.

Reference a W123 or a W126? I don't see any mention of a W126 prior to your attempt to confuse the discussion with irrelevancies. Or maybe you just don't know what a 300CD is.

vstech · #21 07-02-2012, 03:43 PM

Quote:

Originally Posted by qwerty

Just one question: Is this thread about a W126 or is it about a W123?

Reference a W123 or a W126? I don't see any mention of a W126 prior to your attempt to confuse the discussion with irrelevancies. Or maybe you just don't know what a 300CD is.

you win.
I will edit my post.

mach0415 · #22 07-02-2012, 03:49 PM

Quote:

Originally Posted by vstech

where did you get your reading skills? I SPECIFICALLY said 126 body and above.

I meant the information to be general, not specific to the car above. in general, MODERN cars NEED the fan to operate at highway speeds.

Yeah, I believe there was a thread about someone who took the fan off their W126 entirely in a cold foreign climate, just running off the electric fan in front...where escapes me, but they noted increased temp at highway speeds, town driving, as well as idle etc. Does anybody remember the thread?

npretnar · #23 07-02-2012, 05:08 PM

Quote:

Originally Posted by vstech

I also think the problem is in the radiator though. high speeds generate high horsepower loads, and high heat loads. any difficulty with the radiator and it's going to show as high temps.

this said... a cracked head will also perform this way.

No other symptoms that would indicate a cracked head are present –– white smoke, loss of coolant, etc., though as a precaution and because it's been about 5,000 miles since I last did it, I am going to change the oil and look for any signs of coolant. I went ahead and ordered the Nissens radiator today, as I noticed that my original Behr was starting to leak a bit anyway, so I will replace that and then while I'm at it, figured I'd take out the vacuum pump and examine the rocker arm for wear, so I ordered a new gasket there. All in all, just going to take this opportunity to make a general overall to a few things that need to be addressed and see where it takes me. I'll post results when available.

Thanks for all the input thus far!

rscurtis · #24 07-02-2012, 05:21 PM

I would suspect that changing your coolant to a 40% concentration of AF would improve heat transfer enough to solve your problem. Granted, your radiator may not be perfect, but at 40%, may be good enough, at least for the time being.

As far as the aerodynamics of newer vehicles is concerned, why would you design a vehicle so that is has to have an engine driven (or electric) fan at highway speeds? It becomes a fuel waster in an era when fuel economy is king.

When I had a '95 Dodge with the Cummins engine, I installed a Horton fan which was operated through an electric clutch. Except for condenser cooling when sitting in traffic, the fan was unneeded as long as the truck was moving.

npretnar · #25 07-05-2012, 03:46 PM

Alright, so to finalize, I replaced the radiator yesterday and changed the oil while I was at it also dropped the oil pan and changed gasket (was leaking), topped off with a 50/50 solution Zerex to distilled water, 15w40 dino in the engine and a new filter, etc. burped the car to the best of my ability and let it idle up to operating temperature then took it for a spin with ambient temps reading 101F. This was at about six o'clock so the sun wasn't as high in the sky but it was still hotter than a ___________ out, if you get my drift.
I kicked on the AC in town and watched the temperature rise to about 90C which is what my T-STAT is rated at and it leveled off there but inched up idling at stoplights. Not bad. I then took it out on the interstate and floored it to 85 mph, cruising for about seven miles and watching the temp gauge but again it was steady 90C. I brought the car up to 90mph and watched it seem to creep up just a fraction of a hair but still well below 100C mark. When I returned home I checked the coolant level and noticed that it had fallen off a bit, so I checked for leaks around all the radiator hoses and the T-STAT but couldn't find any, so I figured it just belched out an air bubble cruising at high speeds. Topped off with distilled water and now everything is peachy.
Thanks for the help, everyone. I'm hoping these noticeable changes last and the outside temperatures drop a little –– SOOO hot and SOOO dry, just not good for anybody and taxing on our cars I would imagine.

qwerty · #26 07-05-2012, 09:48 PM

Quote:

Originally Posted by npretnar

...and now everything is peachy.

I reckon that pretty much shoots down the "bad fan clutch" theory.

Likewise for "the radiator has to be good."

86-300sdl · #27 07-05-2012, 11:14 PM

Quote:

Originally Posted by qwerty

I reckon that pretty much shoots down the "bad fan clutch" theory.

Likewise for "the radiator has to be good."

I believe the comment "the radiator has to be good" meant that you have to start with a good radiator

Your a nut....the other member offerings posted remain valid in many cases. This fella happened to get some joy with only replacing the radiator.

Please try to stay focused on helping members rather than shooting down suggestions & floating your ego.

You may also want to do a little more reading up on cooling systems, especially fan clutches so you don't look so silly.

AZreGuy · #28 07-05-2012, 11:36 PM

not to interrupt you diesel folks but I have the same issue in my 450SL.

Swapped it with another radiator, same problem, had the original rod and cleaned, no diff, swapped t-stat no change... What next?

vstech · #29 07-06-2012, 06:36 AM

Quote:

Originally Posted by AZreGuy

not to interrupt you diesel folks but I have the same issue in my 450SL.

Swapped it with another radiator, same problem, had the original rod and cleaned, no diff, swapped t-stat no change... What next?

Hmm.
the v8's can produce serious heat without a cracked head, but first it's best to verify and deduce.
do you have a IR thermometer to verify the motor is getting hot? gauges are known to fail/read wrong.

is your fan clutch new? have you checked to see if it's operating properly at temp? YOUR car is pretty aerodynamic... what year?
with cooling problems, it's gotta be methodic.
you got your radiator verified, did you pull the waterpump? have you verified the thermostat is opening at temp?
once all cooling components are verified... it's the motor.

qwerty · #30 07-06-2012, 08:39 AM

Quote:

Originally Posted by 86-300sdl

You may also want to do a little more reading up on cooling systems, especially fan clutches so you don't look so silly.

If you can provide a reliable source that supports your theory, I would be more than happy to read it. Every thing that I can find suggests that a failed fan clutch is problematic at idle and low speeds, and is less of a factor at higher speeds.