M103 running warm on freeway, water pump? - PeachParts Mercedes-Benz Forum

ps2cho · #1 06-11-2018, 10:33 AM

So it hit 110F yesterday and i almost feel like cooling is slightly worse than last year.

Fan clutch was new last year and locks up/roars as it’s supposed to
Radiator is 2 years old, condenser 2 years old.
Water pump now has 120k on it...thermostat is a couple years old
Coolant level is good, reservoir cap is good holds pressure (2 years old as well)
Coolant mix leans 70/30 water G05

On the freeway at 3pm at the hottest part of the day at 75mph it’s still running at ~96C...slowing down it hits 108C (30-40mph). I know this environment is the extreme.

The fact that it still runs at 96C at 75mph tells me:
A) radiator is blocked, but that can’t be true because it’s new (no leafs/debris all clean no bent fins)
B) coolant flow is low so the heat isn’t being circulated fast enough, which would be pump related. I’m leaning replacing the pump, but I don’t know if I have no rust in system that I’m condeming pump for no reason.

Anything under 100F and ZERO issues, cools fine.
Any thoughts?

porkface · #2 06-11-2018, 02:38 PM

did you get a behr radiator? i've had higher temps with other brands. not as efficient. water pump would leak before i'd replace it. the impellers USUALLY don't slip like you're thinking. at least, haven't seen it yet. good luck, chuck.

ps2cho · #3 06-11-2018, 03:05 PM

Yes radiator is Behr. No signs of any leaks from the weep hole in the pump

Sugar Bear · #4 06-11-2018, 03:30 PM

Check the radiator for cool spots indicating a blockage which is not likely due to it's age and then try a new quality thermostat.

Water pumps rarely cause overheating unless the impeller is corroded. Did this pump ever run normal temps?

Good luck!!!

Hit Man X · #5 06-11-2018, 05:00 PM

M103 cars have undersized radiators to me, I just do not think they can keep up in your temps. When it is really hot and humid here, I run similar temps.

79 or 87 stat in yours? I am running the 87

rob300e · #6 06-11-2018, 07:48 PM

FWIW...
I just replaced my radiator 2 weeks ago with a Nissens from *******. Original cracked at lower right corner. Thermostat last year. Everyday for the last 2 weeks has been a heat index of 103+. Car still runs at normal temps with AC on in city driving and that's down here in the Texas Gulf Coast. Only issue is no AC through the center vents!

ps2cho · #7 06-12-2018, 12:13 AM

Quote:

Originally Posted by rob300e

FWIW...
I just replaced my radiator 2 weeks ago with a Nissens from *******. Original cracked at lower right corner. Thermostat last year. Everyday for the last 2 weeks has been a heat index of 103+. Car still runs at normal temps with AC on in city driving and that's down here in the Texas Gulf Coast. Only issue is no AC through the center vents!

Out of curiosity do you have R134a or R12?

Here's a test I ran on the way home from work today; first pic is AC ON, second pic AC OFF. You can see how much the condenser adds to the heat load...I wonder if R134a in this environment is too much.

rob300e · #8 06-12-2018, 10:06 AM

Sorry for the late reply. Using R134. Interestingly, this winter, such as it was, I thought my WP was on its way out as well. With the heat on, and at idle the air was lukewarm. Once I got under way the heat was at normal temp. Then the weather got warm again and didn't need the heat. Also, the car was not getting up to temp so I replaced the thermostat which appeared to be stuck open. New one works great as the car gets to normal temp and stays there.

Duke2.6 · #9 06-13-2018, 11:17 AM

The higher he glycol percentage, the lower the heat capacity, and 50 percent provides good corrosion protection, so it might make a difference if you drop the glycol to about 50 percent.

The aux. electric fan should engage at 105C. Is that happening? On the very rare occasions when the dual aux. fans on my 190E 2.6 engage I can literally see the temp gage moving down.

Duke

Mxfrank · #10 06-13-2018, 11:21 AM

A common cause of running hot at speed is a soft lower radiator hose. At higher engine RPM's, it can partially collapse due to pump suction.

tjts1 · #11 06-13-2018, 11:34 AM

The cooling system on inline 6 w124s and w201s is marginal. The radiator and viscous fan is undersized and the aux fans kick in at much too high a temperature. There are several things you can do to improve the situation. Run a smaller fan pulley, increase the water to coolant ratio, run a colder aux fan switch or add a manual switch in the dash for the aux fans. As much as some people hate to hear it, this is a design flaw that only becomes apparent in hot climates. All the inline 6 w124s suffer from it. There isn't enough room for a properly sized radiator and viscous clutch fan.

Hit Man X · #12 06-13-2018, 12:40 PM

Hey! Someone agrees with me on this one. I been saying this for years and years.

I checked all the fans I had around, BMW M30 ones. 603. 606...all have wrong pitch blades. Even considered a V8 radiator in the 300SEL and figuring out some sort of radiator hoses to work. Closest I found I recall was an SDL radiator and one of the hoses matched close, but one was crazy out.

tjts1 · #13 06-13-2018, 01:49 PM

Quote:

Originally Posted by Hit Man X

Hey! Someone agrees with me on this one. I been saying this for years and years.

I checked all the fans I had around, BMW M30 ones. 603. 606...all have wrong pitch blades. Even considered a V8 radiator in the 300SEL and figuring out some sort of radiator hoses to work. Closest I found I recall was an SDL radiator and one of the hoses matched close, but one was crazy out.

The best solution I've found for my om603 is electric puller fans behind the radiator in place of the viscous fan and eliminate the pusher aux fan to expose more of the condenser and radiator to airflow. The problem is most Efans are too thickto fit between the radiator and engine. Right now I'm using a pair of puller fans from a first gen Prius. They're the right size and shape and very powerful. I trigger them with a 91c temp switch in the thermostat housing through a relay. My temp gauge never exceeds 90c.

Hit Man X · #14 06-13-2018, 03:00 PM

What is the width of them?

The damned M103 radiator core is right around 20" x 20"

tjts1 · #15 06-13-2018, 07:55 PM

23.5", perfect fit on the 603 radiator.