Doesn't sound like much of a mechanic.

Assuming this model has a clutched fan, that would be my first point to review.

Don't think waterpump is issue since the engine cool immediately when load is reduced.

Other option is stuck tstat- i.e. open to position that will only allow normal temp when engine is operating at moderate load. Tstat determine minimum operating temp when under low loads, but if got stuck partially open could account for the issue.

Ask the mechanic for your money back - last I checked, radiators are expensive, too! Wait - it is actually the most expensive component of the cooling system - now I get it!

__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg

Thanks, I'll check the fan later today.

How could I tell if the thermostat is stuck?

Thanks
Tim

Check fan first, then replace tstat if that isn't the problem ...

__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg

Your cooling fan isn't locking up. The clutch probably leaked out all the oil.

When you shut the car down the fan should stop really fast, if it keeps spinning its dead.


With those symptoms the radiator is the logical place to start, since it was original replacing it was a good idea. It probably would have failed soon anyway.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Hey,

I drove the car for about 15 minutes. It was a hot day, almost 90 Fahrenheit. The temp gauge was showing about midway between 80 and 100.

I stopped the engine. The belt stopped immediately but the fan behind the radiator continued to spin freely for about 3 or 4 seconds afterwards. The fan in front of the radiator was not moving when the car was idling.

Does this indicate a bad fan clutch? I kind of thought the cooling fan normally didn't do much once you're up to highway speed, but the engine definitely gets hotter going up a hill even at highway speed.

Thanks for any advice

Tim

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1987 300TD wagon 193,000 miles

Hi Tim:

Oh...sounds so familiar. I struggled for a year, finally fixed the problem. I should have listened to Hatty and Brian and would have saved a year of stress!

Anyways, first thing I did when I had the problem was check for coolant levels. If it was dropping, I understand it indicated a possible leak and therefore, a potential water pump problem. My coolant level only dropped when it BOILED!

So, I changed the thermostat. You can tell how well the thermostat is working by watching the engine temperature. You'll see it rise above 80 degrees, spike and then drop. If it doesn't spike fast, I think that it could be the thermostat as it has a problem opening and allowing the coolant to freely flow.

This didn't help me.

Next, I was worried as I didn't think the Aux. fan, (in front of the engine) was kicking in when it got too hot and there wasn't enough air flowing past the radiator. So, I changed the Aux. fan switch. (this was easily a DIY project.)

This didn't help me.

Finally, we examined the radiator. It was changed by MB a few years ago, so I assumed that it was ok. Well, when we examined it found that at operating temperature, only 1/4 of the rad was warm the rest was "ice cold." This indicated a flow problem so I changed the rad.

Problem solved. It was hot today and yesterday and the temp didn't rise much past 80 degrees.

In your case, check to see if the Aux. Fan is kicking in when the engine temp rises above 100. My understanding is that the switch recognizes that the coolant is too hot and the fan kicks in. If the Aux Fan doesn't kick in, try replacing the switch. (Easy and relatively inexpensive.)

I look forward to seeing how you make out.

Good luck, and listen to these guys...they know their stuff....

Brad.

__________________
Dr. Brad

2003 C320 4Matic Station Wagon
2002 C240 Elegance
1982 380 SEL Star Certified

While the proper function of the aux. fan is desirable and necessary, it won't affect anything until the engine temp climbs to 105C.

His situation is the range between 90C. and 100C.

While there will never be any issues of operating the engine in this range, if he wants to have the engine running cooler, he'll need to look at the clutch fan for more airflow if the radiator has been replaced.

The only other possibility, and one that should be verified, is potential clogging of the condenser with debris. While this is less likely due to the construction of the fins........it needs to be checked.

FWIW, the '86 runs up to 100C. on every workout........uphill.......at high power.........at any ambient temperature. I'm hardly worried about it and won't spend a dime on a new clutch fan. I will, however, install the red temperature switch........which will energize the electric fan at 100C.

Hi Brad,

I actually had the radiator replaced as my first course of action after reading this thread.

It hasn't changed the behavior of the temp gauge. However, it also seems like there's a lot of different experiences out there as to how these w124's behave under load, temp-wise.

I haven't seen it climb over 100, but here in NYC the hills are pretty small. I got concerned seeing it go to 100 when climbing the Verranzano Bridge, especially since it hadn't done that previously. It's not a slow heat-up. I can watch the temp needle move.

Tim

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1987 300TD wagon 193,000 miles