I've explained on several posts regarding the very fine passages through the fins.

If you are grasping this concept, then you'll realize that you cannot take photo of the surface of the radiator and expect to obtain any valuable data from it. The problem is between the fins.

Hold the radiator up to the sun and peer up between the fins and see if you can discern any debris that blocks the airflow. It will be immediately obvious if you can see straight though the fins or whether the fins are partially blocked due to fine debris (likely).

So, just forget the photo and perform the task as recommended and report back with your results.

Problem Finally Solved
 

Well its been a while since I had the overheating problem. It's been cool or cold here in Canada so I haven't had the problem all winter long. (Makes sense.)

Well as sping has arrived, so has the warmer weather and the problem is back.

A brief history:

• car ran fine until driving up a long steep hill.
• the temperature guage slowly rose and boiled when I got to the top of the hill.
• first I changed the thermostat
• the condition did not change.
• changed the aux fan switch
• the condition improved but the weather had also cooled by then
• Brian on this thread wanted me to clean the rad. As you would have read, the rad was changed a few years back so I hesitated.
• this spring the problem returned with the warmer weather.
• I finally bit the bullet and brought it in the shop.

Well, at the shop they replaced the thermostat again. Finally, they looked at the radiator. When the car was hot, 3/4 of the radiator was "ice cold". It looked like there was a coolant flow problem. They pulled the radiator opened it up and tried to fix the flow. Ended up changing the rad.

All's fine now. Temp. barely goes above 80 now. Even under stress in the warmer weather, the aux fan doesn't have to kick in and the temp remains constant.

Brian was right...I needed to check the rad.

I hope this helps others. Thanks to everyone on the forums for their assistance.

Brad,.

Cough post #17.;)

Glad you fixed it!

My forgiveness...

Hats off to Hatty for recognizing that indeed it was the rad. Replaced as Hatty suggested....

Sorry...

I'm just messing with you, I couldn't resist!:D

No need to forgive him...........I taught him everything that he knows..........:D

I was waiting for you to chime in.:D

I still beat you to it, post 17. You beat me like 500 other times, but I got you once!:D:P

You did.......and I'm proud of you.......;)

Replaced radiator, temp still climbs on hill
 

Hi All,

I've been following this thread since I have similar symptoms on my 1987 300TD. Recently, the temp has started climbing on hills. By flooring it going up a long hill I was able to get it to just touch 100 degrees C. The temp drops almost as soon as I crest the hill.

I took it to my mechanic. Since the radiator was original with the car, we assumed it was probably due to that and he replaced it with factory-new.

Sadly, as I drove home last light, it climbed near 100 again just going up a bridge (the Kosciusko on the BQE for those who know NY's outer boroughs).

For nearly a year, the temp gauge has sat just above 80 and wouldn't move to matter what.

I'd like to check out the water pump as suggested in another post but I'm afraid I don't know what the water pump looks like. Could anyone describe where in the engine bay it would be?

Thanks for any suggestions

Tim

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!

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 ...

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.

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

What I Did
 

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.