These cars shouldn't run near 100C during normal driving.

I've always read that 82 - 92 is the normal operating range for these cars.

The thermostat on the 617 is fully closed at 80°C. and fully open at 94°C. The gauge on the panel will probably climb a bit higher than this figure due to the location of the sensor.

By 100°C. on the gauge, the thermostat is certainly fully open and the cooling system is doing all it can possibly do with the airflow that it has through the radiator. Radiator airflow is assisted by two different fans and further assisted if the owner would clean the fins periodically.

Fin Cleaning
 

Thanks Brian, LGB and Hattie

What's the best way to maintain the rad? i.e. What's the easiest way to maintain fin cleanliness?

I think I'm running within normal range for temperature. The needle typically sits between the 80 degree and 100 degree marks, and only rises to the 100 degree mark when I go up the hill.

.........post #33.

Easy!
 

Thanks Brian:

I did read your previous post on how to clean the rad.

I was hoping there might be an easier way to do this. I'm not sure I want to tackle taking the rad out....

Brad.

Just for some perspective:

I took the rad out and spent two hours with compressed air and some foaming bath cleanser.

It was not all that clean when I finished, although it was significantly better than when I started.

Don't even bother to clean it in the vehicle.

Next time I use a commercial condenser cleaner or I'm not bothering either.

I did several 0-80mph WOT pulls today, 90 degree temps. I just managed to get the needle to almost move a bit, she was almost up to 85C!:D

Hill still the problem
 

Ok...I've been driving for a few days with the new sensor.

Under all driving conditions the car temp guage remains between 80 and 100....I assume it is running in the high 80s as it is closer to the 80 degree mark. I never hear the Aux. Fan kick in under normal city driving with the ambient temps in the mid 20s.

HOWEVER, the temperature continues to rise to just above 100 degrees celcius when I tackle the hill. No matter what the ambient temperature is, the Auxillary fan has to kick in to keep the temperature at just over 100 degrees. The car has NOT boiled, but it sure does rise when put under the stress of driving up the hill.

I am seriously considering pulling the rad out and doing the cleaning as Hatterasguy and Brian have suggested.

Any other ideas?


Brad.

Just as a reminder, it's a slow and tedius job. You can't clean the rad in 30 minutes due to the multitude of fine passages.

I have not mastered the art of the cleaning yet and will make an attempt with condenser cleaner, and, possibly some pipe cleaners.

Hold the radiator up to the sun and look between the passages..........you'll see what your task will be. When you get done, it should be perfectly clean through the passages..........not an easy task by any means.

If you have any tips after you do the job, please advise.

BTW, a temperature of 100°C. is nothing to be concerned about. Two of these will also bump 100°C. on any significant load.

What is a WOT pull?

Wide Open Throttle

Wide Open Throttle Take-Offs... You know, hot-rodding like the good ole days. Mash the accelerator and GO! Kinda fun, in the right vehicle.

[QUOTE=Brian Carlton]This task is not the most simple of tasks.

The solution is the use of a commercially available condenser cleaner in conjunction with compressed air. Careful use of a pressure washer will also assist in the task, but, extreme care must be used to prevent bending any fins.

You can buy this solution at most plumbing supply shops..... this is what the home repair guys put on your a/c condensors and then charge you 189 dollars for..... it now comes in a non-acid formula...very safe....

costs about 15 dollars a gallon... then you can do your home unit once a year....

Thanks Lee:

Do I still have to pull the rad? I'm tentative to tackle pulling it out...

Brad.

WOT = Wide Open Throttle or Italian Tune-Up.

Burns carbon deposits.

Dr. Brad:

Have been reading this thread today, and thought I might add to the 'diagnostic algorithm'...

Don't think enough attention has been paid to the possibility of a dying water pump. Had a situation very similar to yours a few years back (no, no mountains in New York City, but a few very hot days with nasty stop-and-go traffic). Symptoms: water pump was gradually weakening, with the gradual loss of coolant at the pump's 'weep hole' as others have noted here. But it still worked for a heck of a long time - (months!), with the car driven virtually every day. Assumption?: water flow was at least adequate for most situations. It boiled over once when pressed, fully loaded, on a very hot day. Clearly, your mountain climb is this stressor.

By the way, when healthy, this car never gets to 90 degrees under any driving conditions. Radiator was replaced about ten years ago, but because of a leak, not for overheating. Also, though apocryphal: I think the car runs cooler since I started using full-synthetic oil (many years ago).

On the coolant: Ethylene Glycol is Ethylene Glycol, whether expensive or cheap, and whether USA or German-manufatured... Yes, chemically, there is a coolant-water ratio which is the optimal one for cooling, but this optimization is marginal - it wouldn't account for 20 degree difference in running temp.

Auxiliary Pump: Very important, but mostly to handle the augmented thermal load - which is huge! - produced by the A/C condenser. Its primary purpose is to make this recondensation of the A/C coolant more efficient, thereby lowering the strain on - and increasing lifespan of - the entire A/C system. I am in the process of rebuilding mine myself, saving a several hundred dollar replacement with about $10 in parts. Point is, with the A/C off, the aux fan should not even enter the calculus re engine cooling.

In fact, even with our 100-degree weather these days, with the A/C running, and with the aux fan out of the car while I fix it, the car is still running cool.

Granted, my beast is a diesel, so runs cooler anyway, but still...

Differential Diagnosis: R/O impending H20 pump failure.
The Patient's Care Plan: Normal activity, including daily stress test. Monitor fluid output carefully!

Lou

PS - Have given up my practice so I'll have more time to work on my car!

I just got back home from an errand. It is 97°f outside now and my temperature gauge was on about 115°c in town. It wenr back down to 100°c back on the highway and even a little lower.

I cant' make the call on pulling it out..... it is a leisurely Saturday job...but if you try to do it after working a full day...you may be tired and make a mistake...

drain it, clean it....run it with water around town..... see what happens.

i do discount the clogged exterior fin thing a bit.... but with a 20 year old car
you never know..... the fins on my home condenser get pretty darn dirty in a couple of years... that's why i clean them once a year....

Agreed--- auxiliary fan is critical.... however it doesn't go on until the temp goes over 100 or so.... most likely in an extended in town idle..

zerex and mb coolant are better aluminum protectorants. the best combination is probably water and water wetter... but then you wouldn't have any anti corrosion protection

100-103 degrees today, AC blasting about as high as it will go. Driving in stop and go traffic, and it was up to 90C.

These cars should never run over 100C if the cooling system is in shape.

Heavens. Then I suppose that mine is not in proper working order. It was 97° here today, one of the hottest days we have had this year, so I was interested to see how high the gauge would go today. I did not even have my A/C on and it went to 3/4 way up on the scale. :uhoh: I do not even care anymore... what, with the stalling when the engine heats up and the not knowing when the timing chains were replaced and the worn camshaft, I will just drive it as long as it will go. I have already got my $1000.°° worth out of it. :thinking:

I am guessing that my radiator may be clogged, since someone has been using "GREEN" coolant in the cooling system. :sick:

Don't worry the chains will snap before it overheats!:D

I was on the freeway today and did two WOT for about 3 or 4 seconds each. Ambient temperature was 21 degrees celcius, the temperature guage was at about 90 degrees. The only needle that moved when I did the WOT was the one on the fuel guage.......

I also drove up the hill to pick up my son, then went down the hill and came back up, all within about 15 minutes, and the temperature guage rose to 100 degrees...mind you the aux. fan had kicked in....

So, she's still running hot, but not boiling over yet...we're suppose to hit the high 30s this weekend so we'll see how she hold out. I may pull the rad out this weekend and try to clean it. I'll post a picture and let me know if you think its dirty....

Brad.

Thanks Doc:

I considered the water pump in the differentials, but concluded that since the cooling system appeared to be well hydrated and not losing any fluids, I ruled it out.

However, I will continue to monitor her fluids and report back to you after 48 hours.

Cheers,

Brad.

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.

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