82 380 SEL Overheating on Hill
 

My 1982 380 SEL is overheating. The wierd thing is that it only overheats when I push the engine going up a long steep hill to my home. Othewise the temp gauge hovers just under the 100 degrees level.

So while driving around the city, the engine temp is fine. But when I go up the mountain to my home, the temp rises and the car over heats.

I changed the thermometer this weekend and it didn't make a difference. I don't lose any fluid unless it over heats. I checked the fan and it is running when the engine is at running temp.

Any suggestions?

Many thanks for your help....

did you change the thermoSTAT? if so what temp stat are you running? how big is the hill?

if you are running too high a stat, you may not have enough reserve cooling capacity available when encountering a hill.

hovering just under 100 seems too high for a normal op temp.

also your radiator may be marginal, either plugged internally or externally.

tom w

MB Thermostat
 

Thanks T:

I bought the thermostat directly from our MB dealer. So I really don't know what temp it runs at. Sorry for calling it a thermometer....work term....

The hill is about 3 KM and runs to an elevation of 1200 ft.

So your theory might be correct and the coolant might be too hot at the bottom of the hill. I guess the engine runs pretty hard getting the beast up the hill and the coolant boils.

The radiator was changed by MB a few years ago, so I assume it must be a good one.

So your suggestion is to change the thermostat to one that runs cooler? I've read about running without a thermostat, what do you think?

It was a VERY difficult project to change the thermostat as one hose on the housing was really difficult to work with.....

How would I find out what temp the thermostat runs at?

Many thanks T! and everyone else....

You definitely don't want to run the engine without a thermostat. The temperature should be stamped on the thermostat. Call your local MB dealer and verify that the thermostat you bought is the correct one for your engine. Assuming it's the correct thermostat, is it installed correctly and is your cooling system filled with a 50/50 coolant mix? You may need a new cap for the expansion tank.

Correct Thermostat
 

Hi Fred:

Thanks for your post.

I am looking at the MB box the thermostat came in, and it doesn't say what temp it runs at. I don't want to take the thermostat out if I don't have to. I've also looked at the old MB thermostat I took out and it doesn't have the temp on it.

I'm pretty sure I installed the new thermostat correctly. The car runs fine until I encounter THE HILL! I refilled the fluid with new 50/50 coolant.

Good point about the cap for the expansion tank. When the fluid boils, the cap appears to be fine, because the fluid leaks from the small valve on the side of the expansion tank.

Any other suggestions?

Thanks again Fred.

100 is too high for normal running I think. Should be more like 85. Have you been using MB coolant? How often have you changed the coolant? Might want to try a bottle of Water Wetter. Although it is not designed to reduce normal operating temperatures, it may prevent the coolant from heating up as much as it does on the hills. Is your coolant level correct?

Len

Water Wetter?
 

Hi Len:

No, I didn't use MB coolant. Does it really make a difference?

What is water wetter? I've never heard of that? Do most automotive stores have this?

Yes, the coolant level is correct. Slightly low today as it boiled over and leaked a little last night when I drove up THE HILL!

Thanks Len...

At the risk of starting a holy war, I'll say that not having MB coolant in your '82 MB isn't your problem. I would ensure that the concentration of coolant is no more than 50%. These engines actually run cooler with < 50% coolant concentration. I run approx. 40% coolant - 60% water and live in a hot climate.

Water Wetter - visit their WEB site and you'll learn this product only helps when a VERY low % of coolant is used.

Ensure you have sufficient air flow; water flow.

Here's a pointer to an old thread that covers the overheating on a hill issue. In the end, the orig. poster solved the problem by replacing a worn out fan clutch.

http://www.peachparts.com/shopforum/showthread.php?t=102579&highlight=overheats+hills

Some believe that the fan clutch only serves to cool at lower speeds and at idle. Years ago I battled an overheating issue on another car. It only ran hot on the highway. I replaced everything there was to replace, then had a conversation with a veteran tech about the fan clutch. Sure enough, it turned out to be a tired fan clutch.

I'm not saying this is your problem. Just something else to consider.

Sounds about right.
 

Hi Mike:

Thanks for the link. I read the other thread and it sounds very similar. (Tried to do a search on the subject but didn't see this thread.)

Now a few questions:

1. How would I check to see that this could be the problem?
2. How big of a job is this? Is it a DIY or MB job?
3. Costs?

Hopefully, problem solved....

For me. it was a diyer job. I bought the 2 special tools used.

a. 8mm Stahlwille allen head socket - loosen fan clutch bolt.
b. foot long metal rod - hooks in back of clutch to prevent it from spinning in order to loosen bolt mentioned in a.

Doc is at the following WEB site. For your car, they show operational theory and not actual disassembly. You can fish around for the actual process looking at other models of 126 cars - cooling system - to get the process. It's covered in one of them - which I don't know.

http://mb.braingears.com

The tools may be obtained from Baum Tools -> baumtools.com

Brad, I'm unfamiliar with a valve on the side of the expansion tank ... it's probably the level sensor. It's important that your cooling system is leaktight, especially in your situation where you are taxing the cooling system with your steep hill. The cooling system is designed to be under pressure which increases the boiling point of the coolant. Since your cooling system leaks it cannot maintain pressure and the coolant is boiling off.

Hi Mike/Dr. Brad - not suggesting that recently filling the car up with non-MB fluid caused this problem. However, long term use of non-MB coolant and especially not changing the coolant on the prescribed schedule could lead to cooling system problems. Need to also make sure there isn't an air bubble in the system after the thermostat replacement. As to Water Wetter, my experience has been positive. My 240D used to creep up to 95+ or so during a hard hill climb and in stop and go traffic. After adding Water Wetter in conjunction with a cooling system service, my temp gauge is rock solid at about 85 now under all conditions. It's been that way now for at least ten years, although I do change the coolant every three years. Now, maybe the fact that the system was serviced at the time I added the Water Wetter comes into play, but I've heard similar stories from others too. Certainly I'd look at the coolant level, the concentration, the air flow, fan clutch, etc. There are lots of things that need to work right.

BTW, Water Wetter is available at most auto parts stores.

Len

Next Step
 

Okay...the next step:

- I will take the car out today and drive up the hill. According to the other thread, once the car gets really hot, I'll pull over, turn off the engine and check to see if the fan stops spinning after less than five rotations. I understand this will tell me if the fan clutch is worn.

- secondly, I may have to flush the cooling system. I trust this is quite simply to open the drain valves and then flush it with a hose and refill?

I'll report back in a couple of hours on the status of the clutch.

Wish me luck in getting back up the hill.

Brad.

Len - I hear ya.

Dr. Brad - You don't necessarily have to "go to the mountain" to test the fan clutch. If it's worn, it's worn and everyday driving will show this.

Do drive the car 'til it's good and warm, then pull over. Leave it idling. Pop the hood. Close front door - leave window down. Reach in and turn off car and quickly look fwd. to engine bay. Fan should not be spinning.

I find it helps to do this test with a second person sitting behind the wheel. Have then shut off the motor while you watch the fan blade. If the engine is fully warmed up, the fan should stop spinning as soon as the engine is shut off.

Will do it now
 

Hi Mike:

Ok...since I'm not working today, I'll drive the car around the block a couple of times and report back to you in 10 minutes.

Thanks for your assistance.

Brad.