Greetings fellow 500E owners,

Ever since my ill fated trip to the dealer my car has been running hotter than ever, almost redline. So I've been revisiting the cooling issues with the 500E and have come across a few things. My dealer still wants to try and fix for free but I'm looking to help them.

1) it runs cooler with some of the engine encapsulation underneath removed.
2) it runs hotter at higher rpms with no other changes
3) it runs hotter at lower vehicle speeds
4) Water wetter helps but not enough
5) Aux fans come on at 108 degrees
6) Renntech recommends removing engine encapsulation, then trani cooler, then oil cooler, then bigger radiator.
7) Mercedes service bulletin says cars run hot and its okay!

Questions:

1) Has anyone used a lower temp thermostat
2) Where is the bleed screw for the coolant?
3) Has anyone used a speed reducing pully on the water pump? or has any evidence of cavitation at water pump?
4) What's the lowest ratio of water/coolant that can be safely run in fair climates?

Data:

My car used to run at 85-95 degrees 90% of the time. Stock car but with water wetter.

Then 105k service replace thermostat, flush coolant, and replace engine encapsulation (I tore mine off - don't ask) Installed precision auto performance chip.

Now my car runs 90-120 degrees regularly.
Aux fans work, come on hard at 108 with A/C off and at lower speed/temp with a/c on.

Help!

If this were my problem, I would work backwards to try to isolate the effect of your various changes. First, Iwould re-install the stock chip (ya never know, it could be the performance chip causing all or part of the problem). Does the car still run hot? If yes, remove the engine encapsulation. If the car now runs significantly cooler, I would nevertheless feel that I still had problem since the car was designed to run at the proper temp with the encapsulation in place. I assume that the car didn't run hot before you tore yours off, so I am guessing that removing it will not have much effect, particulary when driving at low speeds/idling. That leaves three possibilities.

1) Either the thermosat is incorrect or not functioning properly; 2) as was implied in a previous post by benzmac(?), there are portions of the engine which has not been filled by coolant; 3) something else went awry, coincidentially, at the same time as your 105K service. There is always the possibility, I guess, that in replacing the thermo or flushing the coolant, the tech simply screwed something else up.

Just for kicks, you may want to check the coolant temp directly (there must be a way to do this) to check that you temp gauge displays the correct temp.

Finally, I would be loathe to accept a service bulletin that the car runs hot, but its OK. I would certainly want to see what they mean by "hot". Remember that (per Lee) these cars start to loose horsepower as the temp creeps over 100 degrees. Your car may no blow up at the higher temps, but part of the reseason it doesn't is because MB dials out the power.

I am not a tech, and cannot give any more specific advice than this. But as a fellow 500E owner, this is how I would approach it.

And tell Oscar that a fellow 500E/2.3-16V/6.9 owner says to treat you right! (give him the list of cars and he will will probably figure out who I am). Oscar is a pretty stand-up guy who has often been personally involved in diagnosing some problems I have had –– make him live up to his hard-earned reputation (with, at least, one satisfied customer).

John

[This message has been edited by revbond (edited 08-16-2000).]

What about the viscous fan clutch? It might be "weak" and not be pulling enough airflow through the radiator? Just thought it might be worth it to check, if it may have been overlooked.

As a side note,,,,it has been over 100 degrees here for almost a week, and I have been driving my (wife's)500e. Even with the Renntech radiator, my 500 gets a little over the 100 mark after idling around in traffic w/a-c on. If I get up to about 60mph for a few blocks (or if I turn off the a/c for about 5 minutes)it cools down to "just under" the 100 mark.

I believe that "AIRFLOW" is the key element we need. I wonder if there is a way to get a more efficient engine fan (and/or clutch).
I (as I'm sure most) would be happy to put up with some "fan noise", if a stronger fan would cool the car better.

Hmmmmmmmmmmm, maybe someone can go raid a benz partsbin to see if there are any fans from "other models" that have more blades (600sl maybe?) & are interchangeable with the 500e unit?

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You may have a coolant flow problem. This involves tests like removing the thermostat temporarily (not a big deal in SoCal) and checking for a collapsing coolant hose. The latter is not uncommon in older cars. If the fans are coming on it is less likely since hot coolant is reaching the radiator.
The rad might be restricted. The fins could be full of debris
The best bet is to return the car to pre service condition and see what happens...even Mercedes parts are defective sometimes
Good Luck
John
92 500e

Thanks for your suggestions guys.

I did swap the chip...still hot. Dealer installed new thermostat 1st time, new thermo clutch 2nd time. I am hoping that there is something wrong with bleed proceedure or thermostat has been installed with the air valve in the wrong position, which according to AllData makes the coolant system harder to purge with air.

Eric

Though not to doubt the wisdom of the techs involved I would suspect air in the system. If it has been properly purged the problem could be airflow. My 92 500E always wanted to run 100C or above when it was 90+F outside. New radiator, thermostat, fresh coolant, fan clutch locking up like a beartrap, bottle of water wetter, electric fans working as factory intended, etc. If it wasn't moving quickly it ran hot. Never gets past 110C or so. The low speed cooling just isn't adequate. Yes the car can run above 100C and be "okay" but you lose massive amounts of power and fuel economy doing so. Since most 500E owners bought the car for power, having 50HP lopped off isn't the best. I don't know of a good factory solution. Benzmac and I have toyed with the idea of ripping out the clutch fan (turning at the low idle speed of 500-700rpm) in favor of a pair of huge electric fans inboard of the radiator. They could easily be rigged to turn on (at lower speeds) at 80-85C, then at high speed at 95-100C. This should pull MANY times more air through the radiator than the clutch fans and small electrics. You would also free up a few HP since the electric fans would not really cost you any HP's as the "dead weight" of the clutch fan does. I don't know of anyone who has done it yet, but it should be "do-able" for less than a Renntech radiator.

I know whatcha mean about the underhood temp issue... I've seen the heat radiating up from in front of the windshield fogging the glass and otherwise distoring vision. (it also remains hot for so long that you have to wear gloves to touch anything underhood several hours post shut-down) In my opinion this is the greatest weakness of these awesome cars.

Hang in there...Lee

Lee, all,

At what point does the oil get "cooked"? My 600 SEL wanders up to 110 degrees C sitting in traffic in the hot Florida asphalt that retains and reflects back the sun's heat. (Last month, the outside aimbient air temperature gauge hit 114F; I'd never seen it past 106F before.) As with Lee's 500E, if I'm moving it could be 100+ degrees outside and the coolant temp sits just over 80 degrees C. Conversely, however, it could be 85F outside and if I'm stuck in traffic, the coolant temp will creep up over 100 degrees C. Again, as with Lee's 500E, it doesn't go over that, but it makes me a little uneasy seeing it go that high.

Should I consider synthetic? It's run on dino oil all it's life.

Thanks,

Brian

There's gotta be air in the system..only thing that explains the acute flare-up.



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Best regards, Michael
'92 500E
'88 300TE

I don't mean to add insult to injury, Eric, but I am thankful to report that after benzmac got my aux fans back online my car reacts appropriately in traffic. Last Friday, on my way home, it was 105 degrees ambient. That's asking a lot of a cooling system, especially in a 500E. AC on while rolling in the city it was hovering around 100C and I could hear the aux fans on low. Sitting in a long line of traffic during three cycles of a traffic light the temp cruised up to 115C and there came that welcome sound of aux fans kicking into high gear. Temp needle stopped it's rise and sat steady until I started rolling and it was back down to 100C in less than half a mile. Thanks again, benzmac; job well done.

Eric, I agree with the people who have suggested there is air in your cooling system. I have heard several techs talk about how easy these cars are to get an air pocket in the system. I know what a terrible feeling it is to sit in traffic watching that needle rise and wondering what is going to pop first. I hope you get this cured soon.

My car's NEVER seen 115 degrees, and that includes stopping after banzai runs on a hot day, and drag-racing!

Are you guys running Water Wetter? If not, perhaps that'll lower y'alls temps a bit.

Keep us posted.

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Best regards, Michael
'92 500E
'88 300TE

dfndr,
If your COOLANT is hitting 110-115C, that's close to 240F...and that's where the sensor is (which is probably near the edge of the engine block?).

Now consider what the temperature of your OIL is at the bearings, or cylinder walls...probably easily approaching 280-290F or more on a hot day at high loads.

Your dino oil starts to break down at about 300F. To my way of thinking that's not much of a buffer. Mobil 1 will not start to break down until 500 or 600F, if memory serves me.

There's no doubt in my mind on what to use. :-)

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Steve
1979 240D
1990 300E

Just thought you all might want to know. I took my belly pan off today and it definatly ran COOLER. It was 103 degrees outside this afternoon here and on my drive home today, the engine temp never even got to the 100c mark! Wow! That is a noticeable difference from yesterday! With the panel on, the car got to just a hair over the 100 mark, but with it off- it ran UNDER 100 c!

Go ahead, try it on yours....it just takes a few minutes with an 8mm socket.

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Thanks, Steve,

It sure gives you a queasy feeling when you're just stuck, stuck, stuck in traffic and you know if you could just get rolling the needle would back off.

I would put in the synthetic in a heartbeat, except from reading the threads, it apparently will leak at all the seal and gasket points. If it's simply seepage, I could live with that; does anyone know whether the synthetic breaks down the seals/gaskets after using the dino oil for 8 years and 95,000 miles?

I may also try taking my pan shroud off to see what effect it has.... You would think that it would be a factory recommendation or something in hot climates. Can anyone think of a downside to removing the cover?

Thanks to all for sharing your experiences.

Brian

Brian,
A year and a half ago, I purchased my 1990 300E which had 85,000 miles. It had always had mineral oil in it (from the maintenance records). At 90,000 miles I put in 10W30 Mobil 1. I now have 103,000 miles on it and have seen no additional sepage of oil. My oil consumption has not gone up (about 1 qt per 3000 miles). I think most modern engine seals will take synthetic oil with little problem. If you live in a very hot climate, you could go to 15W40 or 20W50 (both approved weights by MB). These weights might be better for your Florida temperatures. If I lived in Florida, I would definately use Mobil 1 in my car and not be concerned about my oil temperature.

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Steve
1979 240D
1990 300E

With apologies for wandering a little further off topic and into the topic of Mobile 1, but when I read about the intended applications, it seemed that all that Mobil 1 suggested to be a point of concern was the minimum temperature the car/oil would be started in. Given this, what other differences in viscosity choices should one consider?

Dakota: Your comments about switching a broken-in benz to Mobile 1 are inspiring! Doubly so since you live in a climate that's a mere 30 or so miles different from mine. I was thinking of switching to Mobile 1 on one of my cars but worry about oozing seals has stopped me from taking the plunge.

And to try to bring this back to topic, does the 500e use an external oil cooler? If so is it possible that this, or the radiator is partially blocked by an unfortunate bird or a buildup of debris or something blocking the cooling fins, and is causing the excess heat build up?

…tracy