Warm running - concern?

[Berggreen]

Dear All

This afternoon I got caight in traffic in the city, and as it is an extremely hot day today (over 30C), then to my surprise the temperature started rising driving/stopping in  walking phase.

At times it reached close to and maybe also a bit over 100C on the gauge. Never happened before, but also very rare temperatures to be driving in here in Denmark.

I checked the oil before driving, and it was pretty dark. But after the trip it is now all clear and very lightly coloured. Why is that? :-/

Do I have reason for concern that the engine may have been harmed showing these symptoms?

It’s a 1971 280SL with automatic gearbox.

Thanx,

Christian

[Pawel66]

I am not in position to comment on temperature and oil state, but what I have noticed in my car:
- when I stand still on a hot day in traffic for longer time with gear in, the temperature raises to close to 90 from 85
- when I stand still in similar conditions with gear in N, the temperature stays at 85 - no matter how long I stand

I explain this to myself that with gear in the engine is under load and works harder - it will heat up more.

I know this does not explain your key concern.

[wayne R]

Christian, Will try and give you a few tips on trying to find any cooling problems
that can arise. You are correct getting up on or near the small red square 250f-100c
on dial is getting abit hot, but should not do any damage to engine, if only for short periods.
1,--check engine oil  level and colour when next time cold, dark colour is normal and ok,
but if its slightly lighter and not clear --milky-- colour,this could mean water entering engine
head gasket or similiar to repair.
2--check your radiator coolant  overflow bottle for correct level. and know leaks.
3--check your front water pump belt for correct tension ,not loose.
4--check your front  radiator fan clutch,most 280 have one,to test and its harder
on a Pagoda because of access,when cold at approx 70 degress, f should be able to spin with
your hand, and should only turn about one circle.-----sorry ran out of room

[wayne R]

Following on,
4--next you will have to go deeper to check thermostate not opening fully.
5--next you could try a reverse flush on the whole system, this is done by
removing the bottom radiator hose,and flushing right through to the overflow bottle.
6--remember to  turn heater on when refilling.
7-- engine timing is another thing if not set correct,but if car is running great-ok.

Another thing that can happen is the actual water pump it self internal vanes can
wear right down so thay are not moving the correct amount of coolant.
I hope you find the problem in the end with out to much cost.--regards.

[Berggreen]

I hope you find the problem in the end with out to much cost.--regards.

Thanx a lot Wayne for you very nice “cook book” on what to do about my cooling problems.

Actually 250F is about 120C, thus I was not all the way up to the red dot.

The engine should be in a good condition, but I have to confess that I have never had the thermostat out to inspect. Thus I don’t know which thermostat is installed.

Which thermostat do you recommend in terms of temperature?

Also, the previous owner has used yellow cooling fluid in the system, and I have continued to top it up with the yellow type. But now that I maybe have to replace the fluid, what color/type would you recommend?

I will start to get a new thermostat and also buy a shroud for the radiator, which my car is missing. Then I will report back if this has solved the problem.

Pawel, thank you as well. Good point about the P/N to put less stress on the cooling system.

Cheers,

Christian 😎

[FGN59]

MB recommends (and sells) its own formula (MB 325.0), which is blue.

[Pawel66]

Berggreen,

I think even with my limited knowledge, I can say what I know from the forum and my own experience.

1. I would do the checks that were recommended by Wayne (I had something like you described in W463 with M103 engine and it was fan clutch problem)
2. Thermostat, I think, should be 79 degrees (some recent discussions on the forum also about pump replacement)
3. Personally I use the MB blue coolant, bought at the dealer (more expensive, but simpler for me); anything from the market should deliver on MB norm 325.0
4. There are a lot of posts on flushing/cleaning the cooling system with citric acid; check the Tech Manual for this as well
5. In the Tech Manual you have procedure how to fill the cooling system
6. Our maintenance Manual says coolant level should be 4cm below filler neck bottom edge.

Details of coolant:

Mercedes MB 325.0 blue, 50/50 with destilled water, cooling system capacity 14,75l
5l  PN  A000989082511
1l  PN  A000989082510

Hope this is nothing serious.

And one more thing: if you are caught with overheating engine somewhere where you cannot pull over and stop, make sure you move on high gear, low revs and make sure you fully open cabin heating - max heat and open all vents.

[Berggreen]

Great, thank you very much François and Pawel. I will proceed as you recommend.

Cheers,

Christian