Overheating Success Story of a 1969 Pagoda 280 SL

[Rolf-Dieter ✝︎]

Well as the subject line points out ... nothing better then "Success"

Some of you may recall that I reported a while back my 280sl was overheating in 30C (86 F) or around that range. Also in city stop and go traffic. Some of you may have seen when I went to Dan ... Benz Dr's place of business and we installed the new clutch fan among other things. One of those steps was replacing also the thermostat with a new one then Dan carefully checked the coolant strength. Dan used test strips to compare my coolant to a fresh batch and found that mine was rather weak. So we did 4 things to the cooling system a) new fan clutch, b) new coolant, c) new thermostat and d) added a bottle of Water Wetter to the new coolant batch.

Normally (back in my business life) I like to change one thing at a time when doing "Trouble Shooting" most of you do too I know. Anyway when we did all that the ambient temperature was in the low 20s and I was not sure yet if we did any good with all we changed. Well this past week we had a couple of hot days near 30 C ...

So it was time for a test run. I repeated the city stop and go runs in heavy city traffic I made before the changes a, b, c and d mentioned above my temperature now stays steady at just a shade over 180 F (my estimate would be 182 to 183 F).

I can now say we were successful in eliminating my overheating issue. If I ever make it to the Mohave Desert this might change I'm sure of it, when I was last there in a late model car it was 120 F at the lowest point (6 feet above sea level ~ if I had an egg at the time it would have fried very nicely on the pavement).

Anyway ... sweet success ... Thank you Dan

PS. In my case the clutch fan was earlier diagnosed as defective and not operating properly. I ordered a new thermostat from Dan prior to going to his garage, my thought at the time was I may as well make sure we have a new one on hand just in case so we used it also.   

[ptooner]

Did over 120 miles of city traffic today varying between stop and go and 80mph Interstate loop roads.  The ambient temperature was around 90 or a bit better (NE Florida).  My normal temp is just on the upper edge of 180 mark.  Today I found in traffic that it ran about two needle widths above the 180 mark in stop and go traffic and a little less than that at speeds above 80mph.  I'm not certain whether I have a problem or not.  So far as I can tell, I don't have a fan clutch.  It seems to be a direct connection.  (1965 230SL).  How do you tell about the clutch?  I'm planning on trying to pressure wash the radiator to see if the fins are clogged.  I'm looking for other ideas.

So far as I understand it, the later model cars had the clutch and a larger fan.  Is that interchangeable with the earlier 230?

Gerry

[Rolf-Dieter ✝︎]

Hi Garry,

I don't think you have a problem based up on your miles driven in the city at 90 F ambient temperature. If however you are concerned then I recommend you do one item at a time.

A) check your coolest strength

B) Change the thermostat

C) add a bottle of Water Wetter

Sorry I don't know if you have a fan clutch or not (I assume you do have one, perhaps Benz Dr. can confirm, he has seen many in his shop).

If all. He above does not work for you then  radiator backwash or re-core may be in order. Mine would hit the red line in 80 F ambient in city traffic now she holds steady at 180 F

[mdsalemi]

Rolf,

Glad you had the overheating fixed.  I changed my radiator in 2011 to one re-cored from Gernold and my cooling issues went away.

Some comments however--

1)  Coolant strength has to do with freeze point and little else; pure water actually has better heat removing capacity than anti-freeze, but the mix strength just has to do with the freeze point and probably little else in the way of keeping your car's temperature cool.

2) Thermostat?  Yeah, it's a big deal.  Have the right one in there, and ensure it works.

3) Water wetter?  I don't believe it; and the testing isn't proving anything: http://www.thetruthaboutcars.com/2008/01/redline-waterwetter®-review/  I don't think there's any kind of magic additive you can use to reduce your operating temps by 30 degrees.

4) Fan clutch? Yeah, that too is a big deal.  If it doesn't work, you'll have issues.

Dr. Benz will always tell you that a good deal of the heat removal is done by the oil.  Thus clean oil, and an oil cooler are part of the equation, too!

[Benz Dr.]

You can make water wetter - it's fact. It might lower temps by 5 degrees and that might be all you need.
 Coolant strenght does affect running temps as the more anti freeze you run the more it affects how well the coolant works. I use a 50/50 blend on most cars.

230SL's normally run an aluminium fan, or plastic if it's a euro car. You can run a fan clutch but you would need to change the water pump so that it has a 4 hole flange on it because the mounting on a fan clutch requires four screws. I ended up using a sedan fan on my car which barely fits in the opening but it never runs hot regardless of ambient temps.

[Tomnistuff]

Benz Dr,

When you say, "I ended up using a sedan fan on my car which barely fits in the opening...", what do you mean by "opening"?  Do you mean inside the opening of a shroud or do you mean between the radiator and the waterpump?

Since I'm planning to use sedan brackets and pulleys for a Sanden AC installation, I suspect that I will need a four-hole sedan waterpump and probably should go with a sedan FAN (modified) as well, if it will work.

Also, are you baiting us with the statement, "You can make water wetter..."  Are you going to tell us how or should I try to find it on the internet?

Tom Kizer

[mdsalemi]

If 5 degrees is all you get out of some additive, don't bother. That won't be all you need.  Yes you can make water wetter--just add soap!  I think all the reviews from independent people on this are that their may be some coolant change, but it's negligible at best; to me that means a waste of time or money.  If you run hot or on the hairy edge of hot, it's going to take more than some additive, and more than balance of coolant/water to solve your issues.  I've read plenty of reviews.  The good ones (rare) say "it works"; the majority of the reviews are not that great, and have specifics about how there was little drop in temperature.  About the best the pundits can come up with is it eliminates hot spots. How would you know if you have hot spots in your engine's cooling system?  I surely don't know.

50/50 coolant is standard in most climes as it is good to -35F or so.  Rarely does it get that cold except in outlying areas (who know all about what it takes to keep things from freezing).  Most antifreeze mixes will turn to slush as they approach their freeze point, which is why you need a good deal of margin. Slush doesn't flow too well in an automotive water pump...

Getting into technicalities here, the safe stuff (PG) doesn't transfer heat as well as the bad stuff (EG).

http://www.veoliawaterstna.com/crownsolutions/ressources/documents/2/21823,Glycol.pdf
http://www.umich.edu/~nppcpub/resources/compendia/CHEMpdfs/CHEMV.pdf

[Rolf-Dieter ✝︎]

Great stuff Michael ... thanks for posting the 2 links ...

All I know is ... before Dan and his Mechanics went to work on replacing the fan clutch, changing the coolant to a 50/50 mix and adding my Water Wetter my situation was this ...

Overheated going to the red line at 80 F ambient in city stop and go traffic ...

After adding the Water Wetter (same ambient temperature as before) it still overheated, however, stayed clear of the red line. So it helped somewhat.

After the work was done ...

Once Dan and the boys changed my fan clutch (that was loose) the new thermostat, the new coolant and added a bottle of Water Wetter in 80 F ambient it stays steady at 108 to 182 F

This weekend we expect 102 F ... a little heat wave ... I'll check it then Right now I'm happy with he results.

[Benz Dr.]

OK, let me be clear here:
 Some suff is snake oil and I think we would all agree to that. I tried water wetter 30 years ago in a 190SL I had. I filled the rad to almost full, added the water wetter so it was completly full, and left it run outside in the heat.  Normally, the rad would start pushing out coolant once it became too hot. ( A 190SL will often go to 215 F if not driven. Air flow through the rad and over the oil pan is key) While hardly scientific, it didn't spill one drop so I know it works to some degree. Dropping temps by 5 degrees for maybe 20 bucks or less isn't a waste of money if it works which my results seem to prove out. It may not work for you but it's not exspensive and it's easy to use.


I used to use an adjuant in my agricutural sprayer to make herbicides work more effectively. It breaks down the surface tension on some plants that have waxy leaves. I'm not sure how water wetter works but it seems that it helps to remove small bubbles in the coolant and it makes the cooolant bite into the metal by reducing suface tension so it aids in the heat exchange process.  


Let me be also extra clear. The repairs we made to Dieter's car may not work for your car because you could have any number of over heating problems not adddresed by what we did. This repair was sucessful ( so far ) probably more because the fan clutch was toast. Once you over heat your engine, all fluids are also toast, or should at least be considered as suspect. The coolant would be comprimised to some extent by every over heating which my test paper showed. Constant running hot will lead to head gasket failure and a warped cylinder head. Severe overheating WILL result in engine damage - don't try and drive that last mile or couple of blocks to get home if you see something going wrong.

Tominstuff:
I'm talking about the clearance across the rad cradle from side to side. My car is a 230SL and the fan blades are about 15 - 20mm from the edge of the air filter canister bracket. There is no shroud on my car  and it wouldn't need one anyway because it never runs hot.

[magicman]

I want to change the antifreeze on my 250SL this weekend, what brand is recommended? thank you

[mdsalemi]

Believe me Dan, I'm very happy for Rolf having been in the same place he was.  Having the problem essentially solved is a good thing.

I'd bet, however that the thermostat and the particularly the fan clutch solved most of the problem, along with a proper coolant mix.

The problem with these additives are that they are band-aids, and can begin to mask other issues.  Cars are NOT delivered with "water wetter" or "Be-Cool" or whatever in them; they are delivered with a careful mix of chosen coolant.

I've also heard that modern coolants, formulated today, do contain surfactants; therefore adding more of them is like adding oil additives to your oil.

If you have a cooling issue, the issue would not be because you don't have the right additive in the coolant; that's my point. A proper cooling system doesn't need additives.

[Rolf-Dieter ✝︎]

Mike I have to agree with you the thermostat and the fan clutch solved my problem, the car was not designed to need other solvents to keep the heat in check. Those solvents were designed and developed as an after thought and mainly used in bikes and cars that spend a lot of time on the tracks

[Benz Dr.]

I believe I used MB coolant. Deiter can look and see if it's blue or green in colour. If it's blue, it's MB and if it's green I got that at NAPA. The problem for me with getting MB coolant is all about distance. My nearest dealer is too far away so I pick up a bunch of it when I'm at one of my suppliers near Toronto. Shipping costs are far too much on something like coolant which is bulky and heavy.

Hey, sometimes I run out so I have to use the green stuff.


 The coolant PH test strips I use are made by a company called Radcheck. A bottle of 50 lists for 70 bucks around here so they're exspensive but the best I've ever used so far. Most test strips will give you coolant strenght and PH but these go one step further and also give you alkalinity reserve. Three different squares will change colour and then you compare it to the chart on the bottle. Easy to use and there's no guessing.

[mdsalemi]

Most test strips will give you coolant strenght and PH but these go one step further and also give you alkalinity reserve.

THAT is very important! The coolant "ages" from hi pH (alkaline) to lo pH (acid) and alkaline reserve is the one measure of age and how corrosive your coolant will become.

[langa01]

Hello all,

I have been reading mostly old posts trying to understand/find out a cure for overheating in my 1971 280sl. First of all a bit of background on the car:
Engine fully rebuilt less than 800 miles ago. Pistons, rings, valve stems, the lot.
At the same time radiator was recored and so was oil cooler
New water pump and new fan clutch
The car is manual and fitted with AC which was also completely overhauled
Still it would overheat in heavy traffic or after prolonged motorway use in summer conditions (Madrid, Spain regularly 40C in July/August). But, it is really "over"heating or was it designed from scratch to run hot? A look at the thermostat (again new but these components can fail nevertheless) confirmed that the range of the stat was somewhat on the high side, circa 90C so it is conceivable that these engines may run hot no matter what, particularly with current fuel composition which incorporate alcohol...
So, after a lot of trial and error we found a mechanical cure for the problem by inserting a collar in the thermostat stem so that it never completely closes. We tried this with the old stat first and it worked so the same trick was applied to the new one and re-installed in the car.
The result is a car that needs a bit more waiting in winter to reach operating temperatures but would run all day in all conditions with AC in the heat of the summer and would not go far beyond 180F it at all.
I attach pictures of the collar installed (as sophisticated as a plastic tie to start with subsequently a brass collar).
Hope this helps
Best regards

[114015]

So, after a lot of trial and error we found a mechanical cure for the problem by inserting a collar in the thermostat stem so that it never completely closes.

Sounds to me as if you thermostat is shot.
 You should get a new one. Preferably the one which opens at 79°C (centigrade). Just forgot the MB parts number for that one.

There ought to be also a thermostat around which opens at lower temperature, at 71 °C,
the part's number was A116 200 0015 or 0215 .... I forgot.

My porous memories...


Achim

[Benz Dr.]

I've never seen one that was lower than 79C  for our cars. We often drill a small hole in the thermostat which allows air to bleed through. Trapped air can lead to rapid overheating if it gets trapped in the block.

[Shvegel]

I was just about to say what Dan just did.  Normally there is what we used to refer to as a "piddle valve" on the edge of the thermostat which was simply a small hole through the flange with a little brass needle valve installed in it.  The needle had no spring so when you were filling the cooling system the needle valve would be open to allow any trapped air to escape but when you ran the car the coolant flow would push the needle against the seat and the valve would close.  in the case of an air(exhaust) leak into the coolant exhaust is pushed into the coolant through a leaky head gasket or a cracked cylinder head.  this air would get caught behind the thermostat and build up.  When that happens the spring part(bi-metal) of the thermostat would get partially or totally uncovered and the thermostat spring would not sense the heat properly and would not open which would cause the car to overheat.

 Drilling a small hole on the thermostat flange or cutting the needle out would allow this trapped air a way to escape.  It was also a trick some of us starving mechanics would use to avoid having to fix a leaking head gasket or cracked head on our own cars. I see in your photo your thermostat's needle has already been cut away.    I am curious as to if your engine was rebuilt due to overheating.  I think there is a possibility that maybe your engine is leaking exhaust into the coolant.  There is a tester that senses exhaust in the coolant.  it involves a special adapter and an indicator that senses Carbon Dioxide(I think?)

Also with you thermostat propped open like that there is a slight chance your oil is not reaching 100 degrees C which is needed to boil off any moisture present which prevents corrosion and deposits.