temperature???

[n/a]

I have been driving my 280SL a lot, as it warms up here in Maryland, and have noticed that it runs rather warm- the needle is about 2-3mm above the 180 degree mark, if I am driving on the highway during the day, 60-65 mph, and it's warm out, say 75 degrees or above. At night the engine seems to run at the normal temp- at 180 or a little lower. Items replaced before the car was put back into service from its long spell of inactivity: new MB water pump, new hoses, new thermostat (all MB parts) radiator removed and tanked and cleaned, replaced. I think we replaced the viscous fan clutch, I am fairly sure. Also I run Redline water wetter in the system which I regret to say has made no difference at all. If I turn on the heater, the engine temp goes down. This is okay when the top's down but not so good when the top is up.
   I think my cooling system is running pretty near its' limit in normal temperature air and runs out of reserve when the ambient temp goes up. Any ideas? My other MB cars have not given me this sort of problem.

[Cees Klumper]

There have been many posts about cooling problems. You can check the technical articles as well for tips & trics. For starters there is an air bleed bolt on top of many thermostat housing caps. Also I disassembled an engine the other day that had a lot of crud inside the coolant passages that would restrict the flow of coolant. Backflushing may be helpful there. Also, are you sure you temp gauge reads correctly? May be worth getting the temperature double checked at a garage.
My car always runs on the very low side of the '180' number. Only in prolonged stop-and-go traffic does the needle creep up to the high side of same number (which is quite a safe distance from the danger zone).
Some have reported good results after having the radiator recored with 3 cores. Also some have added an electric fan. I would assume neither should be necessary if the system is operating as originally designed and built. Nevertheless, running hot is a problem that can be hard to cure.
Good luck,

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[Mike Hughes]

It never hurts to check the timing periodically, especially if you have traditional points and condenser ignition.  If the timing is retarded enough, the engine will run hotter than usual.  Normal wear of the rubbing block will actually change the timing slightly, as well as close up the points.  There is a special lubricant sold in most auto parts stores that one applies to the tip of the rubbing block and the distributor cam to minimize this wear.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[A Dalton]

Often over-looked is h2o/af mixture ratio..
 Never go beyond 50/50..
Water transfers heat away  better than af/ so never have more af than h2o...............

[jeffc280sl]

I have a 1970 280SL 4 speed and live in MD also.  My A/C compressor is broken so I have removed the condensor.  I also installed an electric fan which has an adjustable thermostat.  The highest my car has gone this summer is 180 degrees.  Don't know how much the fan helps.  Temperatures do not go down when it comes on like it does when you turn on the heat levers.

Jeff C.
1970 280SL 4-speed

[n/a]

I reviewed the service tickets from Euro Motorcars and in fact the viscous fan clutch was NOT replaced. Could this be the culprit by itself? Also, does anyone know of a descaling treatment for these engines that does not involve taking the engine apart or the head off? I suspect that the engine was NOT backflushed when the cooling system work was done- as it ought to have been.
   I am going to check the engine temp with my IR thermometer on a warm day- we'll see if it agrees with the cars water temp gauge, or the gauge is optimistic/pessimistic.

[ja17]

Hello Jim,
At highway speeds an engine fan should not be needed at all. At these speeds plenty of air is moving through the radiator and the fan is just dead weight. So I would not run out and get a very expensive fan clutch yet.  The fact that the temperature will decline when the heater is turned on  and that the car runs a little hot at highway speeds tells me that the engine radiator is not up to specs. Turning the heater on is like adding a few more rows to the radiator.

A radiator problem can be hard to diagnose. Boiling it out will not always bring it back. Check to see if you have any detached or decaying fins. These radiators can be recored with original looking coring by a good radiator shop if needed. An extra heavy duty core can be used with an extra row of cooling tubes may be used especially if you have AC.


Joe Alexander
Blacklick, Ohio

[n/a]

Joe, I am sure you are right and I thank you for the lucid and logical explanation. I will bring the car to a local radiator shop and see if a thicker core can be fit to the existing tanks. They will also have something to say about what can be done to clean the coolant passages. They did the aftercoolers for my Caterpillar marine diesels and did a good job. Your comment about the air flow and fan clutch makes good sense. Thanks!

[n/a]

I have heard there is a scale that develops in the radiators that decreases the heat transfer ability. Boiling doesn't seem to help. The radiator needs to be replaced. I am in the same boat. I picked-up a new radiator and am about to do the big swap. I also have a decent used fan clutch to replace what I think is a shot one on my car. Hope this does the trick as I can't drive my car very far on warm days. I'm toying with replacing the water pump and all the hoses at the same time. I did buy MB citric acid flush. I think I'll run that through the system before replacing the radiator to get the gunk out of the engine. This job scares me and I've held off getting it started. Not looking forward to taking the hood off. Oh well, time to bite the bullet.

Shawn Rock
Philly, PA USA
1968 280 SL 4 speed

[Mike Hughes]

Doesn't the radiator drop out from below without removing the hood?  It clearly looks like it would on my 230SL.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[n/a]

Well, we think it is the radiator; there is either an obstruction to flow, or it is gunked up inside, or both. A new OEM radiator is $2400.00- this is Ferrari territory. However a repro radiator made in Germany is $700- which is what I am going to get. (from Star Quality here in Maryland). It will take a week or so to arrive. It is also three rows of tubes as opposed to two rows.
   I don't know if the radiator will come out from the bottom. The job is going to get done at my friend Randy Rodman's shop in Silver Spring, MD- I'll ask him if it is possible to take it out form underneath. I'll have to look.
   I am also going to see if the old one can be recored; if so, it may show up for sale here at some point. Although with a new one available for $700, the recore will have to be pretty reasonable to be worth doing. I'll keep y'all posted on whether this solves the problem.
   That set of Euro lights just keeps getting further and further away.....  :evil:

[ja17]

Hello Jim,
A good radiator shop should be able to re-core your radiator with the extra row re-core. they can get core to match the original in appearence. It usually runs between $300.00 and $400.00 around here. I think Tom Sargeant has had this done also. Are you out there Tom?


Joe Alexander
Blacklick, Ohio

[athadani]

Hi all,

1970 US 280SL Auto giving me a terrible time by over heating and threatening to go into the red on warm days. Radiator has been redone and thermostat has been changed to the more effective model 70 degrees I think. Now thermostat has been removed as garage says more water flow could be helpful, but no. garage says the only other thing that could be he matter is that the engine block gasket is used and should be replaced (huge cost). The garage also poured a test liquid into the engine to check for gases and found that the liquid colour changed slightly.

Summer is here and driving with the top down is great but with the temperature needle menacing, the fun is too stressful.

Any help would be appreciated.

Ashok

[George Davis]

Ashok,

complete removal of the thermostat is generally not recommended.   There needs to be some restriction there to prevent the pump from cavitating.  If you want no thermostat, the working parts can be cut out of the center, but the outer disk should be installed.

Make sure the engine is not running lean (check plugs after a run at speed, or do CO testing on the road).  Do a leak-down test to check the head gasket.  Make sure the fan clutch is in good condition, and clean the front of it to expose the heat sensor.  Does your car have the later 8(?) blade fan?  If your car doesn't have a fan shroud, considering adding one.  Consider adding an electric fan in front of the radiator.

Was the radiator rebuilt with a high efficiency core?  If nothing else works, you may want to rebuild it again with a high efficiency core.

Miserable subject.  Good luck!

George Davis
'69 280 SL Euro manual

[SL113fan]

Check the easy stuff first: system pressure (it doesn't have to leak coolant to have an air leak), timing, temp sender + guage, and visco fan (can you stop fan with a cardboard cylinder while turning at idle?)

[Tom]

Joe,

I am all talk and no action on this subject.  I am not having overheating issues as I am not running the A/C.  However, I am planning to re-install the A/C, at which time I will recore the radiator with another row.  Have not found a shop yet but don't think it will be hard to find a shop to do this.

Best,

Tom

_____________________________________________

1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
_____________________________________________

[ja17]

Hello Ashok,
The thermostat on these engines is double acting. As the engine warms they open a passage to the radiator and at the same time they close the radiator by-pass loop.
If you remove the thermostat altogether much of the coolant will not flow through the radiator.  The engine will run hotter with the thermostat out!
If your head gasket is leaking very hot combustion gases are getting into the cooling system and raising the temperature.

You may want to try re-torquing the head with the engine hot. Be sure to remove the radiator cap (relieve pressure) before loosening any head bolts. Retorquing the head can be done by loosening each head bolt a turn, before torquing to specs one at a time. Follow the factory torque sequence.

If your cooling system presurizes too quickly, this can also be a sign of combustion gases leaking into the cooling system. Good luck, keep us up to date.
Joe

Joe Alexander
Blacklick, Ohio

[rwmastel]

Jim Rosenthal,

You said in your initial post that the "radiator removed and tanked and cleaned".  Now you think that this same radiator may be the problem.  Can you (or other knowledgable radiator people) elaborate on why the previous work may not have been adequate?

Thanks,

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[athadani]

Thank you all for your comments. Have tried all and finally have decided to change engine head gasket, hoping things will cool off. Am on vacation at the moment and the work will be done in mid -August. Will let you know.

Have a good summer.

Ashok

PS: Cees: Any progress on the poster?

[n/a]

Update on temperature problems: first, in answer to Rod's post; when the car was at Euro Motorcars [!], the removed the radiator and sent it to a shop of their choice who "allegedly" hot tanked it. This was not adequate. When we took it out, the radiator shop of my choosing (Winegardners here in Annapolis) found that the core tubes were clogged. We tried to get a new radiator- an aftermarket one purchased by mail did not fit the car, and the parts seller paid for it to be returned and will credit me for it. I ended up ordering a high-performance core for the old radiator and having the old radiator 'rebuilt' using the new core and old tanks and straps. The new core is still two rows of tubes, but they are closer together and the fin count is higher per inch. It fits fine. I am picking up the car tomorrow. According to the shop (AutoShoppe in Silver Spring) it runs fine and stays cool. They also put in the Crane ignition conversion I had not gotten around to doing.
    I think the infrared noncontact thermometer that I bought is one of the most valuable and interesting tools I have ever owned. For example, on a hot Maryland day, the pavement temp on asphalt is about 125 degrees. You can see why a car driven at relatively high engine speed on a road that hot would have trouble cooling if any part of the cooling system was not at top performance. The air coming in through the radiator grille is already very warm. Heat, of course, will run down its' concentration gradient regardless of which medium the transfer is occurring through, and the hotter the air that you are using to cool with, the less cooling you will get.
    I find that the first year with a 'new' old car is the one in which you get everything sorted out. I am looking forward to having the end in sight with the 280SL- if the recent work sorts out the cooling, then we will have the rear axle ratio change yet to do, and removing the modern radio and putting the old one back in, and maybe a set of shifter bushings. Oh yes, and heater levers. After that, maybe things will settle down a bit. The car is such a pleasure, though, that the improvements are worth it.  

[J. Huber]

Hello all (especially newer owners),

Jim's comment about "getting things sorted" out in your new Pagoda got me to thinking. It is true that every new "old" car seems to have a set of issues -- some more than others -- that new owners grapple with. Well, having had my 230SL for nearly 20 years, I can sure attest that "there's always something" that needs attention. Comes with the territory. However, the good news is, at some point the joys will far outpace the frustrations... so hang in there!





James
63 230SL

[n/a]

Car is back from Randy Rodman's shop, recored old radiator works perfectly, with or without AC on. AC is surprisingly good, actually. Also had Crane ignition put in, maybe a little smoother but hard to tell. Anyone local who needs a radiator done, email me- the shop was Winegardner's in Annapolis, cost 550$, for a higher-performance core that works very well indeed.

[Cees Klumper]

Congratulations on the cooling fix Jim.

Actually my car took me three years to sort out properly (the engine rebuild last summer was the last major thing to be done on the car) and there's still small things left to do. But even with all of the minor and major improvements I made, the car was fun from day one (even though it stalled about 5 times on that very first day in very busy Saturday Amsterdam city traffic).

Ashok - the poster is now really nearing completion - really! I have almost 40 photos in, with a couple more on the way. In a few weeks the graphical designer I asked to help us and I will sit down and we will start piecing it together. I will update the original post on this topic with an important question next ...

Cees Klumper in Amsterdam
'69 white 280 SL automatic