230SL Overheating

[stephenbeardsley]

My 230SL runs just fine and the temperature guage resides just below the 180 degree mark until I get stuck in stopped or very slow stop and go traffic, particularly on a hot day.  When this happens the temperature guage will begin to rise and eventually hit the red square (HOT!) after maybe 20-25 minutes.  Do any other 230SL owners have this problem?  I am considering an electric fan pegged to turn on at 180 degrees.  Any fix short of installing an electric fan?  Will the electric fan work?  I've been a member for a while and I have learned a lot from the forum.  However, I have not seen anything about this, and I would appreciate hearing your thoughts.  Thanks!

[jeffc280sl]

This is a problem for many of our cars.  Have you tried turning your heater on when near the red zone?  If this improves the over heating condition I would install a heater core bypass hose.  Do a search on that topic and you will find plenty of info.

Good luck

[al_lieffring]

The 230s are less likely to have cooling problems than the models with larger engines. start with the basics drain the coolant, drive for a couple of days with coolant flush in the systen drain and rince then replace the antifreeze the thermostar. My 230 was running hot just like yours but after doing a coolant flush and replacing the thermostat havnt had the problem since.

do not attempt to drive these cars without the thermostat designed for this motor. it will actually make the motor run hotter.

[Benz Dr.]

I agree. 230SL's normally run cool.
 Sounds like a plugged rad if none of these other fixes work. There are different temperature thermostats - 79, 82 and maybe 87C. I'm running a 79C for summer driving on my car. If anything, it's a bit too cool but the engine never goes above 185 regardless of hot hot it is or how long it idles.

Make sure the front of your engine block and the whole oil pan is free of grease or oil. Anything coating these surfaces will act just like insulation on a hot day.

[dixy2k]

Check the thermostat. It might not work properly.

[xcashewx]

check to see if your idle mixture is too lean causing it to run hot .
this was the situation with my car, it would cool right down as i started moving.

also, if your car has one, try the fan clutch.

[julianmaba]

When did MB start using viscous coupling fans? My 1966 250SE had a viscous drive. If the viscous coupling is worn, it will not engage the fan as it should, especially in hot weather or when you are stationary (little air flowing across the radiator). If the cooling system is keeping the temp normal while driving (moving), then the radiator is probably fine. The fan is needed ONLY when you are not moving — so check the viscous coupling to the fan is working correctly.

[dixy2k]

Mine is on all the time. I'm not sure if the previous owner did this way, or it just came out like that.

After changing the thermostat and replacing that broken coolant hose, it takes 15 min of driving to warm it up to 180*

[stephenbeardsley]

Thank you all for your excellent feedback with regards to my overheating problem.  Actually, my radiator is a re-cored replacement done in 2009 and I am told that my thermostat is functioning properly.  However, I'm not sure if the engine block/head was given a good flush at that time.  My feeling is that it wasn't.  My car may be running lean, but after a long time of having it run a bit rough I finally have it running smoothly and I'm reluctant to change it.  I will be sure to try a good flush to the block/head.

My 1966 230SL does not have a viscous clutch, but rather a four blade fan that runs at engine rpm.  So, when the engine is at idle or in very slow stop and go traffic there is not a lot of air going through the radiator which could be causing it to overheat?  Once I get moving again the car cools right down.    Also, my feeling is that there is a reason that Mercedes later changed to a 6 blade fan, and then a 6 blade fan with a viscous clutch (maybe to rectify this problem)?

Has anyone had experience with an auxiliary electric fan with a thermostat set to turn on over 180 degrees?

Again, thank you all for all your help!

[menesesjesse]

Steve
I also have a 230sl that does what your car does.  The engine was rebuilt last year and is clean inside and out.  The radiator is not new but was cleaned. I have the 4 blade plastic fan.  I took my car out on one of the 100 degree days we had in DC and the car ran well until traffic.  The car really did not like this condition and the needle creeped up almost till the red zone.  I noticed that days over 90 degrees the car does this but as long as I am moving I get the same results you do.  I am thinking that a 9 blade fan will help fix my problem but I am also interested in possibly running an electric fan.  I am on the fence with this because driving the car is no fun on hot days anyways and it runs great on nice days. Im not sure if the time and cost is worth it.
Jesse

[stephenbeardsley]

Hi Jessie,
Thank you very much for your input.  This really helps me to make a decision.  Since I am thinking of adding A/C next year I am going to proceed with the auxiliary electric fan and I will let you know how I make out.  I just don't want to take the chance of being stuck in a major traffic jam and watching the needle creep up.  Not a good feeling.  Thanks again, Jessie.
Best,
Steve

[jeffc280sl]

Steve,

Are you considering an electric puller type fan?  Unfortunately there is little room in front and behind the radiator.  With the A/C condensor in place you maybe able to fit a 12 or 13 inch fan in front.  Behind the radiator the only thing I have found to fit is a sidewainder fan.  I don't have any reason to install it now because the heater bypass works well.  If I do re-install my A/C and have an issue I'm going to try the brushless sidewinder.


http://www.sstechusa.com/hightlights/sidewinder.html

[Benz Dr.]

I would think about adding AC. The 230SL crank has a tendancy to crack and break off due to vibration. This was changed to a much stronger system on the 129 and 130 engines. Some of this is simply a problem with York compressor pumps from the time period.

Ther AC system will completly clutter up your engine bay. If you need to work on the engine it will make everything harder to get at and much longer to get done.
 I did an installation for a guy last year. I will never do another one. This was on a fresh 250SL engine with a rotary AC pump as part of a new kit. Even while driving at speed I could feel the whole car slow down every time the pump came on, and the engine had plenty of power.

It ran cold but the fan made a great deal of noise and the evaporator box was kind of cheap looking plastic. It was next to impossible to follow the guy's instructions to install it , '' Attach the curved hose to...... ''
Every hose was a curved end one.

[stephenbeardsley]

This must be why they call you Dr. Benz.  Based upon your experience, as well as the below from jeffc280sl I an going to forget about installing A/C.  Actually, in New England there aren't that many days when it's vital.   Based upon jeffcs80sl's remarks below I'm going to forget the AC in favor of the largest auxiliary electric fan possible.  I'm going to have this installed by a very competent radiator specialist who has looked at my car and feels that there is space in front of the radiator for a fan.  Not True?

Thank you all for all your help!  Any other thoughts keep them coming.
Best,
Steve   

[julianmaba]

I agree, the A/C adds a lot of complexity — and potential problems , I would not add it myself. Instead, try limiting your drives for those perfect moments in the evenings when the sun has just gone down, you are on your favourite roads, and when you can truly enjoy your 230SL!

[DavidBrough]

For those that want to fit A/C don't be put off by some of the comments but do pay heed to Dan's remarks about 230 crankshafts and the gubbins cluttering up the engine bay as it certainly makes changing the fan belt interesting. Also the instructions are usually pants, mine were on the lines of open bonnet fit kit. I have the Buds kit on an early 280 which are the most prone to heating issues in ordinary trim but I managed to make mine run cool eventually. Some kits including mine are very plasticy but I cured that by simply spraying it with trim paint which removed the nasty shine and gave it a very pleasing finish, they also have very noisy fans but that was because mine ran far too fast even on the slowest speed so I slowed it down and its now perfect. If you have a modern compressor on a well tuned engine you will notice it kick in but it doesn't really make any difference. What does make the difference is the comfortable, cool and pleasant feeling when you drive on hot or muggy days. As always it's personal preference but if you want A/C it can and does work in our cars.

[jeffc280sl]

Steve,

There is very little room for a fan in front of the radiator.  It has to be mounted low enough to be out of the way when the hood is opened.  The center part of the fan is the motor and it needs to be placed just above some of the front grill sheet metal just behaind the star.  It makes for a very small fan which in my experience was insufficient. It is a pain to mount any fan in front.   This is why I recommended the bypass and sidewinder puller fan.

[George Des]

I put an A/C in my 230SL with Sanden 508 rotary compressor and an upgraded blower using the original underdash unit and evaporator. I'm running R134a using a parallel flow condensor unit. The bracket I'm using was custom cut from a flat peice of 1/4" steel much like the Bud's Benz bracket. I had to custom cut every hose and crimp using a special tool while the hoses were in situ. It was a lot of work to put in and at the end of the day it blows cold and really cools the car off with the hardtop on. When running, it hardly drags on the engine with no noticeable drop in engine rpm. I put this unit in because as those who live in the D.C. area well know, the summers around here are miserable to drive around in either with an open top or open windows. So, I thought I might use the car more with the A/C. I have been experiencing some elevated temperatures especailly during extended idling like at the many traffic lights we have here in No.  Va. This may be because the large condensor unit impedes the flow of air across the radiator and like like the Dr. say, it really clutters up the engine compartment making all sorts of work in there more difficult. I've toyed with the idea of installing a smaller condensor to address this, but the more I contemplate it, all things considered, I'm thinking of removing the A/C and going back to original i.e. no a/c--the Italians just didn't believe in it back when this car was purchased. Fortunately removal will pretty much return the car to original save for a few acces holes that will need to be covered back up.

George Desiderio
1967 230SL w/ZF 5 speed (Italian)

[Benz Dr.]

I have the same car as you have George but it has a 250SE engine installed.

If you decide to install AC, you better make sure that all the things that could cause you grief later on are looked at. Water pump, front crank seal, short hose between pump and thermostat housing, chain tensioner, chain or anything else that would be impossible to get at after the AC unit is installed.
The short hose, tensioner and chain should be changed anyway unless the parts are known to be good.

[xcashewx]

check the tension of your fan belt as well.
if the raditor,fuel mixture,and waterpump itself are working this is the only thing i can think of. if the belt is a little loose the fan will "slip" at idle, causing decreasaed coolant flow(hence heating up). then when you get moving the pump puts out more volume thus cooling down

if the block/heads were clogged you'd see overheating all the time.
and adding an aux fan would "help" the issue but not fix the root cause.