Overheating Solution?

[awolff280sl]

David, which 80 ltr/min electric pump are you using?

[paulr]

David, I do and I will call you. It might be something for the new year.

p

[DavidBrough]

My pump is a Davis Craig made in Australia and I it got from these people www.mawsolutions.com

I think the problem with the smaller bypass pump is that it only circulates already hot water round the engine as it can’t break the pressure of the engine pump to push more water through the radiator which is the only thing that will increase cooling.

Paul, that’s fine, I should have worked out how to fit it with the standard fan by then.



David Brough
1969 280SL Auto with A/C & 3.46 Axle

[Q45Denver]

What's the advantage of the standard fan over the electric?  I know they sell electric ones that have the same or more CFM's.

[DavidBrough]

I fitted an electric fan a while ago to try and get some extra pull at tick over as they always run at full speed. However, due to the slim nature of the unit needed to fit, the extra air flow was marginal and, whilst it was better, it was not the cure on its own. In addition, its activation is very specific in that it is either on or off at set temperatures unless it’s linked to a very fancy progressive controller which I’m not bothered about trying to fit. The standard fan on the other hand is progressive and starts to lock up at 90c with full speed gained at 95c. At the moment I have the pump and fan linked to a 95/90 temperature switch which works well enough, now I have the electric pump, which can quickly reduce the temperature below 90 and switch everything off. Now I know I can control the temperature I feel that the standard fan offers the best alternative as it will start to lock progressively from 90 whereas the electric set up lets the engine run straight up to 95 before kicking in. I did try some lower start temperature switches but as the smallest throw is 5c they were trying to overcool the engine and sometimes didn’t switch off for a long time and, starting the cooling at over 95 is not really recommended. A bit long winded I know but in general the standard fan set up works well and only really kicks in when needed so, on balance, I feel that this, with the electric pump linked to a 95/90 switch, would be the best setup. However, the proof will be in the pudding and I have yet to try it but from what I’ve seen so far this should be the best answer. The only real problem is the space available to mount the pump with the standard fan fitted as the electric unit sits on the radiator there is much more room for the pump. I’ve purchased various hose bends and some aluminium joiners and will see if I can get it to fit with the standard fan and report back.


David Brough
1969 280SL Auto with A/C & 3.46 Axle

[Q45Denver]

I'm starting to think that all electric might be the way to go.  This would also free up some horsepower and result in a freer revving engine but might require an alternator upgrade.  While the current setup is fairly robust it is not doing the job in traffic and when going up mountains which we have a few of in Colorado.  A fan controller is fairly inexpensive and simple to install so that should not be a problem. The controller might also allow the engine to operate within the narrow temperature range as designed. I have a single Spal 16" puller fan with a shroud that might do the job. My car does not have a shroud currently installed.  Either it did not come with one or was removed by a prior owner. Or I might visit a local wrecking yard and see if I can find a fan out a late model V-8 that might fit.

[DavidBrough]

Hi Werner,

The fan I have is a slimline 16” Spal unit and whilst it does give a bit more pull at low engine speeds I think the standard unit moves more air at higher revs. The standard size 16” fans just won’t fit. I have to say that my engine is much quieter with the electric unit but, as it won’t do the job for me on its own, I would like to run the standard fan set up with the electric pump if I can. Also, being a viscous unit it doesn’t put such a strain on the engine until it has to work hard. A fan shroud should certainly make quite a bit of difference but, due to space constraints, the Spal unit has to go high and right on the radiator so any shroud may have to be custom made. Space is particularly tight on my car though as I have A/C and the condenser means that the radiator has to be mounted well back towards the engine. If you don’t have A/C you may find that you can create a bit more space by pushing the radiator forward as the mounting points are slotted and allow quite a bit of movement and you may be able to get a more central mounting position.

Don’t know about the V8 fan but I would expect it to have quite a large and powerful motor which just wouldn’t fit. Space is a real issue.


David Brough
1969 280SL Auto with A/C & 3.46 Axle

[Q45Denver]

I haven't played with it yet, but space should not be much of an issue as I intend to get rid of my mechanical fan entirely.  I do have A/C but can't use it much of the time due to overheating. Another thing my car is lacking is a pusher fan on the front for the A/C condenser.  I have one from a W126 model which should fit. I will install it inline with the other fan so they both come on at the same time I guess.

[DavidBrough]

Hi Werner,

I think you may find that space is a real issue and only the slimmest of slim line fans will fit on the engine side of the radiator. There is space on the right side by the alternator but the water pump pulley is in the way of anything near the centre and the power steering pump obscures the left side quite badly. Fitting a fan on the condenser is a good idea but you are probably better off wiring that to come on with the compressor.


David Brough
1969 280Sl Auto with A/C & 3.46 Axle

[Q45Denver]

David,
So your saying even with the mechanical fan removed, there is a space issue? I have an M130 in a 1969 W111 coupe (mechanically the same as your W113). I think If I can set both fans to come on at variable speeds depending on the temperature, that would be ideal. Somehow with the summer almost over, this project is starting to lose some priority. Did you notice any gain in heater operating efficiency with the electric pump installed?

quote:Originally posted by DavidBrough

Hi Werner,

I think you may find that space is a real issue and only the slimmest of slim line fans will fit on the engine side of the radiator. There is space on the right side by the alternator but the water pump pulley is in the way of anything near the centre and the power steering pump obscures the left side quite badly. Fitting a fan on the condenser is a good idea but you are probably better off wiring that to come on with the compressor.


David Brough
1969 280Sl Auto with A/C & 3.46 Axle

[DavidBrough]

Hi Werner,

I didn’t leave the small pump on long enough to find out if it increased heater performance, as it did nothing for the cooling I just removed it again. It’s quite likely that a W111 has more space available to fit a full size fan which I suspect would be able to provide sufficient cooling as they move about 25% more air than the slimline versions.


David Brough 1969 280SL Auto with A/C & 3.46 Axle

[DavidBrough]

Well, I’ve now removed the main engine electric fan and refitted the standard viscous unit with the electric pump which went in very easily in the end. I’ve also removed the heater bypass and replaced the thermostat with an 83c one and now it’s not warm enough to get the engine hot to trigger the pump so I’ll have to wait for a better day to properly test the set up. With the electric fan the engine would run up to the fan trigger point (95c) relatively easily but the standard unit needs much more severe heat before it starts to lose control which is one reason why I think this will be the best solution. I’m off to France in a few weeks with a better chance of hot weather so I’ll let you know how I get on.


David Brough
1969 280SL Auto with A/C & 3.46 Axle

[awolff280sl]

David, would you be kind enough to post a picture or describe the location and mounting of the electric pump, when you get a chance?
Thanks.

[DavidBrough]

Hi Andy,

Here are some pictures of the pump with the electric fan fitted, I will take some with the standard fan tomorrow but the mounting hasn’t changed. I first though I would have less room for the pump and would have to be creative with its positioning but in the end I just removed the electric unit and fitted the standard one back without touching the pump mounting. Fitting the pump is very straight forward; I just cut into the bottom hose and fitted it in.


David Brough
1969 280SL Auto with A/C & 3.46 Axle


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[awolff280sl]

Thanks David!
Is the pump fixed/mounted to anything, or does it just "float" on the hoses? (can't tell for sure by the pix)

Did you get the Thermal Switch?

[DavidBrough]

Hi Andy,

I’ve take a picture of the pump with the standard fan but I think the other ones give a better view as the fan gets in the way.

The pump just floats in the standard bottom hose although it is a bit tight against the bottom of the air filter panel so a put a small piece of rubber in between.

I use a standard M22 fan switch to trigger the pump which I had tapped into the top of the radiator but you could use any of the proprietary switches which fit in the top hose. There are lots available with different temperature ranges but I found 95/90 to be the best.


David Brough
1969 280SL Auto with A/C & 3.46 Axle


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[Ziggy]

Today I got into a huge 70 minute traffic jam, couldn't go any faster than 5 miles or 10 km p/h. :x  It was 80 degrees and sunny, which always led to overheating combined with this kind of traffic. It was the first time that I could try the 124 electrical pump together with the electric fan under these conditions, and I am happy to say that it kept the temperature steady just above 80 degrees all the time  

Did anyone ever get any results with water wetter type products btw ?

[DavidBrough]

I think it’s about time for a cooling update; the best laid plans and all that.

During the summer I decided to try the electric pump with the standard MB fan as I felt that this may be the best option. However, whilst this did work OK it was definitely not as good as the electric fan. I think this is because the standard fan just doesn’t pull through the same level of air at low revs as the electric unit which is always at full speed. Additionally, the electric fan and pump set up can be engaged with the engine off giving dramatic results whereas the electric pump on its own i.e. with the standard fan, is not so good. On balance I think the electric fan and pump set up is best so I’ve now swapped back. I also changed my 79deg thermostat for an 83deg one which the engine seems to prefer as it maintains temperature much better. With the lower one I would see some quite wide variations at the gauge but things are much steadier with the higher one.



David Brough
1969 280SL Auto with A/C & 3.46 Axle