Radiator Shroud for 250 SL

[Atazman]

I'm in the process of upgrading my cooling system, and want to build a shroud.  My radiator has the 4 mounting tabs, so fabrication (out of metal) will not be that difficult. 

However, I'm needing the "depth" of the shroud. In other words, how far does the shroud extend from the radiator fins toward the fan?

My fan blade leading edge is 1" away from the radiator fins and the trailing edge is 2" away.  Thus, I'm thinking my shroud should have a depth of about 1.5" so that half of the fan blade is hidden by the shroud and half is outside the shroud.

Does this compare with the depth of your shroud?

Thanks for checking.

[ja17]

Sounds about right.  Also the mounting slots for the radiator allows it to be adjusted front or back about 1/2".

[WRe]

Hi Don,
I've installed a radiator shroud of a w108 4.5 (A1095050855 (66/55/4 cm) in my late 280SL with oil cooler.  With some corrections It fits nearly perfect. It's still available at MB (< 50€).
See here: https://www.sl113.org/forums/index.php?topic=25187.msg180059#msg180059.
...WRe

[Atazman]

WRe...

Can you provide a dab more information on the W108 shroud please.  Is it metal?  Is it a 1-piece design to where the radiator has to be pulled to install or remove it?  And what diameter fan blade is it suited for?  Thank you!!

And, thanks, Joe, for the confirmation on the depth of 1.5" being close.

I'm going "all the way" on trying to milk out maximum cooling. I have purchased a new fan clutch (not sure the old one was bad), a 9-blade fan to replace my 6-blade, a new 79 Deg. C. thermostat (replacing an 87 Deg. C.), and will pull the radiator for an inspection and cleaning or core replacement if needed or if another core (more rows) is available.

Your info is much appreciated.

[WRe]

Hi Don,
to your questions:
- the radiator shroud I mentioned and installed, still available at MB is a plastic shroud
- it's a 1-piece design but it's not necessary to remove the radiator but the fan
- it's suited for our fans.
But it has to be changed a little bit
- one mount does not fit, has to be drilled a little bit higher
- the openings for oil cooler and water hose on top has be widened, so the openings on the bottom, all only a little bit
- the fan opening only a little bit on one side (maybe one can avoid this if you widen the mount holes a little bit - more play)
I tried to figure it out on attached picture. It wasn't much work and really easy to do.
I did it for an electric fan because I didn't trust the visco clutch anymore. It's not effective enough in stop-and-go traffic in summer.
...WRe

[Atazman]

What a nice presentation for me to look at, WRe!  Appreciate it.

When you said...."It's not effective enough in stop-and-go traffic in summer." are you talking about the original viscous fan clutch & fan or your new electric fan and shroud setup?

[WRe]

Hi Don,
I never had problems with overheating except when it was really hot outside together with a traffic jam on the autobahn and stop-and-go same in the city.
I tried to optimize the original cooling system: flushing the cooling system with citric acid, new visco clutch (more than one, new came already faulty), water pump and thermostat, fan shroud as described, heating by-pass, but nothing really helped. Maybe I should have rebuild the radiator block too.
After that I installed the electric fan instead the visco clutch and this helped. No critical situations with overheating anymore.
In my opinion the visco clutch works not effective in these critical situations because of low revs. Maybe it would work fine if everything is in a good condition but our cars are already 50 years old and need attention.
Hope this helps!
....WRe

[Pawel66]

Which type of electric fan fits our cars? It is an interesting modification.

[Atazman]

Thanks, WRe, for the clarification on what works and what does not.  Like you, I'm having trouble determining if my new viscous clutch is working.  Don't see any difference from the old one in sound or resistance to rotation.  However, I must admit.... I'm not sure I have had the new clutch up to the temperature (144 Deg. F the BBB says) where it should engage.  Right now I have to think either both clutches are bad or both are good.  Not a good situation to be in, since I don't understand how to test each one effectively.  I thought about artificially heating the viscous clutch by soaking it in hot water to see if it has more resistance to rotation.  Still may do that.

Getting the radiator out and tested is next since I have gone through all the steps you have with replacing parts.

[WRe]

Hi,
my electric fan is a Spal suction D414-D385 T=52 / VA18-AP10//C-41A 12V
(see http://www.spalautomotive.com/eng/products/view_axial.aspx?id=VA18-AP10_C-41A).
The problem is not the diameter size of the fan but the height of it. It has to fit between the radiator and the water pump pulley.
It's fixed together with the shroud at the radiator access points (see picture above) with the flexible Spal rackets
(see https://www.rennsportshop.com/de-top-marken-spal-luefter-zubehoer-034-102020-Spal-Befestigungslasche.html).
It's controlled with a Revotec thermo switch with a setting range of 70-120°C.
(see https://www.rennsportshop.com/de-top-marken-spal-luefter-zubehoer-temperaturschalter-EFC32-Revotec-Thermoschalter-einstellbar.html?action_ms=1).
Side-effect of it: You'll save some horsepower (~2-3) from the visco clutch and fan, less sound volume and some say a smoother engine run.
...WRe

[Pawel66]

Thank you!

[Atazman]

I thought I would bring closure to this thread.  All indications suggest I have a "winner". 

After changing the thermostat (lower temperature opening), viscous clutch, 9-blade fan (replacing a 6-blade), replacing a 2-row radiator core with a 3-row core, and installing a fan shroud (fabricated it myself), I test drove the car in stop/go service for close to an hour with A/C running.   Then…. gave it a freeway test drive on a 95 Deg. F. day.  The temperature gauge stayed in between the 180 Deg. mark and the white dot above it.

My shroud does not cover the part of the radiator in front of the battery.  I made the shroud so it can be removed without disturbing anything other than removing the upper radiator hose.  It is a 2-piece design where the bottom is removable, and bolted to the other piece once in place.  I slip it in from the top, bolt it to the radiator in 4 spots and then attach the lower piece using 3 bolts.  Made it from 16-gauge sheet metal and mig welded.

It would have been interesting to test the cooling system with and without the shroud to determine the true benefit.  I’m just telling myself “it can’t hurt”.