Water pump & viscous-fan removal

[Bingbong]

Has anyone with a W113 (on the forum) ever replaced the belt-driven water pump, including the blade & fan clutch, and placed in its stead an electric water pump, electric radiator fan, and electric condenser fan?  It seems there is a lot of parasitic loss associated with these devices, and they can be fairly simply replaced using more modern technology (which can be more precisely controlled, both the when & how much).  It looks like I can run a shorter belt directly to the alternator and be done with the entire belt-driven water pump & mechanical fan assembly.

I've done this on other cars, and was just wondering if there might be a "gotcha" to the 280SL I am unaware of, being a W113 neophyte.

BTW, thanks for having me.  I have owned mostly European cars in my life, thus very strangely, never a German one before  (although I once owned a German motorcycle).  My grandfather though had three W113s in the 1960s & early 1970s when I was a wee lad, so there is a definite "coming home" feeling when I sit in this car.

[Tyler S]

If you were trying to squeeze every last pony out of the engine for racing purposes it might be worth it. Others here have installed pusher fans in front to aid in cooling. You would need to look out for the electrical system though. The charging system is marginal at best and you might find that wiring and charging system would need to be beefed up to handle the extra load.
The "gotcha" would be that the WRD (warm running device) requires coolant flow at all times to accurately adjust your air/fuel mixture. Simply shutting off or slowing down coolant flow with an electric pump because the engine doesnt need it would wreak havoc on your a/f ratio.

[ctaylor738]

I now take care of a collection of hot rods, all of which have giant V8 and V12 engines.  They all have massive thermostatically-controlled electric fans.  I am impressed by how they work, providing air movement when needed at idle and low speed when the engines are hot, but shutting off on the highway and when the engine is warming up.

If authenticity and judging by Jon the Merciless are not a concern, I think a fan mounted behind the radiator is a good solution.  I would keep the mechanical pump, though, for the reasons mentioned.

Tyler is right that you need to upgrade the electrics.  It's not unusual for these fans to be rated at 30 amps and I have seen them pull double that when they start up.

SPAL sells a very slick controller that varies fan speed based on engine temperature, and has a "soft" start-up that reduces current draw.  It uses on-off switching rather than resistance to control the speed.

[Bingbong]

Thanks guys!  I'll leave the OEM water pump in situ and splice the electric pump into the lower radiator hose.  I can wire it to run using the same thermal switch the main electric fan uses. That way at higher temps the electric pump comes on as an "assistant" to ensure adequate coolant flow.

If I wire all three new devices to the battery with dedicated relays and (here's my next question for you, or perhaps the answer is on the forum somewhere) upgrade the alternator to say, a GM 130amp unit (what's the highest output alternator which is a known fit?), would that not address the car's electrical shortcomings?

I was thinking of using a two-phase thermal switch to bring the fans online gradually, but I will look into Taylor's SPAL controller before making a decision.  That might be an even better solution.

Thanks again, Matt

[Tyler S]

Matt, There is a direct fit Bosch 60 amp alternator upgrade available. The 3 pin connector on the back needs to be modified. Another issue is the B+ wiring from the alternator to the fusebox and starter (battery) is only 10 gauge. 10 gauge is only rated for 30 amps. Adding a newer style (GM 2 wire) alternator and you would have to get rid of the voltage regulator on the firewall and rewire the connections so the field circuit and dash bulb work correctly. In either case you should add a circuit breaker or fusible link to prevent a potential meltdown.
Make sure that adding an additional pump wont cause a restriction when its turned off.

[ctaylor738]

WRT to circuit breakers, the marine guys are way ahead.  One of "my" cars had a 30 amp fuse on the fan circuit.  It kept melting.  As part of the re-wiring, I replaced it with a 40-amp unit from Blue Sea.  Good products.

http://www.iboats.com/Blue-Sea-Systems-Series-285-Circuit-Breaker/dm/cart_id.618577431--session_id.338180919--view_id.729805

[Bingbong]

Top info Tyler, it will be put to use.  Taylor, I had a similar experience with the electric fans on a 1980 Triumph TR8.  It got so hot that the wiring had melted and shorted itself out against the metal frame.  All those amps had been routed through the fuse box instead of using a separate relay.  I consulted an electrician and in that instance, as you yourself are now, he advised me to use circuit breakers for each fan.

On the TR8 the designers had also failed to put channels in the frame to run the wiring bundles.  They stood proud and chaffed against the carpeting, etc.  That is something I read much later in a book.  It was to be addressed in the next styling update, but Triumph went under first.

Thank you both for your help.