Radiator capacity

[Stork]

Radiator question, I see that the 450 SE/SEL has an expansion tank but the 280 S/SE does not. Is the radiator capacity larger in the 450's? Or is it the the V8 has a greater tendency to run hot?
Since I live in Miami we get around 100 F (37 C) during the summer months, should I think about adding the expansion tank on my 280? Or is this more a factor when at high altitudes?
Robert

[WGB]

I don't know if the V8 cooling system was an advantage or not for a 280 but I do know the original systems were adequate if kept in good condition.

Service what you have and keep your ignition timing correct.

Bill

[jbrasile]

Robert,

280 - 11 liters
V8 - 15 liters

You had mentioned that your 280S came with an expansion tank, 280's do not have them originally. My suggestion would be to bring the car back to original and have your aux fan hooked up so it comes on together with the a/c compressor. This will improve cooling as well as a/c performance in tough conditions while keeping the installation as per the factory.

My old 280S had this setup in Brazil and it never overheated even in 100 plus weather while sitting for hours in chaotic Sao Paulo traffic.

Tks,

Joe

[Stork]

Hello Joe,
Thanks again for the information and all your help! So in theory one can increase the capacity which is good but as you mentioned not necessary unless one is doing some sort of rally racing where that extra can keep things cool in the heat of the race...
My 280S has a made up expansion tank so that is out...
Robert

[calvin streeting]

sort of relevent.. but don't w116's in hot climates, have two fans. One mechanical of engine, and another electric one on the front of rad?

[WGB]

Not all 280's have the electric fan and even if they do have it if it has not been converted it really only comes in very late.

Both cars I have have been converted to H134a and as part of the conversion the electrioc fan is wired up by a relay to also come on when the A-C compressor comes in rather than just coolant and A-C temp sensors.

Bill

[W116-280SEL]

I'm nowhere near the car to have a look at the moment, so this might be a silly question. But...

How easy is it to check that the electric fan is even working at all? Are there are a couple of obvious and reachable terminals there that I can apply 12 V directly to?

[jbrasile]

W116-280SEL

On your receiver/drier there is a pressure switch with two wires plugged into it, just connect them together and the fan should start. The aux fan is activated either by excessive pressure in the a/c system or by the 105C temp switch located on the head.

Joe

[W116-280SEL]

On your receiver/drier there is a pressure switch with two wires plugged into it, just connect them together and the fan should start. The aux fan is activated either by excessive pressure in the a/c system or by the 105C temp switch located on the head.

Hi Joe.

Can you please describe where to find the receiver/drier? What's it look like?

As far as I know the receiver/dryer is an air conditioning component.

- Bill

[jbrasile]

Hi Bill,

The receiver drier is the bottle looking device that sits right in front of the radiator on the driver's side. It is an a/c component and the switch in question is on top of the drier with two wires plugged into it.  The switch starts the aux fan if the pressure in the system increases above 250psi in order to protect the compressor. The extra airflow generated by the aux fan decreases the temperature on the a/c condenser therefore lowering overall pressure.

Hope this helps.

Tks,

Joe

[UTn_boy]

Joe, the switch that turns the electric auxiliary fan on actually closes the circuit according the the temperature in the high side of the a/c system.  In other words, it is a temperature sensitive switch, kind of like the 212 F switch mounted in the head, and not pressure sensitive. 

The pressure sensitive switch, also mounted on the drier, is a low pressure cut out switch only.  It interrupts current to the compressor clutch if the freon leaks out to prevent compressor damage, as the compressor relies on a full system to oil it internally to the fullest capacity.   

The later cars, starting with the last W123, midrange W126 and W107's, and first W124 and W201's, actually had a pressure sensitive switch that would turn the electric auxiliary fan on. 

So, Bill, there are two switches on the drier.  The one you'll need to bridge is the smaller of the two.  Don't bridge the switches wires, bridge the wires that go to it, or the part that comes from the wiring harness.  Make sure your key is turned on or that the engine is running.  If nothing happens, one of two things are wrong.  You have a bad relay, or the fan motor is bad......all the while assuming your wiring hasn't been tampered with and everything else is in check.  Take care, AARON

[jbrasile]

Tks Aaron, I guess my mistake thinking the fan switch on the drier was actually pressure sensitive, I always got that impression from my mechanic, anyway, you learn something new every day... I think I got the wrong idea because he likes to install a high pressure switch in place of the temp one so the fan kicks in based on press and not on temp as you mentioned. I prefer to have the fan start together with the compressor.

Joe

[UTn_boy]

Haha.  No problem, Joe.  I'm the one who really made the mistake thinking the white 6.9 went for $20,000. haha.  It's not a good idea to have the fan running all of the time when the compressor is on because when you are going above 30MPH the fan is useless.  The air going through your grill at speeds is more than enough, but when you have air rushing through your grill from moving while the fan is also running you loose a lot of the cooling effect, and you put much stain on the fan motor.  Top of the day to ya.  AARON

[jbrasile]

Hi Aaron,

I've had the fan mod done on three of my personal cars as well as several client cars without any issues. I do agree that at speed there is more than enough air going through the front grille but in Brazil we see temperatures above 100F with 80% humidity and in cities such as Sao Paulo, traffic is so chaotic that you do need the extra cooling provided by the aux fan.

In the case of my 78 450SEL, I've replaced the fan during the restoration. The green 6.9 is still using the original unit and so far so good.

The other point is that since we must use R134 now and having the aux fan on helps lower the pressure and temp in the condenser which probably offsets a little of the  134's deficiencies when used in these older systems.

Tks,

Joe

[UTn_boy]

Well, I suppose if something proves itself over and over again then go for it. 

So, is it an absolutely mandatory thing that you have to use R134A in Brazil?  I try to stay away from it.  Head pressures do increase using it, and if for some reason the aux fan quits working it is bad news.  I always go back with R-12 if it is in the customers budget.  All of my personal cars get the R-12 treatment.  Our older cars really need a larger capacity condenser to handle the R-134A.  Something that really annoys me is when you buy a new expansion valve it is always calibrated for R-134A.  I have to tweek it to get the correct head pressures for R-12.  If I don't, the cooling efficiency goes down and the air coming out is not too cool.  Aaron