[Zeitgeist]

I started this exploration in another thread, but encountered some issues and took it in a different direction.

I've never had good luck with the cooling system on this car, especially under load in high temps, so I've been looking for ways to make improvements. Besides, the fan clutches are expensive and sometimes troublesome. I've owned dozens of Euro cars with electric cooling fans and never once had a problem with them. Since I had the Audi setup from a recently stripped car, I thought I'd give that a try, but alas it was too deep . During some interwebs investigation I stumbled upon some discussions amongst Camaro guys who used Ford Taurus fans with BMW temp switches and Volvo control relays. I was intrigued with the simplicity of the setup, so I trudged off to the local Pick a Part. $20 later I returned with the proper temp switch/pigtail, and Volvo 940 fan, shroud, harness and control relay. Turns out that with a little trimming and cleverly placed brackets and rivets, the fan and shroud fit my stock 602 radiator like a glove.

At first I was going to just wire the AC temp and pressure switches through this new fan, but I thought that for now I'd keep stock aux. fan in there as a fail-safe measure. I did remove the shroud though. I added the BMW switch to the position in the water neck where the aux. fan switch sits, and relocated that unit down to the waterpump housing. Here are a few pics:

I've only driven it for a brief errand so far, but it has maintained a constant temperature, even under hard acceleration runs. I stopped off at a convenience store and the fan was still running when I came back to the car after little more than a minute. When I got home the fan stayed running for another 20 seconds after I shut down the engine. I really like this feature.

I'll keep running updates on my experiences with the new cooling system over the next few weeks.

 

[Kajtek1]

What is the fan motor wattage?
I still think the fan is a bandage for other problems you have

 

[crs82]

All the classic Saabs I owned had only electric fans (what with the engines facing backward). I NEVER had one overheat. Temps were always acceptable and I never had to replace a costly factory clutch fan.
Mine always ran for about 30 sec to 1 min. after shutdown as well.

 

[Zeitgeist]

What is the fan motor wattage?
I still think the fan is a bandage for other problems you have

I have a 30 amp breaker in there, like stock Volvo. I also have a 115 amp alternator to handle the increased load.

I agree that I may still have other issues contributing to cooling problems, but that's not the only reason why I wanted to pursue this path. I really like the after-shutdown fan, which can help dissipate heat soak, and assist the AC upon start up afterward. I also just prefer electric fans 'cause they're ruthlessly efficient and very reliable. And I despised the deep fan shroud used on the 602, which makes gaining access to the front of the engine a real bitch--much much worse than a 603. With this setup, the shroud will always stay with the radiator, while the fan motor itself can be lifted straight up and out of the way with the removal of two easy to access screws. If I can get this new cooling system to consistently perform, I'm convinced that this is a worthwhile investment.

 

[Kajtek1]

The 99 E class and later models do have electric fans only. But the newer engines run much cooler. I had E320 parked on 140F desert with AC at full blast and the fan did not come on high.
The fans not turning off with the ignition are often creating the problems when the switch stuck, while I don't see much benefit of running them on after engine shut down.
Adding timer to recirculation pump like MB did in ML would help more in evening down engine hot spots.

 

[Zeitgeist]

I've been discussing after-run aux. cooling pumps with some folks in another venue. Apparently that was an option available on 124s in other markets. Probably not too hard to reverse engineer if one were so inclined.

 

[93SoCal400E]

The way I knew that my fan clutch had become ineffectual was the fact that I was aware of LOUD electric fans more often then when I first bought car.

Dropping $500 on fan clutch +labor got the problem fixed but I realized then that MB had those electric fans (in effect) as a backup if the clutch failed. Might be cheaper to just deal with loud fans all of the time, but it seemed that car ran hotter then.

 

[Kajtek1]

I think this topic is due for some technical facts.
The older engines generate pretty good amount of heat and radiators, especially those run with aftermarket coolants lost their efficiency.
That is why some car need fans for normal driving, some only in extreme conditions.
I drove our W124 with engine fan removed in 100F weather and had no problems, but engine is going to 95C. So would I take this car south to 120-130F weather I likely would need the fan, especially on hills.
Now the clutch can power the fans at several HP. The estimates vary, but 2-5 HP is pretty common estimate.
So will the electric fan at 300W= 1/2 HP help? Yes it will.
Will the 1/2 HP fan cool down the engine in extreme temperatures?
dream on...

 

[Zeitgeist]

The way I knew that my fan clutch had become ineffectual was the fact that I was aware of LOUD electric fans more often then when I first bought car.

Dropping $500 on fan clutch +labor got the problem fixed but I realized then that MB had those electric fans (in effect) as a backup if the clutch failed. Might be cheaper to just deal with loud fans all of the time, but it seemed that car ran hotter then.

I don't think MB designed the aux. fans to push enough CFMs for sufficient primary cooling, whereas the fan I installed is quite large and served as the only cooling source for the donor Volvo. For now I've left the aux. fans in place to serve as a back up during my testing phase. Assuming I've properly matched the CFMs of the fan to this engine, there's no reason to believe that this system won't be as reliable and efficient as the stock clutch system.

Since I've turned up the fuel delivery on my injection pump, I have a hunch that it's generating high EGTs under load, so my heat mitigation strategy will need to include the addition of an intercooler and/or water injection...but that's a topic for another thread.

 

[Bangaway]

Did you put a larger radiator in--apparently the 603 radiator is bigger? I'm would like to put a new radiator in with the clutch, but one that's better.

 

[Zeitgeist]

I was going to use a spare 603 core with the Audi fans, but the Volvo shroud fit the 602 core just perfectly. The interesting thing about this Volvo fan motor is that it appears to have the ability to be attached directly to a stock MB shroud with some fabricated brackets and and a little sheetmetal work. I may try that setup with the 606t in my wagon.

 

[vishvamata]

I reduced my coolant thermostat to about 80C and the fan switch to 84-92C. Never reaches 100C, even in desert driving.

A push-pull fan arrangement, through a plenum to equalize pressure turbulence, is the most effective cooling solution. I have fans on both sides wired to turn on together. A fan directly against the radiator is less effective than with several inches of ducted gap.

A big problem is water pump flow at idle, and poor placement of the thermostat in the system. I can coast downhill at 80MPH, the fans turn on, and the temp rises to well over 110. It also tends to overheat when running in ambient temps under 20C, because the thermostat is on the return side of the radiator, and will not sufficiently open when the engine side coolant gets hot.

 

[Zeitgeist]

So far I'm seeing some impressive steadiness in the temps, especially during and after prolonged full throttle runs up hills on the freeway, which was an issue with the clutch system. Under certain circumstances, like a quick acceleration followed by idling for around 5 mins, I've observed that temps will rise just a tick above 100C and then gradually subside down to operating levels. I'm intrigued with the dynamics between the push/pull fans, so I may reinstall the front shroud.

Another option for folks is to bypass the MB aux. fan controls and run them off the BMW/Volvo combo switch/relay, which is a simpler circuitry and one that would allow post shutdown cooling. I may play around with that option next

 

[Kajtek1]

Fans installed in shrouds can't tell the difference if they are "pulling or pushing"
Good shroud is critical as it is the gaps between blade tips and the shroud where turbulence happens.
Did you had a chance to take a look on MB electric fans installed on 99 and newer models? Those might be direct fit and you will not mix brands on your car.
Running 2 fans in the row will bring the risk that they will work against each other. When one is slower than the other that is.

 

[vishvamata]

Fans installed in shrouds can't tell the difference if they are "pulling or pushing" ... Running 2 fans in the row will bring the risk that they will work against each other. When one is slower than the other that is.

The average person here considers a shroud to automatically include a plenum. A shroud reduces wingtip vortices. The side on which a plenum is placed, IS critical. A properly designed shroud with tight tolerance IS dependent upon pushing or pulling due to foil shape and wing flex.

A fan on each side of a cooler has a lower pressure differential across each fan than other configurations. That means they work more efficiently, move more air, and yield more thermal transfer.

The risk of severly mismatched airflow conductance in a vehicle system is possible, but as likely as getting hit in the head with a meteorite. The air pumping system is neither constant flow nor constant pressure. The greater "risk" to which Kajtek1 refers would be that the existing fan(s) would impede airflow at vehicle speed, which they quite obviously do NOT.

And since Mercedes mixes brands, what is the problem if Mercedes owners do the same?

Returning from theory back to reality...

 

[Zeitgeist]

I haven't taken any long trips yet, but I keep going out of my way to push the cooling system by finding all the long sustained hills around here to introduce heat load stresses. So far I'm really happy with the improvements over the previous clutch setup.

The Volvo relay is made by the same company that makes most of the MB "icecube" relays, and the BMW temp switch is also a familiar brand. I don't recognize manufacturer of the fan motor, but I think it's Italian.

I was doing some measurements on my wagon with the 606 engine. I don't think I can fit any known production puller fans in there, so I'd need to spend big $ on SPAL units. For now I think I'll use a known good Sachs clutch and 606 blade, and then use the Volvo/BMW combo to operate the two 9" SPAL pushers already installed in there. They're both single speed fans, so I'll run a parallel BMW aux. fan resister in there for the low speed, and then a straight circuit for high speed. This emulates what the 2 speed Volvo primary fan does internally.

 

[alia176]

Zeit,

Upon studying the elec schematic, I noticed a manual Hi Lo speed switch. Why is this needed? Or is this built in and only appears to be a separately operable switch?

Secondly, do you have the means of measuring the current pulled by the fan? I was merely curious.

 

[Zeitgeist]

The manual switch is optional, and I didn't add it yet. I do plan on adding the hi/lo LED lights in the dash though.

I don't have an inductive ammeter, so I'm not entirely sure how much it draws. Given the size of the stock wiring and 30amp breaker, I don't think it's too much. It's really interesting to have the fan kick on after shutdown, even though it wasn't running while the engine was on. I'm really pleased with the install.

 

[Kajtek1]

The risk of severly mismatched airflow conductance in a vehicle system is possible, but as likely as getting hit in the head with a meteorite. The air pumping system is neither constant flow nor constant pressure. The greater "risk" to which Kajtek1 refers would be that the existing fan(s) would impede airflow at vehicle speed, which they quite obviously do NOT..

I attended schools in different system, so don't know if that would be 3rd grade, or 5th grade physics in US, but to make it easier to understand, I propose simple experiment.
Get 2 bicycle riders, where first would drive at 3 mph , the other at 5 mph.
Now connected them with long bungee cord and ask to maintain their previous performance.
You should find out pretty easy if the slower rider will help the faster one, or drag him down.

 

[Kajtek1]

It's really interesting to have the fan kick on after shutdown, even though it wasn't running while the engine was on. I'm really pleased with the install.

Where did you install the thermal switch?
It is very normal that after engine shut down, the heat from the back of the engine moves forward and raise temperatures. Same you can observe on outside thermometer, where front bumper probe gets engine heat on parking lot.