Fan clutch

[Blaise]

It appears that my fan clutch is not working.

I did some searching on this site and on google to learn more, but still have a few questions/discussions to share.

When cruising at speeds, my temperatures are fine.

When cruising around town, after a long haul, the temperature creeps up.

When I shut down the hot car and immediately check the fan blade, it spins freely.

I took the fan clutch out and put it in my vice, such that I could spin it. Then I heated it slowly with my torch to see if the resistance changed. I took it up to 300 degrees with zero change in resistance.

I am assuming that it is not working as it should. How do these viscous clutches fail? Does the fluid lose it's thickening properties? Am I testing it incorrectly?

My car does not have a radiator shroud, but I plan to add on.

I am running a stock thermostat.

There are a few ideas that I have regarding this overheating problem:

-check and address the fan clutch
-install a shroud
-install a high flow water pump (I have one)
-convert to a flex fan
-install a lower temperature thermostat

[cpalmer]

Hey Blaise,

Not nearly as mechanically inclined as yourself, but have a 78' and been reading through here for a while and this is what I know.

The best thing to do is do find one from an E28. I'm thinking you saw that in the FAQ. I'm also thinking you flushed out the system already when you got your car, well. You might have the ole' thermal reactor heating issue, the main issue for our cars for high temp problems. Especially a problem cruising around town or after the engine has ran in normal to high temps for a long period of time, after shut off. They're blamed for many cracked heads and BMW had to have a recall on the heads.

On my first long drive from Portland to the Bay, I was taking 101 and went through Ukiah at 100 degrees and the temp gauge was HIGH!!!!! (And my blood pressure..................................)

I flushed the system, new thermostat, put fan shroud back on, bled it, and it's barely ever gone above the mid mark since and did two more trips to the Bay last summer through Redding and the Valley in 100 degrees....no problems at all. It would go up a wee bit when I idle, or a bit more when I turned her off. But still, right by the middle mark for the most part. Never to or past the 3rd quarter mark. It did take a few tries to bleed all the air out. I find that a quirky thing on these cars.

You'll get more from the other guys about the fan clutch itself. Pretty sure I read the fluid does lose it's thickening properties after time.
Sounds like everything your planning on doing will take care of this issue. Initially, I thought a new header was a must for me, but don't even think about it now. Helps I'm in the NW and only deal with weather over 65 2 or 3 months a year. Getting rid of the thermal reactors, or upgrading to an E28 are/is the way to go of course, but mine seems fine.

[Odometergears]

If your car is moving on the hwy, you dont really need a fan anyway. Race cars dont use them because they have plenty of air moving.

When you flush your system, pull the plug below the #6 piston on the exhaust side. You will see it better if you remove the front left wheel. It will drain the block. You might have a lot of sediment in there if you never have done this.

Then, instead of antifreeze, get a bottle of Water Wetter. It's much better. It runs cooler than anitfreeze BUT be careful in the winter. I am not sure about freezing weather. I live in a warmer climate.

Jeff C. nn/va

[Blaise]

Thanks for all of the tips.

I have flushed my system carefully, including the engine block. I used oxalic acid and I still have some crud cutting loose. I will likely do a full flush a few more times just to get it super clean. I was saving my bottle of water wetter for my final fill.

I figured that I needed to know if my fan clutch was the culprit to my overheating trend. So, rather than throw a bunch of cooling tricks at the care, I decided to run the fan fixed.

This morning I devised a way to lock the clutch, such that the stock fan turns with the water pump constantly. I drove the car in the heat for a couple hours and even let it idle in the hot parking lot for about ten minutes.

Here are a few photos of how I locked the clutch:

<table><tr><td align="center"><a href="http://picasaweb.google.com/blaisedesco ... site"><img src="http://lh4.ggpht.com/_UZQuuBHQvx4/TFdLd ... Clutch.jpg" width="160" height="160"></a></td></tr><tr><td><a href="http://picasaweb.google.com/blaisedesco ... bsite">E12 fixed fan clutch</a></td></tr></table>


At speed, the temperature stayed at the lower of the center marks (left). Around town it stayed dead in the middle. Just idling in the parking lot for a longer period than normal, it went to the higher center mark (right).

Based on the initial test, I think that if my fan clutch were operating correctly, all would be well.

I also picked up a fan shroud, but have not installed it.

I do not plan to leave my fan clutch like this, it was just for the experiment. I will run it for a while like this just to make sure. Then I can decide what to do next. I figure that I can either throw down the dollars for a fan clutch (ouch...how long can I expect it to last?), or convert to a flex fan.

The flex fan would cost me about $40 in new parts and I would have to make a small adapter to mount the 5/8" (.0625) centering pin spacer to my .60" centering pin water pump nose. To make sure that it is well centered and balanced.

[GripGreg]

Peeking out from my small shade tree again, I think you also need to install the fan shroud as part of the test. It channels the air flow thru the radiator better than you might think. BMW knew what they were doin'. It helped in my '81. Try it while your fan is fixed to run all the time. I think you'll see a temperature change. Greg

[GripGreg]

Sorry for the double post, but, maybe you should try a thermostat that kicks in on the next step cooler. If you have the one marked 91 degrees, go to 86 or whatever the next step cooler is. Good Luck,,,,Greg

[Blaise]

I added a few photos above of the fan clutch mod.

I agree about the shroud. I will install it and see. I am basically trying to find out if it would stay cool in stock form. So far, it is staying cool with a working fan and no shroud.

As for the thermostat, I don't think it would help me much. My reasoning is that the thermostat is fully open when I have my overheating problem. Having a thermostat of a lower setting would only open the door a little sooner, but my system would still not be able to cool down the coolant mixture enough. Make sense?

It is my understanding that using a lower temp thermostat would only lower the operating temperature of the engine, assuming that the radiator system is able to keep it cool.

[cpalmer]

hey Blaise

Excuse my rants. I can talk better than I can wrench.... I really do wish I had the shop and knowledge you did. You an engineer of some sort? You know BMW.

Anyways, I'm pretty sure if you've cleaned the radiator all out, especially with the acid, and you bleed it correctly and such, your good to go. The last thing on my mind on my E-12 is the cooling system. It goes pretty good. And, I am about to flush it for the first time and 10,000 miles later after 2 years after I go through my brakes the next couple days.

I am interested what happens when you put in the hi flow pump. the fan shroud will make a noticeable difference, couple notches down. On the E28 they seemed to be fine without them, but on the 70's 5ers, it a must. I've seen my temp drop to the quarter mark going down hill from my mountain, but, it does creep past the mid mark when hot. My A/C needs a charge, works though and it only puts the needle up a little bit. I'm surprised about yours. Did it run to the 3/4's mark? My day in Ukiah is was up to the end...close to it before I shut her down.

Thanks for all your persistance and pictures and knowledge. Much appreciated by me and the others I am sure.

You have a German version of the 55-58 Chevy in your hands and are doing it right.

PS-Are you keeping the points or going with Pertronix?

[Blaise]

CPalmer:

Thanks for the input.

In short, I think that I figured out my cooling issue. With the fixed fan, the temperature stays where it should. Maybe I was not clear about it in my description.

At freeway speeds, it looks like this:

<table><tr><td><a href="http://picasaweb.google.com/lh/photo/LI ... site"><img src="http://lh4.ggpht.com/_UZQuuBHQvx4/TFhWU ... r><td>From <a href="http://picasaweb.google.com/blaisedesco ... bsite">E12 temperature</a></td></tr></table>

Cruising around town, it looks like this:

<table><tr><td><a href="http://picasaweb.google.com/lh/photo/yV ... site"><img src="http://lh6.ggpht.com/_UZQuuBHQvx4/TFhWV ... r><td>From <a href="http://picasaweb.google.com/blaisedesco ... bsite">E12 temperature</a></td></tr></table>

And finally, idling in a hot parking lot for ten minutes...this is as high as it would go:

<table><tr><td><a href="http://picasaweb.google.com/lh/photo/yP ... site"><img src="http://lh3.ggpht.com/_UZQuuBHQvx4/TFhWV ... r><td>From <a href="http://picasaweb.google.com/blaisedesco ... bsite">E12 temperature</a></td></tr></table>

So, now I have to assume that with a new fan clutch, my car would stay cool just fine. I just don't know if the viscous fan clutch ever pulls air like a fixed fan, or if it always slips to some degree.

Any good sources for a fan clutch? I am not sure that I like the idea of converting to a flex fan, as I think it will add more drag to the motor.

To answer your question about me, I am an architect and have spent much of my life building. I have been wrenching on and riding motorcycles for years. I know BMW through my motorcycles, but this E12 world is totally new to me. The E12 is much more complicated than my motorcycle, but shares some of the same design concepts.

While I certainly do not consider myself as any kind of expert, I have learned from my mistakes in the past. I now like to approach things systematically and see much value in the diagnostic phase of problem solving. I don't like the idea of throwing parts at a problem. These are man made machines and there is always an answer to a problem.

So far, I have enjoyed my E12 experience and like being a part of this community. With the exception of having sent $35 to a guy who never sent me the parts I bought...grrr.

[GripGreg]

Don't forget the shroud!

[GripGreg]

I just got a response from Matt @ Mitchell. He said he will go online to you today @ 4-4:30 to make arraingements to return your bucks. I had to butt in! Couldn't help it!
Again, add the shroud as a test. You'll like the results.
Oh yeah, I got this trick from this website; when installing the fan or radiator, lay one layer of cardboard box against the radiator for protection. Even if it's a gift box, which is thinner. Good Luck,,,,Greg

[Blaise]

Greg.....THANK YOU for your help.

The shroud is in my trunk...I will try to install it tonight. I have plenty of driving to do tomorrow...so it will be a good test.

Thanks again Greg....that is really cool of you.

[Blaise]

I installed the shroud. It looks nice and just like it belongs there

[GripGreg]

I think anyone on this website would've done the same thing if they had a personal contact with Matt or anyone. I look at this website as family; plus it was just a buncha words in an email. I hope things work out. Keep posting your updates, rants & all .,,,,Greg

[Blaise]

Update...hopefully all of this helps the next guy.

Running the car today with the shroud and the fixed fan. It performs a bit cooler than it did without the shroud. But the pattern is similar.

So, I ordered a new clutch. I hope that this will work as well as the fixed fan. Time will tell.