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When the engine is hot, and the car is not moving, the fan clutch engages and sucks air. Yes? When you reach a certain air speed it disengages and spins freely. I got a fan clutch out of a p n p that screws on as part of my conversion to the m30b35 and the engine is getting hot at stops and the longer the hotter. And the fan is not blowing air.

Is there some way to fiddle with it to get it to work?

Or other item not to trust at a pnp?

I am no expert here but my understanding is that this fan should spin free when the engine is cold. As it gets warm, the clutch will engage and remain engaged until the engine cools. It is also my understanding that these do not last forever and should be checked when dealing with overheating issues.

Make sure yours spins freely when the engine is cold. Then shut off your engine when hot....and see if the fan is spinning freely or engaged (engine OFF). It should be engaged. Sounds like yours is not.

As a side note, my car was overheating in the same way...but my fan was working correctly. I flushed my system with oxalic acid and all is well....actually running a bit cool. I had to put a stock thermostat back in. Do a search for that thread...there was a bit of discussion on the topic.

Lastly....I am just telling you what I learned in doing some homework....the experts should be along soon

With engine hot it spins like the "wheel" on "Wheel of Fortune".

Unfortunately the E28/E24 (spin-on) version of the fan clutch does not offer the level of mechanical friction that I'd like either. Not sure why they tend to spin loose when they're supposed to tighten up.

Mine works intermittently.

In theory, these are a bi-metallic expansion clutch. A strip of berylium-copper is soldered to mechanical levers on a different metal base which has a different thermal coefficient. We learned in chemistry that thermal expansion is a non-containable force. As it gets hot and pushes, it causes tightening on the spindle shaft. Pretty ingenious concept, . . . if only it worked reliably.

If I push or pull on the nut portion against the housing, I can get the friction to engage. When the car is warm/hot and I turn off the engine, the fan stops very abruptly (as it should). Occationally it will continue to spin 10 times or so. This is not good, and I can tell while in stop-n-go traffic when it's working properly and when it's not.

Rumor: there was once some "shop talk" that a few drops of locktite in the nut seam/joint will add desired friction and prevent the loose running. At the time, RED loc-tite was mentioned because of it's resistance to high temps - but it is so aggressive it may cause permanent fixation of the joint. The BLUE low-grade may not be as robust and flake-out over time.

Another comment regarding cooling (slightly off topic), is our stock radiators are made of brass. The later E28/E24 versions are the more efficient aluminium. Firstfives FAQs has a <a href="http://www.firstfives.org/faq/radiator_ ... pgrade.htm"> RADIATOR UPGRADE </a>article that is pretty useful. I've done this on a previously owned E12. It's not quite as easy as the article seems to show -- but it's not too difficult either.

I will try the loc-tite.

I already have done the radiator upgrade.

I have had cooling issues with this engine and I want to solve them before the m39b35 conversion. This current problem started when I got a smaller water pump pulley off of a 735. In order to install it (to test my theory-smaller diameter more revolutions) I needed the screw on type water pump and clutch. Both failed from the pnp. I thought it would a great way to test. Luckily, the pulley has not failed.

This may be a clueless comment, but would there be a way to fix the fan such that it turns anytime the engine does? Many cars are this way and it works. The car may take longer to reach operating temperature and be a bit less efficient, but that is better than overheating.

Just a thought.

Removing the fan completely and replacing it with an electric fan(s) would be the best alternative. Most or a lot of new cars go this way. I should investigate.

The later type fan clutches aren't the most reliable, I would expect one from P and P to be bad. They work as follows, cold, they seem to lock up. Warm up and they free up and freewheel. When it gets hot, they should lock up, but if they're bad they don't. Test by rolling up a piece of newspaper, warming the car up and seeing if you can stop the fan with the newspaper. IF you can, the clutch is bad, if you can't it's good. That lockup at initial startup can throw you if you aren't expecting it.

With my new M106 engine, I went with the 735 fan blade and a new clutch. Another alternative I learned was to scrap the clutch/fan combo and install an electric fan from an XJ6. They run about $400. I would go with the seven series fan first. It has more fan blades and is the same size in diameter.

Jeff

I'll have to check out the 7-series fan.
More blades (potentially) means more mass-flow.

I'm hesitant about doing the newspaper test.
Unless there are specific paper weights and number of sheets that have been tried, and proven, there is the potential of damaging the plastic fan blades.
Many of these old fans have been operating for more than 20+ years. They may have become somewhat brittle to the point that a wad of 4-sheets of L.A. Times may mow down the blades instead of the other way around.
I think the street slang is to "have it back-fire on you".

The ideal of a properly working fan clutch is to reduce load on the engine, hence saving fuel consumption (and who wouldn't think that's the greatest "Cat's Meow!")

Buddah-fying the clutch such as it becomes ONE with the other parts of the engine has it's compromises. It's certainly reliable, and reliability carries a heavy stick in my decision making. Then there is the loss in fuel economy. No to mention safety that you NO LONGER HAVE.

I like the old style. No problems with three in fifteen years. The new style looks upgrade for profit margin to me, as lots of little things on '81's do. No, not a huge deal, but the little things are there.

And, I've had four fans off. Reasonably cleaning, no thoughts they'd gotten old and brittle entered the process. Maybe not luxo new, but none felt the least prone to bump and crack.

Maybe I'm lucky, clueless. More than a few posts on such things strike me as strange, mysterious maladies that seem to happen, but how escapes me.

John in Simi Valley wrote:I'll have to check out the 7-series fan.
More blades (potentially) means more mass-flow.

I'm hesitant about doing the newspaper test.
Unless there are specific paper weights and number of sheets that have been tried, and proven, there is the potential of damaging the plastic fan blades.
Many of these old fans have been operating for more than 20+ years. They may have become somewhat brittle to the point that a wad of 4-sheets of L.A. Times may mow down the blades instead of the other way around.
I think the street slang is to "have it back-fire on you".

The ideal of a properly working fan clutch is to reduce load on the engine, hence saving fuel consumption (and who wouldn't think that's the greatest "Cat's Meow!")

Buddah-fying the clutch such as it becomes ONE with the other parts of the engine has it's compromises. It's certainly reliable, and reliability carries a heavy stick in my decision making. Then there is the loss in fuel economy. No to mention safety that you NO LONGER HAVE.

Hmmm. What I think of as a 7 series fan is much deeper which would cut more air, but be an inch too deep to fit in. There is a 9 bladed fan used on E28s and later E24s which are probably lighter and quieter and may or may not blow more air than the 8 blade E12s originally came with.

As far as the newspaper test, take a section, roll it up and gradually stick it in there. Unless you get crazy about it the direction of the engine rotation and the pitch of the fan will prevent you from doing damage with out trying. I've done it on an assortment of high mileage (300K+) fans without issue.

The early bolt on clutches are more reliable IMO, but the later ones are cheaper. I do have several early ones if someone wants to buy one, but I'm running a later one as I can't find the brand of water pump I like for the early one.

Yes, about 15-20mm too deep.. There was a 735 fan and clutch at the pnp that looked good. (The same one with the bad water pump) Note that the fan clutch had a larger diameter and three bolts to the fan, did have 11 blades if I remember. This is the same 735 that I got the smaller (I did not measure) pulley from which is now installed with a new fan clutch and water pump! And it is still not cooling the way I want, which is for the needle to stay in one place and not swing from back and forth left to right

I thought of shaving of some of the fan, but decided that would defeat the whole purpose.

XJ6s are all over the yards, so the electric fan upgrade shouldn't be too hard.

On my M535i, I did the later water pump with the later fan clutch since I didn't want to pay $300 for the correct one. I have a correct one now, though, but it's for sale since I already put the other one in.