New cooling fan = faster warmup?

[crosseyedsniper]

I installed a new set of fan blades on my 540i a few days ago. The old one was looking a little shady so I got rid of it. I drove around for most of the winter without one and I think I got a little spoiled. The engine felt a little smoother and it built revs a little quicker too. While I was running the car with the fan removed I would watch the core temp via test 7 on the OBC. At this point I've got a pretty good idea how quickly the engine heats up with no fan. Imagine my surprise when I installed the fan blades and noticed the core temp shooting up much more quickly! It's not overheating but the core temp rises much faster than it did with no cooling fan in place.

Anybody care to hazard a guess as to why this might happen? I didn't drain any coolant from the radiator so it's not a coolant situation. I've watch the temps on both the OBC and the dashboard temp gauge to confirm they are both working. I would think the addition of a cooling fan would decrease the rate the engine warms up.

I know some people on the boards have been running without a cooling fan year round. I'm considering doing that as well but I'm skeptical as temperatures during summer in Wisconsin will break the 90's and can break 100.

[Schitzo]

It's warmer now than it was in the winter. At least I'm sure that is the case in WI.

[crosseyedsniper]

While that is true Schitzo the rate at which the temp rises is much faster. The temperature around here haven't gone up that much in the last few weeks. Just for reference, when I would run to the store for groceries without the fan installed the temps would be hitting the mid 80's on arrival. Now the temps will hit the 80's in less than 2 miles.The temperature outside has gone from an average of low to mid 30's to mid to high 40's. Maybe I'm just being paranoid but with the reputation of these cooling systems and an aluminum engine I prefer to be cautious. Paranoid or not it still seems kind of odd. I still love this freaking car and I still look back at it whenever I walk away.

[rf900rkw]

The extra heat is from the high load of driving that fan.

[crosseyedsniper]

That seems to make sense Randy. I mentioned that the car seemed to have less grunt with the fan in place but I didn't realize that it put that much more load on the engine. I may have to look into an electrical cooling setup. I want that pep back but I don't want to risk warping the heads to get it. To that end, do you have any long term experience running in summer without the cooling fan?

[rf900rkw]

I was joking. Yes, the fan adds load, but not enough to make such a dent in the engine temp curve.


I haven't used a mechanical fan for over 30 years now. Zero problems.

[m5hoot]

The fan only couples to the engine to supply "cooling" when the block gets hot and this is controlled by the fan CLUTCH. The fan CLUTCH will not engage until the car reaches temperature so while you may see your fan blade turning when the car is warming up, you can literally (don't try at home- use a rolled-up newspaper) stop the fan blade when car is cold and your clutch is working properly with your hand. You should check your fan clutch regularly and the recommended way to do this is to start your car, let it idle a few minutes, and then stick a rolled-up newspaper in the fan blades and the fan should stop turning completely. If the fan is hard to stop or can't be stopped while car still not up to temp, replace fan clutch immediately! Also, when car is hot and you accelerate the vehicle to say 40 mph, the fan should also not need to be coupled as the car moving is giving car all the cooling it needs. When you hear fan matching car revs over say 3000 rpm and it sounds like an airplane taking off and your fan turns at say 4000 rpm or more, the plastic fan blades will separate from the hub and cause massive damage-they can and have gone through hoods. Read Fragzem's post along with countless others of fan exploding. Always a destroyed shroud at least, often radiator and hoses and often this PLUS huge dents in hood causing need for replacement. Please don't drive all year without fan. It will use very little HP if fan clutch is operating properly and will help electric fan satisfy AC load properly.

[crosseyedsniper]

Unfortunately the PO already had the fan detonate on him. When I have the fan in place I do keep a close eye(ear?) on it. The fan clutch is fine at the moment.

Randy, it never even crossed my mind that you might have been fooling around. I gotta drink more coffee before I sit down and start reading these threads!

[SpeedsterBek]

Doesn't the T-stat stays closed in while the engine reaches normal operating temperature? That's why you can rule out radiator and the fan out of the equation. Outside temperature is a main factor in your warm up time. How cold is your engine block determines how fast it reaches the normal operating temps.

[topaz540i]

My car takes so long to get to full ktemp that im usually wherever im going to by the time it hits triple digits. Wish it would heat faster. I deleted my mechanical fan and now the electric one just runs more. I noticed it doesnt go to 106c anymore either. It usually only gets to about 101c

[m5hoot]

Doesn't the T-stat stays closed in while the engine reaches normal operating temperature? That's why you can rule out radiator and the fan out of the equation. Outside temperature is a main factor in your warm up time. How cold is your engine block determines how fast it reaches the normal operating temps.

Yes and NO. The thermostat electrically will not open until given the signal, but if the cooling system is able to keep the temperatures low, longer- then the thermostat may not get the signal as quickly as it once did. I don't think the fan has anything to do with it, but I did not think I read the fan clutch was changed although that would be the normal assumption. I would make sure fan clutch is good and then forget about it.

[rf900rkw]

Just to keep things honest, the thermostat is mechanical. It opens-closes-regulates just as the earlier thermostats except it has an electric heater built in so the computer can force a *slightly* earlier opening. Cold start to normal op temp should still be fully mechanical, and thus nothing changed here.

[EricP]

My thought was that the fan clutch was staying engaged before, causing the fan to pull too much air and over-cool the engine during warmup. Now with a new fan clutch, it can let the fan freewheel properly during warmup and let temps get up faster. The difference when I replaced my fan clutch was ABSURD. Throttle response, noise, blah blah.... all insanely better.