Radiator fan switch

[Jeffy]

I have a 180 degree F thermostat in my '02 MC, but during the hot months the engine stays at 180 for only a few seconds while it continues to heat it's way up to some much higher temp(I have only the stock temp indicator, which never reads past half way up the un graduated scale, though I don't believe the gage). During cooler times, when ambient air temp is below 90F, the gage shows approx. 1/4 way up the scale, so this is how I know it's running hotter than I want. It has never over heated, but I would like it to run the 180F. So, finally I get to the question: How can I get the radiator fan to start pulling in air at a lower temp? I have always had good results running engines at 180degrees F- They give better performance, last longer, no matter what vehicle these engines powered. Here in south Texas, it seems that original equipment radiators are too low capacity to deal with the high ambient temps in this region. Any tips to lower my temp? -Jeffy.

[k-huevo]

The MINI’s cooling system was designed to keep operating temps around 200 – 215F; this is the optimum temp range for power and efficiency as designed; one of the reasons for the stock 195F coolant thermostat, to reach target temp quickly. Sorry, but long term lower temps are not healthy for this motor, for example, accumulated condensation in the oil/crankcase will not be driven off until 212F+. My OEM thermostat starts to open <190F when tested in heated water and as measured via the OBDII. Rarely do coolant temps reach 220F+ in my FI engine and only for peak transients, so nothing to fear.

There are larger capacity radiators available, but they are in their element in extreme road racing conditions which are much harsher than 100F + ambient and street use. The standard slat grill on the bonnet has shown flow diversion at speeds above 85mph, if you spend any amount of time at that speed, some flow improvement can be had with the mesh aero grill and better yet, remove it all together. Also, be sure the license plate isn't mounted to high or low where it would obstruct flow to the radiator.

[Jeffy]

I'd like to ask more questions. So, the engine holds condensation. What harm would this cause? Also, I should explain why I want it cooler: the cyl. head ports will heat the intake charge more when hotter, resulting in less oxygen per unit volume and, since my engine is not force induction equipped, I need as much 02 as I can get. What other problems would I cause by running the temp at 180F? I want you to know that this is not disagreement, but more of a quest for more knowledge. If you will suffer my questions, I will certainly appreciate it! -Jeffy.

[Jeffy]

I thought about what you said about condensation more, and realised that it means the ventilation is inadequate. Hot-rodders with modified muscle cars use a belt driven pump to remove these gasses and on hi-perf motorcycles they use a check valved tube leading to the exhaust to draw out crank case gas. I like the exhaust tube method best. Eliminating gas inside of the crank case would improve efficiency by itself- I wonder if an exhaust tube adapter is for sale, anywhere. -Jeffy.

[k-huevo]

Water is non-compressible and has limited lubrication capabilities; because oil and water don’t mix, moisture will displace valuable protective films needed on start up. From what I know about your commute, there is enough time to attain operating temps needed for removing moisture. For an engine used only on short trips, in cool weather, combined with an earlier opening coolant thermostat, milkshake/mustard/snot oil would be more likely seen.

Our engines have two case vents which function well for its displacement and rpm range, as long as the PCV is healthy.

The intake ports (IM included) will impart little heat to the incoming air charge; negative pressure in the combustion chamber combined with atmospheric on the intake side moves air fast enough to avoid major heat transfer. Extracting air from outside the engine compartment is the best low temp measure you could plan for, and the OEM engineers have already done that.

[Jeffy]

I see that it is right behind the center grill brace. My car is a non-S, so, no hood scoop. Is there a better place to take in outside air than the original? The engine room is tiny and jammed full. I did use the M7 type exhaust header cover to reduce heat under the hood- it really works. Before, I could feel the heat radiate off of the stock heat shield and would have burned my hand to touch it while the engine was running. This cover does not radiate heat, but insulates it- I can touch it with the engine running. Props to the engineer of this device! I appreciate you taking the time to answer my questions- it's enjoyable to talk to someone who really understands how it all works(or could work better). -Jeffy.

[k-huevo]

There are things I’ve left unstated and need clarification, I mixed coolant temp info and oil temp outcomes without delineating between the two. It is oil temperature which will determine whether moisture is driven off or not. Oil temps continue to rise once optimum coolant temp is reached and is the reason why oil can be hot enough to create steam even though coolant is running 200F or less. With the vehicle in motion, coolant temps hover around 200F on the street, even on 100F days.

A thermal blanket will insulate but it can obstruct extraction of engine compartment heat. There is a low pressure area under the vehicle while the vehicle is moving, which encourages flow through the radiator, across the motor, and over/around the exhaust manifold, and out of the engine compartment. I also wonder if a blanket may accelerate degradation of header material in the same way exhaust wrap does because it is not bonded to the metal’s substrate.

The only downside I see on the Cooper’s center intake air inlet is the possibility of water ingress. When the front of the Cooper plows through a water puddle, water goes straight up over the grill. Having disassembled a hydrolock damaged Cooper motor I know what can happen first hand. Other than that possibility which can be avoided with cautionary driving behavior, I think it is a great location of an air inlet, although I think the right angled air path after the inlet is perhaps inefficient.

[Jeffy]

So dis-similar metal corrosion is not an issue. The insulator I'm talking about goes over the heat shield, only contacting the factory heat shield, which seems to be stainless steel, so corrosion-resistant. Most cold air intakes I've seen on cars of any brand take into account the possibility of rain or puddled water induction- usually baffle and drain methods. I still have the stock CAI, but not on the car, because it was too restrictive to air flow, proven by improved accelleration times after changing to a "more air" intake. I'm also concerned with ignition timing and a hotter cylinder head may cause pre-ignition sooner, causing the knock sensor to kick in and retard the timing, reducing power while preventing knock. I wonder if anyone testing flow dynamics through the radiator ever tried running the cooling fan to see if it's assistance drawing air would improve flow, even while on the highway. I can understand why airflow through the radiator is not optimal- there's no space between the engine and the radiator, so air builds up in the engine room before finally exiting(in theory, I can't prove it). I'm still listening if you're still willing to suffer me, it's good stuff. -Jeffy.

[Jeffy]

I installed this switch to determine if running the fan would result in cooler coolant temps- even on the highway, since my '02 has so little air intake area, and found that it does, even on a 97F degree day. My MC has more zip when the coolant temp is lower(I have a 180F thermostat installed). If I leave the overide in "off" position, the radiator fan will run as normal. I have the original coolant temp indicator, so I can't report exact temp readings. I would like to install a degreed indicator and wonder if I have to replace the original sending unit. Would the original temp sensor need to be replaced to get an accurate reading on a degreed indicator? -Jeffy.