I was pretty surprised when I learned there is no block heater option on the E60 / E61 BMW 5 Series - these engines use a wide temperature range synthetic oil to keep the viscosity of the motor oil low even in very low temperatures. Nonetheless, after a cold overnight soak at -20 C / -5 F means that the engine will crank for 3 or 4 seconds before the oil pressure builds and the engine fires.
Ultimately it was the known issue with these cars of difficulty producing heat in cold temperatures that pushed me to do something about engine block heating. When I leave the car outside overnight in very cold temperatures, I want it to fire quickly, use the least amount of energy possible from the battery to help prevent the electrical system from going into a preservation mode and shedding non-essential loads - in this case - the ventilation fan motor. See my other post here regarding the ventilation system not producing heat.
Canadian Tire sells an engine heater that sticks onto the oil pan and sends its heat directly into the motor oil, call the Polar Pad. I originally purchased the 250 Watt model, with approximate dimensions of 5.2 inches by 3.5 inches, shown below:
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| Polar Pad Model CP512 250W Engine Heater Kit - The self adhesive heat pad, sandpaper, silicone aluminum sealant, and a few zip ties. |
The next step in the process was to find a place to install the heating pad. The E60 / E61 5 Series BMW has underbody aerodynamic covers just about everywhere under the car, except in proximity of the exhaust, fuel tank and rear suspension. In order to get access to the oil pan, the car has to be jacked, placed on jack stands, and then the front and front center underbody pads removed. This isn't too difficult to do, but you do need to get the car in the air. Of course - if you attempt to put the car up on jack stands - make sure you know what your doing, and that you double check the stability of the car on the jack stands. Whenever I work under the car - I'll normally put a second pair of jack stands close to where I'm working for a bit of extra safety.
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| There is a jacking point directly underneath the engine on the main crossmember - which protrudes through a hole in the underbody cover - it's very easy to find, and solid enough for jacking. |
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| Jacking the E60 / E61 directly under the motor on the engine crossmember jacking point. |
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| Once the car is in the air, on jack stands, this is the view of the underside of the engine from the front. Note there is an aluminum skidplate / stiffening plate underneath the engine oil pan behind the main crossmember / sway bar that will need to be removed in order to give good access to the oil pan. It is held on with 6 8mm bolts - an air impact makes this an easy removal. |
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| Underbody cover from directly underneath engine. Note oil crud and salt. This cleaned up fairly nicely with some comet and a floor broom. |
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| Aluminum skidplate / stiffener plate from underneath engine / oil pan. |
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| Selected mounting location for the polar pad engine heater. In the photo, just behind the sway bar is the steering mechanism. Just behind the steering mechanism is the oil pan - note the drain plug. The oil pan is pretty complicated with the front differential on the X drive model on the righ, and the driveshaft for the right front wheel runs through the oil pan. The only suitable flat surface is vertical between the steering rack and the oil drain plug. |
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| Comet and some water cleans up the skid plate / stiffening plate quite nicely. |
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| Setting out the underbody covers to drip dry following cleaning. |
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| Underbody covers - cleaned. |
When I went to fit the 250W polar pad, I found it was too large for the only available flat space. Back to the auto parts store for the 125W model, which is about half the size of the 250W model.
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| Packaging for the 125W and 250W models of the Polar Pad. |
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| 125W and 250W Polar Pad sizes compared. |
Now, with the correct size Polar Pad - installation is fairly straightforward. Sand down the mounting location to smooth metal, remove any paint or oxidation.
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| Mounting location sanded down, ready for application of the Polar Pad |
With the mounting location ready, I used a heat gun to heat up the metal surface of the oil pan, and followed the instructions to heat the polar pad for 15 seconds by plugging it in, then removing the protective backing and applying it to the oil pan.
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| Polar Pad stuck into place with its adhesive backing. |
The next step is to seal around the edges of the polar pad with the supplied silicone aluminum high temperature sealant.
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| Edges sealed with high temperature sealant. |
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| Polar Pad intstalled. |
With the polar pad installed, the sealant is left to harden while the electrical cable is routed. I decided to run an extension cord to the back of the car, into the trunk next to the battery, so that my connections for my trickle charger, battery warming blanket and engine heater are all in one place.
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| Zip tying the electrical cables to the underframe. Careful not to route the cables where it will interfere with the skid plate once replaced. |
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| I ran the extension cord to the back of the car alongside the positive battery cable. This way I was sure that I was far enough away from the exhaust not to worry about melting the cable. |
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| The junction between the cord of the Polar Pad and the extension cord. I coated the connection in silicone electrical insulating compound before taping the connection with electrical tape, to ensure no water would be able to enter the plugged joint. |
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| Taping the extionsion cord connection between the extension cord and the Polar Pad.This connection is then zip tied to the bottom of the frame. |
Once I got to the gas tank along the factory battery cable routing, the battery cable runs up underneath the gas tank, and then underneath the rear suspension. I found it impractical to try to run the extension between the gas tank and the body floor, so instead there was a good route along the top of the suspension brace that runs underneath the gas tank. From the rear side of the gas tank, there is a good route to meet up with the battery cable again and run between the rear suspension and the body. Before getting too close to the exhaust, I ran the extension back into the trunk where the battery cable runs. Note this a wagon, I can't tell you if the sedan is similar or not.
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| Cable runs into the trunk, next to where the battery cable runs into the trunk. Cable runs through a grommet to protect the cable from vibration and wear. |
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| Note the extension cable in yellow, running into the trunk next to the battery cable. |
Once at the back of the car - the cable meets up above the battery for simple connection with the battery warming blanket and the trickle charger.
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| Electrical cables in the storage compartment above the battery, ready for connection. |
Conclusion
So - how does the Polar Pad engine heater work? In a word - brilliant. -20 C / -5 F starts are just like they are in normal warm weather, the engine cranks much quicker, and fires in a second or two. Much less work for the starter. The ventilation fan in Auto mode starts blowing air in about 2 or 3 minutes after pulling away - which seems to be a big improvement. This work took the better part of a Saturday, but now I'm happy it's done and hope this will pay off in reduced engine wear and longer life for the car. If you have any questions - just leave a comment below and I'll try to get back to you quickly.
Sources and Links
I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions.
