BMW Cooling System Parts & Accessories for BMW E46 M3 S54 (1999-2005)

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The cooling system is arguably the weakest point in numerous BMWs. If you drive an aging BMW or plan on taking your car to the track like we do, we recommend beefing up your cooling system before going to the track. Generally, the main components in your cooling system that are prone to failure include the following: expansion tank, factory hoses, water pump, thermostat, fan (especially if your vehicle comes factory with a clutch fan), and radiator. Factory BMW expansion tanks are plastic and prone to either breaking off at connection points or combusting. As factory rubber hoses age they either crack or break over time - we offer silicone cooling hose upgrades for most applications to avoid future failures. If you have an older vehicle, your water pump likely comes from the factory with a plastic impeller - we offer upgraded water pumps with metal impellers that are far more reliable. Newer model BMWs utilize electric water pumps - BMW spent millions of dollars engineering these water pumps, but they fail so often that we recommend replacing at 60,000 mile service intervals to avoid being stranded on the side of the road. In terms of thermostats, we offer various upgraded thermostats for racing applications. If your BMW utilizes a clutch fan from the factory, we have several options available in terms of universal electric fans - we recommend replacing these to avoid sending brittle plastic fan blades through your hood. For radiators, we recommend swapping out your radiator for one that does not use plastic connection points like your factory radiator.

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DO88 - Corporate Logo
T#:13891842
Part#: OC150
Ships on Sep 23, 2026
$ 749.99 USD
Free Shipping on orders $49 and up
With a 185% bigger core volume, 50% bigger cooling area, and a 79% higher oil volume, this oil cooler compensates on no fronts. Built for the track but just as capable on the road, DO88's upgraded oil cooler for the E46 M3 gives you maximum performance and compromises nowhere.
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DO88 - Corporate Logo
T#:13891851
Part#: OC120E46
In Stock
$ 646.99 USD
Free Shipping on orders $49 and up
This racing oil cooler shines in low-pressure situations, for example, power steering oil cooling or gearbox oil cooling. This oil cooler comes ready to install with hardware.
DO88 - Corporate Logo
T#:13891809
Part#: WC310S
Ships on Sep 23, 2026
$ 735.99 USD
$ 735.99 USD
The team at DO88 has vigorously tested this radiator to deliver peak performance with the peace of mind of quality for your E46 M3. They guarantee reliability and endurance in all situations to let your car breathe better than before! Boasting a 17% increase in core volume, this upgrade is a no-brainer for petrol heads like us. Keeping core temperatures low eliminates the risk of heat soak leading to overheating giving you max performance at any given moment. no compromise has been made at DO88 leaving you with one of the best radiator options on the market!
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DO88 - Corporate Logo
T#:13924829
Part#: DO88KIT70S
Ships on Sep 23, 2026
$ 256.99 USD
Free Shipping on orders $49 and up
Made out of high-quality silicone, these hoses display the highest levels of durability and quality. With three to five layers of armory the hoses are designed to withstand high pressure and heat for an extended period of time. The OE hoses are known to crack and leak but this hose kit eliminates any chance of that.
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DO88 - Corporate Logo
T#:13891810
Part#: WC310R
Ships on Sep 23, 2026
$ 735.99 USD
$ 735.99 USD
The team at DO88 has vigorously tested this radiator to deliver peak performance with the peace of mind of quality for your E46 M3. They guarantee reliability and endurance in all situations to let your car breathe better than before! Boasting a 17% increase in core volume, this upgrade is a no-brainer for petrol heads like us. Keeping core temperatures low eliminates the risk of heat soak leading to overheating giving you max performance at any given moment. no compromise has been made at DO88 leaving you with one of the best radiator options on the market!
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Bavarian Autosport - Corporate Logo
T#:640208
Part#: 17117639022
In Stock
Sale - Save 15% $ 13.99

This product was last offered at the strikethrough price on
06-03-2026

$ 11.89 USD
Free Shipping on orders $49 and up
Sale - Save 15%
$ 13.99

This product was last offered at the strikethrough price on
06-03-2026

$ 11.89 USD
Free Shipping on orders $49 and up
This radiator expansion tank cap is used most BMW's from 1991-2006. It is a common failure item. When this item fails, it cannot hold pressure which results in your BMW overheating. If you are overhauling your coolant system, now is the time to consider preventative replacing this cap. It is also referred to as the coolant reservoir cap. From 1974 to 2019, Bavarian Autosport was one of the premier vendors for BMW and MINI auto parts. We are happy to preserve the Bav Auto legacy by continuing to carry their high-quality products into the future. All Bav Auto parts will remain unchanged in design and sourced from the same OEM suppliers to ensure long-lasting reliability. We trust these parts, accessories, and upgrades so confidently that we back every Bavarian Autosport branded component with a 2-year warranty.
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DO88 - Corporate Logo
T#:13891811
Part#: WC310B
Ships on Sep 23, 2026
$ 735.99 USD
$ 735.99 USD
The team at DO88 has vigorously tested this radiator to deliver peak performance with the peace of mind of quality for your E46 M3. They guarantee reliability and endurance in all situations to let your car breathe better than before! Boasting a 17% increase in core volume, this upgrade is a no-brainer for petrol heads like us. Keeping core temperatures low eliminates the risk of heat soak leading to overheating giving you max performance at any given moment. no compromise has been made at DO88 leaving you with one of the best radiator options on the market!
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Bav Auto Temperature Sensor - BMW E39 E46 E9X E60 F01/02
10X Entries Into Our F80 M3 Sweepstakes
Bavarian Autosport - Corporate Logo
T#:639833
Part#: 13621433076
In Stock
Sale - Save 20% $ 14.99

This product was last offered at the strikethrough price on
05-03-2026

$ 11.99 USD
Free Shipping on orders $49 and up
Sale - Save 20%
$ 14.99

This product was last offered at the strikethrough price on
05-03-2026

$ 11.99 USD
Free Shipping on orders $49 and up
This is the coolant temperature sensor used in many BMW models from the late-1990s to the mid-2010s. The engine computer relies on the coolant temp to set the fuel mapping for the engine. As the car warms up the computer changes the fuel mixture. If your car is running a bit rich (too much fuel) it could be because this sensor is failing and not sending the correct info to the computer. This sensor is located in a variety of places depending on the engine. But it's one of those easy replacement items 'while you're in there' when doing a water pump or thermostat replacement. From 1974 to 2019, Bavarian Autosport was one of the premier vendors for BMW and MINI auto parts. We are happy to preserve the Bav Auto legacy by continuing to carry their high-quality products into the future. All Bav Auto parts will remain unchanged in design and sourced from the same OEM suppliers to ensure long-lasting reliability. We trust these parts, accessories, and upgrades so confidently that we back every Bavarian Autosport branded component with a 2-year warranty.
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DO88 - Corporate Logo
T#:13924830
Part#: DO88KIT70B
Back Ordered
$ 256.99 USD
Free Shipping on orders $49 and up
Made out of high-quality silicone, these hoses display the highest levels of durability and quality. With three to five layers of armory the hoses are designed to withstand high pressure and heat for an extended period of time. The OE hoses are known to crack and leak but this hose kit eliminates any chance of that.
Show More Show Less