Rein BMW Cooling System Parts & Accessories for BMW 3 Series E46 (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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OEM Rein Upper Radiator Hose - E46 M3
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T#:2306
Part#: 11537830716
In Stock
$ 33.99

This product was last offered at the strikethrough price on
05-06-2026

$ 22.99 USD
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$ 22.99 USD
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Replace your cracked or leaking radiator hose to prevent further leaks and potentially catastrophic failure. This hose replaces the Upper radiator hose that connects the thermostat housing to the radiator.

This Upper Radiator Hose fits the following BMWs:
2001-2006 E46 3 Series M3, M3 Convertible

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Rein Radiator Hose - Upper - E46
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T#:379786
Part#: 17127510952
In Stock
$ 25.99

This product was last offered at the strikethrough price on
02-09-2026

$ 24.95 USD
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$ 24.95 USD
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A common source of cooling system failure
BMW M52 M54 Water Pipe
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T#:594294
Part#: 11537502525
In Stock
$ 55.99 USD
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BMW M52 M54 Water Pipe is an essential replacement part designed to ensure long-term reliability and optimal performance for your BMW's cooling system. Engineered to replace cracked or broken coolant pipes, this high-quality water pipe from Turner Motorsport guarantees a perfect fit and dependable service. Investing in this replacement pipe helps prevent overheating and potential engine damage, maintaining your vehicle's performance and longevity.

  • Reliable replacement: Designed to replace cracked or broken coolant pipes for improved engine cooling.
  • Optimal fitment: Engineered to ensure a perfect fit and seamless installation.
  • Durable construction: Built with high-quality materials to withstand engine temperatures and environmental conditions.
  • Preventative maintenance: Helps avoid overheating and potential engine damage by ensuring a reliable coolant flow.
  • Vehicle compatibility: Specifically designed for BMW M52 and M54 engine models.

Upgrade your BMW’s cooling system with the BMW M52 M54 Water Pipe from Turner Motorsport for enhanced reliability and performance.

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Heater Inlet Pipe
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T#:594330
Part#: 11531705210
In Stock
$ 41.99 USD
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This is the plastic heater inlet pipe that connects the cylinder head to the heater inlet on cars with the M52 or M54 engine.The plastic on this hose becomes brittle over time and eventually leads to failure.
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Rein Radiator Hose - Lower - E46
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T#:379779
Part#: 11531436408
In Stock
$ 31.99 USD
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A common source of cooling system failure
OEM Rein Lower Radiator Hose - E46 M3
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T#:2674
Part#: 11537830715
In Stock
$ 23.99 USD
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Replace your cracked or leaking radiator hose to prevent further leaks and potentially catastrophic failure. This hose replaces the lower radiator hose that connects the radiator to the thermostat housing.

This Lower Radiator Hose fits the following BMWs:
2001-2006 E46 3 Series M3, M3 Convertible

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OEM Rein Expansion Tank Hose - E46 3-Series
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T#:363453
Part#: 64218376153
In Stock
$ 82.99

This product was last offered at the strikethrough price on
05-06-2026

$ 34.99 USD
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$ 34.99 USD
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Expansion tank to heater core
E46 M3 Radiator Hose - Upper And Lower
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T#:20617632
Part#: 11537830715KT
In Stock
$ 53.98 USD
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Both thermostat housing hoses to replace your worn out rubber and brittle plastic connections.

Over the years and with exposure to extremely hot coolant, the coolant hoses in your vehicle can take a beating. Being made of reinforced rubber, these hoses can fail in a number of ways. Splitting at a hose clamp, swelling, cracking, and breaking are just a few of the ways this hose can leave you stranded. Replace it at the first sign of wear to keep your coolant in your engine.

Comes with both upper and lower thermostat hoses: 11537830715 Lower + 11537830716 Upper

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Rein Coolant Expansion Tank - E46, E53, E83
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T#:402141
Part#: 17117573781
In Stock
$ 76.39 USD
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$ 76.39 USD
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Includes cap and level sensor

Expansion Tank Mounting Plate
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T#:402140
Part#: 17111436250
In Stock at Vendor
$ 70.99 USD
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$ 70.99 USD
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Water Pipe
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T#:594365
Part#: 11537502000
In Stock
$ 40.09

This product was last offered at the strikethrough price on
01-10-2026

$ 39.99 USD
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$ 39.99 USD
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Water pipes are essential for proper cooling. If they are cracked, they are going to need to be replaced as soon as possible to avoid overheating your engine. This water pipe runs from the back of the water pump housing to the expansion tank hose. Includes all required seals, needed for the install.
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Thermostat With Housing
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T#:582356
Part#: 11537509227
Ships in 3 Business Days
$ 89.99 USD
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$ 89.99 USD
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Stop leaks before they start with this new Thermostat With Housing from Rein.


BMW Radiator Hose Kit - 11531436408
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T#:46719183
Part#: CHK0002
Ships in 3 Business Days
$ 46.99 USD
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Keep your cooling system sealed, strong, and ready for anything with this Rein radiator hose kit—your all-in-one fix for cracked, leaking, or worn factory hoses. Years of heat, pressure, and age can cause rubber to weaken, split, or swell, setting the stage for coolant leaks and potential overheating. Rein hoses are engineered to meet or exceed OEM standards, built from premium, heat-resistant materials that can take on extreme temperatures and system pressures without faltering. Each hose features factory-correct bends, fittings, and diameters for an exact, hassle-free installation—no cutting or forcing required. Whether you’re tackling a full cooling system refresh or chasing down a small coolant leak, this Rein kit provides everything needed to restore confidence and performance under the hood. Why choose this Rein radiator hose kit: Factory-level precision – Direct-fit replacements that deliver OEM-quality reliability. Built to last – Resists cracking, swelling, and chemical damage from daily heat cycling. Confidence restored – Prevents coolant loss, overheating, and on-road breakdowns. All-in-one upgrade – Includes upper and lower hoses for a complete system refresh. If keeping your BMW’s cooling system running tight and trouble-free is the goal, Rein brings the dependable quality and fitment you can count on—engineered to perform just like factory, mile after mile.
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Automatic Transmission Thermostat
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T#:13661147
Part#: 17111437362
Ships on Jul 16, 2026
$ 43.77 USD
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This unit controls the temperature of your automatic transmission fluid
Rein Expansion Tank Mounting Plate - E46, Z4
For vehicles with automatic transmission only
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T#:402139
Part#: 17111436251
Ships in 1 Business Day
$ 80.99 USD
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$ 80.99 USD
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Mounts to the side of the radiator for retaining the expansion tank

Rein Coolant Bleeder Screw CHW1575 - Priced Each
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T#:591955
Part#: 17111712788
In Stock
$ 4.99 USD
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Coolant Bleeder Screw is a critical component for maintaining your BMW’s cooling system. Designed to release trapped air from the coolant lines, this screw ensures efficient coolant flow and prevents overheating. Specifically engineered for BMW models, it enhances the overall performance and longevity of your engine by maintaining proper temperature regulation. Comes with O-Ring.
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Rein Heater Hose - E46 BMW
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T#:362531
Part#: 64218363198
Ships in 3 Business Days
$ 9.58 USD
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Over time, coolant hoses begin to get brittle and are susceptible to cracking and splitting. Replace your cracked or leaking coolant hose to prevent further leaks and potentially catastrophic failure.
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OEM Rein Expansion Tank Cap - BMW E32 E34 E36 E38 E39 E46 & More ...
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T#:340541
Part#: 17111742231
In Stock
$ 17.99 USD
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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.
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Radiator Support Bracket
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T#:14122755
Part#: 17117514402
Special Order: No Guaranteed ETA
$ 8.99 USD
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Mounts to top of radiator bracket, 2 per vehicle.
BMW Radiator Hose Kit - 11537830715
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T#:46719180
Part#: CHK0376R
Back Ordered
$ 43.99 USD
Free Shipping on orders $49 and up
Keep your cooling system sealed, strong, and ready for anything with this Rein radiator hose kit—your all-in-one fix for cracked, leaking, or worn factory hoses. Years of heat, pressure, and age can cause rubber to weaken, split, or swell, setting the stage for coolant leaks and potential overheating. Rein hoses are engineered to meet or exceed OEM standards, built from premium, heat-resistant materials that can take on extreme temperatures and system pressures without faltering. Each hose features factory-correct bends, fittings, and diameters for an exact, hassle-free installation—no cutting or forcing required. Whether you’re tackling a full cooling system refresh or chasing down a small coolant leak, this Rein kit provides everything needed to restore confidence and performance under the hood. Why choose this Rein radiator hose kit: Factory-level precision – Direct-fit replacements that deliver OEM-quality reliability. Built to last – Resists cracking, swelling, and chemical damage from daily heat cycling. Confidence restored – Prevents coolant loss, overheating, and on-road breakdowns. All-in-one upgrade – Includes upper and lower hoses for a complete system refresh. If keeping your BMW’s cooling system running tight and trouble-free is the goal, Rein brings the dependable quality and fitment you can count on—engineered to perform just like factory, mile after mile.
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