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Bmw 135Is Engine Coolant Bleeder Screws

Bmw 135Is Engine coolant bleeder screws

Starting at $18.95, AutoBuffy stocks 5 engine coolant bleeder screws from SKP, Dorman, and URO. This small threaded fitting sits at a high point in the cooling system and allows trapped air to escape during a coolant flush or refill. A failed or missing bleeder screw prevents proper bleeding, leaving air pockets that cause overheating, heater core failure, and coolant loss on your Bmw 135Is.

Signs your Bmw 135Is needs a new engine coolant bleeder screw

  • Coolant temperature gauge climbs higher than normal shortly after a coolant flush or refill, indicating an air pocket trapped near the thermostat housing or upper coolant passage
  • Heater output is weak or blows cold despite the engine reaching operating temperature, a classic sign of air blocking flow through the heater core circuit
  • Gurgling or bubbling sounds from the dashboard or under the hood when the engine warms up, caused by air moving through the coolant passages
  • Visible coolant weeping or crusty white residue around the bleeder screw location, signaling a stripped thread, cracked body, or deteriorated sealing washer
  • Coolant reservoir level drops repeatedly without any visible external leak, suggesting air is displacing coolant and causing it to overflow or evaporate through the cap
  • Engine overheats only at idle or low speeds after a coolant service, pointing to incomplete bleeding rather than a pump or thermostat failure

Which engine coolant bleeder screw should you buy for your Bmw 135Is?

The most important factors are thread size and material compatibility — a bleeder screw that does not match the original thread pitch or housing material will strip or corrode quickly. Most Bmw 135Is applications use either a plastic or aluminum housing, so the screw material and sealing method need to match. Some designs include an integrated O-ring or copper sealing washer; others rely on a tapered thread, so confirm which your system uses before ordering.

OE-replacement bleeder screw
Best for
Exact fit with no modification, ideal for daily drivers
What you get
Correct thread pitch, length, and integrated seal matched to the original housing material
Bleeder screw with copper sealing washer
Best for
Aluminum or metal housings where a tapered thread alone may not seal reliably over time
What you get
Reusable metal screw plus a crush washer that creates a leak-free seal without thread sealant
Bleeder screw with O-ring seal
Best for
Plastic thermostat housings and upper radiator hose fittings common on newer vehicles
What you get
Nylon or brass screw with a pre-installed O-ring for a positive, coolant-resistant seal
Bleeder screw kit (multiple sizes)
Best for
Shops or DIYers who service multiple vehicles or are unsure of exact thread spec
What you get
Assorted screws in common metric and SAE sizes, often including sealing washers, covering a wide range of applications

Engine coolant bleeder screws brands we stock for your Bmw 135Is

SKP
2 options · from $18.95
Dorman
2 options · from $19.95
URO
1 option · from $21.95

Replacing the engine coolant bleeder screw on a Bmw 135Is

Easy⏱ 20–45 minutesSocket set or wrench matched to bleeder screw head sizeDrain pan or shop towelsCoolant funnel or refill adapterFlashlight (bleeder location can be hard to see)Fresh coolant for top-off

Let the engine cool completely before removing the bleeder screw to avoid burns and excess coolant spillage. Remove the old screw, inspect the housing thread, install the new screw with its seal washer or O-ring hand-tight then snug — never over-torque into plastic housings. Refill the system, bleed air through the new screw as the engine warms, then verify there are no leaks before driving the Bmw 135Is.

Frequently asked questions

How much does it cost to replace engine coolant bleeder screws on a Bmw 135Is?
Parts start at $18.95 at AutoBuffy. The screw itself is inexpensive, but if the housing thread is stripped the repair cost rises significantly. DIY installation typically takes under 30 minutes and requires only basic hand tools, making this one of the lowest-cost cooling system repairs you can do on a Bmw 135Is.
Can I drive my Bmw 135Is with a leaking or missing coolant bleeder screw?
No. A leaking bleeder screw allows coolant to escape and air to enter the system. Even a small air pocket can cause localized overheating, which risks head gasket damage on a Bmw 135Is. Plug the opening temporarily only if necessary, but replace the screw and bleed the system before extended driving.
How do I bleed the cooling system on a Bmw 135Is using the bleeder screw?
Fill the coolant reservoir to the maximum mark, then crack the bleeder screw open one-quarter to one-half turn with the engine cold. Start the engine and let it warm up with the heater set to maximum heat. Close the screw once a steady stream of coolant — with no air bubbles — flows from the port, then top off the reservoir.
What happens if the coolant bleeder screw thread is stripped on a Bmw 135Is?
A stripped bleeder screw thread prevents a proper seal and will continue to leak regardless of how tight the screw is torqued. Depending on where the thread is located — in a plastic housing or metal casting — the fix is either a thread repair insert, a replacement housing, or an oversized bleeder screw designed for damaged threads.
How often should the coolant bleeder screw be replaced on a Bmw 135Is?
The bleeder screw does not have a fixed replacement interval. Inspect it every time you perform a coolant flush, which is typically every few years or per the manufacturer's recommendation. Replace it if the seal washer or O-ring is cracked, if the head is damaged from over-tightening, or if any seeping is visible around the fitting.
Are coolant bleeder screws vehicle-specific or universal for a Bmw 135Is?
Thread size, length, and sealing method vary by engine family, so fitment matters. Many Bmw 135Is applications use a specific metric thread that differs from other platforms. Always verify the thread diameter, pitch, and housing type — plastic versus metal — before ordering to avoid cross-threading or an incorrect seal that leads to coolant loss.

Shop engine coolant bleeder screws by year for the Bmw 135Is

2013

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