MMX Billet Coolant Expansion Tank Cap 60mm For BMW OE 17117639024 Replacement

Compact Radiator Cap With Pre-Installed OE-Spec Valve

The MMX 60mm billet coolant cap replaces the smaller plastic expansion tank cap used on some BMWs. It suits tanks with the approx. 60mm factory cap, OE part number 17 11 7 639 024, which is marked on the underside of the original. If your car has the larger approx. 90mm cap instead, choose the MMX 90mm billet coolant cap.

Like its bigger sibling, it's a true replacement rather than a cover. The cap is machined from billet aluminium on a 5-axis CNC machine, polished and gloss black anodised, then supplied pre-sealed with an OE-specification valve and internal spring already in place. You don't need to remove anything from your factory cap: just swap one for the other.

The shaped grip gives your fingers plenty to hold, which makes the cap easier to fit and the coolant easier to top up, and the full OE-style internals mean you never have to wonder whether it's tightened properly.

Specifications

• 
  Diameter: approx. 60mm


• 
  Replaces OE part number: 17 11 7 639 024


• 
  Pressure valve: OE-specification valve and internal spring, pre-fitted. MMX don't publish a separate pressure figure; the cap is designed to work at the same pressure as the factory cap.


• 
  Material: billet aluminium, 5-axis CNC machined


• 
  Finish: polished, gloss black anodised

Key Features

• Complete replacement for the smaller BMW expansion tank cap


• Arrives pre-sealed with the OE-spec valve and spring installed


• No need to strip the valve out of your old cap


• CNC machined from billet aluminium


• Deep gloss black anodised finish


• Generous grip area for easy fitting and topping up

What's in the Box?

• 1 x MMX 60mm billet coolant expansion cap with pre-installed valve and spring

Fitment

• BMW models whose factory coolant expansion tank cap carries OE part number 17 11 7 639 024 (approx. 60mm diameter)

MMX don't list this cap by model, so please check the part number and size of your existing cap before ordering.

Which size do I need? BMW fit two sizes of expansion tank cap. The smaller approx. 60mm cap (17 11 7 639 024) is replaced by this MMX cap, and the larger approx. 90mm cap (17 11 7 639 021) is replaced by the MMX 90mm billet coolant cap.

Not suitable for: expansion tanks with the larger approx. 90mm cap, which need the MMX 90mm billet coolant cap.

Installation

Wait until the engine is completely cold. Never open a coolant cap while the system is hot or pressurised, as hot coolant can cause serious burns. Slowly unscrew the factory cap, confirm the part number on its underside, then screw the MMX cap on by hand until it's fully seated. No tools are needed. Check the coolant level and look for any leaks after your next drive.

Upgrade Further

Match it with the MMX billet oil filler cap, the MMX billet fuel cap and the MMX billet air conditioning caps.

How do I tell which size cap my car has?

Look at the underside of your current cap. A roughly 60mm cap marked 17 11 7 639 024 takes this MMX cap. A roughly 90mm cap marked 17 11 7 639 021 needs the MMX 90mm billet coolant cap.

Does it hold the same pressure as the original?

MMX don't quote a separate pressure figure. The cap is fitted with an OE-specification valve and spring, so it's designed to work at the same pressure as the factory cap.

Do I need to transfer anything from the old cap?

No. The MMX cap comes pre-sealed with its own valve and spring, so it's a straight swap.

Is it a cover or a complete cap?

It's a complete cap that screws onto the expansion tank in place of the factory one, not a trim piece that sits over it.

When is it safe to remove the cap?

Only when the engine is cold. The cooling system runs under pressure when hot, and opening it can release scalding coolant.

Is it covered by a warranty?

Yes. The cap is covered against defects in materials and workmanship.