On orders over $100
100% Money Back on Select Parts
Product images
Product Media
Subaru 1.3 Bar Radiator Cap (Part Number: )
Subaru 1.3 Bar Radiator Cap (Part Number: )
Subaru 1.3 Bar Radiator Cap (Part Number: )
Subaru 1.3 Bar Radiator Cap (Part Number: )
Community Media
Subaru 1.3 Bar Radiator Cap (Part Number: )
Subaru 1.3 Bar Radiator Cap
Read 4 Reviews | 3 Q&As
Part # ST4511355010

In stock! Ships same day
Universal part

Features & Product Details

RallySport Direct proudly carries Genuine Subaru STI components for those of you who want to maintain your vehicle using a proven product.

On this page, you are looking at the Subaru STI 1.3 BAR Radiator Cap.

Here are the details:

  • Higher pressure than stock
  • Raising the pressure in the cooling system raises the boiling temperature to hold in more heat
  • NOTE: Some models have 2 caps one being in the radiator and the other being in the expansion tank-replace both caps to improve cooling efficiency
  • NOTE: Will not fit BRZ/FR-S models
  • Sold individually
  • Specifications

    Brand: STI
    Opening Point: 1.3 Bar
    Mfgr. Warranty: 1 year
    Condition: New Product
    Return Policy:

    RallySport Guarantee - 30 Days

    Items that are covered under the RallySport Guarantee offer a 30 day no questions asked return policy.

    RallySport Guarantee items may be returned within 30 days of the original invoice date and must include all the original parts and contents for a refund.

    The RallySport Guarantee does not apply to products that have been modified, damaged, misused or abused. All returns require an RMA (Return Merchandise Authorization) Number, and freight charges are strictly non-refundable. For more information regarding our freight refund policy, please refer to our return policy page found HERE.



    4 Reviews
    3.8 out of 5 Stars
    5 Stars
    4 Stars
    3 Stars
    2 Stars
    1 Stars
    Customer Photos and Videos
    Subaru 1.3 Bar Radiator Cap ( Part Number: ST4511355010)
    1 of 2 people found the following review helpful
    pay extra for the Pink STi... 5 years ago
    4out of 5stars

    you must not able to find the difference with others...(ie. Cosworth..) but the price double. Worth or not, make your judge. I paid the extra for the pink label and STi...
    Was this review helpful?
    Same as OEM with cheap sticker 7 years ago
    5out of 5stars

    Looks good under the hood but that's it..
    Was this review helpful?
    0 of 1 people found the following review helpful
    High priced 8 years ago
    3out of 5stars

    This was not worth the money I paid. It looks nice under the hood but it is just a sticker on the cap and I'm expecting it to peel of any day now.
    Was this review helpful?
    1 of 2 people found the following review helpful
     11 years ago
    3out of 5stars

    In my opinion not worth $50. all it is is a radiator cap with a pink sti sticker on it that looks like it will fall off. they have atleast used something like a metal or aluminum logo
    Was this review helpful?


    • Q: Why would you...  mmcnutt5 years ago

      need to use two of these? The stock radiator cap is 1.37 bar, so would you just need it for the upper reservoir? Also, why are the stock caps two different pressure settings? I guess I don't understand what this product would do to increase cooling efficiency if the radiator cap is already a higher pressure
      • 0 of 0 people found the following answer helpful

        A:  This cap will be a stock replacement for the radiator on STI models, but will be an upgrade for other Subaru models. STIs come with a higher pressure cap on the radiator than the expansion tank for proper venting. Many people use the same pressure caps for both the radiator and expansion tanks and we have not had any issues reported, but Subaru does put a higher pressure cap on the radiator from the factory.

        Zach G. @ RallySport Direct 5 years ago  
        Was this answer helpful?
      • 2 of 2 people found the following answer helpful

        A:  No reason to replace the radiator side UNLESS you go to a 1.5 Bar on that side and 1.3 Bar on the filler side. It is important to keep the differential between the two 'tanks' to properly move coolant back and forth. FYI per the Subaru on the STi: 0.965 - 1.240 Bar Filler Side operating range of the OEM cap 1.240 - 1.550 Bar Radiator Side operating range of the OEM cap

        PerryStevenM @
        Was this answer helpful?
      • 1 of 1 people found the following answer helpful

        A:  Your thinking is correct mmcnutt. You do NOT need two of these. This cap is to replace the stock 108kPA cap on the upper Fill Tank near the turbo. It is NOT intended to replace the perfectly round 137kPA (1.37 bar) cap on the radiator. The STi cap should not be called a "Radiator Cap", because it does not actually go on the radiator (unless the upper fill tank has been removed). "Why are the stock caps two different pressure settings?" Good question. The cap on the upper tank is the primary regulator of the pressure in the coolant system. It maintains system pressure during normal operating conditions. It has a two way valve, like normal radiator caps, allowing coolant and vapor to bleed into the "overflow" tank when the pressure exceeds 108kPA (or 130kPA with this cap) and then allowing coolant to be siphoned back into the coolant system once the car cools back down. The higher rated cap on the radiator serves as more of a back-up safety relief valve to provide a second pressure release point if the car overheats. I *believe* the valve in the cap on the radiator is one-way only, out to the overflow reservoir, since siphoning can be handled by the cap on the upper fill tank.

        Was this answer helpful?
    • Q: Color of Rubber in the cap  Gasaraki5 years ago

      I've noticed that your in pictures the rubber parts are black. Are there ones that have the blue rubber?
      • 0 of 0 people found the following answer helpful

        A:  I am not aware of an STI cap with blue rubber.

        guest56ad69792a8d256e198b66b5 @
        Was this answer helpful?
    • Q: potential problems??  ctom247 years ago

      Quick question, is it possible that adding more pressure to the stock cooling system will cause an gaskets to fail sooner like the head gasket? Also is it possible that the hoses may blow as well or is it not THAT much of a pressure difference?
      • 1 of 1 people found the following answer helpful

        A:  That is a great question. Increasing the pressure of the cap will increase the pressure of the entire coolant system, but this is almost negligible when talking about the headgaskets due to the incredibly high pressures they deal with during normal operation. We have not noticed any increased failures with the hoses, but if you are using a high mileage stock radiator, you will want to pay close attention to where the plastic top portion meets the aluminum core as that area is already prone to leaking and higher pressures may increase the risk of a leak. If you have already upgraded your radiator, adding higher pressure caps is always ideal as it will effectively raise the boiling point of the fluid in the system, thus preventing any boil-overs on the street and track.

        Rick C. @ RallySport Direct 7 years ago  
        Was this answer helpful?

    This Part Fits

    Universal Product
    This item is non application specific.
    Please verify compatibility before purchase. May require some modification for proper installation.