Radiator – 4H0 121 251 B
Radiator for the Audi A8 (D4) platform, OE number 4H0 121 251 B. Main group 121 sub-group 251 identifies this as a radiator. Revision index B. Cooling capacity and mounting differ between engine variants on the same platform — confirm against your engine code before ordering.
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Technical specifications
| Part Number | 4H0 121 251 B |
| SKU | AUD-4H0121251B |
| Brand | |
| Category | Radiators |
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3–5 business days. Free on orders over $150.
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Order before 2 PM for next business day delivery.
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Return unused parts within 30 days for a full refund.
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Customer reviews
Verified feedback from Audi owners and independent workshops.
4.2
5 reviews
Adrian Novotny
July 8, 2026
Solved my overheating
Second one of these I have bought, this time for the A4 B8.5. I bled it through the proper procedure and it has held level ever since. The core is thicker than the unit it replaced and the fin density is noticeably higher. Result is the coolant level has not moved in four months. Good value against the dealer price.
Daniel Duarte
April 10, 2026
Better core than the original
Replacement for my 2017 Q5 FY 1.8 TFSI. I pressure tested it to 1.4 bar before fitting and it held without a drop. The transmission cooler lines threaded straight in with no adapters. Result is no more creeping temperature when towing.
Hannah Petrov
February 13, 2026
Perfect fit, no modification
Went on my A6 C6 3.0 TFSI V6 at 140k miles. I bled it through the proper procedure and it has held level ever since. I pressure tested it to 1.4 bar before fitting and it held without a drop. Result is the coolant level has not moved in four months.
Bastian Zimmer
December 1, 2025
Straight swap
Second one of these I have bought, this time for the Q5 FY. The plastic feels substantial rather than the brittle stuff that cracks at the neck. Front end off, old one out, this one in over a long Saturday. Result is no more creeping temperature when towing. Would order again without hesitation.
Aisha Mensah
November 10, 2025
Seeped from the end tank
Second one of these I have bought, this time for the RS4 B7. A weep appeared at the end tank seam after a few heat cycles. Disappointing for the price.