Product Description
The TOPRAN Expansion tank cap (103 643) is an original-equipment-quality replacement pressure-control valve seal designed for the engine cooling matrix. Positioned directly onto the coolant expansion tank reservoir, this cap regulates the internal thermal expansion of the engine's coolant. By holding a calibrated atmospheric layout pressure, it raises the boiling point of the water-glycol fluid mix to protect the engine against overheating during prolonged operation. In the event of extreme thermal spikes, its integrated mechanical safety spring valve vents excessive gas layout pressure safely away from the engine bay.
Product Specifications
- Manufacturer: TOPRAN
- Item Number: 103 643
- EAN Number: 1213230000019
- Product Condition: New
- Colour: Blue (Modern technical upgrade over legacy black versions)
- Material: High-grade structural polyamide plastic
- Mounting Type: Threaded Screw Connection
- Thread Type: Internal Thread
- Opening Pressure Rating: 1.2 to 1.3 bar
- Supplementary Information: Equipped pre-installed with an integrated rubber sealing O-ring gasket
Vehicle Compatibility
This universal M45-threaded blue relief cap accommodates an expansive lineage of classic and modern-classic Volkswagen Group (VAG) platforms stretching across the late 1970s up to the early 2000s:
| Car Model | Compatible Engines / Variants | Engine Power (hp / kW) | Year of Manufacture |
|---|---|---|---|
| VW Golf II (19E, 1G1) / Jetta II (19E) | 1.0 / 1.3 / 1.6 / 1.6 D / 1.6 TD / 1.8 / 1.8 GTI / 1.8 GTI 16V | 45 - 139 hp / 33 - 102 kW | 1983 - 1992 |
| Audi 80 (B2, B3, B4) / 100 (C3, C4) | 1.6 / 1.8 / 1.9 TD / 1.9 TDI / 2.0 / 2.3 / 2.6 / 2.8 V6 | 70 - 174 hp / 51 - 128 kW | 1978 - 1996 |
| Audi A4 B5 (8D2, 8D5) / A6 C4 (4A2, 4A5) | 1.6 / 1.8 / 1.8 T / 1.9 TDI / 2.4 / 2.6 / 2.8 | 90 - 193 hp / 66 - 142 kW | 1994 - 2001 |
| Audi A8 (4D2, 4D8) | 2.8 V6 / 2.8 V6 quattro (Early configurations) | 163 - 193 hp / 120 - 142 kW | 1994 - 2002 |
| VW Golf I (17) / Polo (86C) / LT 35 | 1.1 / 1.3 / 1.5 / 1.6 GTI / 2.4 D / 2.4 TD | 40 - 110 hp / 29 - 81 kW | 1974 - 1996 |
⚠️ Critical Technical Evolution Note: Early classic VAG models originally shipped from the factory with a **black expansion tank cap** rated at a lower relief pressure. This **blue structural cap** is the official factory supersede update designed to replace those obsolete black components. It features a superior, modernized relief valve mechanism that prevents early coolant vaporization and splitting failure profiles common on aging round expansion spheres. Always ensure your expansion tank neck matches the screw-type internal thread style.
Original Equipment Manufacturer (OEM) Reference Numbers
This premium expansion reservoir cap serves as a direct cross-reference for the following catalog original production part codes:
- VAG (VW / AUDI / SEAT / SKODA): 443 121 321, 443121321, 171 121 321, 171121321, 171 121 321B, 171121321B, 171 121 321D, 171121321D, 171 121 321F, 171121321F