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Details
| Specification | Value |
|---|---|
| Brand | TOPRAN |
| Opening Temperature [°C] | 92 °C |
OE/OEM numbers (3)
Search by this OE number to find compatible parts
- AUDI—04L 121 026AG
- AUDI—04L 121 026N
- AUDI—04L 121 026R
Where this part fits
Original-fit position for OE 04L121026N. The red ring marks where this part installs on the vehicle.
About this product
The TOPRAN Thermostat Housing (638 783) is a professional-grade replacement component engineered for long service life and reliable operation across all conditions your vehicle encounters. The part is built to the following specification: Opening Temperature [°C]: 92 °C, Mounting Type: Carbon, Housing Type: 31, Supplementary Article/Supplementary Info: 22, Supplementary Article/Supplementary Info: 98. Each dimension is checked against the OEM reference to ensure the component seats and functions correctly first time. Verified to fit AUDI models. All compatibility data is cross-checked against the TecDoc database — select your vehicle to confirm the part matches your specific engine and year. This part supersedes original equipment references: 04L 121 026AG, 04L121026AG, 04L 121 026N, 04L121026N and 56 more. Matching these numbers confirms a like-for-like replacement with no loss of function. TOPRAN is a recognised supplier of automotive replacement components to independent workshops and dealer networks across Europe. All parts are sourced from authorised distribution channels and carry full manufacturer traceability — you receive exactly the same component supplied to professional garages and dealer workshops. If fitment or specifications do not match your vehicle, our technical team can help identify the correct alternative — use the vehicle selector or contact us with your VIN for a guaranteed-fit recommendation. Replacing worn components on schedule preserves your vehicle's safety, reliability, and resale value — and aftermarket parts from established brands deliver OEM-equivalent performance at a fraction of the dealer price. Every part is dispatched from our UK warehouse with a 30-day money-back guarantee and free hassle-free returns.
Thermostat Housing buying guide
Why replace this part?
The thermostat housing holds the thermostat and routes coolant between the engine and radiator. Plastic housings are prone to cracking with heat cycling, causing sudden coolant loss and rapid overheating.
Signs you need a replacement
- Coolant leak at the top of the engine near the thermostat
- rapid coolant loss
- white steam from under the bonnet
- engine temperature swings
- puddles of coolant after the engine warms up
When to replace
No fixed interval — plastic housings typically last 80,000–120,000 miles before cracking. Replace at first sign of leakage.
About TOPRAN
TOPRAN, part of the Hans Thomsen Group headquartered in Hamburg, Germany, is a growing independent aftermarket brand focused on providing quality parts at accessible prices. TOPRAN offers a comprehensive range covering engine, cooling, electrical, braking, and body components for European vehicles. All TOPRAN products are manufactured to meet OE specifications and undergo quality testing before distribution. Combining German quality management with competitive pricing, TOPRAN is an excellent choice for cost-conscious motorists and workshops who do not want to compromise on part quality.
Suitable cars
Equivalent products (65)
Show all 65 OE numbers
Thermostat Housing TOPRAN 638 783 — compatible car models
| Car models | AUDI: A4 B8 (8K2), A4 B8 Avant (8K5), A4 B9 (8W2, 8WC), A4 B9 Avant (8W5, 8WD), A5 (8T3), A5 Convertible (F57, F5E), A5 (F53, F5P), A5 Sportback (8TA), A5 Sportback (F5A, F5F), A6 C7 (4G2, 4GC) (+6 more) |
|---|---|
| Engines | 2.0 TDI; 40 TDI; 40 TDI quattro |
| Year of manufacture | 2007-2020 |
| Manufacturer article number (MPN) | 638 783 |
| OE part numbers | 04L 121 026AG, 04L 121 026N, 04L 121 026R |
Compatibility check
Loading vehicle data…
Please wait while we load vehicle compatibility information.Description and what's included
TOPRAN 638783 . Housing material: 112. Housing material: 180. Housing Type: 31. Mounting Type: 8. Opening Temperature [°C]: 92 °C. Supplementary Article/Info 2: 212. Supplementary Article/Info 2: 275. Supplementary Article/Info 2: 43
- 1x Thermostat Housing
Shipping, returns, warranty
Free UK delivery on orders over £99.00. Express and standard shipping available.
- Standard delivery: 2-5 business days
- Express delivery: 1-2 business days
- Free returns within 14 days
- All parts backed by manufacturer warranty
Warranty: 12-month manufacturer warranty on all parts. 14-day money-back guarantee if the part doesn't fit your vehicle.
Frequently Asked Questions
Is this Thermostat Housing compatible with my car?
This Thermostat Housing fits AUDI vehicles. Use the vehicle selector at the top of the page to check exact compatibility — enter your car's make, model, and engine for a confirmed fitment match. All fitment data is verified through TecDoc.
What specifications does this TOPRAN Thermostat Housing have?
This TOPRAN Thermostat Housing has the following specifications: Opening Temperature [°C]: 92 °C; Mounting Type: 8; Housing Type: 31; Supplementary Article/Supplementary Info: 22; Supplementary Article/Supplementary Info: 98; Supplementary Article/Supplementary Info: 14. Check the full specifications table above for complete details.
What OE part numbers does this Thermostat Housing replace?
This Thermostat Housing replaces OE part numbers: 04L 121 026AG, 04L 121 026N, 04L 121 026R. Cross-reference these numbers with your vehicle's original part number to confirm compatibility.
How much does a Thermostat Housing cost?
This TOPRAN Thermostat Housing is available for £56.99. Thermostat Housing prices vary depending on brand, specifications, and vehicle compatibility. TOPRAN parts offer a balance of quality and value, backed by our 14-day money-back guarantee.
How do I know when to replace my Thermostat Housing?
Regular inspection of your Thermostat Housing is recommended as part of routine vehicle maintenance. Watch for changes in performance, unusual noises, or visual signs of wear. Consult your vehicle's owner manual for manufacturer-recommended replacement intervals specific to your make and model.
What tools do I need to replace a Thermostat Housing?
Tools required vary by vehicle make and model. Generally, a basic socket set, screwdrivers, and vehicle-specific tools may be needed. We recommend consulting a workshop manual for your specific vehicle, or having the Thermostat Housing fitted by a professional mechanic.
Can I use this part as a replacement for OE 04L 121 026AG?
Yes, this TOPRAN Thermostat Housing is a direct replacement for OE part number 04L 121 026AG. It is manufactured to meet or exceed original equipment specifications, ensuring proper fitment and performance. All cross-reference data is verified through TecDoc.
Related categories
Common OE numbers for this part
Common original equipment numbers linked to stocked alternatives.
