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Reliable sealing for critical bolted joints in heavy‑duty vehicles – The OEM Q/YC149-8 Composite Sealing Washer M8 is engineered to provide a permanent, leak‑free seal under bolt heads in engine, transmission, and hydraulic systems. Designed for SINOTRUK Homan trucks, this washer combines a zinc‑plated steel carrier with a vulcanized NBR rubber sealing bead to withstand high pressure and vibration. For guaranteed compatibility and performance, always choose genuine Sinotruk Homan parts.
The Q/YC149-8 composite sealing washer (M8 size) is dimensioned to fit M8 bolts (8 mm thread diameter). It seals reliably at pressures up to 400 bar (5800 psi) and temperatures from -40°C to +150°C, making it ideal for high‑pressure fuel lines, oil cooler connections, and turbo oil feed banjo bolts.
The Q/YC149-8 composite sealing washer M8 is a two‑layer component: an outer toothed steel washer (zinc‑plated) and an inner vulcanized nitrile rubber (NBR) sealing ring. The rubber bead provides flexible, positive sealing that conforms to uneven surfaces, while the steel washer distributes clamping force evenly and prevents extrusion under high torque. This design is far superior to ordinary copper or aluminum crush washers, which can only be used once and are prone to galling on soft aluminum housings.
Unlike traditional flat washers, the Q/YC149-8 eliminates the need for thread sealants or additional gaskets. The rubber sealing lip extends slightly beyond the metal edge; when torqued to 20‑25 Nm (typical M8 specification), the rubber compresses to fill all micro‑gaps, creating a gas‑tight and fluid‑tight seal. This is especially critical for common‑rail fuel systems, where even a single drop of leakage can cause fire hazards or injector malfunction.
The composite design also allows limited reusability (up to 3 times) if removed carefully without damaging the rubber, though a new washer is recommended for every critical joint. The steel portion provides excellent electrical conductivity where required (e.g., grounding connections), and the rubber resists all common engine oils, diesel fuel, biodiesel blends (up to B20), and coolant.
Tested to 400 bar (5800 psi) without leakage. Ideal for fuel injector hold‑down bolts, oil cooler connections, and hydraulic lines.
Steel core prevents extrusion; rubber bead remains elastic even after multiple compressions. Resists oil, fuel, and coolant.
Inner diameter 8.5 mm, outer diameter 16 mm, thickness 1.5 mm. Perfectly fits M8 bolts (clearance fit).
| OEM Number | Q/YC149-8 |
| Product Name | Composite Sealing Washer M8 (Steel/NBR bonded) |
| Brand | SINOTRUK Homan |
| Bolt Size | M8 (8 mm thread diameter) |
| Inner Diameter (ID) | 8.5 mm ±0.1 mm |
| Outer Diameter (OD) | 16.0 mm ±0.2 mm |
| Thickness (nominal) | 1.5 mm ±0.1 mm |
| Material (Carrier) | Zinc‑plated carbon steel (CR4 grade) |
| Material (Seal) | Nitrile rubber (NBR), 70 Shore A |
| Max Sealing Pressure | 400 bar (5800 psi) static / 300 bar dynamic |
| Temperature Range | -40°C to +150°C (-40°F to +302°F) |
| Recommended Torque (M8 bolt) | 20 – 25 Nm (with washer) |
| Media Compatibility | Engine oil, diesel, biodiesel (B20), coolant, water, air |
| Corrosion Protection | Zinc plating (240h salt spray, ASTM B117) |
| Reusability | Limited (up to 3 times if undamaged), replacement recommended each use |
| Typical Applications | Fuel injector clamps, oil cooler banjo bolts, turbo oil feed lines, hydraulic valve covers |
| Compatible Vehicles | SINOTRUK HOWO, A7, T7H, C7H, plus any M8 fastening with sealing requirement |
The Q/YC149-8 composite sealing washer is manufactured using a precision compression molding process that bonds the NBR rubber directly to the steel carrier. The rubber compound is formulated with a proprietary additive package that resists swelling, compression set, and chemical attack. The steel washer is stamped from CR4 steel and then zinc‑plated to prevent corrosion, with a trivalent chromate passivation for environmental compliance.
The geometry of the sealing bead is optimized using finite element analysis to provide a uniform contact pressure of 20‑30 MPa when torqued to 20 Nm. This ensures that even if the bolt is slightly overtightened, the rubber will not extrude past the steel carrier. Conversely, if slightly undertorqued, the rubber still maintains a seal due to its resilience.
Each production lot is 100% inspected for ID, OD, thickness, and rubber adhesion (peel test). Random samples are subjected to a 1000‑hour oil immersion test (125°C in SAE 15W‑40), a 500‑cycle torque test (alternating between 10 Nm and 25 Nm), and a 240‑hour salt spray test. The washer meets the requirements of ISO 898‑2 for fastening components.
The NBR rubber used in the Q/YC149-8 is formulated to resist mineral oils, diesel, and water‑glycol coolants. It retains flexibility down to -40°C and shows no measurable swelling after 1000 hours in hot oil. The zinc plating provides sacrificial protection to the steel core, preventing rust even if the coating is scratched. The plating thickness is 8‑12 microns, and it passes 240 hours of salt spray without red rust.
The bonding between rubber and steel is achieved using a heat‑activated adhesive that withstands 150°C without delamination. Peel strength exceeds 10 N/mm, ensuring the rubber will not separate during installation or removal.
The Q/YC149-8 is a direct replacement for the original composite sealing washer on all SINOTRUK Homan M8 bolted connections. It is also compatible with many other heavy‑duty engines and components that require a high‑pressure seal under an M8 bolt head.
Installation is simple: place the washer over the bolt with the rubber bead facing the component being sealed (normally the bolt head side). Torque the bolt to the manufacturer’s specification (20‑25 Nm for M8 grade 8.8 bolts). Do not reuse a washer that shows rubber cracking or metal deformation. Always clean the sealing surface before installation.
1) Clean both the bolt head seating area and the component surface thoroughly. Remove any old gasket material or thread sealant residue. 2) Inspect the new washer for any visible defects; ensure the rubber bead is intact and centered.
3) Place the washer onto the bolt with the rubber side facing the component (the steel side will contact the bolt head). 4) Hand‑tighten the bolt until the washer contacts the surface, then torque to 20‑25 Nm using a calibrated torque wrench. Avoid lubricating the washer or threads unless specified.
5) After assembly, perform a leak test by pressurizing the system or running the engine. If leakage is observed, re‑torque the bolt to the same specification (do not exceed 28 Nm). 6) Replace any washer that has been removed, even if it appears undamaged – the rubber may have taken a permanent set.
The Q/YC149-8 washer itself requires no maintenance, but it should be replaced every time a joint is disassembled. Common failure signs: oil seepage around the bolt head, hardened or cracked rubber, or a flattened steel carrier (indicating severe over‑torquing).
If a bolt loosens after initial torquing, check that the washer is correctly seated. Overtorquing can extrude the rubber and ruin the seal; undertorquing leaves insufficient compression. Always use a torque wrench and follow the vehicle manufacturer’s specification.
Do not mix different brands of composite washers – dimensional variations can affect sealability. Always use genuine SINOTRUK Homan Q/YC149-8 washers for consistent performance.
The Q/YC149-8 composite sealing washer is manufactured under IATF 16949 and ISO 14001 certified systems. Each batch is 100% inspected for dimensional accuracy (ID, OD, thickness) using vision systems. Random samples are tested for rubber hardness (70 Shore A ±5), tensile strength (≥ 15 MPa), elongation (≥ 300%), compression set (≤ 25% at 100°C), and adhesion peel strength.
Additional validation includes a 2000‑hour hot oil immersion test (125°C, SAE 15W-40), a 500‑cycle thermal shock test (-40°C to +150°C), and a 500,000‑cycle vibration test (20g, 10‑2000 Hz) while pressurized to 300 bar. The washer meets or exceeds the performance requirements of DIN 125 (for steel washers) and ISO 3601 (for rubber seals).
A batch code is ink‑jet printed on the packaging. Counterfeit washers often use plain steel without zinc plating, or rubber that hardens quickly (EPDM instead of NBR). Always buy from authorized distributors and scan the QR code on the box.
A fleet of 600 SINOTRUK HOWO trucks in Indonesia (high humidity, high temperature) experienced chronic fuel leakages at injector hold‑down bolts with ordinary copper washers. After switching to the Q/YC149-8 composite washer, leak‑related breakdowns dropped by 97% over 18 months. The rubber bead compensated for minor surface imperfections without over‑torquing.
Another user – a mining contractor in Chile using T7H trucks – reported that the composite washers eliminated oil seepage from hydraulic valve covers, reducing engine bay fires and unscheduled maintenance. The washers remained leak‑free even after repeated thermal cycles from -10°C to +110°C.
Each genuine Q/YC149-8 composite sealing washer M8 is supplied in a sealed plastic bag in quantities of 10 or 50, packed in a branded SINOTRUK Homan carton. The box includes a QR code for authenticity verification and a batch number. Each individual washer is not marked due to size, but the bag label contains the OEM number.
Counterfeit products often have a shiny zinc finish that flakes off, a rubber bead that is too thin or off‑center, or a stamped “Q/YC149-8” that is poorly legible. The genuine washer has a uniform matt zinc appearance and a perfectly concentric rubber bead. Always scan the QR code before use. Using a fake washer can lead to high‑pressure leaks, engine fires, and voided warranty.
Summary: The SINOTRUK Homan Composite Sealing Washer M8 (OEM Q/YC149-8) delivers reliable, high‑pressure sealing for critical bolted joints. Eliminate leaks and prevent costly downtime – choose this genuine OEM component trusted by fleets and mechanics worldwide.
If you have any questions about our products, services, or anything related to what we offer, please don’t hesitate to leave us a message—our dedicated team is always ready to provide prompt and helpful responses to address your concerns. What’s more, when you become our valued customer, we’re delighted to offer you complimentary catalog services, giving you access to detailed, up-to-date information on our full range of products, specifications, and offerings to help you make informed decisions.
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