The cylinder head assembly is the top end of the engine that seals the combustion chambers and contains the valve train. A complete cylinder head assembly includes not only the cast head but also all sealing plugs and fasteners. This genuine HOWO cylinder head assembly component kit provides all the necessary plugs and bolts to seal the cylinder head oil galleries and coolant passages. When you choose authentic Howo Parts, you receive a cylinder head assembly sealing set engineered for the MC13 engine.
The screw plug is a threaded plug used to close oil gallery access holes or coolant passages in the cylinder head. Four plugs are supplied, made from zinc-plated steel with a hexagon head. The thread size is M14x1.5, and the plug has a tapered thread that seals without additional sealant. Each plug is installed with a torque of 25 Nm and can be removed for service access. These screw plugs are critical for maintaining oil pressure and preventing external leaks. In the cylinder head assembly, they are located at the ends of the main oil gallery and must be properly torqued to avoid loss of lubrication pressure.
The bowl-shaped plug diameter 25,20 is a cup plug that seals large core holes in the cylinder head casting. Fifteen plugs are supplied, made from low-carbon steel with a black oxide finish. The plug has a diameter of 25mm and a depth of 20mm. It is installed by driving it into a machined bore using a blunt punch. The slight taper creates an interference fit that prevents the plug from loosening under vibration. These plugs seal coolant passages and must be leak-tight to prevent coolant from entering the oil system. In the cylinder head assembly, they are used to close the ends of the water jacket core holes after casting.
The bowl-shaped plug Diameter 32, 30 is a larger cup plug used for main coolant gallery openings. Thirty-eight plugs are supplied, made from deep-draw steel with a phosphate coating. The diameter is 32mm and the depth is 30mm. These plugs are installed in the same manner as the smaller cup plugs, driven into the bore until they seat against a shoulder. The high quantity indicates multiple sealing points on the cylinder head assembly, including the main water transfer ports between the head and block. Proper installation requires a sealant on the outer diameter to ensure zero leakage.
The bowl plug diameter 40,15 is a large cup plug used for the main coolant inlet/outlet passages. Three plugs are supplied, with a diameter of 40mm and a depth of 15mm. These are made from stainless steel to resist corrosion from coolant additives. The shallow depth allows them to sit flush with the head surface. In the cylinder head assembly, these plugs seal the large passages that feed coolant from the block into the head. Because of the high flow area, these plugs must be securely seated and staked in place to prevent blowout under high coolant pressure.
The hexagon bolt with flange Q186 – M8X35 – 8.8 – MAN183 – PHR is a high-strength flange bolt used to attach various components to the cylinder head assembly, such as the fuel injection lines bracket or the rocker shaft pedestal. Fourteen bolts are supplied, each with a thread size of M8, length 35mm, and property class 8.8. The flange head distributes clamping load and eliminates the need for a separate washer. The bolt is zinc plated for corrosion resistance and features a MAN183 marking indicating it meets the MAN quality standard. In the cylinder head assembly, these bolts are used to secure the valve cover, injector clamps, and other peripheral components. The correct torque for these bolts is 18-22 Nm.
Cylinder head assembly – genuine HOWO sealing and fastener kit
| Material Encoding | Name |
|---|---|
| 200V90310-0272 | Screw plug |
| 200V91606-0040 | Bowl-shaped plug diameter 25,20 |
| 200V91606-0036 | Bowl-shaped plug Diameter 32, 30 |
| 200V91606-0090 | Bowl plug diameter 40,15 |
| MQ6-03215-6307 | Hexagon bolt with flange Q186 – M8X35 – 8.8 – MAN183 – PHR |
This cylinder head assembly kit contains all the cup plugs and threaded plugs required to seal every oil and coolant passage in the cylinder head. No need to measure or source individual plugs; everything is included.
The bowl-shaped plugs are manufactured to precise diameters, ensuring an interference fit that will not leak or pop out under pressure. The cylinder head assembly relies on these plugs to maintain coolant and oil integrity.
The hexagon flange bolts carry the MAN183 marking, indicating they meet the stringent quality standards of the original engine manufacturer. This ensures the cylinder head assembly fasteners will not fail under thermal cycling.
All plugs and bolts are zinc plated, phosphate coated, or made from stainless steel. The cylinder head assembly components will resist rust and seizure, making future disassembly easy.
The cylinder head assembly contains complex passages for engine oil and coolant. If any plug leaks, oil may escape externally or coolant may mix with oil, leading to engine failure. The cup plugs are particularly critical because they are installed during manufacturing and are not meant to be removed. Over time, corrosion can cause them to leak. Replacing them during an overhaul with genuine HOWO plugs ensures a leak-free cylinder head assembly. The 38 plugs of size 32×30 seal the main water jacket, while the 15 plugs of size 25×20 seal secondary passages. The large 40×15 plugs seal the main coolant transfer ports.
Before installing cup plugs, clean the bores with a wire brush and apply a thin film of anaerobic sealant to the plug outer diameter. Drive the plug into the bore using a blunt drift of the correct diameter until it seats against the bottom shoulder. For the screw plugs, apply thread sealant and torque to 25 Nm. For the hexagon flange bolts, clean the threads and torque to 20 Nm in a crossing pattern. Always use new plugs and bolts; never reuse old cup plugs as they will have lost their interference fit. The cylinder head assembly will then be ready for valve installation and mounting to the block.
This cylinder head assembly sealing kit is designed for the MC13 engine used in the HOWO MAX 4X2 tractor. The plug sizes are specific to the MC13 cylinder head casting. The kit is not compatible with the MC11 or MC07 engines, which have different plug diameters. Always verify your engine serial number before ordering. The hexagon flange bolts are universal M8 fasteners and can be used on other engine components as well.
Once installed, the cup plugs require no maintenance. However, if the engine overheats, the plugs may loosen due to differential thermal expansion. Inspect for coolant leaks around the plugs during routine service. If a plug leaks, drain the coolant, clean the area, and install a new plug using sealant. The screw plugs can be removed and resealed if they leak. The flange bolts should be retorqued after the first heat cycle.
If coolant appears on the outside of the cylinder head, check the cup plugs for rust or pitting. If oil leaks from the side of the head, the screw plugs may be loose. A leaking bowl plug often leaves a rust stain. To repair, drain the coolant or oil, drive out the old plug, clean the bore, and install a new genuine plug. Do not attempt to reuse an old plug. If the flange bolts are loose, retorque them; if they have stretched, replace them.
Aftermarket cup plugs are often made from soft steel that corrodes quickly or from stainless steel that is too hard to seat properly. Generic screw plugs may have incorrect thread pitch, leading to cross-threading or leaks. The bolts may be class 6.8 instead of 8.8, causing them to stretch. Genuine HOWO cylinder head assembly components are manufactured to the exact specifications of the original engine, using the correct materials and heat treatment. The small additional cost is far outweighed by the cost of engine damage from a coolant leak.
All components are supplied in a recyclable cardboard box with labeled poly bags. The packaging is made from recycled content. The manufacturing facility is ISO 14001 certified. No hazardous substances are used in the production of these parts. The cylinder head assembly kit is environmentally responsible.
This cylinder head assembly sealing kit includes all five line items listed in the parameters table. Individual components can be ordered separately using their material encodings. Authorized HOWO dealers in Nigeria stock these genuine parts. For fleet orders of five or more kits, volume discounts are available. Always provide your engine serial number to confirm compatibility.
Fleet owners who have used this genuine HOWO cylinder head assembly plug and bolt kit report zero post-overhaul leaks. The exact fit of the cup plugs has eliminated the need for rework. The flange bolts have remained tight even after thousands of operating hours. Many operators have standardized on this kit for all cylinder head rebuilds, citing the convenience of having all plugs in one box and the peace of mind that comes with genuine parts.
The kit is shipped in a sturdy cardboard box measuring 30cm x 20cm x 10cm, weight 1.5 kg. Store the kit in a dry indoor area. Do not remove the protective oil from the plugs until installation. The shelf life is five years when stored properly. Protect the cup plugs from deformation by not stacking heavy items on the box.
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