Diesel engine Nissan TD27T - a legendary unit installed on Nissan Terrano II (R20) and other models Patrol/Pathfinder 90s. Despite its reliability, this motor requires regular maintenance, and one of the critical procedures is adjusting valve thermal clearances. Missing the regulations is fraught with knocking under the valve cover, a drop in power and even burnout of the seats.

Unlike gasoline analogues, diesel TD27T has its own characteristics: a different adjustment order, specific clearances and dependence on engine temperature. In this article we will analyze step-by-step algorithm taking into account typical errors, detailed diagrams and recommendations for tools. We will also answer the question why, after adjustment, the valves may knock again after 1000 km.

When is valve adjustment needed on a TD27T?

The manufacturer recommends checking the clearances every 20–30 thousand km, but in practice the interval depends on operating conditions. For example, when driving on gas or frequently overheating, the valves “shrink” faster. The need for adjustment is indicated by:

  • 🔊 Metallic knock in the upper part of the engine when cold (disappears after warming up - a classic symptom of increased clearances).
  • ⚠️ Power drop and “dullness” of the engine at low speeds (may indicate “clamped” valves).
  • 💨 Black smoke from the exhaust pipe (over-rich mixture due to incorrect valve timing).
  • 🔥 Engine overheating for no apparent reason (thermal conditions are disrupted due to poor valve fit).

Feature TD27T: valve knocking is often confused with operation injection pump or piezo injectors. To differentiate the problem, use phonendoscope or a long screwdriver (apply to the valve cover and the handle to your ear). The knocking of the valves will be clearly audible in time with the operation of the camshaft.

⚠️ Attention: If the engine has already overheated, valve adjustment must be combined with checking block head geometry. Deformation of the cylinder head plane leads to uneven wear and “losing” of the gaps even after adjustment.

Preparation: tools and materials

To work, you will need a specialized tool. Do not try to make do with “improvised” keys - this can lead to the edges of the adjusting bolts being torn off. Minimum set:

Tool/material Purpose Note
Stylus type (0.10–0.30 mm) Measuring gaps It's better to take flat probes, and not wire ones - they are more accurate.
Adjustment bolt wrench (10 mm) Loosening/tightening bolts A specialized wrench with a slot for a lock nut.
13 mm socket wrench Crankshaft rotation Preferably with an extension cord for convenience.
Torque wrench Torque control Required for lock nuts (torque - 12–14 Nm).
Sealant Loctite 574 or similar Fixing the adjusting bolts Prevents self-loosening due to vibrations.

Additionally prepare:

  • 🧴 Carburetor Cleaner (for washing the valve cover and rockers).
  • 🔧 Head set to remove the cylinder head cover.
  • 📏 Micrometer (if you plan to check the wear of the rockers).
📊 How often do you adjust the valves on the TD27T?
  • Every 20 thousand km
  • Only when they knock
  • Never regulated
  • I only trust service stations

Procedure for adjusting TD27T valves: step-by-step instructions

The procedure is performed on cold engine (temperature not higher than 20°C). If the engine is warm, wait at least 4-5 hours to cool down - the metal should return to its original dimensions. Algorithm:

  1. Remove the valve cover. Unscrew the 8 bolts (the tightening torque for reinstallation is 8–10 Nm). Clean the surface of old sealant.
  2. Set the piston of the 1st cylinder to TDC. To do this:
    • Unscrew the glow plug of cylinder 1.
    • Rotate the crankshaft clockwise (with a 13 mm wrench) until the mark on the pulley aligns with the pointer.
    • Check that both valves of cylinder 1 closed (rockers swing freely).
  • Check clearances with a feeler gauge Normal values for TD27T:
    • Valve Clearance (cold engine) Tolerance
    Inlet 0.20 mm ±0.03 mm
    Graduation 0.30 mm ±0.03 mm

    If the gap is not correct:

    1. Loosen the lock nut on the rocker with a 10mm wrench.
    2. Rotate the adjusting bolt while checking the gap with a feeler gauge. He must enter with light effort (don’t “snack”, but don’t hang out either).
    3. Tighten the lock nut with a torque wrench (12–14 Nm) and recheck the clearance.

    Engine has cooled to 20°C or lower|

    TDC marks match|

    The valves of the 1st cylinder are closed|

    The probes are clean and free of burrs-->

    After adjusting the 1st cylinder, proceed to the rest, observing operating procedure: 1–3–4–2. To rotate the crankshaft 180°, use the marks on the pulley or flywheel (through the inspection window in the clutch housing).

    ⚠️ Attention: On TD27T with the turbine after adjustment, be sure to check turbocharger play. If the valve clearances were greatly increased, this could be due to oil entering the combustion chamber due to wear on the turbine.

    Common mistakes and how to avoid them

    Even experienced craftsmen make mistakes when adjusting valves TD27T. Here are the most common:

    • 🔧 Adjustment on a hot engine. Gaps on TD27T “float” when heated: exhaust valves can decrease by 0.05–0.07 mm, and intake valves by 0.03 mm. The result is a knocking sound after warming up.
    • 📏 Using worn styli. Bent or sharpened probes give an error of up to 0.05 mm. Check them with a micrometer before use.
    • 🔩 Insufficient tightening of lock nuts. Leads to self-loosening of the bolts and “leaving” of the gaps after 1–2 thousand km. Always use a torque wrench!
    • 🔄 Incorrect cylinder order. If you adjust the valves in a chaotic manner, you can skip a cylinder or adjust the same one twice.

    Another common problem is uneven wear of rockers. On TD27T With a mileage of more than 200 thousand km, rockers often have wear on the working surface. This leads to the fact that even after adjustment, the gaps “go away” after 500–1000 km. The solution is to replace the rockers or grind them (if the wear does not exceed 0.1 mm).

    💡

    If after adjustment the engine begins to run rough, check valve timing. It is possible that when rotating the crankshaft you missed the TDC mark or the timing belt has gone astray.

    Checking after adjustment: what should alert you

    Start the engine and listen to its operation. Normal signs:

    • 🔇 No knocking in the valve mechanism (let's say a slight rustle of rockers for the first 10-15 seconds).
    • 📈 Smooth idle speed (without dips or twitches).
    • 💨 No black smoke from the exhaust pipe.

    Alarming symptoms indicating errors:

    • 🔊 The knock hasn't gone away — “pinched” valves or wear on the rockers are possible.
    • 🚗 Engine troubles - check the compression (the valve may not close completely).
    • 🌡️ Overheating - a sign of too small clearances on the exhaust valves.
    • 💧 Oil leak from under the valve cover — uneven tightening of bolts or poor sealant.

    If problems are found, repeat the adjustment, paying particular attention to:

    1. Correct TDC setting (check the marks on the flywheel through the inspection window).
    2. The condition of the rockers and adjusting bolts (is there any play or scoring).
    3. The quality of valve cover sealing (use Loctite 515 for flange).
    💡

    If, after adjustment, valve knocking appears after 1000–2000 km, the cause in 90% of cases is wear on the rockers or loosening of the lock nuts. Re-tuning is required and parts must be checked for wear and tear.

    Adjusting TD27T valves with a turbine: nuances

    On turbocharged versions TD27T The procedure has several features:

    1. Checking the turbocharger. Before adjusting the valves, make sure that the turbine does not “drive” oil into the intercooler or intake manifold. Signs of malfunction:
      • 🛢️ Oil in the intercooler pipes.
      • 🔊 Whistling or grinding noise when the turbine is operating.
      • 💨 Blue smoke from the exhaust pipe.
  • Boost pressure control. After adjusting the valves, check that the turbine produces standard pressure (0.7–0.8 bar at standard settings). Too large gaps on the exhaust valves can lead to a drop in compression and, as a result, a decrease in boost.
  • Intake tract condition. On turbo versions, the cleanliness of the air ducts is critical. If the valves were not adjusted for a long time, oil could enter the combustion chamber through worn turbine seals. In this case, the intake must be flushed and the oil changed.

    • Pay special attention oil condition. On turbo diesels TD27T it must meet the specification API CF-4 or ACEA B3. Using low-quality oil accelerates wear on the rockers and valve train.

    What should I do if after adjustment the oil consumption increases?

    If oil consumption increases to 1 l/1000 km, the problem is not in the valves, but in valve stem seals or piston rings. Adjusting the valves could temporarily “mask” the problem, since pinched valves created additional resistance at the inlet/exhaust. After tuning, the engine began to work more efficiently, and the defects of the CPG appeared more clearly. The solution is to measure compression and diagnose oil waste.

    Alternative adjustment methods: pros and cons

    In addition to the classic method with probes, there are alternative methods. Let's consider their applicability for TD27T:

    Method Pros Cons Applicability for TD27T
    Zero gap adjustment Maximum accuracy Requires a special tool (indicator) ✅ Optimal for worn engines
    Adjustment by ear Fast, no tools Low accuracy, risk of errors ❌ Not recommended
    Using shims Long term stability Requires removal of camshafts ⚠️ Only for major repairs

    For TD27T the most reliable method is the classic method with probes or adjustment using an indicator (if you have access to the equipment). The “by ear” method is absolutely not suitable - a diesel engine has a high noise level, and it is almost impossible to hear the correct gap.

    If you plan to convert the engine to gas, the valve clearances need to be increase:

    • Intakes: 0.25 mm (instead of 0.20 mm).
    • Graduation: 0.35 mm (instead of 0.30 mm).

    This is due to the higher gas combustion temperature and the risk of valve burnout.

    FAQ: Frequently asked questions about adjusting TD27T valves

    Can the valves on the TD27T be adjusted without removing the valve cover?

    No, that's impossible. On TD27T The adjustment bolts are located under the rockers and can only be accessed after removing the cover. Attempts to “grope” the bolts through the oil filler neck lead to thread breakage or incorrect adjustment.

    Valve knocking appeared 500 km after adjustment. What is the reason?

    Most likely, the locking nuts on the adjusting bolts are loose or the rockers are worn out. Also check:

    • Quality of nut tightening (a torque wrench must be used).
    • Condition of bolt threads (may need replacement).
    • Play in the rockers (if wear is more than 0.1 mm, replacement is required).

    What oil should I fill in after adjusting the valves?

    For TD27T We recommend semi-synthetic oil with a viscosity 15W-40 and specification API CF-4 or ACEA B3. After adjusting the valves, the oil should be changed, as it may contain metal particles from wear on the rockers. Popular options:

    • Mobil Delvac MX 15W-40.
    • Shell Rimula R4 X 15W-40.
    • Lukoil Luxe Turbo Diesel 15W-40.

    Do I need to change the valve cover gasket when making adjustments?

    Yes, it is advisable to replace the gasket, especially if it:

    • Lost elasticity (hard to the touch).
    • Has traces of oil on the outside.
    • Operated for more than 50 thousand km.

    For TD27T gasket fits Nissan 11044-40X00 or analogues from Elring, Goetze.

    Is it possible to drive with knocking valves?

    For a short time (up to 1–2 thousand km) it is possible, but this leads to:

    • Accelerated wear of rockers and camshaft lobes.
    • Risk of burnout of valves (especially exhaust valves).
    • A decrease in power and an increase in fuel consumption.

    On TD27T Valve knocking often masks more serious problems, such as wear hydraulic compensators (if installed) or cylinder head deformation.