Diesel engine TD27T from Nissan - a legendary unit, known for its unpretentiousness and service life, which, with proper maintenance, can exceed 500,000 km. However, even such a reliable engine requires periodic valve adjustment - a procedure that many owners Patrol, Terrano or Navara with this engine they prefer to do it themselves. Incorrect valve clearances lead to decreased power, increased fuel consumption, and in advanced cases, burnt seats or camshaft failure.
In this article you will find step-by-step instructions for adjusting TD27T valves taking into account all the nuances: from preparing tools to checking the result. We will look at what clearances are considered normal for intake and exhaust valves, how to correctly set the timing marks, and why adjustment “by eye” can result in a major overhaul after 20,000 km. You will also learn what mistakes beginners most often make and how to avoid them.
When TD27T valve adjustment is needed: signs and frequency
The manufacturer recommends checking valve clearances to TD27T every 40,000–50,000 km, but in practice this interval may vary depending on operating conditions. If you often travel with a trailer, operate the vehicle in OFF-ROAD or use low-quality diesel fuel, the valves may “go away” after 30,000 km. The following symptoms indicate the need for adjustment:
- 🔊 Metallic knock at the top of the engine when cold or hot (especially noticeable at idle).
- 🔥 Power drop and “dullness” of the engine during acceleration, as if the car “doesn’t pull.”
- 💨 Increased fuel consumption (more than 12–14 l/100 km during normal driving).
- 🔄 Unstable speed idling speed, the engine “troits” or stalls when the gas is released.
If you ignore these signs, the consequences can be serious: from valve burnout (especially graduations that operate in more severe temperature conditions) up to camshaft cam wear and the need to replace it. In worst cases, incorrect clearances lead to broken timing belt and the meeting of valves with pistons - and this is already major renovation.
⚠️ Attention: On TD27T With a turbine, incorrect exhaust valve clearances accelerate turbocharger wear. If you notice oil in the intercooler or blue smoke from the exhaust pipe, valve adjustment should be done as a priority.
Tools and materials for adjusting TD27T valves
To adjust the valves yourself you will need special tool, without which it will not be possible to perform quality work. Here's the full list:
| Tool/material | Purpose | Notes |
|---|---|---|
| Set of feeler gauges (0.10–0.50 mm) | Valve clearance measurement | It is better to use styli with 0.01 mm pitch for accuracy |
| Open-end wrench 13 mm | Loosening the rocker arm locknuts | Preferably with a long handle for convenience |
| 10 mm socket wrench | Removing the valve cover | You will need an extension to access the rear bolts. |
| Flat blade screwdriver | Checking the play of the rocker arms | Do not use instead of probes! |
| Torque wrench | Valve cover bolt tightening | Tightening torque - 10–12 Nm |
Additionally, prepare the following consumables:
- 🧴 Valve cover sealant (For example, Loctite 574 or Permatex Ultra Black).
- 🧻 Rags and degreaser (for cleaning surfaces before assembly).
- 🔧 New gaskets (valve cover and breather if they are worn).
⚠️ Attention: Do not use silicone-based sealant on the valve cover gasket; it may get into the oil and clog the oil passages. Only anaerobic sealants that are resistant to oil and high temperatures.
- Every 30,000–40,000 km
- Only when there's a knock
- Never regulated
- I do it according to the condition (I check it with a dipstick once every 10,000 km)
Engine preparation: removing the valve cover and installing timing marks
Before adjusting the valves, it is necessary provide access to rocker arms and set the engine to a position in which both valves of the first cylinder are closed (the so-called TDC - top dead center). Here is a step-by-step preparation algorithm:
- Remove the air filter and pipesthat interfere with access to the valve cover. On TD27T this is usually the intake manifold and system pipes
EGR. - Disconnect the accelerator cable and other interfering elements (for example, vacuum hoses).
- Remove the valve cover, unscrewing 8 bolts with a 10 mm socket wrench. Be careful - there may be oil residue under the lid.
- Set the piston of the first cylinder to TDC. To do this:
- Unscrew the glow plug of the first cylinder.
- Rotate the crankshaft with a 22 mm wrench clockwise until air begins to escape from the hole (this indicates the start of the compression stroke).
- Continue rotating until the mark on the crankshaft pulley matches the mark on the front cover (usually a mark or letter
T).
After the marks match, check the position of the camshaft: its mark (usually on the gear) should look up and coincide with the mark on the block head. If the marks do not match, repeat the procedure, as incorrect shaft position will lead to incorrect adjustment.
If the timing marks are knocked off and you are not sure of their correct position, take a photo of the current condition before disassembling. This will help avoid assembly errors.
Procedure and clearance standards for TD27T valves
On the engine TD27T valve adjustment is carried out in strict order, which depends on the sequence of operation of the cylinders: 1–3–4–2. This means that after adjusting the valves of the first cylinder, you turn the crankshaft 180°, adjust the third cylinder, then another 180° for the fourth, and finally the second.
Normal clearances for TD27T (cold engine, +20°C):
- 🔵 Intake valves:
0.20 mm ± 0.02 mm. - 🔴 Exhaust valves:
0.30 mm ± 0.02 mm.
If the engine is hot, the gaps will be different due to thermal expansion of the metal. In this case, use the amendments:
- For intake:
0.25 mm ± 0.02 mm. - For graduation:
0.35 mm ± 0.02 mm.
The feeler gauge should go in with a slight force, but not wobble|If the feeler gauge doesn't go in, the gap is too small|If the feeler gauge goes in too loosely, the gap is too wide|Check the gap at least 2 times for accuracy-->
On TD27T with a mileage of more than 200,000 km is often found uneven wear of camshaft cams, which is why the clearances on different valves may differ. In this case, focus on maximum permissible clearance (for example, for graduation - no more than 0.32 mm), but do not exceed it.
Step-by-step adjustment of TD27T valves: from theory to practice
Now let's move on to the adjustment itself. Follow the instructions strictly in orderto avoid errors:
- Loosen the locknut on the rocker arm adjusting bolt (13 mm wrench).
- Insert the dipstick between the rocker arm and the valve stem. The probe should enter with light effort, but don't bend.
- Adjust the gap, rotating the bolt with a screwdriver:
- If the dipstick does not go in - reduce the gap (rotate the bolt counterclockwise).
- If the dipstick dangles - increase the gap (rotate the bolt clockwise).
20–25 Nm.After adjusting the first cylinder turn the crankshaft 180° (the mark on the pulley should move half a turn) and repeat the procedure for the third cylinder. Then another 180° for the fourth, and finally for the second. Do not skip cylinders or change the order!
What to do if the gap cannot be set?
If, after several attempts, the gap “goes away” when tightening the locknut, this may mean:
1. Worn threads on the adjusting bolt or rocker arm - replacement will be required.
2. Rocker arm deformation - check its flatness with a caliper.
3. Wear of the camshaft cam - in this case, the adjustment will give a temporary effect; timing belt repair is needed.
Common mistakes when adjusting TD27T valves and how to avoid them
Even experienced mechanics sometimes make mistakes when adjusting valves on TD27T. Here are the most common ones and ways to prevent them:
- ⚠️ Adjustment on a hot engine without corrections. The gaps on a hot engine should be larger (see section above). If you ignore this, the valves may “squeeze” after cooling.
- ⚠️ Incorrect adjustment order. If you break the sequence
1–3–4–2, set the gaps not at TDC, but in an arbitrary shaft position - this will lead to unstable engine operation. - ⚠️ Using worn styli. Bent or worn probes give inaccurate readings. Check them before work.
- ⚠️ Retightening the locknuts. Excessive force may deform the rocker arm or strip the threads. Always use a torque wrench.
Another common mistake is ignoring camshaft condition. If the cams are scored or worn out, the adjustment will not have a long-term effect. In this case it is required shaft grinding or its replacement. The same applies to worn rocker arms — it is better to replace them as a set.
⚠️ Attention: After adjusting the valves TD27T be sure to check injection advance angle (pumpVEorVP44). Incorrect clearances can throw off the fuel injection pump settings, which will lead to rough engine operation.
Checking the result and assembling the engine
After adjusting all valves, it is necessary check engine operation:
1. Make sure all tools and parts are removed from under the hood.
2. Start the engine and listen to it idle - there shouldn't be a knock.
3. Rev up to 2000–2500 rpm: the engine should pick up speed smoothly, without dips.
4. Check oil pressure (on TD27T it should be at least 2 kg/cm² at idle and 4–5 kg/cm² at rpm).
If the knocking noise persists, the following reasons are possible:
- 🔧 Error in adjustment (check the gaps again).
- 🔍 Wear of hydraulic compensators (if they are installed).
- 💥 Damage to the camshaft or rocker arms (diagnostics required).
When assembling the engine:
- Clean the surface of the block head from old sealant.
- Apply new sealant to the valve cover gasket (a thin layer!).
- Tighten the cover bolts criss-cross torque wrench (torque - 10–12 Nm).
- Connect all removed pipes and wires.
After adjusting the valves TD27T For the first 500 km, avoid high loads on the engine - let the parts get used to it.
FAQ: Frequently asked questions about adjusting TD27T valves
Can the valves on the TD27T be adjusted without feeler gauges?
No, that's impossible. Feeler gauges are the only reliable way to measure clearance. Alternatives like “by sight” or by sound lead to errors. If there are no probes, they can be replaced calibrated foil (for example, from tea packaging), but this is a temporary solution.
What happens if the TD27T valve clearances are larger than normal?
Increased clearances lead to:
- 🔊 Loud knocking noise at the top of the engine.
- 🔥 Reduced compression and loss of power.
- 💥 Accelerated wear of camshaft cams and rockers.
This can also happen on exhaust valves. burnout due to insufficient cooling.
Do I need to adjust the valves after replacing the camshaft on a TD27T?
Yes, definitely! A new camshaft may have different cam geometric parameters, even if it is original. Also, when replacing a shaft, new rocker arms or pushers are often installed, which also requires adjustment.
How often should I check clearances on a TD27T with LPG?
On engines with HBO valves wear out faster due to higher gas combustion temperatures. Recommended inspection interval - every 25,000–30,000 km. Pay special attention exhaust valvesbecause they suffer the most.
Can the TD27T valves be adjusted without removing the valve cover?
Technically possible, but extremely inconvenient. Without removing the cover you will not be able to:
- Completely clean the surface of the block head.
- Check the condition of the rocker arms and camshaft.
- Accurately measure the gaps with a feeler gauge (pipes and manifolds get in the way).
The risk of error with such an adjustment is very high.