Series engines QG And QR, installed on Nissan Primera P12, are famous for their reliability, but the reputation of “eternal” engines has one critical limitation - the life of the gas distribution mechanism. Unlike belt drives, the chain does not require replacement every 60 thousand kilometers, but it is not immortal. Wear of tensioners, stretching of the chain itself and wear of the dampers inevitably lead to the owner having to deal with expensive repairs.
Many car owners mistakenly believe that if the engine runs smoothly and does not make any extraneous sounds, then replacement is not necessary. This misconception can be costly, as critical stretching often occurs suddenly, especially with sudden changes in rpm. Timely diagnosis and understanding the signs of impending repairs allow you to avoid fatal consequences such as valves meeting pistons.
In this article we will look in detail at how to correctly identify wear, what set of spare parts choose for Nissan Primera P12 and how the replacement procedure itself is carried out. We will look at the nuances of working with engines QG18DE And QR20DE, which have their own design features when servicing the timing belt.
Signs of chain wear and risks of ignoring the problem
The first and most obvious signal of problems is a metallic ringing or rustling sound in the area of the engine cover, especially when it is cold. This sound appears due to the fact that the chain tensioner cannot compensate for its stretching, and the link clings to the dampers or the housing. However, it is worth considering that at high mileage the sound may disappear if the tensioner is stuck in the working position, which creates a false sense of security.
In addition to sound, problems are indicated by unstable engine operation at idle and floating ignition timing values. The vehicle's ECU can record errors in valve timing, for example, P0340 or P0345. If you see such codes on the scanner, you cannot ignore them, as this is a direct sign that timing phases displaced due to stretched chain.
Ignoring symptoms leads to dire consequences. When critical tension is reached, the chain may jump onto one or more teeth of the crankshaft sprocket. In series engines QG And QR this is almost guaranteed to lead to bent valves, which turns replacing the chain into a major engine overhaul with replacement of the cylinder head.
⚠️ Attention: Never try to start the engine with a strong metallic clanging sound when starting from cold. This may mean that the chain has already jumped or is on the verge of jumping, and each revolution of the starter brings the moment when the pistons meet the valves.
- Constant metallic noise in the timing cover area at any speed.
- Errors in valve timing (P0340, P0341, P0345) on the scanner.
- Increased fuel consumption and loss of power due to incorrect phase operation.
Selection of spare parts and necessary tools
One of the most important stages is the correct selection of spare parts. Dealer original spare parts are often unreasonably expensive, and cheap analogues may not last even 50 thousand kilometers. For Nissan Primera P12 The best proven kits are from trusted brands, such as Dayco, INA or Skf. A genuine Nissan chain is also a great choice if you can find one at the right price.
It is important to understand that changing only the chain is a mistake. Along with it, it is necessary to replace the tensioners (hydraulic and mechanical), dampers and sprockets. Over time, the plastic of the dampers deteriorates, and its particles can get into the oil channel, clogging the oil receiver mesh. This will lead to oil starvation and scoring in the cylinders. Complex replacement of all timing elements is the key to long-lasting repairs.
You will need a specific tool for the job. A standard set of heads will not help here. It is necessary to have crankshaft and camshaft clamps, as well as a special key for turning the crankshaft. Without these devices, it is impossible to set the correct marks and tension the chain.
- Original (Nissan)
- Dayco/INA/SKF
- Other analogues
- I only buy used originals
List of required tools:
- Set of socket heads and wrenches (from 8 to 24 mm).
- Torque wrench for tightening cylinder head bolts and pulleys.
- Special camshaft clamps (locking bar).
- Puller for crankshaft and camshaft pulleys.
- Timing cover and oil pan gaskets (sealant).
⚠️ Attention: When purchasing a kit, be sure to check the condition of the tensioners. If you buy used or refurbished parts, the risk of repeated repairs increases significantly. It is better to immediately install new hydraulic tensioners with blockers.
Preparing the car for dismantling
Before starting work, you need to prepare the car. Remove the battery to avoid short circuit when disconnecting the sensor connectors. Next you need to remove the air filter, receiver and throttle assembly to gain access to the top of the engine. On QG18DE this also involves removing the intake manifold, which requires care with the vacuum lines.
Drain the coolant from the radiator and cylinder block. This is necessary, since when the timing cover and thermostat are removed, antifreeze will inevitably leak out. Also drain the engine oil if you plan to remove the pan to replace the oil pickup screen, which is highly recommended at this mileage.
Disconnect all sensor connectors going to the timing cover and cylinder head. Don't forget about the generator wiring and generator drive. Unscrew the accessory belt (alternator, air conditioning, power steering) to release the crankshaft pulley. At this stage it is important to secure the motor so that it does not turn when removing the pulley.
☑️ Preparing to remove the timing cover
The process of replacing the circuit and setting the phases
The most crucial moment is setting the marks. Remove the timing cover, having first unscrewed all the fastening bolts. Be prepared for the fact that the gasket may stick, and the lid will have to be carefully pryed off. After removing the cover you will see the timing mechanism. You need to turn the crankshaft clockwise until the mark on the crankshaft sprocket matches the mark on the block.
Next you need to block the camshafts. Install a special metal strip (clamp) into the grooves at the ends of the camshafts. If the bar fits tightly, it means the phases are set correctly. If the shafts do not match, rotate them without touching the crankshaft. After this, remove the chain tensioners. Please note that the tensioners have locking devices that must be released before removal, otherwise they will not be able to operate during installation.
Remove the old chain. Before installing a new chain, be sure to check the condition of the sprockets. If they have nicks or play, they need to be replaced along with the chain. Install the new chain, following the tension order. First, the chain is tensioned along the short branch, then along the long one. Install new tensioners, having first removed the blockers from them.
What to do if the labels don't match?
If, after installing the bar, the marks on the sprockets do not match, this means that the chain was jumped earlier. In this case, it is necessary to rotate the shafts until they coincide completely, using clamps. Do not under any circumstances try to tighten the chain by force, this will lead to breakage of the dampers.
After installing all the elements, perform a control rotation of the crankshaft two full turns. Make sure that the camshaft retainer snaps into place freely and that the marks on the gears match the marks on the block. If everything is correct, you can reassemble the engine in reverse order.
Before installing a new timing cover, thoroughly degrease the adjacent surfaces of the block and cover. Use a quality sealant to avoid future oil leaks.
⚠️ Attention: Remember the tightening order of the timing cover bolts. They must be tightened crosswise with a certain torque. Overtightening can lead to cracks in the aluminum cover, and undertightening can lead to oil leaks.
Checking the quality of work and final recommendations
After assembling the engine, fill with fresh oil and coolant. Start the engine and let it idle. Listen to the sounds of the timing belt - there shouldn't be any. Check the operation of the cooling system and make sure there are no oil leaks in the timing cover area.
Check the engine operation in different modes: acceleration, engine braking, operation at high speeds. If there is no sound and the work is smooth, it means the repair was done efficiently. Do not forget to erase old errors in the ECU memory with a scanner. Quality replacement Timing chains will extend the life of the engine by another 150-200 thousand kilometers.
The table below shows the approximate resources of parts for engines Primera P12:
| Detail | Resource (km) | Recommendations |
|---|---|---|
| Timing chain (original) | 150 000 - 200 000 | Replacement if stretched or noisy |
| Hydraulic tensioners | 100 000 - 120 000 | Replacement with every timing belt repair |
| Calcifiers (plastic) | 80 000 - 100 000 | It is critical to change when worn |
| Camshaft sprockets | 150 000+ | Replacement if teeth are loose or worn |
The final result depends on the accuracy of the work and the quality of spare parts. Never skimp on tensioners and dampers, as their failure leads to instant failure of the entire timing system. Regularly checking the condition of the chain and oil will help you avoid sudden breakdowns.
Frequently asked questions (FAQ)
Is it possible to drive if you hear the sound of the timing chain when cold?
A short-term sound when cold (the first 2-3 seconds after starting) is acceptable, since the oil has not yet had time to fill the hydraulic tensioners. However, if the sound is heard constantly or does not go away after warming up, this is a sign of wear, and driving long distances with such an engine is dangerous.
How often should you change engine oil? QG18DE?
To preserve the life of the timing chain and tensioners, it is recommended to change the oil every 7,500 - 10,000 km. The use of low-quality oil or prolonged replacement intervals accelerates the wear of hydraulic tensioners, which leads to chain stretching.
Do I need to change the pump when replacing the timing chain?
Yes, it is highly recommended to replace the water pump when removing the timing cover as it is driven by the timing chain. This will avoid repeated disassembly of the engine if the pump leaks after 20-30 thousand kilometers.
How long does it take to replace a timing chain?
For an experienced technician, replacing the timing chain with Nissan Primera P12 takes from 6 to 10 hours. For a beginner without special tools and experience, the work may take 2-3 days, since it will take time to study the nuances and select tools.
What should I do if there is a knocking noise after replacement?
If the knocking noise appears immediately after replacement, you may have poorly tensioned the chain or mixed up the marks. Also check that the new tensioner is not jammed. In the worst case, if the marks are set incorrectly, the valves could be bent. Re-diagnosis is required.