Engine VQ series from the company Nissan It is considered one of the most reliable units in the history of the Japanese automobile industry. However, even motors such as VQ20DEinstalled on a popular sedan Nissan Cefiro, require timely maintenance. A critical point in operation is the condition of the gas distribution mechanism, where the correct installation of the phases directly affects the power and service life of the motor.
Many owners are faced with the need to replace the timing chain or tensioners, but not everyone knows how to accurately set the marks. An error of even one tooth can lead to fatal consequences for the valves and piston group. In this article we will look in detail at how to find and align all the control points on the crankshaft and camshafts.
Design features of the timing belt of the VQ20DE engine
Motor VQ20DE - This is a 2.0-liter 24-valve unit with two camshafts (DOHC). Unlike belt drives, it uses chain drive, which is theoretically designed for the entire service life of the car, but in practice requires attention after 150-200 thousand kilometers. The chain stretches, and hydraulic tensioners can lose pressure, which leads to marks jumping.
The main difficulty with this engine is the presence of a variable valve timing system (CVTC) on both shafts. This complicates the installation process, since it is necessary to take into account not only the position of the shafts, but also the phase shifters. If you are planning a repair yourself, you will need a special tool to fix the camshafts at top dead center.
Moreover, it is important to understand that chain tensioner operates on hydraulic oil pressure. When assembling, you must make sure that there are no air pockets in the system, otherwise the chain will dangle at idle, producing a characteristic metallic ringing. This is the first sign that the phases may be out of order.
Preparation for work and necessary tools
Before you begin removing the timing cover, you need to prepare your work area. You will need a jack, trestle stands, a set of sockets and wrenches, and new gaskets and sealant. Don't forget to drain the coolant, as the radiator and pipes often block access to the crankshaft pulley.
Pay special attention to the fixing tool. On Nissan Cefiro with engine VQ20 specific labels are used that are easy to confuse. You will need markers of different colors to mark the position of the gears before removing them. This will help you understand what position they were originally in if you are not planning on completely replacing the chain.
It is also necessary to remove attachments that interfere with access to the front of the engine: the generator, air conditioning compressor and drive belts. Carefully disconnect the battery to avoid short circuits when working on the crankshaft and camshaft position sensors.
Use penetrating lubricant early to avoid stripping threads. When removing the cap, proceed evenly, prying it around the perimeter, so as not to damage the seat, which may lead to oil leakage in the future.
- Once a year
- Once every 2 years
- Only in case of breakdown
- By mileage every 100k
Search and identification of timing marks
The main task during assembly is to align the marks on the camshaft and crankshaft sprockets. On the pulley crankshaft there is a mark in the form of a recess or marks, which should coincide with the mark on the oil pump body or cylinder block. This is usually the top dead center (TDC) position of the first cylinder.
On camshafts There are two gears with colored marks or risks. On Nissan VQ20 marks of three colors are often used: yellow, red and green, corresponding to different links in the chain. However, during operation, these paints can wear off, so it is better to focus on the shape of the teeth and the marks on the body of the phase shifters.
It is critical to check the condition phase shifters (CVTC). If the mechanism is jammed, it will not be possible to set the marks correctly. In this case, the phase shifter must be replaced or disassembled and cleaned, but this requires separate instructions and caution.
If you are using a new chain, it usually comes with colored links. You need to align the yellow link with the mark on one gear, the red link with the other, and the green link with the crankshaft mark. An old chain has its own, already erased marks, so relying only on color is dangerous - use physical marks on the metal.
☑️ Preparation for timing belt installation
Table of correspondence between marks and gaps
For clarity, we present a table describing the standard positions of the marks when setting TDC. This data is relevant for most modifications VQ20DE, but always check the service book of your specific car, as there may be nuances depending on the year of manufacture.
| Component | Tag type | Position at TDC of the 1st cylinder | Note |
|---|---|---|---|
| Crankshaft pulley | Risk on the pulley | Matches the mark on the cylinder block | Usually 0 degrees |
| Intake camshaft | Colored chain link | Matches the mark on the CVTC gear | Often yellow link |
| Exhaust camshaft | Colored chain link | Matches the mark on the CVTC gear | Often the red link |
| Small gear | Mark on the body | Matches the mark on the chain | For tensioner |
| Tensioner | Rod | Extended all the way | Fixation with a pin |
⚠️ Attention: Never turn the crankshaft counterclockwise with the chain removed or the tensioner loose. This can lead to the chain jumping several teeth and disrupting the valve timing.
What to do if the labels don't match?
If after installation you see that the marks do not match, do not try to forcefully tighten the chain. Most likely, you mixed up the installation order or the chain was installed with a jump. Disassemble the drive again, check the condition of the sprockets and make sure that the crankshaft is strictly at TDC.
Chain installation and tensioning process
After all the marks are aligned, you need to set chain tensioners. First, an automatic tensioner is installed, which must first be unlocked. Make sure that its rod extends freely under the action of the spring.
Then install the chain guides. They should fit snugly against the chain, but not block its movement. If the damper is worn out, it must be replaced as it dampens chain vibrations. Without it, the chain will hit the block, which will lead to rapid wear and noise.
An important step is cranking the engine. After assembling the timing cover, manually turn the crankshaft two full turns clockwise. This is necessary so that the tensioner takes its working position and the chains are tensioned. After scrolling, check again that all marks match.
If the marks have shifted, it means that somewhere an error was made in the assembly or the chain is too stretched. In the latter case, replacing the chain is mandatory. Also check the operation of the hydraulic tensioner: when started, it should extend and remove the slack in the chain within a few seconds.
Before final tightening of the timing cover bolts, apply a thin layer of liquid sealant to the joint in the areas indicated in the service documentation to avoid oil leaks.
Typical mistakes when replacing timing belt on VQ20
One of the most common mistakes is ignoring the state chain guides. Plastic guides become brittle over time and may crumble. If you leave debris in the engine, it can get into the oil pump or clog the filter, leading to oil starvation and a major overhaul.
Another mistake is incorrect installation of phase shifters. If you mix up the intake and exhaust phase shifters, the engine will either not start or will be extremely unstable. On Nissan VQ20 they often have different geometries and mountings, but visual similarities can be misleading.
They also often forget to replace the timing cover gaskets. Using an old gasket or improperly applying sealant will cause oil to leak through the joint. This is not only dirt under the hood, but also the risk of oil getting on the alternator belt or sensors.
Sometimes technicians forget to install the tensioner locking pin until the cover is installed, and then forget to remove it. In this case, the chain will remain weak and the engine will run noisily. Always check the checklist before closing the lid.
⚠️ Attention: If after starting the engine you hear a metallic ringing in the timing belt area, immediately turn off the engine. This is a signal that the chain is not tensioned or the marks are knocked down. Further work may cause the valves to collide with the pistons.
Correct installation of the timing marks on the VQ20DE engine requires a sequence: first the crankshaft at TDC, then aligning the marks on the camshafts, and only then tensioning the chain and installing the cover.
Diagnostics and inspection after assembly
After completing all the work and installing the timing cover, do not rush to start the engine immediately. First, crank it with the starter several times without starting (with the fuel pump fuse pulled out) to build up oil pressure in the system. This will allow the hydraulic tensioners to fill with oil and push out air.
Then start the engine and let it idle. Listen for sounds in the area at the front of the engine. The sound should be smooth, without the characteristic “clunking” or ringing of the chain. If there is sound, the tensioner may not have worked or the marks may have jumped.
Use a diagnostic scanner to check for errors. The engine control system can detect phase desynchronization (error P0011, P0021 and the like) if the marks are set incorrectly even by one tooth. Eliminate errors before you begin active use.
It is important to check the oil and coolant levels, as some of the fluid may have evaporated or spilled out when operating without a cap. Also make sure that all sensors (crankshaft position, camshafts) are connected and working correctly.
How to check the condition of a circuit without disassembling it?
If the chain is very stretched, when the timing cover is removed, you can see that it sags at the bottom. You can also try to wiggle the chain by hand (with the engine off), but this requires care and access.
FAQ: Frequently asked questions about timing belt Nissan Cefiro VQ20
What is the mileage before replacing the timing chain on VQ20DE?
Officially, the chain is designed for its entire service life, but in practice it is recommended to check it after 150,000 km. If there is noise or stretching, replacement is required.
Is it possible to change only the chain tensioner?
Technically it is possible, but if the chain is already stretched, the new tensioner may not compensate for the gap, and the phases will be out of whack again. It is better to change the kit (chain, tensioners, dampers).
Do I need a special wrench to fix the camshafts?
Yes, accurate timing on the VQ20DE engine requires a camshaft lock or a specific tool to hold the shafts at TDC while removing the gears.
What happens if the phase shifters are swapped?
The engine will either not start or will operate extremely unstably, with loss of power and increased fuel consumption. In the worst case, this will lead to valve failure.
How often do you need to change the oil when using the VQ20?
To preserve the life of the chain and tensioners, the oil should be changed every 7,000 - 10,000 km. Dirty oil clogs the tensioner channels, leading to their failure.
⚠️ Attention: Operating a vehicle with a faulty tensioner or a stretched chain is strictly prohibited. The risk of valves meeting pistons if the chain breaks or jumps is 99%.