Okay folks, here is a little christmas story for you. A little late one. Before christmas I wondered why my new Nissan Primera P12 1.6 2007 started to work oddly. One day I didn’t manage to start the engine at all, and the engine fault light turned on. When I got the wheels turning, the engine stopped suddenly a couple of times. I read the fault codes, and they said that the problem was in the position sensors of the camshaft and crankshaft. I changed the sensors without luck, because the actual problem was the loose timing chain. Oh damn!
Because I’m a poor DIY guy, I decided to change the timing chain by myself, why I spent most of the christmas with my car. Because the seal of the crankshaft etc. seemed to be in good condition, and I wanted to save money instead of ripping half car open, I took a non-orthodox route and only changed the timing chain itself and the gaskets of the rocker cover. After about 1000 km the car is still working like a charm ðŸ™‚ Nissan Primera has a so called silent type timing chain, but I found a nice tool for conventional chains that worked well in this project (see the photos).
If you get inspired and try to repeat the procedure described here, notice this disclaimer. I do not guarantee this method will work properly and I do not take any responsibility of your acts, why I am not liable of any possible damages these guidelines might cause! Notice that I’m not a car technician. Actually, I’m not even a car hobbyist, I just need a car to get to work and do other stuff. Feel free to comment if you see something silly here, so that I can become even better DIY car technician ðŸ™‚ Notice also that during the project I did a lot of experimenting, and I will describe here only the main points I found important to get the job done. I will first go through the project overall, then I will show you some photos and extra details.
So, I first detached the battery. I removed the plastic engine cover and ignition coils. Then the camshaft sensor, tubes and wires attached to the rocker cover, the rocker cover itself and cylinder head front cover. Remember to loosen/tighten the bolts of the rocker cover in zigzag manner, to evenly loose/distribute the clamping force. Be very careful with the front cover, the cured gasket is very stiff. During the removal I managed to crack one bolt rim, luckily on the outer side of the seal! Gently use rubber mallet, utility knife, flat screwdriver as a crank, and/or wooden punch/lever if necessary. Remember that you are working with soft aluminum, do not damage the mating faces of different parts, or else you might face oil leakage in the end! Do not introduce dirt in the engine! I did, a little, and wiped it off quickly ðŸ™‚ Do not drop tools or parts in the engine either!
I removed the spark plugs to let the pressure out of the cylinders. I put an iron rod through the hole of the spark plug to see the highest and lowest positions of the 1st piston. Then, by rotating the crankshaft (in running direction) I positioned the 1st cylinder to top dead center (the end of the compression stroke). I also checked that the timing marks on the chain matched with the marks on the camshaft sprockets, after which I did my own marks relative to the stationary parts of the engine. I also made a mark on the crankshaft pulley that matched with a mark on the oil pan.
From now on, be careful not to let the chain to slip over the teeth. The new and old chains are cut at the same spots (with the chain tool) and joined together temporarily from the ends (with stiff metal wire). Someone need to rotate the crankshaft under the strict command of the other one who feeds the new chain in the engine simultaneously. If the chain slips only a couple of teeth, in the end you might be able to slip it back so that all the marks are in their original positions. If the chain slips too many teeth, a piston might collide with a valve and might cause damage to your engine! I don’t know how to recover from this situation, if it happens.
Before feeding the new chain in the engine, remove the chain tensioner. Open the plunger ratchet with the small lever in the tensioner, push the plunger in, and lock the lever with a piece of strong wire put in the hole (I believe you will understand what I mean if you inspect the tensioner). If the tensioner is broken or badly worn, change it. If the plastic chain slack guide is damaged, I do not know how to advance.
Although the cylinders do not hold pressure, the valve springs cause varying tension in the camshafts, which is tricky to handle. By overlapping and attaching parts of the new and old chains together with locking pliers, I tried to mimic an intact chain that is tensioned between the sprockets. I clamped the pliers to new positions as needed while the new chain was fed inside the engine slowly by turning the crankshaft. In the end, I had the new chain in its place and both ends again in my hands. I noticed that the mark on the chain didn’t match with the mark on the intake sprocket, but I simply slipped the chain to its correct position. I think the deviation was only one tooth large or two. Then I rejoined the chain with the chain tool, and put the rest of the parts back together.
Notice that due to the new tighter chain the marks relative to the stationary parts of the engine will likely move. The mark I drew on the chain at the intake side was elevated relatively to the upper edge of the cylinder head. I verified that the pistons and valves did not collide by rotating the crankshaft a few rounds carefully. Due to the use of locking pliers, I used a magnifying glass to inspect the whole chain and its pins from both sides and above, to spot possible bents or other damages on the chain.
When installing the chain tensioner, I cleaned the mating surfaces carefully to avoid oil pressure leakages decreasing the pushing force of the plunger. I was also afraid of possible compressible air trapped in the tensioner. Thus, before making the installation, I pumped the plunger a few times while keeping the whole tensioner under the engine oil to release the air.
I scraped, cut, and brushed the old gaskets away before applying thin line of new and putting the front cover back to its place. Remember to seal the inside side of the bolts of course. Above the interfaces of the front cover and the cylinder head I also added small drops of the gasket, which were later overlapped by the rocker cover gasket made of rubber. In the end I changed the motor oil and filter. As an extra job I also cleaned dirty throttle plate to get better idle.
After the job, I managed to start the engine successfully! Okay, here are some snowy photos of the project ðŸ™‚