Service - open timing chain 1,2 HTP 47 kW
For some time now, 1,2 HTP units have been taking up the space under the hoods of most fortunate or less fortunate car owners who belong to the giant VW group. However, few people know what the risks of starting an engine are. To get started, I recommend reading the article on its most common faults and shortcomings.
The basic building block of the 1,2 HTP is a shortened and modified 1598cc four-cylinder engine block.3 with a power of 55 kW. The timing belt was removed from the old “six” that drove the camshaft and replaced with a timing chain, which, together with the hydraulic tensioner, was supposed to provide maintenance-free operation and minimal interference with the normal operation of everything. engine block. However, it was the other way around. After the launch of the first three-cylinder engine, one of the most serious errors began to appear - a shift in the valve timing, often associated with the death of the unit itself. Even the 2007 upgrade did not completely eliminate this problem. A radical improvement did not occur until mid-2009 when the chain link was replaced with a toothed chain.
Why is this happening?
One of the most common causes of chain skipping is driving at less than optimal speed (so-called tractor speed) and push or stretch the car. When the engine is off, the chain is only tensioned by the tension spring, which essentially only serves to temporarily tension until the engine starts to move. In rare cases, the cause is also starting with a dead battery, when the starter cannot develop the necessary speed to start the engine, which is provided by a hydraulic chain tensioner through the oil pump, so the chain is tensioned only by a tension spring, which is not strong enough to repeatedly turn the engine without using a hydraulic tensioner . Due to insufficient spring pressure, it is also not recommended to keep the gear engaged when parking, especially on steep slopes. Many people are unaware of this problem and boldly leave their Fabia, Polo or Ibiza on gentle slopes, braked directly by the transmission, which puts pressure on the tension system. Be sure to use a hand brake, in extreme cases - a fixing wedge under the wheel. This will avoid the problem described above.
What causes the chain to skip?
If the chain slips, there is an immediate shift in valve timing in relation to the pistons. The camshaft gradually "pushes" the valves down, first the intake, then the exhaust (two in the case of 12 valves and one in the case of 6 valves, when there are only two valves per cylinder). While one pair takes care of the intake of fresh air, the other, after ignition, removes the flue gases from the combustion chamber. More information about the valve distributor operation HERE. So we jumped on the chain, the time was broken - changed, the piston in the engine moves down after the explosion, and a pair of exhaust valves should follow. But this does not happen, because the cam is already rotating in the phase difference like a motor. The piston returns, but at this point several valves also extend, and a fatal collision occurs, which ends with the destruction of the valves, damage (piston puncture) and, as a result, damage to the engine itself.
What is the conclusion?
Repair costs are not the cheapest, as in most cases extensive repairs or replacement of the entire device must be envisaged. Therefore, we do not recommend driving at a speed below 1500 rpm (also due to overheating). Never push the car, do not stretch and replace the weak battery, which many honestly charge every day in the basement, with a new, high-quality one to avoid other problems. We wish you many successful kilometers.
