Although it seems that everyone knows about diesel for a long time, it’s worthwhile to recall the pros and cons of these engines in comparison with gasoline engines.
So about the pleasant:
- Diesel is economical, and diesel fuel is cheaper than gasoline – in fact it is the main and most obvious plus diesel.
- Diesel engines have high torque.
- Given the nature of the expected operation, the manufacturer usually lays a great resource in diesel engines.
This is where all the joys end. Now about the minuses.
- Structurally and partly due to claim 3 of the above, a diesel engine is more expensive than a gasoline engine.
- Smaller, relative to the gasoline engine, power.
- Despite all the threats and assurances of manufacturers, still an element of “tractor” in the work of modern diesel engines is present.
- Usually half the life of engine oil (and this is a point that partially eats the savings from item 1 of the advantages of a diesel engine) plus a relatively expensive fuel filter.
- Requires a highly qualified service, even the replacement of the fuel filter is not such an easy operation. Replacing the timing belt and the installation of the injection pump is usually in “garage” conditions as min. difficult.
- In the case of major repairs much more expensive.
- Diesel fuel evaporates badly and its smell, in the case of even small short-term leaks, is long present in the car.
But the most important thing is not even this. The times when the diesel engine was constructively “1 stick-2 string” and had only 2 serious knots – the fuel pump and injectors successfully sunk into oblivion. A modern diesel engine is a complex engine with a turbo-supercharging system and everything that accompanies it, with a full-fledged electronic engine control system with a usual set of sensors, valves, etc., adjusted for diesel specificity. The demand was reflected in the appearance of lambda probes, catalysts and other exhaust neutralization systems. All this significantly increased the requirements for diesel fuel poured in and created a situation where “traditional” diesel specialists were not ready for such a dramatic change in the situation, and the list of defects expanded dramatically and stopped reducing only to the injectors and fuel pump.
Now actually about the subject – Audi V-shaped turbodiesel volume 2.5.
Appearing in the year 97 (AFB code), in 2000 it underwent a small upgrade (AKE), power increased from 150 to 180 hp. Nevertheless, both of these motors are very similar, so all of the following applies to both types. When developing these engines, the VAG went the old tried and tested way – these are the engines “converted” from gasoline V6. But at the same time, there is no interchangeability with the gasoline “relatives”, with rare exceptions, no.
There is an opinion, which is periodically implemented by various services and craftsmen, that the timing belt and the injection pump can be replaced without any adaptations, you just need to make marks on the gears and put the new belt “as it was”.
However, if such a method somehow “passes” on gasoline engines that are not so critical to the installation, this trick will not work with a diesel engine. Ie most likely the timing belts and the high-pressure pump will be replaced and the engine will even work more or less decently, but statistically all of us known cases of such a replacement led to inaccurate installation and as a result the loss of engine traction to a greater or lesser extent. With significant errors, the motor starts to work either too “hard” or vice versa “softly”. Obviously, you can “miss” as when installing the timing belt and the injection pump belt, with the possibility of “strange” errors. Thus, the widely practiced tolerance of the installation of timing for gasoline engines in the range of +/- “polzub” for a diesel engine is completely unacceptable, for it is possible only one single precise installation, which is practically impossible without special devices. Vkratse, the replacement method is as follows: the crankshaft is fixed rigidly in crankshaft in mt with fixture 3242, camshafts (3458) are rigidly fixed, after which the belt is installed, the belt gears on camshafts tighten and fixed. Next, the injection pump stops, the belt is put and tensioned, and then the drive gear of the injection pump belt tightens. Then there is a complete assembly, after which the engine starts and the injection angle is controlled. If it is not in tolerance, then the upper covers open, the pump drive gear is loosened and adjusted in the right direction, after which, tightening the gear, we check the injection angle again. The operation may be repeated several times until the correct values are reached. Reducing the number of interactions comes with experience. Also, if you often loosen the gear pump, as a result, it may be necessary to replace the gear p \ shaft due to wear of the threads for the bolts.
If, however, the angle is not corrected, and the angle does not correspond to the tolerance, the traction characteristics of the motor usually deteriorate and various starting problems arise, including motor failure. The deviation of the angle from the norm is usually characteristic of “lived” moto
Equally, this applies to 4c. a diesel engine, with the only difference that it has only one cylinder head and opportunities to miss with a smaller installation, however, a special device for installing the injection pump (injection angle) is still needed.
The most serious defect and problem of this diesel engine was the wear of the timing system – p \ shafts, rockers, hydraulic compensators, etc.
The defect, or rather its final manifestation, is expressed in the “disconnection” of the cylinders. At the same time, the motor doesn’t “warn” in any way the impending problem. Assess the degree of wear can only remove the valve covers. In case of critical wear, washers fall out or the hydraulic compensator collapses and the valve stops opening. As soon as the 2 valves on the cylinder stop opening, it turns off and the engine starts to troit. There are cases of almost simultaneous shutdown of even 3 cylinders. It does not bear destructive consequences for the motor, but it is obvious that repair is required immediately. It is rather difficult to call exact running numbers, moreover, the mode of operation and compliance with the regulations are more important, or rather, its non-observance in the direction of reducing the time for oil replacement.
The spare parts kit includes 4 camshafts, 24 rockers, 24 washers, 24 lifters and a mass of related parts. As a rule, the entire timing belt changes with all the rollers and pump. It is obvious that the total cost of repairs is high, both in terms of the cost of spare parts and in terms of work. It is worth noting that the pump, like the petrol V6, is the most loaded unit in the timing belt drive, and its replacement is obligatory when changing the belt, and given the extremely serious consequences for the engine from its jamming, it is not worth saving and it is recommended to use only the original. It will not be superfluous to remind you that when the timing belt is cut off / cut off, the cylinder head and pistons are usually destroyed, and in severe cases the whole engine can go to a landfill. Replacing the pump in the event of a leak is similar in cost to replacing the belt. The remaining parts of the timing drive (rollers, belts) are available to non-original and they can be used. The complete set for such a replacement includes 6 rollers, a pump and 4 belts (the State Russian Museum, the high pressure pump and 2 multi-ribbed ones).
Cylinder wear also takes place, however, even with noticeable wear (already “visible” by compression), the engine does not consume oil and continues to operate normally. However, when the wear reaches critical values, a substantial engine vibration may appear, while the oil consumption and traction characteristics remain normal.
It is possible to reduce wear in only one way – forget about the recommendation of the VAG to apply long-life oil and change it once in 15,000 km and return to the usual, “diesel” replacement rate every 7-8 ton. However, for bu cars with unclear mileage, the mode of service by previous owners is very relevant, and, as stated above, you can be sure of the timing condition by only removing at least one valve cover.
Possible failures also include failure of the “brains” of the fuel pump (can be replaced separately, supplied according to Bosch), when they fail, the motor can start to “fool” and can (but not always) give an error to the brain of the injection pump. Sometimes “strange” errors appear first. But more often the motor simply or stalls on the move and no longer starts, or there is no start after parking. In these cases, the ECU usually fixes an error on the pump. In the original, the pump is supplied only as an assembly, but the “restored with the delivery of the old” version, the so-called X-ray, is relatively inexpensive.
Nozzles are very reliable and last a long time. As usual, when worn they can change sprayers.
The turbine fails in the “traditional” order – the boost may disappear, strong oil smoke may appear. Nevertheless, this site is reliable enough, and its replacement is not so difficult, since it is one and access is good. But the cost, like any turbine, is high. Also, like any turbo engine, hose breaks through the air line are possible, but the problem is not as urgent as on gasoline engines – firstly the temperature under the engine hood is noticeably less and the rubber “lives” longer, secondly the boost pressure is low and therefore the hoses no such load.
The thermostat is one of the few parts that is the same with the petrol V6 and the symptoms of its failure are similar – long warming up, cooling of the engine when driving on the highway. Standard parts also include glands.
The balance shaft installed in the crankcase is driven by a chain along with an oil pump; its assembly requires installation according to the mark.
The problem of spare parts for this engine, even in Moscow, is quite relevant – consumables (timing, part of the gaskets) are usually in stores, but everything else is usually only on order.