Engine Failure Causes: What You Need to Know

Hi,

A friend of mine experienced an engine failure today with his older, but relatively new, TD AAZ model from 1992 (with approximately 104,000 kilometers -> hopefully). I took a look at the situation.

The timing belt had approximately 10,000 km on it, was properly tensioned, and showed no fraying or other signs of wear. However, one hydraulic lifter was torn, and the corresponding camshaft also had some minor damage. All the other lifters were intact, and the engine could be cranked over with the starter motor, making a "ticking" sound. What could be the cause of this defect? If there was a problem in the area of the timing belt (e.g., skipped teeth?, screw loosened), shouldn't several valves be damaged? Could a valve spring have broken? ...could a piece of a turbine blade have gotten inside, etc.? How good are the chances that the corresponding piston/connecting rod is still okay? What do you think about this? Thank you in advance .

As an additional detail: it affected the second valve, viewed from the camshaft wheel. The corresponding hydraulic lifter was no longer visible; it had disappeared into the oil channel .

@Haehnlein:

Quote:

Could it be that a valve spring is broken?

That sounds quite plausible to me, as there are no other visible signs of damage to the valve mechanism.
Were you able to identify any fragments of the valve spring?
Was the engine severely stressed shortly before it failed?

Regards,
Alex.

donalexo wrote:

Were you able to see any remnants of the valve spring?

Hi Alex,

I didn't examine it closely, but all that was left of the hydraulic lifter was its core (the part that sits on the valve). The valve spring retainer wasn't visible either. Is it even possible for the upward movement of the piston, due to a broken spring, to transfer enough energy to shatter the lifter? It's conceivable at 4000 rpm.

donalexo wrote:

Was the engine severely stressed shortly before its failure?

I don't know that . He probably didn't have any starting problems; however, he had quite a bit of power loss in the first and second gears after a cold start. On the highway, he apparently jerked suddenly and then eventually stalled.

It's quite strange, especially since you can still turn the engine over -> which means a defect in the timing belt area should really be ruled out. I think the issue with the spring sounds very plausible.

Hi,

Okay, so the car was taken to a very good independent workshop for an inspection (including checking the top end), and the mechanic said that a faulty hydraulic lifter was the cause. He disassembled it so thoroughly that the lifter could no longer be found in the cylinder head area – it went down through the oil channel. The symptoms (low power after a cold start) also suggest that the valve wasn't closing properly at first. Problems in the timing belt area were ruled out because the valve timing was still correct. He said he had seen thousands of engine failures, but he hadn't encountered a case where a damaged piston (which is also broken) was caused by a faulty lifter. I have the feeling that extremely rare and unusual problems are occurring within my circle of acquaintances (including myself ), .

Hi!

Perhaps it's a case of material fatigue, or maybe the engine previously had a timing belt failure where a part was swapped or forgotten .

cu: Marko

Hello,

"There's one more thing I need to mention. Before the engine failure, the car was accidentally filled with gasoline, and it was driven for a short distance. Could there be any connection between this and the engine failure? I seem to remember reading something about accidental refueling where the risk of engine damage was mentioned ."

Hello Hähnlein,

Do you mean this here?

/viewtopic.php?t=3384

According to this, incorrect fueling could be a cause.
Most likely, the pump seizes due to poor lubrication, which then causes a timing belt rupture.

Markus H. wrote:

Do you mean this here? /viewtopic.php?t=3384 According to this, incorrect fueling could be a cause. Most likely, the pump seizes due to poor lubrication --> timing belt failure.

Hi Markus,

certainly.

The timing belt and valve timing were, however, in good condition (see above). Only one lifter was shredded for inexplicable reasons (possibly due to lubricant film problems caused by gasoline hmm).