Pistons have cracked and put a hole in the block

[audi q5]

TL;DR Summary

Audi q5 2009 injector and Alternator and auxiliary belt work gone wrong

Hi all so I had a injector go on my audi q5 2009 and had a mechanic to put a new injector in it and a Alternator and auxiliary belt so after the work be done I take it for a drive did about 2miles than Start it to make Allowed tapping noise so get hold of mechanic and he's said get it home than he will come and have a look at it so start my journey again but before I get back home properly do 5/6 miles a Warning light saying oil too hot over turn engine off before I Even had the chance too Pullover a big bang and engine cuts out so gets out car oil everywhere he comes and has a look the pistol has cracked and put a hole in the block Either on chamber 3 or 4 now what I need to no is how dose a piston just do that and if the mechanic do something to it or is just bad luck

 

[berkeman]

Welcome to PF.

if the mechanic do something to it or is just bad luck

But from your description of the work the mechanic did, they didn't go near the pistons. They only worked on the injector, alternator and belt, right?

 

[Mark44]

I agree with what @berkeman said, that the mechanic's work didn't cause the problem with your engine. From your description, you're going to need a replacement engine if you want this car to run again.

 

[audi q5]

Welcome to PF.But from your description of the work the mechanic did, they didn't go near the pistons. They only worked on the injector, alternator and belt, right?

No he did not working on the pistols but iv read online that if the injector is putting to much fuel in the chamber it could cause the pistol to get too hot there brake

 

[jack action]

When he removed the injector, something might have fallen into the cylinder. That can be really bad if it blocked the piston motion somehow. At this point, something has to give.

 

[berkeman]

TL;DR Summary: Audi q5 2009 injector and Alternator and auxiliary belt work gone wrong

has a look the pistol has cracked and put a hole in the block Either on chamber 3 or 4

In which cylinder did he replace the injector?

 

[anorlunda]

When he removed the injector, something might have fallen into the cylinder. That can be really bad if it blocked the piston motion somehow. At this point, something has to give.

I thought of that too. But finding the debris of the dropped piece is unlikely, so the smoking gun proof will never appear.

 

[audi q5]

In which cylinder did he replace the injector?

Number 4

 

[berkeman]

Number 4

Why are you not sure which piston failed? It it's for sure the same cylinder where the injector got replaced, that is a lot more suspicious.

 

[Baluncore]

What is the engine type and capacity ?
Is this a petrol or a common-rail diesel engine ?
If too much fuel was injected into one cylinder, then it would blow black smoke until the ECU cut the fuel supply to that cylinder.

I would;
Identify the engine model.
Pull the injectors and visually compare them.
Check the physical length and part number of the replacement injector.

 

[Tom.G]

A cracked piston can be caused by pre-ignition, often called 'pinging' under load.

Pre-ignition can be due to:
1) Ignition timing advanced too far
2) Lower grade of gasoline ( the Audi q5 requires Premium gas)
3) Air/Fuel ratio being too high (running lean, fuel starved)

The details are that the fuel in the cylinder ignites while the piston is still moving up in its compression stroke. If the cause is a lean fuel mixture, the temperature is also increased. The resulting extremely high pressure and high temperature can, as you found out, cause severe engine damage.

Tom

 

[Baluncore]

When the engine is pulled down, examine the big-end joints. It is possible that a lubrication failure seized the big-end of the connecting rod and broke the piston later in the process. That mode of failure, an event from below, would be unrelated to fuel injection.
If the big-end joints are good, then piston failure, caused by events above, would be part of the chain that caused the destruction.

 

[256bits]

I thought of that too. But finding the debris of the dropped piece is unlikely, so the smoking gun proof will never appear.

check the oil sump.

 

[256bits]

TL;DR Summary: Audi q5 2009 injector and Alternator and auxiliary belt work gone wrong

Warning light saying oil too hot over turn engine off

When he removed the injector, something might have fallen into the cylinder. That can be really bad if it blocked the piston motion somehow. At this point, something has to give.

Could these be related.
Or just a coincidence, that the engine decided to fail after leaving the shop.

Something to consider an investigation.
For the oil temperature sensor to pick up an increase in temperature so quickly, exhaust gas could have been bypassing the piston and entering the sump.
In this scenario, either the piston rings and piston side became quite damaged, or a hole was punched into the top of the piston.

You, as the driver, would not notice any funny exhaust, like black or grey smoke, through the rear view mirror, before failure for three reasons.
1. you are not looking for it.
2. the smoke dissipates and blends in quickly with the vortex(es) of the rear of the moving car. ( check diesel exhaust upon heavy load, and how quickly it becomes not noticeable )
3. the smoke blends in with what is seen through a rear view mirror.

A person on the side of the road would notice.

 

[Baluncore]

Hot engine oil usually results from a seized bearing.

If the injector was replaced with the wrong part number, the injector might protrude too far into the combustion chamber and damage the piston. That error would come back onto the mechanic and business insurance.

But we don't even know the engine model, is it gasoline or diesel ?

 

[audi q5]

Hot engine oil usually results from a seized bearing.

If the injector was replaced with the wrong part number, the injector might protrude too far into the combustion chamber and damage the piston. That error would come back onto the mechanic and business insurance.

But we don't even know the engine model, is it gasoline or diesel ?

Hi thanks for your replys the engine is a 2.0 tdi Diesel engine number caha

 

[Lnewqban]

Hi thanks for your replys the engine is a 2.0 tdi Diesel engine number caha

Welcome and sorry for that damaged engine.

What was wrong with the engine before the last repair?
Why was that injector replaced?

It seems to me like the typical failure by hydrolock.
Prior or after the injector replacement, liquid (coolant or diesel fuel) could have leaked inside the small combustion chamber #4 only, due to unknown causes.

Please, see:
https://en.m.wikipedia.org/wiki/Hydrolock

“Diesel engines are more susceptible to hydrolock than gasoline engines. Due to their higher compression ratios, diesel engines have a much smaller final combustion chamber volume, requiring much less liquid to hydrolock. Diesel engines also tend to have higher torque, rotating inertia, and stronger starter motors than gasoline engines. The result is that a diesel engine is more likely to suffer catastrophic damage.“

Look for a bent connecting rod, which is a typical damage by hydrolocking.

 

[berkeman]

Hi thanks for your replys the engine is a 2.0 tdi Diesel engine number caha

Have you been able to download the event history from the car's ECU? You may want to have a different mechanic do the download, BTW.

 

[audi q5]

Welcome and sorry for that damaged engine.

What was wrong with the engine before the last repair?
Why was that injector replaced?

It seems to me like the typical failure by hydrolock.
Prior or after the injector replacement, liquid (coolant or diesel fuel) could have leaked inside the small combustion chamber #4 only, due to unknown causes.

Please, see:
https://en.m.wikipedia.org/wiki/Hydrolock

“Diesel engines are more susceptible to hydrolock than gasoline engines. Due to their higher compression ratios, diesel engines have a much smaller final combustion chamber volume, requiring much less liquid to hydrolock. Diesel engines also tend to have higher torque, rotating inertia, and stronger starter motors than gasoline engines. The result is that a diesel engine is more likely to suffer catastrophic damage.“

Look for a bent connecting rod, which is a typical damage by hydrolocking.

Hi thanks for the reply and information
Iv just been out to check the injector codes and the one the mechanic has put In has a different code to the rest so I Believe hes put the wrong injector in

 

[Baluncore]

Iv just been out to check the injector codes and the one the mechanic has put In has a different code to the rest so I Believe hes put the wrong injector in

It may still be the correct injector, but from a different manufacturer or supplier.

Injectors come in different lengths. I expect the most likely bad mistake would be to fit an injector for the V6, to the I4 engine of the same year. I had trouble identifying the relevant injector codes because some references suggested your vehicle injector code changed twice in 18 months.

You will need to pull the replaced injector, along with at least one of the other injectors, then you can compare the length and other physical dimensions, and look for physical damage due to possible collision with the piston.

 

[Averagesupernova]

My guess is that the injector that was replaced was defective as a symptom. There was likely something going on with that piston or it's rings that caused the injector to become sooted up or something like this. I've seen it in a diesel where the intake was choked off and the injectors soon became sooted up and it started missing.
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In the OP's case, poor compression on the cylinder in question probably caused this injector to go bad. That poor compression was likely caused by something going wrong with the piston or it's rings. I've seen in a gas engine where the top ring broke and after a few thousand miles ended up on top of the piston. It might seem that a piston coming apart is an all at once operation but it's not so.