Catastrophic engine failure

[Bendy_182]

Hihi, first post so go easy on me.

Last Sunday, I was headed off to drop some polish off to one of the boys in my 2004 Clio 182. Driving onto the bypass, 3rd gear @ WOT, 4K rpm, I heared a big bang, bits of engine coming out of the exhaust and a whole lot of smoke.

The car sat for a week until my new engine arrived, pulled the old engine out, new one in etc etc.

Now, in the meantime I thought I'd strip the original engine just to see what actually when wrong.

Number 4 intake valve was sat on top of the wrist pin, with a lovely big hole in the top of the piston. Exhaust valve bent like a dog's back leg. Timing belt covered in oil however timing seemed fairly good, but I couldn't be certain as I had no timing tools to check. Nothing at all salvageable. The car has been overfuelling at WOT since I bought it, with black smoke on WOT mixed with blue smoke, and the timing belt looked very ropey indeed.

Anybody feel as though they have some sort of explanation for this failure? Piston looks as though it's melted however I can't imagine that causing valvetrain failure, moreso a lot of smoke and a misfire.

I have a few ideas but I can't settle on one.

- Timing slipped, smashed valves, snapped number 4 intake valve and the subsequent rattling about put a hole in the very hot piston

- The valve just decided to fail, and caused the hole by the valve head flying about

- Overfuelling caused the piston to melt, however this doesn't explain the valve going Pete tong.

I should add, this is the 3rd engine this car has had, one prior to my ownership. The second engine seemed to be very high mileage though going by all the oil leaks and blue smoke.

 

[JamesBryan]

Its dropped a valve, fairly common.

Doubt the overfuelling caused it and it certainly wouldn't melt the piston if anything the overfuelling would lower cylinder temps.

 

[JB21]

Unlucky mate, I feel your pain. Happened twice to me in 300 miles. First it snapped the belt bending valves, then straight after the re-build dropped a valve seat

 

[DickP]

Hi

What contributes to these engines dropping valves?

I recall reading the factory valves are manufactured in two halves and this is where the failure happens. Is that right?

Thanks,

 

[JamesBryan]

Hi

What contributes to these engines dropping valves?

I recall reading the factory valves are manufactured in two halves and this is where the failure happens. Is that right?

Thanks,

Yeah they are 2 piece and friction/fusion welded, as most production valves will be. It's cheaper.

High revs and hitting the limiter will put extra strain on them as will pops and bangs map (extra heat).

 

[Bendy_182]

Hi

What contributes to these engines dropping valves?

I recall reading the factory valves are manufactured in two halves and this is where the failure happens. Is that right?

Thanks,

The valves are two piece friction welded valves. I can confirm that the failure point of the valve (at least in my case) was indeed on the weld. Stupid design when you consider the nature of the engine and the way the car was intended to be driven, but hey ho, one new engine later and she's back on the road

I just thought it was a bit strange as to how the valve snapped under relatively low load.

 

[Brigsy]

Can only assume the valve has failed due to fatigue, might have had lots of abuse from previous owners?

 

[Bendy_182]

Can only assume the valve has failed due to fatigue, might have had lots of abuse from previous owners?

Like I say, the engine that failed is the 2nd engine the car has had, with the shell only being on 82k. I'm going to guess that it's been battered haha. Looking at the belt that was on the old engine, if it has had a belt change like the previous owner claims, it was easily on over 120-130k.

 

[JamesBryan]

A set of Supertech valves would be a future proofing insurance if you can do the work yourself.

Would be quite costly for a garage to do the work.

But then there is always the next weakest point, where do you stop ?

 

[Krarl]

A set of Supertech valves would be a future proofing insurance if you can do the work yourself.

Would be quite costly for a garage to do the work.

But then there is always the next weakest point, where do you stop ?

Buying something that isn't a Renault is the only cure ?

 

[Bendy_182]

A set of Supertech valves would be a future proofing insurance if you can do the work yourself.

Would be quite costly for a garage to do the work.

But then there is always the next weakest point, where do you stop ?

A full rebuild with completely uprated parts is the next plan mate!

 

[JamesBryan]

A full rebuild with completely uprated parts is the next plan mate!

Mega money mate.

 

[Robbie Corbett]

Are two cylinder showing damage above?

Nothing has melted there, thats just the valve which has pounded the absolute s**t out of everything. But no3 is damaged too? With all valves still in place?

 

[Robbie Corbett]

Thinking about it, occasionally when one cylinder fails badly bits of piston/valves can be ejected back into the intake manifold and sucked into an adjacent cylinder - think this is what has happened here?

 

[JamesBryan]

Thinking about it, occasionally when one cylinder fails badly bits of piston/valves can be ejected back into the intake manifold and sucked into an adjacent cylinder - think this is what has happened here?

More than likely I'd say.