Cylinder head valve failure mode

[inkubate]

Hi all,
I have been suffering a cylinder 3 misfire problem on my Seat Ibiza 1.4l for some time and I had the exhaust valves replaced back in April due to low compression causing this. This however failed to fix the problem and the garage denied it would be an issue with the work that they did replacing the valves so wouldn't do anything further. Having some time during the last week and taking the issue into my own hands, I refurbished an old scrap cylinder head and swapped it myself which has now totally fixed the problem!

However looking at the condition of the valves and seats that were replaced in April on the old head I would like to ask your opinions please. Pictures are below of the new valves and seats that the garage fitted and I would appreciate any advice as to if this was caused by poor workmanship or something else - 4 months doesn't seem long for them to get like that!

I have learnt a lot from various visits to this site which helped me even do this job so thought this a good place to ask.

Many thanks for looking.

[Pumaracing]

Firstly you don't replace seats, you recut them unless they are actually cracked or broken. Those seats weren't recut four months ago. At most it seems you got the valves replaced and put back on the old seats. However looking at a photo isn't exactly ideal for diagnostic work.

[andyiley]

^^^^ Wot 'e said.

I don't think even the valves look 4 months old, I have seen better when I did my last head on my last track day car & they were 12 years old at the time!

But, as PR says it is hard to say difinitively from a couple of pics.

[inkubate]

Thanks for the feedback and I understand that images aren't ideal. My thoughts were that if the new valves had just been fitted but without cutting or at least lapping the seats to verify the contact width and consistency that exhaust gasses would leak through causing the deposits / burning.

I was interested in others opinions as this is the first time I have worked with cylinder heads / valves so am not 100% on diagnostics but am getting there. I would expect a garage doing the work to ensure that the valves seats are in a good enough condition to accept new valves but I doubt they did from my own feeling and your feedback.

Many Thanks.

[227bhp]

It largely depends on how many miles you did in 4 months, 60 or 50,000?
I'm not sure, but it looks like the valve wasn't actually sitting on its seat, could this be the case? Surely not...

[inkubate]

Hi again,
The valves were sitting in the seat when I removed them but there was some leakage when I did a water test and compressed air underneath. The thing is that I've only done approx 2000 miles since the work was done!

Many Thanks

[Pumaracing]

Valve seats tend to burn out or distort on the spark plug side and you can see the carbon build up there which is where they're probably not sealing to the valves. Your photo is showing the wrong side of the seats for what I'd ideally like to see. Give them a quick lap and see which bits are seating properly.

[stevieturbo]

So what exactly does the receipt for the work say ? If it details work done ?

[inkubate]

The receipt says that cylinder 3 exhaust valves have been replaced. Earlier in e-mail correspondence after they took off the head they mention that the valves were most likely not seating properly so they'll be replaced. When I asked for warrenty repair I was told the valves would not have failed and the fault would be "the valves haven't been sealing correctly, the seats get weakened and they fatigue" which they said was a head fault and not a fault with the work done. I'm not convinced as I suspect these seats will lap / machine OK - I don't want to do that yet until I've put my evidence forward in case they want to see!

Many thanks for all your help so far!