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Removed cylinder head, and I saw THIS...

cylinder head

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#1 domc

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Posted 19 February 2012 - 08:41 PM

Hi all,

I need some advice/opinions on the condition of my cylinder head. My mondeo 2002 2L Duratec was using a lot of oil, so I decided to remove the head and do the valve seals. It's also had an annoying rumbling noise that I couldn't place, a bit like a misfire or leaking exhaust even though it had plenty of power. The noise always comes on at about 1600 rpm(ish), gets louder as power is applied and then disappears about 2300 rpm upwards.

Anyway. A few hours, scraped knuckles and torn fingernails later I got the head off, and the attached images show what it looked like. Pistons 1 and 2 had fairly big flakes of carbon on them, piston 4 had something like burnt sugar on it, very hard in texture, almost impossible to remove. Looking at the head, 1 and 2 looked fairly normal to my eyes (browny colour valve heads, no heavy deposits), but on the top of 4 there was thick burnt oil on the exhaust valves, again very hard in texture, and there was IMPACT DAMAGE on the land. I can only describe it as if a dog had chewed on it!
head 4 jpg.jpg
cylinder 4 jpg.jpg
Now, I feel fairly confident taking stuff apart, but I'm happy to admit I don't have the experience to say what is normal wear and what is unusual. Could something have been ingested into the engine and been thrown about before getting melted to the top of the piston? Is this related to the rumbling noise? Would leaky valve stems cause that oily burnt mess?

Please check out the photos, any thoughts much appreciated!!

Last thing, I checked the compression just before I took the head off. With a warm engine and wide open throttle, I got the following readings:

Cylinder 1 : 240psi
Cylinder 2 : 240psi
Cylinder 3 : 230 psi
Cylinder 4 : 220 psi

Thanks!!
Dom

#2 wobble67

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Posted 19 February 2012 - 09:03 PM

Dom,

Its' now a mucky mixture of throttle butterflies been eaten by the engine is it? Have you checked the inlet manifold and accounted for all the bits that are there?

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#3 siruncle

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Posted 19 February 2012 - 09:05 PM

have you checked the flaps in the inlet manifold? they are plastic and that does resemble burnt plastic. Do yourself a favour and remove them and fill the hole left when the bar is removed with araldite. :L
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#4 domc

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Posted 19 February 2012 - 09:19 PM

Thanks for the replies guys. I changed out the manifold butterflies when I bought the car a couple of years ago, thanks to the warnings on this site. It was a good job I did, they were all fairly loose. I did check them again when I pulled the head off, and the replacements feel solid. Still, maybe a previous set got eaten earlier in the car's life..?

#5 Mart1001

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Posted 20 February 2012 - 03:12 AM

It certainly looks like burnt oil to me. Maybe number 4 had previous swallowed an inlet flap, which had got stuck in the valve seat and destroyed the valves, leaving that scarring on the cylinder face. A previous owner had removed the head and replaced the valves but not the guides, maybe not even considering the guides. But the guides had been ovalled as a result of the damage(possible broken or bent valve stem) and the new valves have simply destroyed the new stem seals as they now move up and down with a circular motion. Oil runs past and down the stem(rotting the seat in the process causing your lowering compression to that cylinder) and the rest is in your pictures.
That's my diagnosis anyway ;-)

I would consider replacing your valve guides among other things but, if you can aford it, it might be better to have the whole head checked out by a pro ?

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#6 domc

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Posted 20 February 2012 - 08:29 AM

Mart1001,
Thanks for the analysis, it sounds very plausible. I couldn't understand why the head was damaged but not the valves, but this explains it. There was also more fore-and-aft tipping of the no.4 piston compared to the others,there weren't any marks on the cylinder so I wonder if there was damage to the gudgeon pin bearing or they'd changed out the piston. It doesn't have a lot of movement, so maybe it is responsible for the rumbling sound. Bit disappointing really, I always used to drive scrappers, and this was an expensive (for me!!) car when I got it. Guess you never know what the previous owner has done to it.





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