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Piston rings, valve guides or what?

2003 ford focus 2.3l, 5 speed manual with about 146k on it. I pulled the head after the misfire was diagnosed as a blown head gasket, which it was not and found an exhaust valve cracked. I replaced it, all seals and gaskets and when I fired it up it still has the misfire and oil on top of the #3 piston. I will do a compression test but want to know what it could be IE valve guides, rings, something else?


Where can I put more pictures to include a timeline of symptoms?

Valve stem seals?

Have you checked the compression?

I would perform a dry and wet compression test . . . in that exact order . . . followed by a leak down test

please give us the numbers, if you do indeed perform those tests

I will perform a wet and dry test soonish. The leak down test may not happen. If I hadn’t just put brand new valve stem seals in then I would agree granted, that doesn’t mean I didn’t damage them putting them in.

Those cylinder walls do not look too good and in all honesty a dry/wet compression test should have been done before tearing into it regardless of the alleged bad head gasket diagnosis.
Sounds like a ring issue to me.

A shop did a compression test and diagnosed it as a bad head gasket. I trusted that determination but now doubt everything they have done or told me.

So I put conventional oil in it so hopefully I could see smoke, well I did, a bunch on start up and puffs while running. The compression test is as follows #1 194, #2 195, #3 92, #4 192. Wet #3 94. Note: each cylinders pressure went up by about 30psi every revolution until they hit their peak.

The 190s are fine. The No. 3 cylinder shows a valve problem. Whenever a cylinder head is off the valve should be leak tested no matter the reason for the head removal.

This is done by filling the combustion chamber with liquid (I use mineral spirits) and allowed to sit for a short time. If the fluid level goes down in say 5 or 10 minutes that means a valve job should be performed or the head replaced. The leaking fluid will dribble down through the intake or exhaust ports; or both.

You say you found a cracked exhaust valve and replaced it. I assume this means the compression is still way low even after that? If so, were the other valves checked and was the new valve lapped in properly?

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Exactly who replaced that bad valve. A new valve requires that the seat be reground and I would have had a complete valve job done myself including seals

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I am learning as I go so I really appreciate the input, with that said, no I did not lap them I just put 2 new ones in because I was naive. I cleaned the valves and seats but nothing more. I replaced the valve guide oil seals but still have these issues. So the valves need to be lapped but could it also be a ring issue? My plan (please critique) is to pull the head, do the liquid leak test, lap the valves, leak test again, put in new oil seals, put new rings on all 4 pistons, re-hone all 4 cylinders and replace piston #3 to be safe. Once I’m in there I will see if the crank and rod bearings need replaced and take bore measurements.

I would concentrate on the head and valves. The fact that your dry compression was the same as the wet compression on #3 probably means it’s a valve, not a rings, problem. No way you can afford a professional valve job?

You need a pro to look at this head to see if it’s worth fixing, and to determine what needs to be done.

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It’s not just a matter of lapping the valves in. Lapping is finish work AFTER the valve seats are ground and the seat valve face contact area is checked.

In a case like this what should have been done is to just have a valve job done at the local auto machine shop. Around here they charge 5 bucks a hole; meaning 5 for each properly ground and fitted seat and valve. In your 4 valve head that would mean 80 dollars plus valve stem seals. That’s cheap.

I think that if you bring that cylinder up; to TDC on the compression stroke and apply some compressed air to it you will hear it hissing out the exhaust, intake, or both.

Another quite often overlooked thing is checking the head surface to make sure it’s flat. I don’t know what the spec is on your Focus but generally speaking .002 to .,003 thousandths of an inch is the point at which the head needs to be surfaced. And that ain’t much wiggle room at all.,

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I will be taking it to a machine shop to have it worked on but for $300. One shop wanted to do everything they can think of on it for $600.

Valve clearance: Exhaust tolerance .010-.013; (1) .008 (2) .007 (3) .005 (4) .006 (5) >.0015 (6) >.0015 (7) .006 (8) .006.
Intake tolerance .0011-.008; (1) .004 (2) .005 (3) .004 (4) .004 (5) .003 (6) .003 (7) .004 (8) .005

Clearly #3 is open.

There’s a real problem with the exhaust valves on 5 and 6. Those .0015 numbers are horribly tight and that is cold. Once heat sets in those numbers will decrease to the point that the valves will remain open a bit. Since exhaust valves can only cool themselves by dissipating heat into their respective valve seats that means they are usually not long for this world.

The .004s and .005s are worrisome but not as much as the .0015s as that is less than .002 of an inch and I’m not aware of any mechanical lifter engine that will hold up under that. For what it’s worth, that tightness is generally caused by stem stretch of the exhaust valves over time.