Mondeo Mk4 - valve stem seal replacement
Discussion
MOT time today and a very borderline pass. Emissions were terrible.
The car has 143,000 on the clock... original clutch and exhaust.
Diagnosed as either a ring has gone or the value stem seals have failed. I will pressure test the cylinders at the weekend but my friendly MOT tester was 99% certain it will be the valve stem seals. Apparently, I will need 2 new lambda sensors whilst I am at it.
I love the car and would like to keep it going as long as possible. My options are:
DIY outside with engine in situ
DIY inside after removing the cylinder head
Take to a garage and suffer the cost
Sell the car
DIY obviously would be cheapest but all the YouTube videos are done in workshops with the entire engine on the bench. If I were to remove the cylinder head to work indoors, would it make sense to get it skimmed and the valves reseated at the same time?
I'm keen to keep the cost down because when the clutch does go, from what I've seen it's not the simplest job ever.
Does anyone have experience in this area?
The car has 143,000 on the clock... original clutch and exhaust.
Diagnosed as either a ring has gone or the value stem seals have failed. I will pressure test the cylinders at the weekend but my friendly MOT tester was 99% certain it will be the valve stem seals. Apparently, I will need 2 new lambda sensors whilst I am at it.
I love the car and would like to keep it going as long as possible. My options are:
DIY outside with engine in situ
DIY inside after removing the cylinder head
Take to a garage and suffer the cost
Sell the car
DIY obviously would be cheapest but all the YouTube videos are done in workshops with the entire engine on the bench. If I were to remove the cylinder head to work indoors, would it make sense to get it skimmed and the valves reseated at the same time?
I'm keen to keep the cost down because when the clutch does go, from what I've seen it's not the simplest job ever.
Does anyone have experience in this area?
People love to tell you "it's the valve stem seals". I remember having a Sierra that burned oil 20 odd years ago and a colleague told me it would be the the valve stem seals. When quizzed, he didn't know what they were and had never had an engine apart in his life.
A pressure test (leak down or compression) isn't going to test the valve stem seals. You may already know this of course, apologies if I've misunderstood your comment.
What engine is in your Mondeo?
A pressure test (leak down or compression) isn't going to test the valve stem seals. You may already know this of course, apologies if I've misunderstood your comment.
What engine is in your Mondeo?
If you're burning enough oil past the Stem seals to be "borderline" fail on HC (I assume) on the MoT, you would see it out the back... 
If the car doesn't puff out a little cloud of blue smoke on startup the Stem Seals are fine.
Why 2 Lambda sensors? is it a V6, which it isn't as you said Cylinder "Head", he's talking bobbins, the second sensor does nothing for fuel control.
Can you post the emissions test result page?
Sounds like you have an air leak somewhere to me.
If the car doesn't puff out a little cloud of blue smoke on startup the Stem Seals are fine.
Why 2 Lambda sensors? is it a V6, which it isn't as you said Cylinder "Head", he's talking bobbins, the second sensor does nothing for fuel control.
Can you post the emissions test result page?
Sounds like you have an air leak somewhere to me.
Richard-D said:
People love to tell you "it's the valve stem seals". I remember having a Sierra that burned oil 20 odd years ago and a colleague told me it would be the the valve stem seals. When quizzed, he didn't know what they were and had never had an engine apart in his life.
A pressure test (leak down or compression) isn't going to test the valve stem seals. You may already know this of course, apologies if I've misunderstood your comment.
What engine is in your Mondeo?
2 litre petrol. (2011)A pressure test (leak down or compression) isn't going to test the valve stem seals. You may already know this of course, apologies if I've misunderstood your comment.
What engine is in your Mondeo?
The pressure test is to confirm that it's not the piston rings.
The 2 previous answers are both correct. The fresh ticket gives me the luxury of time. Selling it (realistically scrapping it) or waiting for something else to give way are both logical.
Which engine? Petrol or diesel? Turbo? V6? A lot of information is missing which affects the complexity of the job, for example a turbo always adds a few hours of work and messing around trying to get a head out.
I've heard stories of various workaround to allow valve stem seals to be done without removing the head but I'd not fancy it, trying to compress the springs and deal with the tiny collets etc would be a nightmare.
So, I'd always recommend removing a head to replace valve stem seals. A skim isn't needed unless the head isn't flat, which usually occurs after an overheat event. But if the head is off and the valves are coming apart, its worth cleaning it up, checking valve guides, cleaning valves, re-lapping valves ( a top end rebuild). More for longevity than to fix anything actually broken.
While the head's off, you can test rings by filling the cylinder with oil when its down and seeing if it leaks out. Also obviously, a visual inspection can reveal gross issues with the bores. Replacing rings once the head off isn't that much more of a job, so long as the pistons and bores are undamaged, but only worth doing if there's an issue there.
I've heard stories of various workaround to allow valve stem seals to be done without removing the head but I'd not fancy it, trying to compress the springs and deal with the tiny collets etc would be a nightmare.
So, I'd always recommend removing a head to replace valve stem seals. A skim isn't needed unless the head isn't flat, which usually occurs after an overheat event. But if the head is off and the valves are coming apart, its worth cleaning it up, checking valve guides, cleaning valves, re-lapping valves ( a top end rebuild). More for longevity than to fix anything actually broken.
While the head's off, you can test rings by filling the cylinder with oil when its down and seeing if it leaks out. Also obviously, a visual inspection can reveal gross issues with the bores. Replacing rings once the head off isn't that much more of a job, so long as the pistons and bores are undamaged, but only worth doing if there's an issue there.
I thought probably 2L Duratec but wanted to be sure. The 1.8 version has a very common issue with gumming up the oil control rings (I've rebuilt a couple of these for this fault). I don't believe the 2.0 suffers as badly for this fault but it's still a possibility if you're burning oil. I should have asked first but... is it burning a lot of oil?
ridds said:
If you're burning enough oil past the Stem seals to be "borderline" fail on HC (I assume) on the MoT, you would see it out the back...
If the car doesn't puff out a little cloud of blue smoke on startup the Stem Seals are fine.
Why 2 Lambda sensors? is it a V6, which it isn't as you said Cylinder "Head", he's talking bobbins, the second sensor does nothing for fuel control.
Can you post the emissions test result page?
Sounds like you have an air leak somewhere to me.
Thanks. Yes, it's not the V6. If the car doesn't puff out a little cloud of blue smoke on startup the Stem Seals are fine.
Why 2 Lambda sensors? is it a V6, which it isn't as you said Cylinder "Head", he's talking bobbins, the second sensor does nothing for fuel control.
Can you post the emissions test result page?
Sounds like you have an air leak somewhere to me.
It is definitely oil being burnt, as I'm topping it up after any longer drive - but I hadn't noticed plumes of smoke until today but obviously there must have been. My bad for not taking the trouble to investigate. Deferred maintenance...
paul_c123 said:
I've heard stories of various workaround to allow valve stem seals to be done without removing the head but I'd not fancy it, trying to compress the springs and deal with the tiny collets etc would be a nightmare.
This is my thinking, all the YouTube videos of the workaround are done with the engine out. Trying to do it with the engine in the car, outside, in the current weather I think would be really difficultPetrol BA7 145bhp engine
Andy 308GTB said:
Thanks. Yes, it's not the V6.
It is definitely oil being burnt, as I'm topping it up after any longer drive - but I hadn't noticed plumes of smoke until today but obviously there must have been. My bad for not taking the trouble to investigate. Deferred maintenance...
How much oil over how many miles? I'm still not convinced on it being the reason for the marginal MoT pass.It is definitely oil being burnt, as I'm topping it up after any longer drive - but I hadn't noticed plumes of smoke until today but obviously there must have been. My bad for not taking the trouble to investigate. Deferred maintenance...
Andy 308GTB said:
Thanks. Yes, it's not the V6.
It is definitely oil being burnt, as I'm topping it up after any longer drive - but I hadn't noticed plumes of smoke until today but obviously there must have been. My bad for not taking the trouble to investigate. Deferred maintenance...
Realistically that level of oil burning is not going to be the stem seals. That leaves 2 likely routes, the rings and the PCV valve. It is definitely oil being burnt, as I'm topping it up after any longer drive - but I hadn't noticed plumes of smoke until today but obviously there must have been. My bad for not taking the trouble to investigate. Deferred maintenance...
I would rule out the PCV system first as it takes very little time/effort to do. If I remember correctly it's built into the inlet manifold on this engine. You can reach the hose with just the vanity cover removed. At idle it should be sucked closed so there should be no vacuum on the line. If it's stuck open it will hoover oil into the manifold. If my memory is out and it's built into the cam cover...disconnect and plug hose then see if oil usage stops. I think it's in the manifold though.
Edit: corrected to front of engine, forgot which way round the Duratec was for a mo.
Edited by Richard-D on Monday 20th October 23:55
My reasoning for suggesting checking the PCV first was that that test is definitive. If your PCV is shut at idle it's not the problem. If it's open it is the problem. It's also the quickest/easiest test.
The rings you actually need to test are the oil control rings. These are the first to get gummed up and may not give a definitive result on your compression test. ie. a good compression test does not mean your oil control rings are still effective. So you could end up doing that test but still having no more information.
Obviously you'll do whatever you want, just explaining why I would test in this order.
The rings you actually need to test are the oil control rings. These are the first to get gummed up and may not give a definitive result on your compression test. ie. a good compression test does not mean your oil control rings are still effective. So you could end up doing that test but still having no more information.
Obviously you'll do whatever you want, just explaining why I would test in this order.
Richard-D said:
My reasoning for suggesting checking the PCV first was that that test is definitive. If your PCV is shut at idle it's not the problem. If it's open it is the problem. It's also the quickest/easiest test.
The rings you actually need to test are the oil control rings. These are the first to get gummed up and may not give a definitive result on your compression test. ie. a good compression test does not mean your oil control rings are still effective. So you could end up doing that test but still having no more information.
Obviously you'll do whatever you want, just explaining why I would test in this order.
A quick peak inside the Intake Manifold, post PCV entry would be a good tell here. The rings you actually need to test are the oil control rings. These are the first to get gummed up and may not give a definitive result on your compression test. ie. a good compression test does not mean your oil control rings are still effective. So you could end up doing that test but still having no more information.
Obviously you'll do whatever you want, just explaining why I would test in this order.
The breather circuit is active at Part Load conditions, it's just controlled by the PCV Valve, which limits the depression on line from the Intake. it allows some gas transfer without sucking the Crankcase (or more importantly all the seals) inside out. The Full Load side of the Breather circuit should be closed though.
1 litre in 250 miles is a lot.
Audi was chastised for using 1 litre per 1000m (maybe km) during running in on their engines.
Andy 308GTB said:
250 mile round trip gets through a couple of pints of oil I reckon. Probably more. I'm doing that run at the weekend and will measure it properly.
I'll do a compression test tomorrow evening & report back.And then go through the other tests before pulling stuff apart.
Thats not valve stem oil seals on their own.I'll do a compression test tomorrow evening & report back.And then go through the other tests before pulling stuff apart.
Agree with others above, that level of oil being burnt is 100% not being caused by valve stem seals.
Typical visible signs of valve stem seals would be blue smoke at start up or "on the overrun". (best seen when off the throttle for a long time from speed, such as a motorway exit slip road)
Also, as others have said the actual emissions print out would help here.
Typical visible signs of valve stem seals would be blue smoke at start up or "on the overrun". (best seen when off the throttle for a long time from speed, such as a motorway exit slip road)
Also, as others have said the actual emissions print out would help here.
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