As some of you may know I have been burning a bit more oil than I would like to and I am in the process of narrowing it down to my valve seals. It sometimes blows a bit of smoke at startup, when revving, or at the start of a hard pull. I am going to do a compression test to eliminate other possibilities.

If it comes down to me needing to replace the valve seals is there anything else i should replace/upgrade while I am in there? Do I have to take the whole head off or can they be replaced from the top?

I already have ZZP's stiffer valve springs. If I need to take the head off is it worth replacing the valves while I'm at it? Any other helpful information you may have on this would be appreciated. I just like to have a good plan before I jump into things.

 

Bump. Should this be posted in a different area?

 

You can do the seals with the head on, but it's a process.

You'd have to go through the same steps as doing valve spring replacements, using compressed air to hold the valves up, and then pull the seal off and install the new one while the spring is out.

Definitely do-able, but not a simple job either way. I'd leave the head on though, just pull the cams, use the kent-moore ecotec valve spring tool and go to town on it.

 

So if I take the head off do you think it would be worthwhile to put in new valves? I don't have the kent-moore valve spring tool but I have this.



Just not sure if I will have enough clearance to use it with the head installed in the car.

 

Idk, I would personally remove head and measure the valve guide and make sure the bore is in spec. Usually smokes on deceleration if the guides are worn on exhaust. And they are it will leak past and burn, for intake side it would get sucked into the intake air coming into the engine and burn oil and cause excessive wear on the valve seat, valve stem, and valve face.

 

Oil shouldn't be getting past the valve guides to the point where it burns oil really but I guess it would if there was enough vacuum to pull it through.

 

What's causing excessive wear on the valve seat, valve stem, and valve face? The leaking oil?

I checked compression and I am at 200 psi on 2, 3, and 4 while at 170 psi on number 1 cylinder. Being low on number one is something I am going to track down later and don't think it is directly related to the oil consumption because I looked at the plugs and they indicated that I am burning oil in cylinders 2 and 3, the two middle cylinders. I have read that oil or coolant burning in two consecutive cylinders can sometimes be attributed to blown head gasket.

So I am not sure it is valve seals that are leaking but it doesn't appear to be oil getting past the piston rings. If the sun is right and the wind is not blowing I can clearly see if puff out some bluish smoke if I rev it. I'm open to suggestions for other potential causes of burning oil if you have any ideas.

 

Oil leaking through will cause the excessive wear. If you did a compression test coolant may have shot out if the radiator if you had it open. You can test for combustion gasses in the radiator with the test kit if you have one, it is the easiest way.

 

Low compression could be a cracked piston, which would cause the smoke as well... i'd say you better pull the head and investigate thoroughly. There is something going on, and it's probably more than valve seals.

 

Thanks joe for usually coming to the rescue of the newbies asking questions. You da man!

 

He said he's got oil on plugs 2 and 3 idk how that contributes to cylinder 1 having low compression. Possibly could have oil getting into other cylinders raising the compression in the other cylinders. If he did a leak down on cylinder 1 that would provide more answers.

 

Compression test tells whether rings or valves are leaking compression so it's not a precise test as to what's going on.

 

ItalianJoe has forgotten more about cobalts than you know. If a cylinder is low on compression and signs of oil burning on different cylinders (now 3 of the 4 have issues) which the OP noted could be signs of a bad head gasket, as ItalianJoe suggested he should be pulling the head and figuring out whats going on before he fills his oil or cylinders with coolant or a piece of piston gives free.

 

So the general consensus is pull the head. No problem, will give me something to do in the evenings this winter.

I did the compression test to rule out if it was getting past the rings. Dumping oil in the cylinder with lower pressure raised the psi only by about 5 so I assumed it wasn't the rings. I was thinking more that it was the valve to valve seat seal but now you are thinking cracked piston? Whew I hope that is not the problem. The one thing that doesn't line up with that theory is that the spark plug is clean on that cylinder. The cylinder is a pretty damn new Wiseco forged piston too. I don't seem to have excess blow-by. It burns oil when I am traveling long distances with the engine running in vacuum pretty much the whole time.

What all is required for a leak down test?

Yes I am a newbie. I am learning as I go here. I'm sure all of you didn't just wake up one day with experience. You have to start somewhere. And what better platform to learn on than something as cheap as an L61 Cobalt. If I **** something up, it can be fixed without breaking the bank, generally.

I appreciate everyone who is bearing with me here and trying to help.

 

So I have a bit more data that points towards valve seals or any other problem that would go away after my car warms up. When I first start the car after it has been sitting all night it is rough to start. Engine sounds like it is clearing the cylinders and stumbles unless I wait it out or give it a blip. Last night I started it after it had sat for a day and went and inspected the exhaust with a flashlight to better see smoke if there was any. There was smoke for probably about 6 minutes until it got warmed up and then the exhaust was clear as far as I could tell with the flashlight. I definitely don't think it is a cracked piston.

Has anyone ever seen a head gasket seal act this way?

 

I missed this part originally... was the block machined when the pistons were installed? If you are getting oil in the cyl it could very well be coming past the rings with aftermarket pistons. I have seen WAY more of these cars have issues with the aftermarket pistons (installer/build errors, not bad pistons), than successful builds. High vacuum as you said could still be valve seals, but the non-OEM pistons make them much more suspect in my experience.

How is your PCV system, ever change the valve?

 

The block was not machined. Chances of installer error are high as I did it myself and it's the first time I've ever done anything like that.

PCV valve is completely blocked off when you put an LSJ manifold on L61. Not sure if there are any good ways around that. So PCV at this point is just a breather filter.

 

Ok, if you dropped pistons in a stock ecotec block, your cylinder sealing is no good. I'd bet you have oil getting past the rings then. If you've got no PCV left, and the pressurization of the block has nowhere to go, it can push oil in all sorts of places.

At this point, I'd say toss some valve seals on there and see if it fixes it. If not, deal with the smoke until you rebuild another engine for it.

 

Oh you're right, I'm probably retarded and what I said isn't just general things that couldn't be wrong with it

 

My cylinder sealing is good in 3 out of 4 lol. I did use a ball hone to deglaze. I do have crankcase ventilation so it's not like I'm popping out my dip stick or building pressure. I just don't have any kind of vacuum PCV mechanism.

If it is rings you think it is just the higher viscosity cooler oil making more get by the rings when it isn't warmed up yet?

I'm considering trying to find a lower milage L61 somewhere and getting it ready off to the side.

 

Is there any reason I should replace my lash adjusters or cam followers while I am in there or are they typically parts that don't wear out?

 

The adjusters, probably, if you don't have the newest version. They did get an updated part # at some point. They aren't really a wear item, but the stock ones aren't designed for severe abuse and if they are weaker than they should be, you will lose power and run the risk of floating valves at high rpm/boost levels. There have been very few incidences of failure though.

The followers should be fine to reuse unless you see any damage.

 

Top side of gasket


Bottom side of gasket

I know, use oem gasket. Even though this is a generic gasket I was wondering if the "damage" shown indicated a head gasket leak or failure? The head also has a carbon streak in the same location. This is on the number one cylinder with the low compression.

 

If it was pushing through the gasket like that, it lost clamping ability. Either the bolts were not holding properly, or the block/head is warped and not flat in that area. Gotta have everything checked carefully, then replace the gasket and bolts and torque to spec if the mating surface is perfect.

These newer engines with MLS gaskets have extremely minor tolerance for sealing surface irregularities. They need to be perfectly smooth and flat to seal right, but they will last almost forever if they are.

 

I'm taking my head to a machine shop today to have them check/prep the mating surface on the bottom of my head. My block is hopefully OK because I can't really move it right now

When I put this head on the first time I followed the torquing instructions the best I could. I did have a hell of a time trying to get that damn angle gauge to work so I did end up just going with a torque value. There's a decent chance it was my fault.