Gary 95 Z28 M6

I have had an oil consumption probem for a while now which I believed was normal until now. I used to go through a quart and a half between oil changes but now its alot more. Yesterday I was driving in front of my gf on the way to a golf course when she called me and said the car was blowing blue smoke out the tailpipes pretty bad when I would get on it just a little bit. I switched cars with her and watched her drive my car and she was definetly right! Anywhere about 2500 rpms and you can see a bunch of blue smoke coming out the tailpipes. About a month ago I took the car to the track and my buddies all said I was blowing a ton of smoke out too. My times were nowhere near where they used to be either. I believe its one of 3 things. #1 is the intake gaskets leaking and sucking oil into the heads, #2 is valve seals, which I really don't think it is cuz I dont believe it smokes on start up, and #3 which I hate to admit I think it is, is the piston rings. Granted they are only 18,000 miles old, but twice in the last 4 years the temp gauge got up to 3/4 high for a minute due to a faulty connection on my electric water pump. What I want to know is, where should I start? Cylinder leakage test? Pull off the intake? Pull the motor and start tearing it down again? I did a search and really didn't come up with anything solid. Thanks for any help guys!!!

Fastbird93

Personally I'd start by checking a couple of plugs for any fouling/wetness.

When you had the motor done, did the heads get milled, and was the manifold milled to match?? If the manifold isn't matching up, you'll stand a real good chance of getting the gasket failure.

How's the cars running and driveability?? Is it surging at all, or stumbling or seem like it's running really rich?

Gary 95 Z28 M6

I put new plugs in about a month ago. They all looked OK except for cyls 1 and 2. They both had a light tan color that would indicate a lean condition. It has been running worse lately and it has a stumble on acceleration. That is the reason I changed the plugs in the first place, but the plugs didn't help the condition at all. I did have the heads milled when they were ported and the block was decked to 0 when I redid the bottom end. The intake manifold is bone stock and unmolested. I think I may pull it off this week and start there. I should be able to see some oil residue on the intake ports if this is the problem. Also, if it is an intake leak, that may explain why it seems the car is running lean when i get on it.

Gary 95 Z28 M6

Well I pulled the intake off today and I don't really see anything solid that would indicate that its a problem with the intake or gaskets. The gaskets are fine with no cracks at all. I looked at all the runners on the heads and a few had a very light film of oil but nothing that I would call excessive. Does anyone have any other ideas or should I just stop beating around the bush and get the motor out and go from there? Thanks for any help guys!!

Gary 95 Z28 M6

Well I figured I'd give an update on what I have found so far. I pulled all the plugs out this weekend and I really didn't see any oil evidence on any of the plugs. I did notice that they all appeared to be very light in color which looks like all the cylinders are running lean. After that I loosened up all the rockers and did cylinder leakage tests on all the cylinders. At 100 psi all of the cylinders were right around 98 psi with 94 psi being the lowest on cyl. 2. with the amount of blue smoke coming out of the tailpipes I was sure I would see something with the leakage test but everything appears fine to me. Whats left besides valve seals? This problem is driving me nuts trying to figure out!!! If anyone has any ideas on what to do now please let me know!!!!

Guest47904

If it's burning in the cylinder, you would see it on the plugs. PERIOD. you have to solve that mystery first. Could it be an exhaust valve seal????? Think long and hard about that one. If it is the cause, I'll bet it's toward the back of the engine.

Gary 95 Z28 M6

you may be on to something with an exhaust valve seal. that would explain why there is no problem with the cylinders and the plugs all look ok. i am still leaning towards the intake leak though. any other ideas???? this is driving me nuts!!!!

matLT1

I'd start with the cheap stuff. You may even want to see if your pcv system is causing excessive oil to go in the TB. I'd do the intake gaskets first because $20 gaskets sure beats the price of a rebuild.

You may also want to replace the valve seals. If you do tear into the valve train to replace the valve seals you may want to check the valve guides for excessive wear. This can also cause excessive oil consumption.

Guest47904

Come on man, think. You already did the intake and said it was ok. You looked at all the plugs (?) and said they showed no signs of oil fouling. If the intake was the problem it would show up on the plugs cause it has to go through the cylinder to go out the tail pipes.

The exhaust valve seal is the only answer that makes sense. One other thing I didn't mention before. SBC's at least up to GenII had a problem with the rear oil return passages in the heads clogging. This would cause the oil to pool up toward the back of the head and any weak seal was inundated with oil and did what you are talking about. Naturally if the intake seal was the bad guy, it would show up on the plug and eventually foul it out.

If you removed the exhaust manifolds, I bet you will find the one that's the problem.

Gary 95 Z28 M6

another good call speedy!! i already have the right header loose so im gonna peek in the exhaust ports today and i might as well unbolt the left header and look inside. ill post my results later.

Gary 95 Z28 M6

well, with both headers off i was able to look inside of the exhaust ports and i didn't see anything significant on any of them. so i took a good look at all the plugs again and i think i may have found a problem. cyl. #2s plug was black all over the inside white part that the electrode sits over. i compared it to all the other plugs and the other plugs are all fine. also, cyl.#2 had the lowest reading out of all 8 cylinders during the leakage test. it was 94psi at 100psi which meant it had 6% leakage which i dont think is anything to worry about. what should i do next guys????

Guest47904

Now you may be talking a whole new ball game. The logical choices are intake gasket, head gasket, seals, rings or a crack. BUT, you did the intake. A crack is unlikely. You did a leak down test so that should have eliminated head gasket, crack and rings. There's more to the story, wait. The last thing left is the seals. However, the symptom you reported is not indicative of a seal problem.

Now comes the interesting part. If it where me, I'de still replace the seals. Out of the choices you appear to have left, that's the easiest. Try this tool.
http://buy1.snapon.com/catalog/item....re&dir=catalog
You'll have to pressurize the cylinder but you already have a leakdown tool for that.

Here's the interesting part. You could still have a problem with the rings in #2, or should I say the oil ring. The leak down test usually doesn't see a bad oil control ring and there in lies the possibility for the leak. BUT, (don't you just hate those) you will have to eliminate everything else beyond a shadow of a doubt before you want to jump into that one. And we have not done that yet.

Be damn sure you don't have an external leak dripping on pipes that looks like it's coming out the back.

I still find it odd what I thought you described as a lot of smoke, not leaving enough evidence on the plug the way you described it.

Gary 95 Z28 M6

exactly, thats what makes this so frustrating. this is my plan: im going to check the valve seals on cyl#2 and replace them if necessary. next im going to put it all back together with new intake gaskets and run it for a while. if i am still blowing smoke im going to make sure its nice and hot and then do leakage and compression tests again and go from there. im also going to make sure the pcv system is all working as it should. i will post results as soon as i get all of this acomplished. thanks for the help so far!!!!

Gary 95 Z28 M6

well i figured i would give an update to let everyone know what i found. as you can see with the above posts, i was not able to find anything significant while looking at things with the motor in the car. saturday i decided to pull the motor and go from there. today i tore the motor down and found the problem. first off, on cyls. 3,5,6, and 7 the 1st and 2nd compression rings were lined up right on top of eachother. the other thing i noticed is that on all of the pistons, the 2nd compression rings looked like they never fully seated. when i had the bottom end redone a few years ago, it looks like they just used .030 over replacement rings. in any event, i am going to put new total seal rings in, along with new rod bearings and possible main bearings. thanks for everyones help!

Guest47904

If you're talking about Total Seals Gapless rings, I do not recommend them unless you understand FULLY all the things the rings require from an installation stand point and later what is required after using them.

You must have an extremely smooth bore so the shop has to do that. You do not use lubricant when installing them but rather this:
http://www.jegs.com/webapp/wcs/store...tegoryId=20181

Now the fun begins. The gapless rings (which I have) pull so much vacuum, unless you restrict the PCV system, you're gona pull oil into the intake.

Stick with a good high quality conventional ring set.