How do you check for worn valve guides?

[axl911]

I've heard you can try to wiggle the valve stem.

But how do you do this? Do you need to do this at TDC?

thanks,
anthony

[Rot 911]

Do it like you would the valve adjustment. You need the pressure off the rocker arm to wiggle the valve stem.

[john walker's workshop]

that method may give you a clue, but the guides wear the most on the end toward the valve head, and the valve is sitting on the seat under spring tension, so it doesn't show up as loose. high mileage and oil consumption are better clues.

[axl911]

Thanks. I am concerned for my 964 which recently begin spewing out blue smoke.

Oil consumption is 1K miles per quart.

I guess that pulling and inspecting the plugs would also indicate oil in the cylinder as well right?

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anthony

[HarryD]

Originally posted by axl911
Thanks. I am concerned for my 964 which recently begin spewing out blue smoke.

Oil consumption is 1K miles per quart.

I guess that pulling and inspecting the plugs would also indicate oil in the cylinder as well right?

----
anthony

Also, when they are worn, you will see copious clouds of blue smoke whenever you lift off of the loud pedal.

I was at 200 miles/qt when this shot was taken:

[john walker's workshop]

crusty oil buildup on the plugs is another clue.

[Por_sha911]

Do a leakdown test to be certain.

[HarryD]

Originally posted by Por_sha911
Do a leakdown test to be certain.

If I am not mistaken, a leakdown down test may not detect worn guides since the valves are closed when the test is performed.

Maybe one of our experts can give us the straight skinny.

[Por_sha911]

Harry-actually you may be right there.

[ischmitz]

Anthony,

give us a little more details for the armchair diagnosis. What mileage on the engine and is it transplanted into an earlier car or are we talking C2/C4 here? Is the smoke always there or only on decel (guides)?

Generally, you get oil into your intake. Valve guides are only one reason. If you overfill your oil tank you'll see the same effect. Your oil breather system not being up to par can be another reason that you suck oil. Broken rings causing too much blow-by can put oil into the intake.

One solution is use an oil breather bottle vented to the atmosphere instead of connecting the oil tank vent to the intake.

Ingo

[axl911]

It's a C2 with 87K. The car has been consuming 1qt of oil every 1000 miles. The other day when I topped the oil up /w one quart.

I noticed a little bit later that I would get occasional puffs of blue smoke coming out of the car at the stop. The same amount as white condensation out the tail pipe in the morning. It never did that before. I am sure I haven't overfilled or spilled any oil.

Strange thing is that I was getting blue smoke yesterday, but none today so far. There is no leak. Car doesn't even leave any mark on the floor anymore. I am sure I did not overfill or spill any oil.

I am worried about valve guide as these engines can run hot with the undercover still in place.

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anthony

[axl911]

Oh, haven't checked for smoke on decel yet since I don't have anyone to follow me on the road.

I did rev the engine and let it fall back to idle while watching the tailpipe for smoke. It's the same thing right? As the rev come down, oil would still be pulled into the cylinder right?

Didn't see any smoke.

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anthony

[ischmitz]

Hm, no oil leaks anymore. Is there any oil left in the car... Just kidding.

I had one episode where I drove my 3.6 very hard then shut it off. The next morning I had a monster smoke clould in the garage when I fired it up. This happened after about 1000 miles on the rebuild motor. Never before and never after. At the time my oil level was pretty high. I almost overfilled it. My theory is that I had some oil sitting above the valves that simply got burned on startup. I sucked it in through the intake and it accumulated at the intake over night. Now I am running with a much lower oil level and I don't seem to burn much oil anymore.

As to the decel what happenes is that while the engine is at high revs it pulls lots of air through the intake plenum. Now you lift off the throttle while the engine stays at those high revs (car is still in gear and coasting) you suddenly close the throttle. Vacuum spikes up in the intake plenum and makes oil creep by the valve stem. In other words most oil gets sucked in at high revs with the throttle closed. Blipping the throttle with the car stationary is not exactly the same since the engine revs drop very fast.

On a stock car it is not unheard off that the valve guides are shot after less than 40.000 miles It's usually the exhaust guides that go first. And the undertray makes things worse. It keeps even more heat inside making the degradationfaster. Why don't you loose it.

Good luck,
Ingo

[ischmitz]

Wait a second. After rereading your post this one struck me: If you say there is no leak and no drops today and no blue smoke.

Are you sure the blue smoke came out of the tail pipe or just from the exhaust area. Maybe you have a simple oil leak somewhere that allows oil to collect in the engine undertray. Once you get this oil onto your heat exchangers at operating temps you generate smoke and the distinct acid smell of burning oil. It's either blue or greyish. I had lots of that and finally decided to take care of it by rebuilding the engine.

ingo

[axl911]

Car used to have 1-2 drips every couple of days, but since I've switched to 10w40 for winter it's drip free.

Today while driving and watching, I don't see anymore blue smoke coming out.

I am pretty sure the smoke came out of the tail pipe. Not when engine is cold.

Yep. First thing I did was to chuck the undertray.

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anthony

[Tinker]

Axl911,

How noisy are the valves? It's not unusual for those 3.6's to require a top end rebuild prior to 100k if the owner left the underpan and all the uncapsulating pieces on the car. Personally, I wouldn't be concerned about it until starts to foul plugs.

Mine has about 50k on it and the valves are noisy, even after adjustment. I don't drive it enough to guage consumption, but it does burn about a quart on a weekend at the track, which is not unusual.

Tinker