Valve seal questions

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LeakySeals

LeakySeals

Joined
Feb 18, 2011
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Hudson, NH
I have the classic blue startup smoke experienced with bad valve seals. I'm living with it running High Mileage oil with seal conditioners/swellers. Oil consumption isn't too bad, 1qt every 5k. I can't run extended intervals, the oil gets fouled pretty bad beyond 7k no matter what oil I use. The oil on the stick looks like blowby, fuel, etc.

There is also a nagging rough idle. More like a skip. Its had everything cleaned or replaced I can think of, but every so often it appears. Gave up assuming ist just an underpowered I4 that struggles with the AC and fans on.

So now I'm wondering if the symptoms above are related to the valve seals. I don't have a full grasp on what else ignoring the seals may be causing. Wondering if somebody can explain what valve seals are responsible for other than oil seep. Lack some knowlege here. Compression? Blowby contaminating the oil?
 
Originally Posted By: LeakySeals
Wondering if somebody can explain what valve seals are responsible for other than oil seep.


That's it, really. BUT, oil seeping past, over time, can cause build-up, leading to poor valve seal, sticking valves, etc.
 
Is this your Camry?
Heck, with only 220K on it, you'd think everything would seal like brand new.
 
lol.gif
Yeah. Bought it cheap as a commuter beater. The PO neglected it. Put 90k on it so far with the blue smoke, not sure how much longer the seals can go. Trying to find out if there are other reasons to get the seals replaced beyond tailpipe aesthetics. I had a hunch that if the seal wasn't tight on the valve stem, there could be compression loss, oil fouling from insolubles, etc. Not sure. Something like that would be a good reason to get it fixed.
 
I had a Ford 429 cu in V8 with leaking valve seals once, it still idled fine. It just embarrassed my dad, so he helped me replace them.
Troubleshooting rough idle:
http://share.qclt.com/%E4%B8%B0%E7%94%B0Toyota%20RAV4%20Repair%20Manual/2AZ-FE%20Engine%20Control%20System/SFI%20System/005006.pdf

(I see you posted a year back about the rough idle.)

I wonder if it's a vacuum leak. You've tried propane gas around the usual places to test for vacuum leaks (and underneath the hard-to-reach places)? I knew one DIY who didn't do the hard-to-reach places, and finally got around to doing them and found his vacuum leak. Latex tubing helps, and hard tubing with bends in it helps.

Googling for 2z-afe engine control system
turns up nice technical info, such as:
http://www.mr2.com/files/mr2/techinfo/Random FSM Data/2azfe-12.pdf

The next info may not apply to you, but may help to read anyway:
http://www.motor.com/article.asp?article_ID=987
If you poke around in the "Foreign Service" article series (it runs from Jan 2006 through October 2006) you may get some insight into another potential place for excess air to enter the system. Again, I'm assuming you've thoroughly probed for an obvious vacuum leak and found none. Oh, and download the .pdfs. They contain pictures that the plain text omits.
 
Got one I4 Camry with 300K on it. Rotella T6 cut the little puff of blue smoke on start up to the point that I don't see it any longer (and I DO look for it). Worth a try. Changing the seals on the I 4s is not a difficult job for someone who is handy. Remember, if the women don't find ya handsome at least they can find ya handy. Red Green (the Red Green Show)
 
Valve seals will not cause copression lost or a rough idle. Atleast as far as i know. Back in the day some engines didnt even have valve seals. The puff of smoke is the only symptom ove ever heard of or seen
 
Originally Posted By: spackard
I had a Ford 429 cu in V8 with leaking valve seals once, it still idled fine. It just embarrassed my dad, so he helped me replace them.
Troubleshooting rough idle:
http://share.qclt.com/%E4%B8%B0%E7%94%B0Toyota%20RAV4%20Repair%20Manual/2AZ-FE%20Engine%20Control%20System/SFI%20System/005006.pdf

(I see you posted a year back about the rough idle.)

I wonder if it's a vacuum leak. You've tried propane gas around the usual places to test for vacuum leaks (and underneath the hard-to-reach places)? I knew one DIY who didn't do the hard-to-reach places, and finally got around to doing them and found his vacuum leak. Latex tubing helps, and hard tubing with bends in it helps.

Googling for 2z-afe engine control system
turns up nice technical info, such as:
http://www.mr2.com/files/mr2/techinfo/Random FSM Data/2azfe-12.pdf

The next info may not apply to you, but may help to read anyway:
http://www.motor.com/article.asp?article_ID=987
If you poke around in the "Foreign Service" article series (it runs from Jan 2006 through October 2006) you may get some insight into another potential place for excess air to enter the system. Again, I'm assuming you've thoroughly probed for an obvious vacuum leak and found none. Oh, and download the .pdfs. They contain pictures that the plain text omits.

Thanks, will dig into them. I took steps to lessen the rough idle problem posted a year ago. But sometimes its still there, sometimes not. Cold days, hot days, doesn't matter. The exhaust air flow is inconsistent when its happening. There is only one way to describe it...(without laughing)... if you put your hand on your lips, blow out flapping your hand. What it sounds like, what the exhaust air flow is like. Like a skip, or a vibration. I have not noticed that with other cars I've owned even when the idle is rough.

Anyways, if valve seals don't help seal the combustion chamber during combustion, there should be no relationship to the idle.
 
Originally Posted By: HerrStig
Got one I4 Camry with 300K on it. Rotella T6 cut the little puff of blue smoke on start up to the point that I don't see it any longer (and I DO look for it). Worth a try. Changing the seals on the I 4s is not a difficult job for someone who is handy. Remember, if the women don't find ya handsome at least they can find ya handy. Red Green (the Red Green Show)

I used T6 on another Toyota I4, it seemed to like it. May try it at some point, see what happens. But no doubt keeping the oil thin has helped the idle. From what I've read, the seals on this engine are hard to access under the cams, requiring removal. Add the stripped headbolt issue in this year, I'm better off letting a mechanic do it so he can pressurize the cylinders without head removal. Apartment dweller right now. Can't get that involved here unfortunately.
 
Bad valve stem seals cause oil consumption in the 100s of miles, if it's only using a qt in 5Kmi, they are not your problem(at least not enough to be concerned about)...

All the stem seal does is prevent oil from being sucked by the intake valve stem and into the cylinder... They can lead to carbon build up but are NOT responsible for blowby, which is the result of worn cylinders and/or rings... Blowby will contaminate the oil... Maybe if it were using copious amounts of oil, the rings would be stuck from carbon, not the problem here...

If you suspect blowby, a compression or leak down test should be performed...

If it has a miss/skip the PCM should be setting a code...
 
LeakySeals,

Have you done a compression test? I bet one or more of the exhaust valves have a burnt spot. They're supposed to rotate. When they hit the corresponding inperfection in the valve seat you get the stumble and change in the exhaust note.

Listen to an old 70's or 80's american V-8 beater engine as it accelerates away from a stop light. The exhaust sounds exactly like that.

I'm sure you checked the usual list of possible causes, vacuum leaks, dirty injectors & intake valves, etc. Bad valve seals don't affect the exhaust. And I doubt you have sticking rings using Mobil 1 High Mileage oil.

Take care,
Gary
 
In most cases the seal has cracked, fallen apart, pieces missing, and not doing a whole lot. No oil or additive will help.

When I was a HS kid I machined the valve stem area to take a special valve stem seal from Perfect Circle. But that was around 1969 or 1970 on a 65 Mustang 289.
 
Originally Posted By: Tucson Five-O
LeakySeals,

Have you done a compression test? I bet one or more of the exhaust valves have a burnt spot. They're supposed to rotate. When they hit the corresponding inperfection in the valve seat you get the stumble and change in the exhaust note.

Listen to an old 70's or 80's american V-8 beater engine as it accelerates away from a stop light. The exhaust sounds exactly like that.

I'm sure you checked the usual list of possible causes, vacuum leaks, dirty injectors & intake valves, etc. Bad valve seals don't affect the exhaust. And I doubt you have sticking rings using Mobil 1 High Mileage oil.

Take care,
Gary

No, havent done that. Would a burnt valve exhibit an increase in oil consumption, or is this "in addition to"? Would a burnt valve take the seal with it?
 
Originally Posted By: Donald
In most cases the seal has cracked, fallen apart, pieces missing, and not doing a whole lot. No oil or additive will help.

When I was a HS kid I machined the valve stem area to take a special valve stem seal from Perfect Circle. But that was around 1969 or 1970 on a 65 Mustang 289.

Could be. I found strange rubber like debris in the oil pan during the initial cleanup of this engine. I made an assumption on the seals because High Mileage oil has a huge effect on oil consumption and the startup cloud. Without the seal swellers consumption doubles. Go back to High Mileage oil, consumption drops in half. Same weight.
 
Valve stem seals aren't really seals, they control oil flow to the stems and guides. Some older vehicles don't have them and others have a wiper. When they go bad they allow more oil to flow. Often worn valve guides will make the leakage worse.

The type of material they are mode of, usually Viton, is extremely chemical resistant. Nothing you put in the oil is going to soften Viton, and if it did the seal would fail because the chemical structure of the material has changed.
 
LeakySeals,

You're talking about two separate things here. A rough idle/funny exhaust sound isn't caused by bad valve seals.

A puff of smoke on start up could be the seals which as several posters have suggested may be non-existent for all practical purposes by 220k miles.

Don't confuse the two issues. Your oil consumption is quite low by any standard so replacing the valve seals is certainly not a mandatory repair.

Gary
 
Originally Posted By: tom slick
Valve stem seals aren't really seals, they control oil flow to the stems and guides. Some older vehicles don't have them and others have a wiper. When they go bad they allow more oil to flow. Often worn valve guides will make the leakage worse.

The type of material they are mode of, usually Viton, is extremely chemical resistant. Nothing you put in the oil is going to soften Viton, and if it did the seal would fail because the chemical structure of the material has changed.

Something in the High Mileage oil is producing a 50% swing in oil consumption. I'll try to block out Pat Goss's video etched in my memory for now. Anyways if I get this, its the guides that seal combustion gasses. While guides could be a problem, they are less likely to seize up/fail with leaky valve seals providing more than enough oil to the guides and stem. ???
 
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