Oil consumption, blue smoke, spark plug condition and compression test results - what do you think?

mdawg

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Hi, all,

A little background info to start... my cruiser (see signature line) has 278k on the odometer. I purchased the vehicle when it had 242k on the odometer. I have no idea if the head gasket has ever been replaced. Average mpg is between 12 and 14 mg. It "feels" like it has adequate power, but I live on the North Texas blackland prairie, so there is that. The big issue I am trying to resolve is oil consumption and the smell of burning oil. As for relevant repairs, valve cover gasket is new, new spark plug tube seals, new pcv valve and grommet seal. Most oil leaks resolved, except for maybe upper pan arch seal.

Here are my symptoms:
* I add around 1 qt of oil every 400 miles or so (I use Mobil1 TDT 5W-40).
* I see blue smoke after starting up an already warm engine. I might have also seen it when accelerating from a long idle.
* There is an ever-present exhaust smell (I assume burning oil) whenever running it; the exhaust shop says all is well.

So, I decided to pull the spark plugs and do a compression test. I've posted the results below, but I would like your input on the results. What do you think? And is the only possible culprit at this point the valve stem seals?

Spark plug condition:
IMG_1025.png

IMG_1026.png


Compression test results (hot engine, dry, cranked 7-8 times with throttle fully open, efi fuse pulled)
#1 - 200
#2 - 205
#3 - 195
#4 - 180
#5 - 205
#6 - 215

Obviously #4 is quite a bit lower than the rest, especially since 14 psi is the maximum variation spec. I don't know a lot about what the numbers should be given mileage and age... do they seem unusually high?

Thanks for any thought!
 

thatcabledude

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Are those the same plugs that were in the engine when you replaced the valve cover/tube hole gaskets?
 

mdawg

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enox

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I had oil consumption issues at 240k mi, at that point I had had the 80 for like 18months. I threw a lot of time into trying to sort it out... The p.o didn't do the best mechanical maintenance soo...I ended up rebuilding it.
 
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I would maybe try some 15 or 10w 40 and see if it slows down. I had my headgasket done at 240k and it burns hardly any oil. Valve seals should fix your problem.
 

mdawg

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I would maybe try some 15 or 10w 40 and see if it slows down. I had my headgasket done at 240k and it burns hardly any oil. Valve seals should fix your problem.
I have tried heavier oils in the past, like M1 15w-50, and did not see much difference in oil consumption, and actually heard some lower end knocking when the engine was cold, so i switched back. I agree with you, given the compression numbers it must be the valve seals.
 
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Everything you have listed points to valve seals.
Possibly time to do the HG and have the head rebuilt as PM.

Constant blue smoke under acceleration = rings
Blue smoke under deceleration = valve seals / guides
Puff of blue smoke at sudden acceleration from a light = valve guides / seals
Black smoke on acceleration = too much fuel
White smoke = coolant (head gasket)
 

SteelHunterFJ80

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Everything you have listed points to valve seals.
Possibly time to do the HG and have the head rebuilt as PM.

Constant blue smoke under acceleration = rings
Blue smoke under deceleration = valve seals / guides
Puff of blue smoke at sudden acceleration from a light = valve guides / seals
Black smoke on acceleration = too much fuel
White smoke = coolant (head gasket)
This should be on a poster😁
 

mdawg

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The Colony, TX
Everything you have listed points to valve seals.
Possibly time to do the HG and have the head rebuilt as PM.

Constant blue smoke under acceleration = rings
Blue smoke under deceleration = valve seals / guides
Puff of blue smoke at sudden acceleration from a light = valve guides / seals
Black smoke on acceleration = too much fuel
White smoke = coolant (head gasket)

This is awesome - thank you!
 

mdawg

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<== UPDATE ===>

So, fast forward to now (Jul-26-2021)... I decided to pull the cylinder head and have a valve job done. I just heard back from the machine shop and the guy says that he can see that a couple of valves are leaking oil past the seals... but nothing that would explain the 1qt every 400 miles of oil consumption. Hmmm, ok. He said that the other likely culprits are a dirty/clogged PCV system or worn piston rings. Maybe it is wishful thinking on my part, but I "think" my rings are okay, based on the symptoms described above.

Also, he stated that he wanted to surface the head to remove an abrasion from the head gasket. Looking at the FSM, I do not see any spec for surfacing the cylinder head deck. Is this pretty normal treatment? Should I be concerned that there is no spec for this in the FSM?
 
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Surfacing the head will not be a problem. I just did this job last fall and had the head surfaced for a compression ring leak. Mine was burning about a quart every 600 or so miles. So far after 1500 miles havent used any oil. I went back to using 5/30 in synthetic.
 
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sacramento
<== UPDATE ===>

So, fast forward to now (Jul-26-2021)... I decided to pull the cylinder head and have a valve job done. I just heard back from the machine shop and the guy says that he can see that a couple of valves are leaking oil past the seals... but nothing that would explain the 1qt every 400 miles of oil consumption. Hmmm, ok. He said that the other likely culprits are a dirty/clogged PCV system or worn piston rings. Maybe it is wishful thinking on my part, but I "think" my rings are okay, based on the symptoms described above.

Also, he stated that he wanted to surface the head to remove an abrasion from the head gasket. Looking at the FSM, I do not see any spec for surfacing the cylinder head deck. Is this pretty normal treatment? Should I be concerned that there is no spec for this in the FSM?
to buttress some other comments re: head resurfacing, it shouldn't be a problem. I'm in the middle of a complete rebuild ('97 LX450). When I took my head in the machinist, he said it'll be warped. I said "how do you know?" 'cause a straight 6 is long. Today I got a look at the head while I was dropping the block off. It looks brand new. For background this vehicle has 372k miles. Passed CA smog in Feb. doesn't burn oil, smoke, etc. 99% sure PO did head gasket, but when??? The machinist said bring me new seals, that's all it needs. He cleaned up the valves - they look brand freaking new.

God I love Toyotas! (except the PHH :bang: )

Is a complete tear down and re-build more than a 1 :banana: job ;) ???
 
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Surfacing the head is fine but make sure it is straight first. You don't want bent camshaft bores forcing a reversing .030" bend in your camshaft with every rotation, that'll break it after enough rotations, look up "Rotating beam fatigue test". It's literally how we test materials for their resistance to fatigue cracking.

Mine was warped 30 thousands and none of the head straighteners thought it would straighten without cracking due to the age, so I ended up getting a new china head.
 
Joined
Jan 19, 2017
Messages
280
Location
Apache Junction, AZ
<== UPDATE ===>

So, fast forward to now (Jul-26-2021)... I decided to pull the cylinder head and have a valve job done. I just heard back from the machine shop and the guy says that he can see that a couple of valves are leaking oil past the seals... but nothing that would explain the 1qt every 400 miles of oil consumption. Hmmm, ok. He said that the other likely culprits are a dirty/clogged PCV system or worn piston rings. Maybe it is wishful thinking on my part, but I "think" my rings are okay, based on the symptoms described above.

Also, he stated that he wanted to surface the head to remove an abrasion from the head gasket. Looking at the FSM, I do not see any spec for surfacing the cylinder head deck. Is this pretty normal treatment? Should I be concerned that there is no spec for this in the FSM?
I had plugged baffles in my valve cover, my rig would drink oil through the PCV.
 
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How did you fix?
The proper way to fix it would have been to let it soak in diesel for a couple days to break up the sludge or buy a good used one. I being the high level moron I am, drilled out all of the spot welds and cleaned it then welded it back together. I do not recommend my approach. I didn't have time to let it soak or buy a new one.
 

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