We bought a 2003 Toyota Sienna with 50k miles on it. We’ve had it for about six years and it now has 108k miles. It has never used much oil until about 6 months ago. I probably went longer than I should have between oil changes (don’t ask me how long; I have no idea) and when I checked the oil one day it was probably at least 3 quarts low. Ever since then it has been burning about a quart of oil every 400-600 miles. It usually smokes out the exhaust on startup, especially after sitting for a while. I’ve had one mechanic tell me I need a new engine but all he did to diagnose it was start it up and watch it smoke. I changed the spark plugs this weekend and I’ve attached a picture of what I found. Is there any way to determine whether the problem is rings, valve guide seals, or both? Is there any hope for my engine or did I destroy it?
The first step on an oil consumption complaint is to perform a compression test; both dry and wet. Compression and leakdown tests are not 100% definitive but it’s all there is and is generally good enough to tell if there’s a problem with rings/valves or not.
On a good engine you should see readings in the 180-190 PSI range on the dry test. If this is followed up with a wet test and if the readings go up considerably then you can figure on the piston rings being worn or frozen in the ring lands.
Running an engine low on oil and/or extended oil changes can also contribute to piston ring problems.
As to valve seals, there is no test for those. They’re a replace and pray item but should not be considered without doing the compression test first.
Those plugs are utter garbage actually and should have been changed eons ago; platinum or not.
If you do the compression test pay special attention to cylinders 1 and 2.
Spark plugs 1 and 2 look like the spark plugs that came out of my 1970 Plymouth, (180,000 miles) not good.
I have replaced valve seals on Toyota’s slant six (this engine is tilted with the rear bank facing the firewall). The usual complaint is oil smoke on start up, however your oil consuption is more than usual. Replacing the valve seals involves removing all four camshafts, not for the novice.
Perhaps the unintended example of why not to follow so many examples of “fleet” vehicles that have been reported to go 10,000 mile between oil changes.
Before you condemn the engine, service the PCV system from end to end, not just the valve…If the crankcase venting gets plugged up, it can force oil back into the air-cleaner box and throttle body. This area should be DRY, no oil residue…
You’re obviously burning oil. Like Caddyman said, service the entire PCV system. ok and Nevada are right about the problem likely being internal, like valve seals and rings, but I’d try one more thing. Get the engine good and hot. Change the oil using 5W20. Drive it like you stole it–hard–for a week–and change the oil again. Do this a couple of times and see if you can get some of that sludge/gel to break free. What have you got to lose other than some time and a case of oil?
How is your coolant level, are you loosing any coolant at all, even as little as a cup every couple of months? I ask this because that #1 plug looks like it might have some antifreeze contamination on it as well as oil burning.
The first thing I would do is pretty easy. Remove the valve covers and check for sludge build up on the top of the head. Also check the oil drain back passages. These should be at the lowest points on the head, either at each end or in the center but on the exhaust side. The heat from the exhaust, especially when the engine is first shut down, tends to cook the oil coating the drain back passages causing them to get increasingly narrow until they can’t drain the oil back as fast as it is being pumped up there.
When this happens, the oil floods the valve guides and gets into the combustion chamber. If you see a lot of sludge under the valve covers, clean it out completely. Use scrapers and brushes and solvents as needed. Clear the drain back passages and clean them good. Then drain the oil, replace the plug and dump a gallon of solvent into the oil pan, pull the plug and drain into a fresh oil pan. If you get a lot of lumps, filter them out with a screen and dump it through again. Finish off with fresh oil and oil filter.
If the oil gets dirty real fast after that, do another oil and filter change. Watch it close.
Just started experiencing a quart of oil consumed per every 300 miles on my 1990 Suburban, 215,000 miles, 350 cu. in. engine, 3/4 ton, C2500, automatic, 4 WD. No oil on driveway. No smoke on startup or while driving uphill, but a little on reving the engine while parked. Do all these suggestions above apply to my Sub for tracking down the problem., even the 5W20 oil flushes? Without having any diagnosis done, two shop want to stick in a rebuilt engine, i.e., $3500 to $4500.
Same as above the first step on an oil consumption complaint is a compression test; both dry and wet.
And hopefully the person doing the compression test will be able to differentiate between real world numbers and the tripe that is published in the service manuals.
In 1964, before being drafted, my old 1953 Chevrolet used a quart of oil every 30 miles. I simply added a quart every 30 miles or so, even made a 1120 mile round trip that way. It also didn’t especially smoke. Someone said later it was probably main seals.
I came home from Fort Lewis about 10 months after being drafted, and put in a rebuilt engine and transmission, drove that car 2050 miles to Fort Lewis, and drove it a year or two after finishing my two years, then gave it to a brother and bought a new 1967 Chevy II.
Thanks to you both. The (30 miles/quart) sounds like your pulling my leg, Irlandes, but I appreciate your post.
I’ve never done a compression test, let alone one wet and one dry. I guess I’ll dig out my old Helm manuals to figure out how to do them and then try to differentiate between real world vs. service manual numbers. Can you give me some details, OK4450, on the proper way to do the test and interpreting the numbers correctly? If not, I’ll submit a new thread.
Just remove all of the spark plugs, prop the throttle plate open (brick on the pedal would work), screw the compression tester into one of the spark plug holes, and crank the engine over for 4 or 5 revolutions. Note the reading and write it down. Repeat on all of the other cylinders.
You should see readings of 180 or so on a good engine.
This should be followed up with a wet test. This means going back and performing the test again but a small squirt of oil should be added to each cylinder before it’s tested.
Write down each reading on the wet test next to the one from the dry test.
If you see a noticeable jump upwards in the readings during the wet test (say 20, 30 PSI etc) then this is a sign of a ring problem.
It’s also possible to have good compression and still have a ring problem. The upper 2 compression rings may be fine but the oil control, or wiper ring, may be frozen in place due to oil coking, any prior overheating episodes, etc and is not wiping the cylinder wall of engine oil on the piston downstrokes. Hope this helps and if you do the test you might post back with the numbers. Best of luck.
(The reason I’m so critical of manuals, both factory and others, is that a lot of non-real world specs are published in there and I can only theorize is that these numbers are something a slide rule guy came up with. Erroneous compression numbers, oil pressure specs, you name it; a lot of it is flawed. I’ve got some factory Subaru service manuals that state 130 PSI of compression is the norm and that’s not just wrong; it’s absolutely ludicrous and downright laughable.)
Thanks for the prompt reply, ok4450. I’ll give it a try in the next few days and see what happens.
OK is kind of a fanatic about compression…Few cars with over 100K miles will pump 180psi …More important is that they are all EVEN…you can live with 130-140 pounds as long as they are all the same, or within 5 psi. Should you find one or two way below the others, that’s the kiss of death…
These days I would be frugal and top the oil each fuel fill. The engine may or may not have issues that can be fixed. On the other hand it will take many cases of oil to equal the cost of service for these issues. A quart of oil is 4$. A serious top job on this engine if that is where the leak is is $1500. How much oil can you buy for 1500$. It is a lot of tank refills. You could drive 40,000 miles before you pay back the cost of repair.
Thanks to everybody for the tips.
ok4450 - I was told by the mechanic that I took it to that a compression test would be a waste of money. I know he wasn’t just trying to sell me an engine since he told me that his engine rebuilder didn’t even have those engines. He pretty much told me my engine was shot and said there wasn’t much I could do. Would a compression test really tell me anything I don’t already know?
keith - I did recently have to top off the coolant. I don’t know how long it took to get low but I’ll keep an eye on that. Does that mean I’ve got a head gasket issue too? I plan on pulling the valve covers to check for sludge as soon as I get a chance too.
euryale1 - If it requires a rebuild or new engine I had planned on just feeding it oil until it died.
Another question for everybody - any ideas how long I have before I kill the catalytic converter(s)?
My opinion on compression testing is based on my aircraft days. One does not wild guess at things and a compression test is something I’ve always done with any engine performance issue, tune-up, or basic maintenance service; even on a low miles car.
The numbers I mention are real world based on doing more compression tests (thousands) than I can even start to remember. After awhile one starts to see the norms and 130 is not it unless the engine has problems. Some aircraft and automotive air cooled engines have lower compression by design.
I had mentioned the Subaru manual being wrong by stating 130 PSI. After countless compression tests on Subarus I find that cars with good engines carry 180 or better.
This means either the cars are abnormal or the manual is wrong and I don’t think it’s the former.
The mechanic is probably correct about theorizing the engine is on the way out. The issue I have here is that I don’t think a diagnosis like that should be given without providing some hard numbers.
You could even run the compression test yourself. A tester is not expensive and actually, would have been a good idea while the plugs were out.
For what it’s worth, many of my past and current high miles cars still carry 190 or so even at a quarter million miles and use no oil.
My oldest son still has his 96 Camaro with over a quarter million miles on it and during the last compression test at around 230-240k miles that 3.8 still carried 190 on all cylinders.
@ok4450, Ever tested compression on a late-80’s Chrysler 360? If I remember those things had such a low compression ratio (8 to1?) for smog reasons that it didn’t take much valve wear to end up with a dead hole. I’d have been thrilled to see 130 on one of those.
Surely you’re not getting paid to do a compression test as part of a routine tune-up?
Anymore I rarely use a compression gauge with an engine performance problem. I’ll hook a labscope with an amp clamp to the starter cable and another channel to #1 plug wire. Cranking amps and rpm will give me a lot of info. I know that’s of no help to the guy working on his own car though.
The general rule of thumb on compression pressure is 20 X the compresion ratio and I’d say that a 360 that is at 130 is on the way down. Will it run at least apparently fine at that? Yes, but that doesn’t mean that it’s up where it should be and if the valve wear you mentioned is contributing to it then that means it’s decision time.
As to running compression tests as part of a performance complaint, tune-up, or basic maintenance service, yes I’ve always done it and done it for free. I consider that few minutes of freebie time to be time well spent by heading off any parts shotgunning in an attempt to cure a low cylinder, or more than one of them.
I do this even on very low miles engines because I’ve seen too many cases of compression faults at well under 30k miles. In one case, a Subaru was so far gone on the cylinder heads that both heads had to be replaced and that poor car only had 7k total miles on it.
Every day, countless vehicles get everything in the parts inventory thrown at them by car owners and even shops in an attempt to cure a performance problem when the root cause is a mechanical issue.
I Just never wanted to be someone who resorted to that kind of repair and believe me; I know a few like that. One was a shop owner friend of nearly 40 years who passed away last year and was about 15 years older than me. He was a mechanic all of his life and a great guy. Everyone around liked him; including the people who were shotgunned repeatedly and downright screwed over.
Heck, I like him a lot, worked with him for a time, and hated to see him pass. Would I let him or his son touch a car or even a lawnmower of mine even if he wasn’t swamped in work? Not for one nano-second. 
So suppose I were to do a compression test. Walk me through the different scenarios and what would be the next steps. I can see three possible outcomes:
- All cylinders approximately equal and within normal expected range
- All cylinders approximately equal and below normal expected range
- Some cylinders within expected normal range and some cylinders below normal expected range
What would I do in each of those scenarios?
The (30 miles/quart) sounds like your pulling my leg, Irlandes, but I appreciate your post.
Actually, I said it used a quart every 30 miles only because it used a quart every 30 miles. It is too easy on the Web to accuse a person of lying when you do not have to look them in the eye. And, though you tried to soft soap it by using the term “pulling your leg” that is what you were doing.
Just because you have not seen something does not mean it did not happen.