N62 engine valve stem seals

[X5only]

Originally Posted by Westlotorn

I have not been on this site for a long time and I am amazed that guys are still targeting the valve stem seals and exhaust guides as the main cause of oil leaks.
There is good information already on this forum but I will hit the basics.
If you have a smoking BMW V8, burning oil the VERY FIRST thing to do is to pull the hose off the front of your intake manifold, right where the throttle body attaches. There are two hoses, one from each valve cover, they merge and plug into the front of your intake manifold. These are the engine vents or Posistive Crankcase ventilation.
BMW uses a different name but this is what they are.
They are supposed to pull vacuum against your sealed, air tight engine.
When you pull this hose off your intake, look inside. If you see oil you have a ventilation issue. These should be nearly dry. Some Oil vapor travels through the vent but no oil should be in there. Use a pen light and look inside the manifold where this hose hooks up.
If you see oil you have found your oil consumption issue.
To fix this issue you have to seal the engine up. There are many potential leak spots on these engines. If oil leaks out of this engine, air will leak in. If air leaks into the manifold, vacuum will pull oil into the intake manifold and you will burn oil.
This type oil burn issue will burn more hot than cold.
Actual valve stem failure will burn most on cold start and clean up after it runs a short time.
Exactly the opposite of what many BMW V8 drivers report but still they blame valve stem seals.

I will share that doing a valve stem replacment will fix this issue also because to replace valve stem seals you remove all the guilty leaking gaskets and O'rings and replace them as part of the valve stem seal replacement job.
Valve cover gaskets and all the O rings that help seal the engine will be brand new so the air leaks will be plugged and your oil consumption issue will go away.

I read that some have used Oil Stop leaks to fix this issue. It may help but I warn you very seriously that oil stop leaks do a lot more than plug oil leaks and so many parts in an engine need to be lubricated constantly you should not risk cutting off a small oil supply with stop leak.

Some of the components that can be the source of your air leak.
Valve cover gaskets
Dip stick O Ring
Vanos O Rings
The sensors that plug into the valve cover have o rings
the front covers on both heads have gaskets, if they are leaking, (mine were) they can pull air and leak oil.
The Vacuum pump on the front of the pass side head can leak oil and air.
The stupid O rings on your oil cooler hoses, I say stupid because the $6 orings on the oil cooler hoses can take 15 hours or more to replace. This alone is enough to hate the engineer that designed it. If these are leaking oil out, rest assured the Crankcase ventilation is pulling air into the engine. If air goes in, oil will be in the intake manifold.

Oil in the intake can't get there from the valve stem seals.

There are more potential leak spots but these are the main culprits.

If your engine has 250,000 miles it may need valve guides and valve stem seals.
At 70-140,000 miles. No way in my opinion.

I have repaired 3 of these V8 X5's and all three stopped using oil.
none got new vavle stem seals and all use 5-40W oil or 0-40W oil.
My 2008 X5 at 108,000 miles uses about 1/4 quart of oil in 5,000 miles and no longer has any oil leaks at all.

One side benefit to fixing all the air leaks is it corrects the vacuum signal to your computer which affects the way your tranny shifts. With all leaks fixed my tranny now shifts just like it did when the car was new. Incredibly smooth shifts. I had not realized how it was not shifting well prior to these repairs.
Gas Mileage is darn good. 20-22 on Hwy trips at 75-85 MPH.

I will finish with, I did not make any of this stuff up. I am Gold Certified as an Engine Machinist, Certified for Engine Repair and Engine performance and have 30 years in the business at the manufacturer level. I am not strong on repairs outside the engine but Internal engine parts I know pretty well.

I wrote this book again as I am pretty concerned when I see someone on here state they have Oil Consumption and exhaust blue smoke and 15 guys quickly tell the owner to replace his valve guides or valve stem seals. This is based on phooey not facts.
As I stated, if properly done replacing valve stem seals will include replacing all the gaskets and O'rings I mention so of course it will fix the issue but you are also paying to replace valve stem seals that don't need replacing.
If the engine is at 200,000 plus miles I would agree it might need valve stem seals but if you have taken good care of the engine with frequent oil changes the valve stem seals and valve guides should last longer than 200,000.

Start with the basics. Look in the crankcase ventilation tube at the intake manifold.
It will tell you what you need to know.

Then look for the sources of your oil leaks. If Oil can leak out air can leak in.
Air leaking in is what puts the oil in your intake manifold. It does not belong in there.
My son's 2005 X5 4.4L got new gaskets and O'rings at 145,000 miles 5 years ago.
It was burning oil like crazy. Now at nearly 200,000 miles it does not use any oil and does not leak any oil.
We fixed a 4.6l for a friend of his back then also. Same result.
Fixed my wifes 4.8L two years ago.
I hope this helps some of you. It is not magic, just engine basics.
Heavy oil smoke on start up after the car has been parked at least an hour = Valve Stem Seals
Oil in your intake manifold = Air leaks and external oil leaks.

So does this explain the plumes of smoke after extended idle and then revving the engine?

[Westlotorn]

Valve stem seals cause smoke on start up because oil sitting on the top of the valve stem will drip down past the intake valve into the cyl head chamber where it burns on start up. This happens with the engine off. You see the accumulation of oil burning on initial start up then it calms down once this has burned off.

At idle you have the highest vacuum signal in the engine. This is when oil is pulled into the intake manifold if you have air leaks in the engine.
You rev the engine and this oil in the manifold goes into your cylinders and burns making blue smoke. Oil does not belong in your intake manifold. If you just take 5 minutes and remove the hose from the front of your intake manifold and look inside you can see if there is oil in there or not. Look in the hose also.
If oil drips out and you see wet oil in the manifold you found your problem.

Third scenario, you are going down a hill in your car with the foot off the gas, you hit the gas after this and blue smoke comes out. This is normally piston rings failing.

A fourth thing to think about. If you pull your spark plugs out and 1 or 3 have heavy black carbon on them and the others are clean this would be an indication of valve stem seal failure. The bad plugs are running in cylinders with high oil consumption.

This spark plug test is a good indicator of how well your engine is running.
If all 8 look equally good your oil issue is spread out through all your cylinders again pointing to the PCV or Positive Crankcase ventilation. Again, BMW calls this something else but crankcase ventilation is what it does. If oil is beng sucked into this system it hits the manifold where it will go all through your engine to be burned not just into one or two cylinders so all 8 plugs will look pretty much the same.
Before we fixed my son's car he came home from college and told me his valve stem seals were bad. He researched it on the BMW forums.
When I asked how he knew it was valve stem seals he said everybody on the forum told him it was a common problem. His 4.4L was at 140,000 + at that time.
I told him to pull the spark plugs and look at them. They looked brand new but he was burning a quart of oil in less than 500 miles.
I told him it was not valve stem seals and being smart and in college and with all the notes on the forum backing him up we discussed this issue for a couple days. ( argued ). I showed him the wet crankcase vent and oil in the manifold. I finally convinced him to just seal it back up, he had several oil leaks. He fixed it in stages as he had parts and time. One valve cover, then another, then O'rings etc over a couple months. Oil consumption kept getting better and his engine kept running better and shifting better. His was getting 24 MPG on the highway at 75 MPH pretty consistently on his trips back and forth to college, once the final oil leaks were repaired he no longer burned oil.
His intake manifold was very wet with oil inside on tear down and was not easy to clean. Hot Soapy water and small scrub brushes and a lot of time got his clean again. If we did this again I would pour solvent or diesel fuel inside first and swish it around for a while, dump that and then start with hot soapy water. If it is wet with oil it will attract dirt, you want it clean.

[xbimma]

Westlotorn: Thanks for taking the time explaining. Very helpful.

[X5only]

Westlotorn, I'm just thinking aloud as a DIY'er...do valve stem seals last the life of the engine? If not, why target only the leaking seals (valve cover gaskets etc) when that task covers a significant portion of valve stem seals replacement? The AGA tool is cheap to rent nowadays (approx. $200 for 2 weeks) … and if valve stem seals will eventually leak, I'd rather target them as well while doing the other seals, no?

[mr_robot]

I've always wondered why it only smokes during extended idle. My 4.8 doesn't do it on cold starts or at traffic lights. Only after minimun of 5 minutes of just idling.

Also only smokes if I free rev the car hard after the extended idle. If I just drive off normally no smoke either.

My oil consumption is not bad maybe 1/4-1/2 quart every 3000 miles or so.

Also Lucas Oil Leak Stop does not swell seals and gaskets like some old skool "leak stops". Some old timers I know they used to use brake fluid to swell up the gaskets lol.

But in modern engines seals are made out of viton which is very durable to heat and wear but eventually lose their elasticity over time and what Lucas does is add plasticizers which brings back their elasticity to "seal" what ever it's trying to seal.

I also think there are revised/aftermarket vss that have an improved seal design to prevent it from failing.




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[X5only]

I'm going to replace the valve stem seals using rented AGA tool and a rope (to keep the valves up instead of air). It's not difficult, only tedious and time-consuming. Replacing the valve covers is the most difficult component of the whole project. Here's a facebook group for rental and description of the rope process. The rope technique makes the whole project much easier - no air compressor is needed for the project - and you can take your time and do the job carefully. No rushing due to fear of losing air and dropping the valves. The rope keeps up and prevents the valves you're working on from dropping.
https://www.facebook.com/groups/BMWAGAN62TOOLRENTAL/

[jpcallan]

Originally Posted by X5only

I'm going to replace the valve stem seals using rented AGA tool and a rope (to keep the valves up instead of air)....

Neither rope nor air pressure is absolutely needed as long as you are certain the piston is at TDC on the compression stroke.


I just finished a valve guide/stem seal job for my friend in my driveway on a 2008 X5 E70 4.8L N62TU. While doing bank 2 (I started on the driver side), I worried constantly about dropping a valve into the cylinder. At the same time I kept asking myself "How can a valve drop into the cylinder on a high-compression engine at TDC? Since the combustion chamber volume must be small to create the high compression, the clearance to the top of the piston at TDC must be tiny."

Calling and talking with AGA about that very question - they said I was correct; with no air pressure at TDC, the valves would drop onto the piston top, moreover, are serviceable by replacing the valve keepers using a flat screwdriver with a pat of grease to hold and position the keepers. The down side to the rest-on-the-piston method is the valve stem drops too low for the AGA Keeper Tool to be used. One of their mechanics told me he never uses the compressed air method, preferring the speed of not having to deal with attaching the air supply via the spark plug hole.

[Westlotorn]

I see a couple people have changed the valve stem seals. Did you look inside the intake manifold prior to doing this job to see if you really needed Valve stem seals?
If your intake was wet with oil your issue was not valve stem seals.

[jpcallan]

Originally Posted by Westlotorn

I see a couple people have changed the valve stem seals. Did you look inside the intake manifold prior to doing this job to see if you really needed Valve stem seals?
If your intake was wet with oil your issue was not valve stem seals.

Yes, there were blow-by deposits just behind and beyond the throttle body: degraded oil, dark brown soot, etc. The backside of the throttle body and its butterfly valve were both heavily coated with same. As part of the service work, I flushed the valve cover's PCV passages and the three-connector PCV hose with solvent to clean away as much blow-by gunk as possible; the throttle body got a thorough cleaning as well.

I don't believe the smoking had any anything to do with air leaks. The valve guide seals were in bad shape, it smoked. Now they're new; it doesn't smoke any more.

[X5only]

Originally Posted by jpcallan

Neither rope nor air pressure is absolutely needed as long as you are certain the piston is at TDC on the compression stroke.


I just finished a valve guide/stem seal job for my friend in my driveway on a 2008 X5 E70 4.8L N62TU. While doing bank 2 (I started on the driver side), I worried constantly about dropping a valve into the cylinder. At the same time I kept asking myself "How can a valve drop into the cylinder on a high-compression engine at TDC? Since the combustion chamber volume must be small to create the high compression, the clearance to the top of the piston at TDC must be tiny."

Calling and talking with AGA about that very question - they said I was correct; with no air pressure at TDC, the valves would drop onto the piston top, moreover, are serviceable by replacing the valve keepers using a flat screwdriver with a pat of grease to hold and position the keepers. The down side to the rest-on-the-piston method is the valve stem drops too low for the AGA Keeper Tool to be used. One of their mechanics told me he never uses the compressed air method, preferring the speed of not having to deal with attaching the air supply via the spark plug hole.

You're the first person whom I've seen that has debunked, without fear of contradiction, the fear of valve stem seal replacement - thank you I've always wondered about how the stem would disappear into the cylinder when it's at TDC. By the way, I'm in the middle of valve stem seal replacement. I bring the piston near TDC, insert a bungee code in the spark plug hole, continue to bring the piston towards TDC until I feel resistance. This way the valve stays up and you can even press it down with your finger and feel it will not go anywhere. You can clean the stem off carbon build up, etc. To remove the bungee code, just turn the engine backwards just a little bit to let the piston off it. There's a guy in ebay renting out the AGA tool for $199 for 2 weeks and $10 per day after the two weeks or $50 for each additional week. Very reasonable. Anyone who can replace the valve cover gaskets can do the valve stem seals. The valve cover replacement is the hardest part of the project in my opinion - it's just that it's time-consuming and requires great care not to loose the keepers inside the engine.