Are there any brands of valve stem seals to go for or do avoid?

Is OEM best?

If in doubt, go OEM, best option

Seeing as it seems these motors are prone to valve seals leaking, is it due to OEM issues, or is it some kind of design error in the head?
I was told that the oil doesn't quite drain from the heads and hence the issue

Seeing as it seems these motors are prone to valve seals leaking, is it due to OEM issues, or is it some kind of design error in the head?
I was told that the oil doesn't quite drain from the heads and hence the issue

Previous service history habits is more than likely the case rather than inherent OEM problems.
I'm not saying the 6G head design is without faults but maintenance would be a more significant contributing factor, otherwise there would be significantly more Magna owners experiencing this issue and Adelaide would have been smoked out long ago.

This is though from what I can tell a somewhat common issue.
Of all Magna owners I've known in person (about 5-6) it seems half had oil burning via valve seals

This is though from what I can tell a somewhat common issue.
Of all Magna owners I've known in person (about 5-6) it seems half had oil burning via valve seals

So, based on that, are you saying that half of the users on this forum have had valve seal issues?
Somehow I don't think its the plauge-like affliction that you're making it out to be.

I can say without hesitation that I have seen more Mitsubishi's with valve stem seal leaks than any other brand of car. Magna's (Verada's) and Starwagons mostly. There is coincidence and then there is a hell of a lot more blue smoke coming from the exhaust when accelerating off idle than your average car.
I always understood it was simply because the seals dried up and shrunk letting the oil seep through.

I am not making it out to be a ""plague like affliction". I think it is obvious to all but a select few, or maybe just one, that the sample group I was referring to is far too small to draw any empirical conclusions from and base any strong opinion with them in mind.

However I searched some forums (including forums for other cars that use these motors, eg, Pajero and some US vehicles that use these) and it seems a general consensus on these forums that it is a common issue.
Also from talking to a few head rebuild workshops they also seem to have the impression that it is not an uncommon problem.

In absolute terms it's probably not common, maybe only one in ten or twenty cars over 200K have this issue, but it's probably common enough for there to be a root cause of it hence the question as to what causes them to fail, and specifically if that cause is sub-par quality OEM valve seals; all coming back to the original question as to what brand is best to use and/or avoid.

....
I always understood it was simply because the seals dried up and shrunk letting the oil seep through.

Any idea as to why this would happen though?
ie, head design, poor quality OEM seals etc?

EDIT:
I've checked the part numbers for the OEM seals and they are used in quite a few motors from Mitsubishi. Though these are much less common motors it didn't seem like forums with these specific motors were filled with valve seal questions (for example the FTO uses these, and though FTO numbers are just a fraction of 3rd gens, the FTO forums very rarely mention valve seals leaking) which may point to some issue with the heads?

A wise old man who worked at a engine machine workshop told me once that the oil burning past the valves was caused by wear on the valve guides on high km engines. The valve stems can move laterally and allow oil past the valve stem, and new seals would only be a temp fix.
He put in something called K-line valve guides.

Spetz, it's caused by normal wear and tear. Stop looking for someone to blame. In the old days of the Sigma engines, an engine with 160-180,000 km on it would need a crank grind, rebore with new pistons and rings and extensive head work to bring it back up to as new condition. We never accused Mitsu of bad engine/head design or substandard seals. Owning or looking at buying a Magna with 200,000+ km on it and expecting the engine to be as new is just unrealistic. lol

I've also heard that the valve guides are soft though nothing concrete.

It's not that I expect a high mileage motor to be as new, but seeing as my car uses oil and I have no immediate plans to sell it I am looking at what to do to fix the issue

It is the wave spring....




Seriously, these cars are getting old ffs, you dont know the history of the car, if low mileage may have gone for 2 or 3 years between oil changes and no matter what oil you use you will have issues with that

Brendon used to be an engine reconditioner before starting here, Magna heads for the third gen were the LEAST worked on heads in his work. They do not have soft guides or issues with stem seals. Most of the cars I have seen with stem seal issues in the third gen series are TJ or TL's which have been run on Magnatec oil for most of their lives.

If you are doing stem seals then I say good luck as on a third gen is a prick of a job. I personally will not do them heads on and if you are taking off heads you are better off just replacing the motor. A waste I know but lets face it, it is a far cheaper option

I did mine about 6 months ago with the heads on and it is a bit time consuming. I used genuine seals as I got them very cheap.

It is the wave spring....

:D That destructive little bugger sure gets around, huh!

Anyway, as for the best brand to go for?

I've also heard that the valve guides are soft though nothing concrete.

No, they are not made of concrete (JoKe), some sort of bronze I believe. And yes, they are soft, that's how they are meant to be.

Just use the standard valve stem seals from a Mitsu dealer. Check for sideways play on each of the valve stems when you have the springs off.

When you think about it, it is fairly simple. If your valve guides or stems are worn and you install new seals, you are expecting the seals to act as guide bearings. They will do that - for a short time until they wear out again. The only way, if the guides are worn, is to replace them.

The k-line are inserts, the valve guide is honed out and a sleeve is inserted to bring the clearance back to specification.

I was under the impression it was not possible to replace valve stem seals on 24 valve Magna motors. GQshorty, is your car 24 valve 3.5 litre? If it is, I bet it was a challenging job. I did valve stem seals on my v6 TS (3 litre). Any tips will be welcome. Doing them on TS was tricky but very rewarding.
Cheers, John

I did mine about 6 months ago with the heads on and it is a bit time consuming. I used genuine seals as I got them very cheap.

Did oil consumption/smoke go away?
Any signs of issue returning?
km on car if you don't mind?

Car has done almost 290,000km no more smoke after idle. Yep 24 valve 3.5 v6. You need to use a skinny valve spring compressor (ABW brand) to get between the spark plug tubes and wall of the head. I have done valve stem seals on the 3.5 v6 about 8 times now.

How many km since you've changed the stem seals?
And, have smoke/oil consumption issues returned on these cars?

Did oil consumption/smoke go away?
Any signs of issue returning?


How many km since you've changed the stem seals?
And, have smoke/oil consumption issues returned on these cars?
Spetz, you don't seem to be paying attention:

If your valve guides or stems are worn and you install new seals, you are expecting the seals to act as guide bearings. They will do that - for a short time until they wear out again. The only way, if the guides are worn, is to replace them.
Replacing the seals on their own is not a cure if the underlying problem is that the valve guides are worn. And that's something that needs a dial-micrometre or the like for measuring. Without knowing the answer to the guide wear question, answers based on seal replacement have little value.

You might be paying less attention than you realize. The questions as to whether the oil consumption came back and km since stem replacement was targeted directly towards getting an idea of whether the guides were worn or not on his motor due to the exact comments that you highlighted.

Whatever you say - your questions showed no interest in valve guide wear, only in the seals...

The seals are the only thing I'd be interest in changing as a DIY project.
Pulling heads off and paying to rebuild them is not worth the money.

Of course if it is guaranteed that doing the seals would be a very temporary fix then there is no point in even doing them.

If GQshorty says he did them 50,000km ago and still no oil consumption then it'd be enough reason for me to DIY replace them especially seeing as my motor has 100,000+ km less than his

If your car needs valve stem seals replaced with less than 190,000km on it, I'd say you've got far more to worry about than just those. Needing them so early in your KJ's life suggests a poor service history and/or the use of the wrong oils.

The service history is good and everything on it is in good condition. No lifter noise and runs quiet and smooth.
It doesn't smoke or anything, but if I idle it 10 mins and blip the throttle it will smoke.
Uses about 1L of oil per 2,500km, so I generally fill it up 2-3 times in between 8,000-10,000km oil change intervals on fully synthetic oil.

In the service history though it show Magnatec being used at least once which from what I've read here possibly hardens the seals

The service history is good and everything on it is in good condition. No lifter noise and runs quiet and smooth.
It doesn't smoke or anything, but if I idle it 10 mins and blip the throttle it will smoke.
Uses about 1L of oil per 2,500km, so I generally fill it up 2-3 times in between 8,000-10,000km oil change intervals on fully synthetic oil.

In the service history though it show Magnatec being used at least once which from what I've read here possibly hardens the seals

What brand and grade of oil are you using currently?

"It doesn't smoke or anything, but if I idle it 10 mins and blip the throttle it will smoke. Uses about 1L of oil per 2,500km,"

If that is all it does, leave it well alone. Oil is cheap, even if your consumption doubles it is still cheap. It is nice to have everything perfect, but to get it that way will cost a heap of money in materials alone.

One thing to check, if you haven't already, is your PCV system. If it's blocked it can have a similar effect, ie. smokes after a few minutes of idling. I had got used to it and just assumed it was worn valve stem seals/guides (280k engine so not unexpected), but after replacing the PCV hoses and clearing out the rocker cover baffles it's mostly gone, no more filling up car washes with blue smoke on exit!

Ammerty, first oil change since I bought the car was with HPR 10 (10-50 I think?), second oil change is Castrol Edge 5W40 (bought it 45% off + free oil filter, too good to pass up).

Oil consumption between the two oils is the same from what I can gather.

Erad, the PCV valve is fine since when I take it out and block it I can feel it open/close. Not sure about the rest of the system though as I haven't checked it. It idles really poorly at times, and other times it idles fine.
The intake manifold is all black inside (not sure if this could be the PCV system letting oil into the intake?)

I know oil is cheap, but the valve stems are under $100, I can borrow all the tools and I am not averse to doing it DIY

Your oil consumption is certainly excessive - about 6L per 15,000km standard service interval. Are you sure you don't have a few leaking gaskets or a crook PCV valve? Another possibility is that the motor has been overheated (lack of coolant) and that's hardened the seals and burned the oil in the ring gaps, making them seal less well. Overheating could even contribute to leaking gaskets (i.e. crushed by extra compression due to the expansion of the metal castings either side when overheated, then unable to take up the slack again when cooled down).

My Magna, with about 15,000km less than yours, doesn't require any topping-up between services (at 15,000km intervals). I've never bothered with 'fully synthetic' oil and I certainly wouldn't be throwing money away changing it at 8,000-10,000km intervals.

I doubt that replacing valve stem seals is going to solve your oil consumption problems, since a lot of it is probably getting past the gaskets and/or rings too. A compression test should tell whether it might be the latter. If so, and given that you're coming up to a major service, perhaps you should consider waiting till the next major service is due and replacing the motor.

As for Magnatec hardening seals, you'll also find suggestions that Magnatec makes them swell which, if anything, means softening them and could improve their sealing capabilities... IMHO, it's probably just a bunch of people looking for something to blame without any evidence to back up their claims. There have been threads here too about Magnatec, with OldBoy saying he's used it for close to a decade without problems. Waynvb14 claims to have used it for 7 years on a 1999 Magna with 410,000 on the clock, again with no issues. At least one member has used Magnatec on a mechanic's recommendation to cure engine problems. Others disparage it no end. Frankly, one or two services using it is unlikely to be of any consequence one way or the other.

Another option, instead of replacing the seals is to use one of the additives that are supposed to rejuvenate them and/or clean up varnish/gumming.

There are no leaks at all, and the PCV valve itself is working fine (not sure if there is more to the system than that though).
Don't know if it was ever overheated as I bought it second hand.

A dry/wet compression test was something that I would do before changing stem seals in case it was the rings.
Would oil getting past the rings cause blue smoke after extended idle though? It seems a valve seal issue on that basis

I used an engine flush during the last oil change, I am now measuring the oil consumption again.

EDIT:
And yes, because the 200K service is coming up I want to get all the info I can to make a decision when the time come.
I don't really want to swap in a motor I know nothing about though, especially as I've taken the car to a number of mechanics and they said they haven't seen a better running 6G74 unless I am sure this motor is no good (valve seal in themselves are probably not a good enough reason to swap motors I think)

Leaving any engine idling for 10mins is liable to result in a puff of smoke (black, if not grey), without that being an indication of problematic valve stem seals. That's more likely to be evident any time you decelerate then accelerate and could just as easily be an indicator that the valves & guides need replacing; indeed, there would be minimal oil leakage past good guides. Worn exhaust valve guides/seals wouldn't be apparent from this, though, as there'd be insufficient vacuum to pull extra oil through them. Ring problems are usually indicated by blue/grey smoke while driving the car normally or accelerating. In both cases, you'd need someone travelling behind you to tell you what's going on, as it might not be apparent from inside the car.

Nothing much more to the PCV system but the hoses can block up easily, particularly the one that runs between the valve covers. Simple test, with engine off pull the PCV valve out of the valve cover grommet and pull the PCV inlet hose off the intake pipe. Use your finger to block the grommet and blow (with your mouth) into the PCV inlet pipe. With the grommet unblocked you should be able to blow through the system, with it blocked you shouldn't be able to. There's a series of baffles in the valve covers designed to prevent liquid crud from blowing back (not terribly effective it seems), these block up fairly easily. The manual suggests replacement, I've found they can be cleaned out with a soaking in degreaser for a few hours and a good blast with the garden hose. Hoses are oil-proof and available from Mitsu dealers or someone like Mal.