# Valve Seals - Can They be Replaced without removing the head?



## Lionheart (Oct 5, 2015)

Hi guys

On the 3.5, can the valve seals be replaced without removnibg the head???

It seems (from my research) that they can on many models, but I'm not sure on the Murano?

I'm thinking maybe the cam chains are an issue?

I don't want to remove the head as I beleieve that's engine out (?) and major work!

Any help welcome!!!


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## Glenn01 (Oct 10, 2015)

Looks like that motor will have to come out. Mostly I'm sure because of the timing being chain driven. I'm not aware of any vehicles that can have valve stem seals replaced with the head on. Someone correct me if I'm wrong. 

What is the problem exactly?

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## Lionheart (Oct 5, 2015)

*(*

Yes, that's what I think will be the most likely outcome (

The car has excessive oil consumption, and lots of smoke on start on (and holding revs stationary).

Also engine management light comes on.

I think the previous owner packed the car full of Stop Smoke or a similar product as the engine management light only comes on since I changed the oil (major service including spark plusg etc). Also far smokier since the service. So pretty sure they must have used a product to reduce valve seal leakage.

I wondered if it may be possible to remove the cams in some way without having to remove the engine?

The cams sit on top of the valves it looks like, so they need to come out (?) but can't see a way to do it without having to remove the full large cam chain cover which is engine out.

Any ideas????


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## Glenn01 (Oct 10, 2015)

Before stripping do a compression test and a cylinder leakage test. This will give you a clearer idea if it's top end(head) or bottom (worn rings) 
Maybe also get the code for the EML 

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## Lionheart (Oct 5, 2015)

Oh yes, BTW (as you mentioned it) many cars can indeed have the valve seal replaced without removing the head, including Nissan's - Google 'changing valve seals without removing head' or similar and you'll see numerous video's. 

But they are generally for single cam where the cam runs along the centre of the valves, whereas the Murano is twin cam and the cams sit on top of the valves it appears.

I did see a twin cam video, but I guess the engine is not chain driven and so removing the cams to access the valves is a lot easier.


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## Lionheart (Oct 5, 2015)

Hi there

Yes, I was going to do a compression and leak down test before getting stuck in, but if the valve seals cannot be replaced without pulling the engine then pointless anyway as that's into some major work.

I was hoping that the cams (and therefore valve seals) could be removed with the engine in situ?

The official manual naturally says pull the engine, but was hoping there may be a practical workaround?


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## smj999smj (Jan 1, 2006)

You'll need to pull the engine and even with the engine out, it's still going to be a major job. Front timing cover and three timing chains will have to be removed, four cams will have to be removed, and then, if you can find a valve spring compressor that will work without pulling the heads, you will need to pump compressed air into the combustion chambers to keep the valve from falling down into the combustion chamber. Make sure you have a way to remember which lifter and adjustment shim goes to which valve. 
That all said, late model Nissans use Viton valve seals and valve seal failure in a VQ motor is practically unheard of. I would definitely check the PCV system and do a cylinder leakdown test, first.


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## Lionheart (Oct 5, 2015)

How would I test the PCV system? I have replaced the valve.

Would that cause it to use lots of oil (1 liter every 3 hours of driving approx)?


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## Glenn01 (Oct 10, 2015)

Sounds like your rings are bust TBH 

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## SPEEDO (Jun 9, 2003)

+1 ^ I would lean with the rings before valve seals, have you pulled the plugs? which ones are oily etc


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## Lionheart (Oct 5, 2015)

Hey guys

It seems there are three possible causes:

1) PCV valve: But I have just replaced this with a brand new one. Also, if this were faulty I assume it would not make oil build up overnight so a cold start blows out a lot of smoke initially?? Noted it's smokier since doing the service and replacing the valve etc.

2) Valve seals: But many people saying they don't fail often. But definitely get a big cloud of smoke after cruising downhill (no accelerator) and then hitting the accelerator again. Not sure if piston rings would cause this same symptom? Would have seepage into cylinder overnight.

3) Piston rings: Would this make a build up of oil in the cylinders overnight to cause the extra smoke on cold start?


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## Lionheart (Oct 5, 2015)

Yes, the spark plugs were changed. All had traces of burnt oil on the ends and were in a poor state.


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## Brad53 (Feb 21, 2016)

*smoking on startup after oil change*

Hello, my 2003 Murano smoked on startup with non synthetic oil after oil change, but on synthetic (dexos) there is no smoke, how ever oil consumption is high 1L/1000km, smoke on startup only with non synthetic oil indicated valve seal leakage, have not done compression check yet, pulled a plug and it looks grey (normal) and the correct gap at 0.043". Check engine light coming on due to low cat eff on bank 1, pcv valve may be cheap and easy to change but cannot imagine it is the problem. Insofar as "unheard of for viton seals to leak", that is encouraging but i am skeptical. Even pouring the oil in the tappet cover to fill the engine seemed to flood the cylinders with oil that burned off on startup with a lot of smoke, like there were no valve seals present. There are 185,000 km on it. 120,000miles. Any thoughts?


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## Sooty&sweepbus (May 19, 2021)

Lionheart said:


> Hey guys
> 
> It seems there are three possible causes:
> 
> ...


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## Sooty&sweepbus (May 19, 2021)

Hi new member hoping to revive your thread! Here’s hoping did you ever manage to resolve this issue? I recently bought an 2002 3.5 elgrand with the exact same symptoms, compression is good, pcv valve was blocked, it has all the same characteristics you described and the right bank of the V seems worst affected, I’ve been looking at sourcing a replacement engine but have been advised that the heads are unique to the elgrand so murano etc no use


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## VStar650CL (Nov 12, 2020)

If the PCV was blocked, make sure the plumbing inside the valve covers isn't also blocked before condemning the valve seals. The PCV passages on both sides have baffles, and if the oil got gummy enough to block the PCV then it may also have blocked a baffle. You should be able to blow compressed air into the VC on either side and hear it come out the other. If not, replace the VC's.


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## Sooty&sweepbus (May 19, 2021)

Thank you very kindly for your reply ill hopefully try this later today but I’m worried about blowing lots of crap back into the pcv, ideally I think I would need to disconnect it and as access is very tight it’s a upper intake off job. At that stage I should probably just pull the covers and have a look, I regret not doing this last time I had them off to get to the valve. Where would you recommend getting valve covers if they’re bad, I’m based in Belfast Northern Ireland kindest regards


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## VStar650CL (Nov 12, 2020)

You don't need high pressure, just enough to make sure the plumbing is open. Even canned air or lung power will work fine just for checking. I have no idea about parts in Ireland, but if the skirts on the VC's are good you can probably save them with a bath in solvent and then blowing them out.


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