Valve clearance adjustment necessity?

[HeavyPizzaz]

Poor choice of title perhaps as I’m not suggesting valve clearance check/adjustment isn’t necessary, but my question is... if you don’t check / adjust valve clearances, what’s the worst that is likely to happen as a result? Poorer economy? Decline in power? Anything major? Increased cylinder / ring wear from unburnt carbon due to incomplete combustion or something or other? I’m just spitballing.

My MY16 is about 110,000km (I got it at about 82k) and I don’t imagine it’s ever been done. And I believe it has the revised timing chain guide. But that will likely be original too.

Just wish my former mechanic had mentioned it earlier when he took it apart and cleaned out the inlet manifold etc at about 90k, instead of just “you’ll be due for valve adjustment next service” when I picked it up. My understanding is he’d had it all apart ready to do. Not that I asked for it. But he coulda told me earlier is all.


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[Seigried]

the worst that is likely to happen as a result? Poorer economy? Decline in power?

Yup. At the very least. In extreme cases valves can be bent which can lead to even more serious problems.

Having said that my nw didnt have the valves done at 90k km because the "audible check" at the dealership said it was ok. But thats another can of worms.


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[disco stu]

I had a gen 1 pajero where the one of the valves had such large clearance for so long that the top was mushroomed out from the hammering, happened before I got it. I think you'll know if you're at that stage though

[pharb]

In the old days, with lesser technological advanced materials valves usually slowly wore the valve seats. As the seats wore the valve travelled up further, reducing tthe clearance between the valve tip and the valve actuating mechanism.
If the clearance was to reach zero, then the valve may not close properly and allow combustion pressure to escape through the gap. This leads to wearing away of the valve head and valve seat surfaces creating a valve that will never seal until it is repaired or replaced.
As alloy heads became common there used to be issues with the valve seats gradually recessing into the head, again allowing the clearance between valve tip and actuating mechanism to reduce, with subsequent longterm issues.

Modern materials, both valves and valve seats, has seemed to ellviate a lot of these valve head, seat issues.

Alternatively, there is occassions where the valve actuating mechanism, or valve tip wears, creating more clearance. This causes the valve to open later, open less, and close earlier, effectively changing the tune of the engine (like using a "milder" cam), and reduce the quantity of air going into and exhaust coming out of the combustion chamber.

[Dicko1]

My NW had the valves done at 40,000klms. My mechanic said nothing needed adjustment. Told me to bring it in at 120,000 and stop wasting his time...lol. As he said..these motors are bulletproof and just ensure you get a valve check done before 100,000klm and all will be good....MM only do audible checks 90% of the time anyway.

[DibbyDibbyDJ]

MM only do audible checks 90% of the time anyway.

50%

[Nab]

As above, there may be issues with valves recessing into the head but mainly smoother, more efficient running is what you get. Nothing "needs" to be done, but preventative maintenance is about keeping the car reliable for many 1,000s of km. Just like you can change the engine oil and filter every 30,000km instead of 15,000km but the long term engine life will be affected.



It's quite a simple job to adjust the valves if you're mechanically minded, there's more work involved in removing the EGR, injector pipes etc etc. 3hrs labour and a rocker cover seal is all that is required. The injector pipes need to be replaced after being removed 6 times (from memory) so you shouldn't need them. Just do it on the next service.

[Dicko1]

50%

You have to be an optimist. Many on here can attest that they have been charged huge amounts of money for a valve check that they believed would be physical...not audible....

[Seigried]

Yup. Have had that argument with the sevice manager when qouted for the next service. Couldnt explain to me why i was charged a huge amount for what was meant to be an adjustment. Only to be qouted same amount again for the next service.

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[erad]

Anything which shows up in an 'Audible Check' means that the tappet clearance is too much. Excessive clearance isn't going to do too much damage. Yes - it alters the valve timing and also the duration of the valve opening if the clearance is exessive, but that will result in maybe a dropoff in performance. The dropoff will be so gradual that you probably won't notice it. An audible check is useless. Anyway, there is so much clatter when the diesel is running I cannot understand how a mechanic can hear if the tappets are noisy or not.

Now, if your tappet clearances are too tight, this is another story. The clearances reducing means that the valve or the valve seat is wearing and the valve is boring itself into the head. Again, you may lose a little performance, but probably not notice it, but when the valve or seat wear to the point where the seating of the valve is affected, then you get hot gases leaking past the valve seat and this will burn the valve or the seat. Then you have big troubles.

The petrol engines have hydraulic tappets and for the life of me, I cannot understand why they are not used with the diesel engines. I guess it is the fact that diesels are old technology and maybe they manufacturers are looking ahead to when they no longer make or sell diesels.

[Keithyv]

the worst that is likely to happen as a result? Poorer economy? Decline in power?

Yup. At the very least. In extreme cases valves can be bent which can lead to even more serious problems.

Having said that my nw didnt have the valves done at 90k km because the "audible check" at the dealership said it was ok. But thats another can of worms.


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Would have to be a pretty extreme clearance problem to lead to a bent valve?
Surely this would be basically impossible? (Due to lack of clearance checks I mean)

[DibbyDibbyDJ]

You have to be an optimist. Many on here can attest that they have been charged huge amounts of money for a valve check that they believed would be physical...not audible....

I can guarantee that has NEVER happened in my place of work.

[Pajshomoneroguntero]

I marked the rocker cover and a few of the bolts holding it along with the injectors when I had it done at the dealer. I also asked for the measurements before and after which was supplied. I am reasonably sure it was done.

[Dicko1]

I can guarantee that has NEVER happened in my place of work.

Maybe so mate...but it is common at plenty of other places. As is a lot of other bullshit services carried out. Everyday in various forums people whinge about shit service and being ripped off from various mechanical shops.

[Jasonmc73]

I can guarantee that has NEVER happened in my place of work.

If your over the shoulder of the tech thats fair enough, but make for an easy few hours with great efficency for a tech whom is not so honest of course.

I work in machinery not something as a company we would condone or expect from tech's though.

Cannot see how a dealer would be any less reliable in this area than any other human??