Valve adjustment not needed, LMA's sticking...

Went to do a little maintenance, and changed the plugs, and went to adjust the valves because I thought several had to be loose due to some ticking.
Pretty sure the ticking is the Lost Motion Assemblies (LMA's) sticking.
Valves were all good.
Arghhh.
Good Winter project.

http://www.youtube.com/watch?v=q4eRQf7kkhc

LMA's? Explain please?:redface:

Lost Motion Assemblies

they basically provide constant pressure to the rocker arm that the vtec lobe travels on.

Your little youtube video was great showing the "sticking" action. Please document and take pictures of every step here, a great DIY for all of us, these things have been moving up and down, hundreds of thousands of times over the life of the car and should be replaced.

Is this a rare occasion? There has'nt been much if any discussion that I've seen.

I do not see this too often, mainly abused engines. dirty oil, high mileage, and track use all help these wear out. They make a unique clicking sound when worn. I have only had to replaced them on 3 engines in the course of many. I am not saying it would be a bad preventative step during a rebuild, just that I do not see them bad too often.

In regard to the track use, it is when a car is tracked and extra fluid changes/maintenance are not done. A well maintained track car will not see this failure on any regular basis, at least that is my experience.

JMO.

Regards,
LarryB

When you say unique clicking sound when worn, I'm assuming you mean it would be pretty obviously different than the usual Honda engine sewing machine/ticking/injector noise?

davidsk said:

When you say unique clicking sound when worn, I'm assuming you mean it would be pretty obviously different than the usual Honda engine sewing machine/ticking/injector noise?

Click to expand...

Only slightly different in operation, but really sound different when you have one in your hand and you are compressing it.

Regards,
LarryB

So this a "high dollar" repair. Do most good techs check this during valve adjustment?

I think mine just hadn't been used enough.
The car has 48,000 miles, everything is clean and fresh inside and out.
It has just sat. A lot. It needs to be used more.
Because of this disuse, it now needs what is called in the aircraft industry as Hanger Maintenance.
I need to drive it more.

If you are replacing them, I would consider the SOS LMAs, in case you weren't aware they had a better design.

http://www.scienceofspeed.com/products/engine_performance_products/NSX/ScienceofSpeed/LMA/

davidf said:

So this a "high dollar" repair. Do most good techs check this during valve adjustment?

Click to expand...

Can't speak for others, but I do

clr1024 said:

If you are replacing them, I would consider the SOS LMAs, in case you weren't aware they had a better design.

http://www.scienceofspeed.com/products/engine_performance_products/NSX/ScienceofSpeed/LMA/

Click to expand...

All three I have done I have used these, good stuff.

Regards,
LarryB

Can the OEM revised (2000) version be used in place of the old version?

racer9x said:

Can the OEM revised (2000) version be used in place of the old version?

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I was under the impession they made an OEM "replacement set" for the pre 2000 engines. Think I read it here.

Regards,
LarryB

What's a good time/mileage to do this as preventative maintenance? Or should we wait until the symptoms?

I've heard about this a lot but don't think I would be able to detect it from the cabin...

furinax said:

What's a good time/mileage to do this as preventative maintenance? Or should we wait until the symptoms?

I've heard about this a lot but don't think I would be able to detect it from the cabin...

Click to expand...

Should be checked whenever a valve adjustment is due, unless you hear a consistent ticking from the valve train.

HTH,
LarryB

There is an updated OEM LMA from Honda.
I forget the year they changed but Kaz has spoken on this before and has posted the new style p/ns so maybe check his NSXCB NSX "refresh" blog or his DIY there.

Cheers
nigel

Thanks for the info, this is what I found as the new replacement for the early motors, PN 4820-PCB-305.

Wow, very old thread....

Any way, it’s not just the mileage that makes the classic LMA tired/sticky but also the time the engine is sitting without running.
You will notice much more spring rate imbalance between each LMA on the low annual mileage NSX than the regularly driven one.

This is because when you stop the engine, some of the valves are kept open.
This means that some of the LMA is also compressed.




[Latest design LMA for pre-LEV engine at the top, Classic LMA at the bottom (this one is the 2nd gen, looks similar to the 1st gen but bit better against the sticking issue.]

The classic LMA had somewhat complicated design like two different spring rates enclosed in that small diameter cyl that if the car was kept in the storage for months, some of the LMA will lose spring tension more than others resulting in tappetty sound.
It’s the result of mid rocker arm not following the profile of mid cam robe and simply both are hitting each other making the mechanical noise.


This is the typical sound of tired LMA. The noise is always there from the beginning but suddenly disappears around 0:40 - 0:45 and 0:56 - 1:05.




This is what’s happening with the tired LMA. As you can see, the spring rate is different from one LMA to the other.


With the latest LMA design, it’s much simpler design with just the spring and with no cyl surrounding, the gauge diameter and spring body diameter are much larger than the classic one that the initial spring rate is much higher.
Should last for a long time.

The changeover happened at the time when LEV engine was introduced in 99 but depending on the market, it’s probably called as 00 model.
As the introduction timing depends on each market, best to enter the VIN in the online parts website based in one’s country.
If your engine is pre-LEV, the latest LMA is 14820-SL0-305.
You will see thin metal silver colour spacer and hat at both ends of the spring.


If your engine is LEV, you already have the latest LMA design from the factory and it can survive for a long time.
So far, I have never replaced the LMA on LEV engine.
The last 3 digits of the parts no. is -003 and it will have just the silver hat at the top without the spacer at the base.
Again, if you see -003 for the LMA when you entered your VIN, your NSX already has the latest LMA design so unless you have a reason to do so, no need to replace.


Kaz.

Although technically possible (Britlude did it) to replace these with engine in bay, you will want to do this as a 'sub-frame out' procedure to preserve your sanity.

after you lift off the camshafts, you will need to slide out the rocker shafts. You can use one of your side engine mount bolts to screw into the rocker shaft once the 20mm sealing bolts removed and pull it out.
The rockers will be free, elastic-band them (don't lose the synchronizer pins), move them out of the way, hook the top part of your old LMA and pull it up and out.

If you are doing this in the engine bay, you will need to remove the 3 main coolant hoses to provide enough clearance to pull the exhaust side rocker shaft all the way out.

I'm very appreciative that we have the expertise of Kaz, and on our side of the pond Larry B that offer their time in explaining the finer details of our beloved old nsx.....thanks again.

I have the classic ticking/ knocking noise as well. [MENTION=25737]Kaz-kzukNA1[/MENTION], as others mentioned here is this possible to replace with engine in the car? Also, can this damage the engine if gone untreated?

Hi, Jinks.

It can be done as per NSXCB member britlude's post here.

However, you must remove all four camshafts, rocker shafts/arms plus VTEC spool valve within very limited space and then adjust all of the valve clearance that you are better off taking the eng/gbox assy out of the bay.
You will know what I'm talking about if you have ever adjusted the rear bank exhaust side valve clearance while keeping the eng inside the bay… I used to do it that way but took more time than doing it with eng/gbox out of the bay.

It will also allow you cleaning the difficult to access LMA pockets, inside/outside of the eng, etc very well.


It's metal on metal noise caused by first LMA hitting the mid rocker arm and then depending on the cam timing and how much spring rate left inside the classic LMA, it may hit the cam lobe as well.
So strictly speaking, eventually, it will cause mechanical wear but how much or how soon depend on so many factors that no one will be able to predict it.

Based on what I saw in Japan and UK, if you are mainly street driving and covering moderate mileage each year, then probably best done at the next TB/WP service by taking the eng/gbox out.

Kaz

Just as an additional info on the LMA design (not to contradict the pros). The design of v1 had also the function of a 'built in' shock absorber. An undampened spring has a resonance frequency with ill effects if the resonance frequency gets reached (like vales hitting the pistons during overreving). The design of v2 was possible because the frequency was designed high enough.

Sticky LMAs are mainly due to residues inside of the LMA valve body (and maybe a weaker spring).

There is absolutely no need to remove the engine to do this. Respectfully, I did this on several NSX's without removing the engines or any coolant hoses. It does not take that long either. If you are a descent wrencher, you should be able to manage it without issue. I do greatly respect Kaz and his contribution to this community as well as others in this thread. Just wanted to share my experience. I am different though as I do not angle the motor when I do timing belts and I have done head gaskets with the motor in the car. [emoji851]


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I just so happen to be in the middle of this job right now and am not removing the engine to do so. Access really isn't that bad...just the rear bank exhaust cam is pretty far down there.

The only thing I found angling the motor helped with was getting the front timing cover out of the way.

Here's a quick video I made of my sticking LMA's. Car is a 1992 and has 96k miles on it.