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Valve Stem Seal Replacement 
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Post Valve Stem Seal Replacement
Hi everyone,

I have a feeling that my valve stem seals have harden from the car sitting without being started for the last 7 or so years.
The car smoked up a lot at the beginning and has now mostly subsided but there is a bit of a puff of smoke after idling a while and then stabbing the throttle.
I'm not sure if this will get better still as the engine has ran about 2 hours since first start up all up.
Either way I am doing the timing belt before driving it and hence it would be an opportune time to change the valve stem seals too (without removing the heads).

I've done this on my 6G74 before, however being a SOHC only the rocker arms had to be removed to get to the valve springs.

I assume with the MIVEC motor the cams need to come out to get to the valve springs?
Do the heads have caps that can be removed so the cams can be lifted or do they slide out from the side?

Any other considerations when doing this?
Are the valve stem seals specific to the MIVEC head or will the DOHC ones fit too?


Thu Aug 04, 2016 12:27 am
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Post Re: Valve Stem Seal Replacement
There is cam caps they don't slide out


Thu Aug 04, 2016 12:31 am
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Post Re: Valve Stem Seal Replacement
The MIVEC engine has a "cam carrier" it is sealed to the head using RTV sealant. The half moon seals go between this and the head.

You just remove the 12mm bolts on the cam caps (leave the 10mm bolts) and the whole carrier lifts out with the cams and rocker arms attached and gives you access to the valves/springs.

From here you just remove the springs like any other engine.

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Thu Aug 04, 2016 12:34 am
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Post Re: Valve Stem Seal Replacement
Thanks for that.

I'll have a look through the engine manual and see what torque specs are there too.
Since the timing belt will be off anyway this hopefully shouldn't be any bigger of a job than when I had to do the 6G74 valve stem seals.

Does anyone know if any specific valve spring compressor fits there?


Thu Aug 04, 2016 12:47 am
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Post Re: Valve Stem Seal Replacement
I've only done them with heads off so not sure what tool would fit. But there is a mitsi tool used in the manual.

The torque settings are 24nm for the 12mm bolts and 11nm for the 10mm bolts if I recall correctly.

There's a lot a certain order you need to undo/do them up in.

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Last edited by Vectose on Thu Aug 04, 2016 12:41 pm, edited 1 time in total.



Thu Aug 04, 2016 1:09 am
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Post Re: Valve Stem Seal Replacement
Meek sell the tool to do them with heads on: http://www.meek.com.au/tools/valve-spri ... -tool.html
Been meaning to buy one myself.

Torque order is to do the centre ones in first & work your way outward on each side, much like torquing a head.

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Daniel2019 wrote:
I found it easiest to start getting it off from there and then just run your hand down along the side and across the top.

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Thu Aug 04, 2016 10:53 am
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Post Re: Valve Stem Seal Replacement
But you wanna be careful, if any of the plastic collets on the tappet screws are broken you will lose the metal shim down the engine when you lift the cam carrier out.

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Thu Aug 04, 2016 5:39 pm
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Post Re: Valve Stem Seal Replacement
Thanks everyone.

When I did the valve stem seals on my 6G74 I covered everything in gladwrap to avoid contamination plus to make sure nothing falls somewhere and is lost.
I ended up compressing the springs in a C clamp and holding them down with metal zipties. This made installation of the collets quite easy, so if all else fails I might do the same for the 6A12

Pics of my 6G74 valve stem seal replacement:
Image

Image

Image

Image


Thu Aug 04, 2016 9:32 pm
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Post Re: Valve Stem Seal Replacement
Does anyone know if the valve stem seals are shared amongst any other motors just to see what aftermarket replacement seals are available since there does not seem to be much for the 6A1X motors.

Part numbers are MD184303 for the intake and MD302338 for the exhaust.
Meek sells some but I am not sure of brand or quality?


Sat Aug 06, 2016 10:22 am
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Post Re: Valve Stem Seal Replacement
Inlets are common to a stack of Mitsis, the exhaust really only the Legnum & 1 Lancer..

For a little bit of rubber, I don't know if you're gonna get much variety in brand shopping. If it was me, I'd go genuine.

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Daniel2019 wrote:
I found it easiest to start getting it off from there and then just run your hand down along the side and across the top.

Sahin wrote:
I'd fix your box if you were in Queensland!


Sat Aug 06, 2016 11:40 am
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Post Re: Valve Stem Seal Replacement
Thanks Bennoz,
The CK6A Lancer is the 6A11 equipped one so it seems the exhaust stem seals are unique to this series motor.

I am not against OEM, and the $50-$80 extra is no concern considering the amount of hours it takes to do, I just want the best available option.

I do know that the older Mitsubishi engines are notorious with leaking valve stem seals and my concern is that this might be due to the quality of rubber used in OEM parts that ends up hardening over time.

When I first started my 6A12 after a few years of not being started it smoked up a lot, so I assume that the seals dried and hardened. The smoke has mostly subsided now but like I mentioned since the timing belt will be off it is an opportune time to swap these out.
Additionally the heads have been ported and polished, 3 angle valve cut etc, but I have no idea whether the stem seals were changed, I assume this should be normal practice, which means I do not know what brand seals are currently in there


Sat Aug 06, 2016 12:17 pm
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Post Re: Valve Stem Seal Replacement
Yep, my 6A13 seals needs doing. Just about every bit of rubber in it from half moons to the crank seal needs doing in it. It is 20 years old, I'm not surprised.

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Daniel2019 wrote:
I found it easiest to start getting it off from there and then just run your hand down along the side and across the top.

Sahin wrote:
I'd fix your box if you were in Queensland!


Mon Aug 08, 2016 4:00 pm
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Post Re: Valve Stem Seal Replacement
I was thinking about how to tackle this job, and when I did it on the 6G74 I used rope down the cylinder to prevent the valves from dropping down.
I spun the motor to BDC for each cylinder I was working on, fed rope, then spun it up toward TDC to compress the rope.
Now, with the SOHC 6G74 the cams and hence the timing belt were not taken off.
With the MIVEC since they do need to be taken off, I assume I cannot spin the motor unless all 4 cams are removed? Otherwise the cams that are in place still will have some valves interfering with the pistons?

Is there a way around this other than to manually rotate the cams half as much as the crank?

I would prefer to do one bank at a time but it is looking like I need to remove everything in one go.


Sun Sep 04, 2016 3:43 pm
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Post Re: Valve Stem Seal Replacement
Just pull the heads off.

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Sun Sep 04, 2016 5:07 pm
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Post Re: Valve Stem Seal Replacement
I'd rather change the valve stem seals with the heads left on.
It'll be cheaper and for me easier, as I've replaced valve stem seals before but have never removed a head off of a block


Sun Sep 04, 2016 7:24 pm
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Post Re: Valve Stem Seal Replacement
It's eight more bolts lol


Sun Sep 04, 2016 7:51 pm
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Post Re: Valve Stem Seal Replacement
Sahin wrote:
It's eight more bolts lol

Nah f**k doing it the easy way.. would rather struggle for triple the amount of time :lol:

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Mon Sep 05, 2016 12:05 am
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Post Re: Valve Stem Seal Replacement
Yes but the cost of OEM head bolts + OEM gaskets.
Also I am in no rush so I don't mind changing a couple of valve stems each night after work over 2 weeks or so.


Mon Sep 05, 2016 12:37 am
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Post Re: Valve Stem Seal Replacement
You don't need new head bolts unless they've stretched. I've done a few rebuilds now and none have been out of spec.

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Mon Sep 05, 2016 5:11 pm
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Post Re: Valve Stem Seal Replacement
Correct. There will be a measurement in the workshop manual for bolt length and possibly thread pitch.

Mine were in spec when I rebuilt my motor.

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Mon Sep 05, 2016 5:45 pm
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