MLS head gasket?

amaurer

 
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Forgive me for cross posting from the diesel section, but this is a general issue.

Due to a shoddy, and unnecessary, previous head gasket replacement, I'm experiencing the fun all over again. This time I got an OEM head gasket and was surprised to find that the new gasket is MLS (multilayer steel) (the original p/n has been superceded several times)

I know MLS gaskets are superior in many ways, but I've heard they're very picky about flatness and low-roughness surfaces. While I have had the head resurfaced, I wasn't expecting an MLS gasket so I didn't pay any attention to the finish the shop created. I also have no real way to resurface or even measure the block's flatness (short of pulling the whole engine - but this is my DD and I've been already down for a week).

So, am I in for trouble with this MLS gasket, or does Toyota know best?
 

bsevans

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I guess I need to be schooled on what a MLS gasket looks like. Could you post a photo. I know that Toyota went from head and manifold gaskets that were metal (dimpled) on the contact surface (both sides) to a non metalic contact layer on both sides. If your gasket has an exposed metal layer then you have the old style gasket.
 

amaurer

 
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i can snap a pic tonight, but this is not the old dimpled style. MLS gaskets are several layers of flat (non dimpled) steel thats been coated with black rubber (ok, its fancier than rubber, viton i think).

the original gasket and my first aftermarket replacement were dimpled. this one is smooth, has a viton coating, and feels heavier/stiffer. it has the right pn stamped on it, and is the right dimensions, so no question there.

do i use all the same torques and such too?
 

bsevans

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i can snap a pic tonight, but this is not the old dimpled style. MLS gaskets are several layers of flat (non dimpled) steel thats been coated with black rubber (ok, its fancier than rubber, viton i think).

the original gasket and my first aftermarket replacement were dimpled. this one is smooth, has a viton coating, and feels heavier/stiffer. it has the right pn stamped on it, and is the right dimensions, so no question there.

do i use all the same torques and such too?
That's the HG I used when I had a valve job done. Same torque and then re-torque after the engine idled at temp for 15-20 minutes. I like the new design and feel it will seal better than the dimple design.
 

Rice

 
 
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You should have no trouble with the MLS. While the big advantage is their ability to seal metals with different expansion rates they also do well with like metals. Regardless, if this is your second time doing the job certainly take the time to verify a flat mating surface.
 
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Thanks, DuPont!

Most late model engines now use Multi-Layer Steel (MLS) head gaskets because they are much stronger and more durable than nonastestos or graphite cylinder head gaskets. Aftermarket MLS head gaskets are now available for many "problem" engines that are known to eat head gaskets............

MLS technology was developed to overcome sealing challenges. The number of layers in an MLS gasket ranges from two to five, depending on the engine's sealing characteristics. Generally, the more layers, the more motion the gasket endures.................

Felpro now has introduced the "New Breed" (PermaTorque) mls head gaskets that requires no re-torque installation............:clap:

Man, I gotta say; They sure got close with the hole punch on your gasket there...

Are the fire rings distorted enough to cause worry?
IMG_4809-800 copy.jpg
 
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Felpro now has introduced the "New Breed" (PermaTorque) mls head gaskets that requires no re-torque installation............:clap:
QUOTE]

I don't see where they make one yet for the 4.2L straight 6.
Not yet Big Boy!..... later on this fall is the skinny, besides the one in the pic above doesn't resemble one either..........just saying, in case there are some problematic 3L or 3.4L lovers viewing..........
 

amaurer

 
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Man, I gotta say; They sure got close with the hole punch on your gasket there...

Are the fire rings distorted enough to cause worry?
The design of the fire rings is kinda funny, unlike on a composite gasket where the ring is a metal ring that surrounds the cylinder and then is folded back over the upper and lower surfaces of the gasket, on this one the rings are formed by the uppermost steel layer of the gasket wrapping through the holes and then bending back over the other layers.

So what you're seeing is the side without a fire ring per se; you're seeing the side of the gasket that bends down through the holes. The difference in coloration aren't from fire rings, for some reason they saw fit to not apply the rubberized coating in those areas.

Here are two zoomed in pictures of the top and bottom of that spot near the "fire ring". The top photo is the top of the gasket, which folds down through the cylinder holes - you can see it just looks close because of some spurious rubber. The botton photo is the other side, which shows the upper layer folded back onto the lower face.
firerin2.JPG
firering.jpg
 

amaurer

 
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That's the HG I used when I had a valve job done. Same torque and then re-torque after the engine idled at temp for 15-20 minutes. I like the new design and feel it will seal better than the dimple design.
A little confused on the re-torque. Do I idle until the engine is at temp (going to take an HOUR!) or do I bring it to temp with some driving and then idle for 15-20? And do I let it cool before retorque or do it hot?
 

amaurer

 
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Would it get up to temp faster if you restricted airflow through the rad?
Maybe, maybe not. Tstat will be closed while warming up so radiator shouldn't be doing much.

EGTs while idling are only ~180F, there just isn't a whole lot of heat available.
 
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