MLS head gasket failed

paulb

paulb

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At the end of this season of racing I started to get some combustion gases in the coolant. It would only happen after a couple of all out passes. After that the level in the overflow jug would go up by about 4 inches. Other symptoms were that the truck didn't spool as well when staging, and mph in the 1/4 mile was a little lower then earlier. Here is a picture of #2 cylinder on the head gasket:
DSC00354.jpg


As you can see a piece of the gasket is blown inward towards the cylinder. #4 cylinder showed signs of the same thing happening but not as bad. This was after about 200 1/4 mile passes, all of them in the 11's, most of them low 11's. I installed ARP New Age 625+ studs before any passes were made on the truck. The studs were torqued to 160ft lbs. The truck makes ~ 830hp, running #2 only, and has not had nitrous or any other power added run through it yet. It runs 82psi of boost, with 38 being made on the bottom turbo.

In short I don't think that anything caused the head gasket to fail other then pure hp. The timing wasn't over advanced, and the pistons don't show signs of excess heat. Here is a pic of a piston top:

DSC00349.jpg


That was taken as it looked when the head came off, before clean up. I'm very impressed with that.

Oh, yeah... I won the NHRA division 6 divisional race with the blown head gasket... :hehe:

Paul
 
Geez Paul - now there's only a couple of rides left that I know of which are still successfully running an MLS at those power levels... going back in with O-ring/12V HG combo?
 
I'm in the same boat as you. The concensus is at or around 7-750hp+ these gaskets are at there limit
 
Yes, it's because of the layers.

A single sheet is mechanically deformed by the O-ring throughout it's thickness with little variation in vertical profile from top to bottom; multiple layers will cushion & reduce that deformation through the stack, and in the case of just the OEM fire ring there simply isn't enough psi loading available for it.

The MLS is great for soaking up surface irregularities to keep a good seal, but having 6 potential leak paths through the installed assembly (instead of 2) is obviously going to present more points of possible failure.
 
XLR8R said:
Geez Paul - now there's only a couple of rides left that I know of which are still successfully running an MLS at those power levels... going back in with O-ring/12V HG combo?
Click to expand...

Yep, it's already together. o-ring with .014 protrusion, and a 12v marine gasket. I just finished the third re-torque tonight. I also sent the Flux 4.7's back to Don M, and he upgraded them to Flux 6's, while I had it torn apart. The pistons didn't look like they had enough heat...:hehe: I have not driven it hard yet, but I can't believe how nice the Flux 6's are. Both idle and cruise speeds are very smooth. There maybe a little more smoke when it's idling when it's cold, but that could also be the thicker head gasket. It's very slight in any case. I can't wait to see what it will do at the track.

Paul
 
HIGH TECH RAM said:
I'm in the same boat as you. The concensus is at or around 7-750hp+ these gaskets are at there limit
Click to expand...

I think there are more blown ones out there then we really know. On my 02 when the head gasket blew on it, you could hear the coolant hitting the cooling fan. Kinda like the sh*t hitting the fan, so to speak. And once they blow, they stay blown. The MLS will start to leak only at higher power levels, but I suspect they would get worse, the more people drive them. On my truck if you kept it below probably 600hp, it didn't leak (at least as far as I could tell).

Paul
 
paulb said:
I think there are more blown ones out there then we really know. On my 02 when the head gasket blew on it, you could hear the coolant hitting the cooling fan. Kinda like the sh*t hitting the fan, so to speak. And once they blow, they stay blown. The MLS will start to leak only at higher power levels, but I suspect they would get worse, the more people drive them. On my truck if you kept it below probably 600hp, it didn't leak (at least as far as I could tell).

Paul
Click to expand...

Agreed!!:rockwoot:
 
I guess I'll find out what hp a MLS will blow out as well, no one up here is competent in oringing a head. Got a ungodly amount of torque on those 625's now though, inserted the whole block.
Lloyd Mills got away with a ton of hp for quite a while. Don't think he was even running the 625's yet.
 
paulb, did you start to heard odd motor noises, like a knocking on a door kinda sound? I'm curious how far along my gasket it from popping.
 
LOL your gasket's calling you! Its sick and tired of standing up under the pressure.....
 
JasonCzerak said:
paulb, did you start to heard odd motor noises, like a knocking on a door kinda sound? I'm curious how far along my gasket it from popping.
Click to expand...

I have a regular cab, with a short stack. Everything always sounds rosey to me! :hehe:

I can't say that I had a noise like you are describing. I can say that at an idle and at cruise the truck is now quieter. What I would call a timing rattle is now gone. It could be the thicker head gasket, the injector change, or the head gasket itself. I would also not say that my gasket completely or even mostly failed. In the last race it was running consistient 11.32's. This was with mild launches. So while it was down on power, it still ran pretty good.

Are you getting any air/combustion gasses in the radiator? If you take the cap off, it should be completely full of fluid. The cap and overflow have to be working of course. If it's full of fluid, and then you take it out and run it hard, do you get any air in the radiator? I would get about a quart of air.

Paul
 
Joesixpack said:
I guess I'll find out what hp a MLS will blow out as well, no one up here is competent in oringing a head. Got a ungodly amount of torque on those 625's now though, inserted the whole block.
Lloyd Mills got away with a ton of hp for quite a while. Don't think he was even running the 625's yet.
Click to expand...

Well I hope you don't find out, but I think if you run the long enough and hard enough, they are going to start to leak. Looking at my log book, from when I'm pretty sure it wasn't leaking to when I think it started. I lost a little over a 1mph and about .12 in the 1/4 mile.

Paul
 
paulb said:
I have a regular cab, with a short stack. Everything always sounds rosey to me! :hehe:

I can't say that I had a noise like you are describing. I can say that at an idle and at cruise the truck is now quieter. What I would call a timing rattle is now gone. It could be the thicker head gasket, the injector change, or the head gasket itself. I would also not say that my gasket completely or even mostly failed. In the last race it was running consistient 11.32's. This was with mild launches. So while it was down on power, it still ran pretty good.

Are you getting any air/combustion gasses in the radiator? If you take the cap off, it should be completely full of fluid. The cap and overflow have to be working of course. If it's full of fluid, and then you take it out and run it hard, do you get any air in the radiator? I would get about a quart of air.

Paul
Click to expand...


as a matter a fact the level in the radiator is low. but the over flow is at the normal level.

so, if i just stud the thing, chance of the gasket holdin? or should I just replace the gasket before something else bigger goes?

and, on a cr, what is the best way to go about the replacement as far as thinkness. plusses and minuss of oem thinkness vs 10 over

I'll for sure just do the oring.
 
JasonCzerak said:
as a matter a fact the level in the radiator is low. but the over flow is at the normal level.

so, if i just stud the thing, chance of the gasket holdin? or should I just replace the gasket before something else bigger goes?

and, on a cr, what is the best way to go about the replacement as far as thinkness. plusses and minuss of oem thinkness vs 10 over

I'll for sure just do the oring.
Click to expand...

Make sure the cap is good, and fill it up. Take it for a hard drive and see if the air comes back. If it does...bad sign. You can get a test kit for combustion gases, but I don't think you would need to bother.

Studing it now, would be like closing the barn door after the horse is out.

As far as thickness of the gasket. There are a lot of different ideas, and each has it's place as far as what the truck is being used for. What I did (keep in mind what I use my truck for and what my goals are), was to use a stock thickness marine 12V gasket. To the best of what I can tell, it's compressed thickness is about .015 thicker then the MLS that came on my truck. There are two different thickness for the MLS gaskets. Cummins can tell you based on your engine number, what came stock. The head was machined .006 to make it flat again. That means that I moved the injector .009 farther from the piston. I did not want to go farther then that. Moving the injector to far from the piston can cause the injector to spray fuel outside of the bowl (the pilot injection does some anyway), and cause cylinder wall scoring, and piston damage. You can not shim the injectors to correct for this like you can on a 12V, because the cross tubes won't line up on a CR.

IMO the 12v gasket's water passages need to be modified to match the size of the ones in the MLS gasket. The passage by #6 is a lot smaller on the marine gasket. I used a titanium step drill to do mine. Others use punches, and see even water jet them.

I don't want to recommend anyone else doing this (even though there are quite a few others that have), because until I make a few hundred passes down the track with this setup, I would still consider it experimental.

Hope this helps.

Paul
 
paulb said:
Make sure the cap is good, and fill it up. Take it for a hard drive and see if the air comes back. If it does...bad sign. You can get a test kit for combustion gases, but I don't think you would need to bother.

Studing it now, would be like closing the barn door after the horse is out.

As far as thickness of the gasket. There are a lot of different ideas, and each has it's place as far as what the truck is being used for. What I did (keep in mind what I use my truck for and what my goals are), was to use a stock thickness marine 12V gasket. To the best of what I can tell, it's compressed thickness is about .015 thicker then the MLS that came on my truck. There are two different thickness for the MLS gaskets. Cummins can tell you based on your engine number, what came stock. The head was machined .006 to make it flat again. That means that I moved the injector .009 farther from the piston. I did not want to go farther then that. Moving the injector to far from the piston can cause the injector to spray fuel outside of the bowl (the pilot injection does some anyway), and cause cylinder wall scoring, and piston damage. You can not shim the injectors to correct for this like you can on a 12V, because the cross tubes won't line up on a CR.

IMO the 12v gasket's water passages need to be modified to match the size of the ones in the MLS gasket. The passage by #6 is a lot smaller on the marine gasket. I used a titanium step drill to do mine. Others use punches, and see even water jet them.

I don't want to recommend anyone else doing this (even though there are quite a few others that have), because until I make a few hundred passes down the track with this setup, I would still consider it experimental.

Hope this helps.

Paul
Click to expand...

Thank you very much! I'll stick with the OEM gasket + oring then. I'll fill the radiator tonight and on my way home tomorrow I'll toy with it and see what happens. I did recently do a radiator fluid change but I don't recall checking it. maybe I'm just down on fluid cuz some air got out that got in with the change.
 
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