MLS head gasket leak
01-20-2019, 05:46 PM
#1
On The Tree
Thread Starter
MLS head gasket leak hey all I’ve recently built a lq4 bored .010 over with a summit truck cam and 862 heads for a little bump in compression. Before everyone chimes in and tells me they won’t flow this truck lives under 5000 rpm and I wanted to upgrade from the high mileage 5.3 for pulling my camper on the weekends. Motor is in and runs great my issue is right away I seemed to get a slight Coolant leak on the outside of the block on both sides towards the rear corner. The more the engine has run it seems to have gotten better and even holds 15 psi for over half an hour with the pressure tester on. I did not use copper spray and used gm ls2 gaskets. I seem to remember seeing somewhere that sometimes mls are finicky and take a few heat cycles to seal up which sounds incorrect but just curious if someone else has run into this issue. Thinking I can fine the composite equivalent and switch it out with no more issue.
01-20-2019, 06:03 PM
#2
I would probably say more unforgiving than finicky. They require a very flat surface to properly seal. If you torqued the heads down properly I’d say you didn’t have a flat deck or head surface. If I recall the flatness needs to be within .003”. Hope you get it straightened out.
01-20-2019, 07:17 PM
#3
On The Tree
Thread Starter
Yes unforgiving is more accurate for sure. Doing more research I’ve come across that pre 2002 heads are not machined as smooth and if you desire to use mls you should go with fel pro perma torque or cometic. They have coatings across the whole gasket surface and allow for more surface imperfections. I should have done more research and used aftermarket gaskets instead of gm.
01-21-2019, 06:33 AM
#6
On The Tree
Thread Starter
I looked and don’t remember seeing the notch. I was aware of that and checked before I decided to go mls. Kind of second guessing myself now. I ordered some steel core composite gaskets and more new bolts and will change out when they show up. I’ll update and plan on kicking myself if there is indeed a notch.
Last edited by andy burdess; 01-21-2019 at 06:51 AM.
01-21-2019, 08:46 AM
#7
Good deal then! but never use copper spray.
Ive also seen accidental issues with head castings cracking, being porous, clamping a foreign object between the head/gasket/block, or even issues with the cyl head dowels.
Hopefully you find your issue!
Ive also seen accidental issues with head castings cracking, being porous, clamping a foreign object between the head/gasket/block, or even issues with the cyl head dowels.
Hopefully you find your issue!
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01-21-2019, 08:55 AM
#8
ModSquad
iTrader: (6)
Have you guys found issues with spraying your gaskets?
01-21-2019, 02:51 PM
#10
ModSquad
iTrader: (6)
Just wondering. I’ve sprayed every mls gasket I’ve ever installed, and even sprayed the coated Cometics without issue. The spray (lightly sprayed) is insurance for me. Lots of guys spray them on here as well.
01-22-2019, 08:30 PM
#15
11 Second Club
iTrader: (3)
I'm wondering why the LS2 head gasket? Anyway I use Cometic MLS gaskets and I've installed them with and without the copper spray and never had an issue.
01-22-2019, 08:33 PM
#16
11 Second Club
iTrader: (3)
I see it was an LQ4 my bad! 
01-23-2019, 08:01 AM
#17
On The Tree
Thread Starter
Got it apart and pending weather the new gaskets will be delivered today. There is no notch. I went with steel laminate and hopefully it works for me. If not I’ve got a set off my old 5.3 I know will work fine.
Last edited by andy burdess; 01-23-2019 at 04:48 PM.
01-23-2019, 08:13 PM
#18
I bought MLS head gaskets from the ws6store and have had zero issues with them. I did not spray anything on them. You have to make sure that your head surface and deck surface are flat. I had my heads resurfaced to true them up and checked the deck with a precision straight edge.
01-23-2019, 09:31 PM
#19
I often hear people say things like "I know X worked because I never had a problem" I usually say well I didn't use that and never had a problem either. So my thing with the copper spray is (and other "problem solvers"), if _______ rarely, if ever, has a problem then what exactly are we fixing? My other thing is, if it rarely if ever fails, are we now introducing variables that could actually create an issue?
Had a conversation with someone about magnets that wrap around the oil filter the other day, they claimed it was better for the engine and made it last longer.. well they commonly go over 300k as it is without anything but regular oil changes and maintenance.. Does it really help when they go that long without failure already? And how will we know? If motors are generally outlasting cars, there's not much point in buying all these things that make them last longer lol.
To each their own, but I see the copper spray the same way I see using RTV all over a gasket. Take a water pump gasket for example.. The gasket is made to make contact with the water pump and the block. If you smear both sides with RTV you now have 2 additional contact points that can fail. You now have 5 contact points/layers and any can fail.. When the 3 contact points generally never leak, ever. Why are we fixing problems that don't exist..
I have seen a lot of vehicles with RTV smeared all over both sides of a gasket come in leaking, where I don't normally see a leak in said area..
01-24-2019, 07:00 AM
#20
ModSquad
iTrader: (6)
I certainly didn’t mean to start a debate here. I only asked WS6Store about spraying theirs, because I use their gaskets...most of the time, unless I need something custom...and he posted in ALL CAPS to not spray their gaskets, so I thought I better ask him in case they found that the spray is eating their particular gaskets or something weird.
I spray my headgaskets, and it’s a light spray, not dripping wet or anything, just to make it tacky and give the surface a little bite, because I’ve sprayed my headgaskets for the last 28 years. Just the way I do things. It’s not right or wrong, just the way I do it.
After thinking about this, I did build a 5.3 that I didn’t spray and it worked great for 20k miles, and got pulled for a 6 liter build.
I spray my headgaskets, and it’s a light spray, not dripping wet or anything, just to make it tacky and give the surface a little bite, because I’ve sprayed my headgaskets for the last 28 years. Just the way I do things. It’s not right or wrong, just the way I do it.
After thinking about this, I did build a 5.3 that I didn’t spray and it worked great for 20k miles, and got pulled for a 6 liter build.