Head gasket replacement without pulling the block out.
Hello, just bought a opel Astra f 1995, and it needed a head gasket replacement, doing to low compression on cylinders 4 and a lot of smoke.
Turns out it was the gasket was blown between the water chamber and the cylinder.
The head was sent to machining but the block wasn’t removed from the car.
I’m doing the machining of the block by hand, with a machined block of steel to hold the sandpaper and I’m checking for the warping and flatness with another steel machined ruler.
As of today the surface between the cylinder and the water chamber has less than 0.05 mm of deviation and the water chamber to the outside has less than 0.15 mm of deviation. Started as less than 0.15 mm and less than 0,25 mm.
I bought a mls steel gasket and copper spray gasket. What’s your opinion on that, should I stop here, or do I need to go through it all (I’m tired boss).
Yeah… took one look at the surface and man, that’s a big red flag. No real way to verify while in there. Commenters are impressed though lol. Might work, but if so, OP is incredibly lucky. Crazy bad idea to try to do this by hand while still installed, passing a relatively small “sanding block” over everything.
OP, make sure you really thoroughly clean those oil and coolant passages… not really sure how you’re going to get all the metal out while it’s installed, but you need to try. Especially on the coolant side where a filter won’t save you. Those shavings will eat seals.
Copper spray defeats the whole purpose of MLS, it's one of the worst combos you could do for head sealing. That black coating is a sprayed on layer of viton that gets smashed between the outer layer and your block or head to seal it. If you have anything but clean bare metal the viton will slowly separate itself from the gasket making little cracks that coolant can pass through. Not long after that you get a blown head gasket. These gaskets are completely different from older graphite, composite, or solid copper gaskets.
Do not use copper spray with an MLS gasket, your getting some terrible advice here. Anything but clean metal defeats the entire purpose of an MLS gaskets viton surface coating. If you can, for your purpose, I would get a standard composite gasket, hands down. When I machine a block for MLS gaskets I target a 150Rz surface to make sure they seal properly, but with composite gaskets I only shoot for 400 Rz and it can easily be 500 or 600 and still seal properly. If you take your time you can get a 500 finish in your garage was a thick glass plate or ground block of steel, but there's no way you're getting anything better than 450 maybe 400; MLS requires 180 max. Throw a composite on it and you'll be fine.
Number 1 NEVER ever use 3M pads on a drill. It rounds off all the edges of everything.
Block off any oil returns or passages clean the area with spray and use tape if necessary
Cast-iron or steel block you can clean it with a scraper and a wire brush. If it’s an aluminum block, you have to be super careful in razor blade at 90° angle dragging it is probably the safest.
And then I saw the after picture awesome job man for sure that’ll be fine
I’ve done my share of replacing head gaskets, and never ever pulled a block out for this. Just a little touch up by hand to make the surface smooth. If the engine was running hot, machined the head, otherwise, if only low compression or coolant leakage, again, a little touch up by hand and check for warping. Never had any issues.
As someone else said, if you're planning to leave the surface like that, while it looks like you did a great job, there's no way its as flat as if it was machines. If your goal is to avoid machining the block, use a composite graphite gasket. They're much more forgiving. You dont need to use that copper spray. As far as MLS and copper spray, it's not advised. Every manufacturer I've ever used expressly states to install on a clean and dry surface. If you have a coating on it you inhibit that MLS gaskets viton coatings ability to properly adhere to the block and you can have premature failure of the gasket.
Bottom line, machining and using an MLS gasket is best for longevity. If you just want to get a couple of years out of it, assuming its not a turbocharged or super high compression engine (like a diesel engine,) the composite gasket is more than adequate on its own. Regardless of what you do, I would get the head machined so you at least have one perfectly flat surface to give whatever you use the best chance of sealing.
I tried to skip machining the block and didn't get lucky, but it was a simple 8 valve 4 banger like the Astra probably is so it took me less than an hour to remove the head again since the exhaust manifold didn't have time to get stuck on the second time
So you could try your luck depending on how easy the head removal was, imo pulling the whole engine seems like a lit more hassle
I've done this with a 3cyl Daihatsu. It Was in very bad shape, been run hot loads and low oil. Got the car for free not running.
Pulled the head.. bad pitting on the top face and cylinder walls. Glued sandpaper to a mirror and worked the surfaces, and filled small pits with JB weld.
This was over 2 years ago and I still drive it everyday hahaha. with no signs of head gasket leaking... yet :)
Opel ist echt einfach zu reparieren Nehm feines Schleifpapier und zieh grob drüber Die kopfdichtung gleicht einiges aus… Mach nicht zu viel…das hat voher auch Jahrzehnte gehalten
Get some of the high heat silicone made for exhaust gaskets and put a skim coat on each side of the gasket clean the block and head until you can wipe it with a white paper towel and it not be discolored then torque your head down and wait atleast 24 hours before adding coolant or oil to allow the silicone to fully cure and it will be fine.
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