cleaning prep for head gasket replacement

[98sub2500leg]

I am just getting ready to install the machined, cleaned heads back to the block with the new head gaskets. I used gasket remover, xylene(carb cleaner), ect to clean the residue on the block side. It is imbedded into the groves around the cylinders and it is major baked on. I believe this is a combination of solidified coolant, gases, that just won't come off. I have read too many instances of failed head gasket installs even when it was done by the dealer or reputable shop. I believe some of these could be possibly attributed to not properly spending the time to clean. I have spent hours over days trying to get this clean. The baked on carbon in comes off from the pistons. I don't want to compromise the integrity of the mating surfaces.

Those grooves around the cylinders are thin and not very deep.

[Legacy777]

Have you tried a very high grit sandpaper? I wouldn't go nuts with it, but it shouldn't bother the mating surface.

[davebugs]

I can usually get it accomplished with some scotchbrite.

 

Someone here in the past recommended very fine paper on a piece of Plexiglas - sounds logical.

 

Yet another reason to do this out of the car.

[98sub2500leg]

Thanks for the posts guys. The job is done and I just got this post. Still, all good info.

I did end up using mainly the (fine-green) Scotchbrite. Someone else told me before about using 600-800 grit sandpaper. The gasket remover (chemical)was useless. I used a lot of fingernail with the Scothbrite to scrub it off and choke cleaner(xylene). For some strange reason the factory used (believe it or not) #2 phillips machine screws on both the oil pump and the separator(baffle) plate. Apparently, they now have replacement hex machine screws, which is what they originally should have used for this application. One good word for them is that it did hold ok and there was never any leaks after 11 years of driving and 107k miles, but they definitely didn't have service on their mind when they originally designed this.

[davebugs]

All the oil pump and baffle plate screws that I have ever seen have been Phillips.

 

Glad you got the heads cleaned up.

 

Tell us again why you messed with the rear main? It's not part of thoroughness - it's asking for trouble most of the time.

[98sub2500leg]

I can usually get it accomplished with some scotchbrite.

 

Someone here in the past recommended very fine paper on a piece of Plexiglas - sounds logical.

 

Yet another reason to do this out of the car.

 

Dave,

 

One comment here on doing the HG while out of the car:

 

I can't imagine doing any of this work while the eng. is in the car. For starters, I'm not sure how someone could do it properly or what someone would ultimately gain especially with the amount of close attention to detail.

I say this because I have read dozens upon dozens of failed HG jobs before starting mine.

One guy paid 3x to have it done and it fail consecutively. There is too much detail and inspection to be done that would be very difficult at best to do with it in the car.

I personally don't believe one could properly do all the necessary work and inspections unless the work was done with the engine being out. Plus I believe It would also be hard on someone with even the best back to be bending over in the car to do it (and also their knuckles).

[davebugs]

I agree completely. I believe the best work is done with the engine out of the car.

 

I'm not trying to prove anything to anybody. I'm trying to do the best, most thorough job possible. Others will argue - but I just don't see how they can do as good of a job. Whatever works for them. I'll continue to pull them. In the end I don't believe that it takes any longer to pull the engine to do the work. Especially if you factor in possible issues from things not noticed or handled well (block prep comes immediately to mind).

 

Gotta run.

[Olnick]

Hey guys, don't know that I'll ever go as far as tackling head gaskets, but I am so enjoying the discussion in this thread. Keep us up on your progress, 98sub2500leg.

[98sub2500leg]

Ok, here is the latest update:

 

Dave,

the screws are all phillips. When I removed most had to use a lot of hand torque. This dug into some of the screw heads so I am concerned when I go to reinstall they won't grab as well and I won't be able to re-torque to spec. Subaru says they replaced all of the phillips head screws with hex head, which is what I would have expected them to have used in the first place with them being on there that tight.

 

I have been very reluctant to touch the rear seal. On this car with 107k miles there have been so leaks yet, however every part has it's limit. The train of thought is that since I have the engine out, to change out what I can that can go bad. I tried getting info from the dealer for what range of mileage they see those rear seals going bad are. The answer was by one mechanic that there is no definite mileage where they go bad (I was looking for a range). The same guy also said they see more separator or baffle plates going bad and the piston pin plug(small plate).

Another mechanic said they are easy to replace and they never see any come back after they have been changed.

I was told the preferred method for removal is to use the pick tool and dig in the seal in the center of the exposed outer edge then rotate the pick and pull out. I was told they come right out, but I haven't done one yet so I can't be sure. I still want to re-analyze the seal and pick to make sure I will be able to do it right. I am confident I can get the new on seated well.

 

Personally I believe it may be possible that failures can be from not using OEM and possibly the tolorance not being as tight. It has to be manufactured very tight(no room for wide tolorances). Also, contamination can cause failure.

Other failures can possibly be from caused from seating issues. After examining the front seal. It first looked like it was seated ok, but it actually was off roundness. That is where I used the calipers to check uniformity. I had to fine tune it roughly every 10-15 degrees around the seal until I reached the desired result.

 

Have you had any go bad after installing them? I am still reluctant on changing it and may end up leaving it alone.

[ShawnW]

Subaru put out a bulletin stating to use a rubber nubbed tool that 3m makes. Its white and has little nubs. It is used with a surfacing gun on a fairly low speed.

 

Found example on their site here:

http://solutions.3m.com/wps/portal/3M/en_US/Manufacturing/Industry/Product-Catalog/Online-Catalog/?PC_7_RJH9U5230GE3E02LECFTDQGLE0_o=HTML&PC_7_RJH9U5230GE3E02LECFTDQGLE0_nid=GSPVVWTFSCgsSQSFJR0R56glLZM4D26C64bl

 

They call it a roloc bristle disc. You should be able to find these locally without ordering 100 bux worth online but im not sure where from.

 

Green Scotchbrite by hand should be ok if you dont press too hard. You are only trying to remove the black residue left by the old head gasket. I spray a little brakeleen on the scotchbrite to make it clean a little faster and I get a freebie out of it sometimes. Just kidding. Actually the brake cleaner slows down your progress but makes you notice its clean before you are taking divots out. You can remove aluminum with this product so be careful.

 

The new breather plates are a stamped steel and come with allen type screws. A black screw for the arrow indicated hole and the rest. The black already has locktite on it.

 

I havent seen any changes on the screws for the oil pump. I too use locktite red for them.

 

I dont change rear mains unless they are leaking or are not a factory brown seal.

[davebugs]

I use an impact tool to remove the baffle plate screws. One of the ones that you smack with a hammer. Sometimes you can bugger up a phillips head.

 

I resently ordered (form the local bnody supply shop) one of those white disks to have "next time" after probably doing 10 HG jobs.

 

I had trouble finding them. Most places stock yellow and Green I think, but not the white.

[johnceggleston]

the screws on the old plastic seperator plate are machine screws with a tapered head, the screws for the new metal plate are round head. you can't use the old screws on the new plate. if you have a round head phillips screw on a new plate, i don't know. but buggering during removal should not effect correct torque for installing. you are bearing on different surfaces.

 

use lock tite if in doubt.

 

the new screws are expensive, but will not break your bank. even if they are $1.00 each it's still only 6 bucks? but i don't think they are that much. the real drag is waiting to get them from a dealer.

[98sub2500leg]

I do have the new plate and they did me the new screws for the separator plate. I just couldn't get the small 2 screw access plate off, so decided to leave that and the rear seal to heed advice.

 

I would have bought the white plastic. As I was already leaning towards using UHMW(plastic), but didn't have any. I had already bought some green 3m Scotchbrite and 800 grit sandpaper, but reluctant to use the sandpaper so I cleaned the areas as well as I could hand scrub with carb cleaner and the residual areas with a the Scotchbrite. I also went light & easy on those areas.

 

Thanks for the responses.

[bgambino]

the gray scotchbrite is finer than the dark red/maroon....where does the green fall as to courseness/fineness? I've never seen it