prepping the block for new head gasket
 

how should I prep and clean the block for re-assembly? some of the old gasket is stubborn and stuck.
also I read in the repair manual that after removal of the head, there is a oil return tube that something has to be done to. I dont quite understand what the manual is trying to say. other than that, all is well. the head is at the machine shop getting a valve job at the cost of $450. parts are on their way and I am prepping away.

I replaced my head gasket on my 97 E320 a few months ago. Like you, I had trouble getting the old gasket off. I ended up carefully scraping it off with a paint scraper, and then with a razor blade (with a handle - like the one used to scrape off your inspection sticker). I also sanded the top of the block with fine sandpaper. I was worried about small metal and sand particles in the cylinders, so I stuffed them with rags before I started, and blew them out with an air hose after I finished.

You could also try some gasket remover. I tried it, but didn't have much luck.

So far, no oil leaks.

How many miles on your 97 e320 when you changed the head gasket?

After you've used gasket remover and a razor blade, go at it with a bench stone and stone oil or kerosene.

I would personally not use ANY abrasives of ANY kind. I have a large, flat mill file ground on the end to a 45 degree angle making a paint scraper of sorts. I use that and a razor blade on a scraper handle.

The WORST thing to use is the air powered tool that uses an abrasive wheel. I have heard of engines lasting as little as a thousand miles after this grit is distributed everywhere. They have now seemed to lost popularity, thank goodness.

It is time consuming, but a worthwhile step. Make sure you don't slip and score a cylinder wall with your scrapers.

Good luck,

just finished 300e
 

just finished 300e and of course the head comes back perfect
and you have to worry about the bottom of the engine... most importantly are the bolt holes... i used q tips to get the water out and then i
used a tap i bought in a set from autozone for 18 bucks....

the tap really cleaned the holes... and it was important the get the absolute right size......i bought a nut for the bolts....



i used a razor scraper from big lots. 3 bucks... long handle it worked great.. and we used fine wet sand paper.... then i washed it 3 times with alchol...

the next time i do this i would like to use a copper head gasket... and i
would like some other way of cleaning the top...

i used a vac in the cylinders.

sorry, I should have read youir post more carefully. For some reason I was thinking about taking gasket material off a block alone, not realizing that you are just taking off the head. Please DON'T use a stone in this case, as you'll get some abrasive in the cylinders. I was thinking about a bare block that you'd wash afterward. 5 years of college, you'd think I could read :(

I keep an assortment of scrapers on hand... chisel, putty knife, and others. I use all of them, depending on how difficult the material is to remove. You don't always want to use the sharpest scraper, it can dig into the base material. You should start with a dull scraper, remove what you can. For the more tenacious material, move up to a sharper blade, use less pressure and more care. I like to finish the surface with Scotchbrite and oil.

I scrap block surfaces with a razor scraper and the nozzle end of my shop vac right down as close as I can get it to the scraper. Stuff the cylinders with paper towels first and when you are through scraping suck the paper towels out with the nozzle removed from the shop vac hose. Helps prevent small debris from going into the cylinder. Vacuum the cylinder out anyway to be sure. Run your bare finger over the block surface as we are able to feel very small imperfections by touch. I have also used an oil soaked ScotchBrite pad to thorougly clean and it won't leave any grit behind. Lastly, just before putting the head gasket on, I wipe the surface off with contact cleaner.

Tim

wow
 

I appreciate all the responses. I used the old exhaust manifold gasket as a scraper. I could not find anything else suitable with a flat edge. I also used a 220 grit sandpaper and wetsanded the block. I prefer wet so the dust and metal does not fly up and get into the cylinders. it just wipes up clean. I stuffed the cylinders with a couple of shop rags. I also went out and got a tap 12mm1.75 pitch and chased the threads for the head bolts. this removed some nice debris. I will do this again after giving it another fine sanding and a acetone wash right before putting on the new gasket. I hope all this is acceptable, if not please tell me. one more thing though, as far as coolant goes. I plan on using a bottle I have leftover from the 944 days, ethylene glycol free antifreeze for aluminum engines. is this suitable or should I only use mbz coolant?

just use water
 

i used wet sand paper but no water... your water will go into your oil..

i used a tap.... and it worked great...

and i followed up with alchol.... but a cleaner is good to get the grit up..


i used straight water.....and after driving for an hour i have been flushing out the oil from the cooling system.... remember i had oil in my water..

so i also plan on changing my oil real soon... so if i were you i would just use water then flush for a while after its been running...

on start up leave the preasure cap off for the first 15 minutes of ideling...this keeps the cooling system from building up preasure... the put it on and go driving.... then that evening flush it real well and then put coolant in..

use MB coolant or Zerex G05

the block is sanded. there are still some areas where the surface is covered in brown stuff, prob from the old gasket. the finish seems even and I sanded this down a few times. running my finger across the block I feel undulations where in between the coolant passages. I fear oversanding these areas for the sake of a even metallic finish. am I crazy or keep sanding until it looks even?

no
 

stop sanding....

now try to get the grit out... use alchol or some sort of contact cleaner..

all your trying to do is remove dirt, and old gasket and goop not metal..
if there is a metal problem then you have to take the whole motor out and
take it to a specialist for resurfacing....

dont be over zealous your probably just imagining things...