The ole head gasket job - PeachParts Mercedes-Benz Forum

gmask · #1 09-23-2002, 09:48 PM

So I got my NEW head, NEW valves, NEW springs, ground camshaft and polished rockers.. boy are they pretty.

Anyway just wanted some tips for assembling the head on the block..

I have my Elring gasket set ready to go.

How should I clean the mating surface and the pistons crowns?

Should I oil the gasket .. I remember reading that somewhere?

Anything special I should do to make sure I get a good seal with both the head gasket and manifold gasket?

I still have to reassemble the camshaft, rockers and ballstuds. Any notes on that?

I may still need to get a new chain guide and tensioner...
The chain I have should be good with only a few thousand miles on it.

I have rea dplenty of diagnosis here for reasons to repalce the gasket but not so much about how to do .. It's relatively simple but I have only assited in two and this is my first solo attempt so I could use some sage advice.

TIA

Adrian

psfred · #2 09-23-2002, 11:26 PM

Adrian:

Place gasket on clean block. I clean with a blunt scraper (you don't want gouges). You can clean piston crowns with a blunt scraper or a hand powered wire brush. Don't use a powered one, you are likely to gouge the surface too much. Not really necessary to get them absolutely clean. You may want to run a thread chaser down the head bolt holes if they are dirty. This will allow you to torque the head properly.

Make sure the gasket is right side up (sometimes marked "top" or "oben" -- Elring comes with instructions, usally). Probably won't fit wrong way round. Some of the holes for the water passages may be smaller than the holes in the block (larger at the rear than the front). This is normal, pushes water to the back of the block, otherwise it would all go round the front couple of cylinders only!

Place head on block. There are usually two rings in the water passages to help align things, but some older heads don't have them. In that case, it helps to have some headless bolts the same size as head bolts with a slot cut in the end that are long enough to stick up through the head. Install two -- one on each end of the block

Place head on gasket using the studs or rings. Install some head bolts. Remove your "helper" bolts if used by using a straight bit screwdriver in the slot.

Install the rest of the head bolts after wire brushing the threads and lightly oiling them. DO NOT oil the gasket, only the threads on the bolts.

Thread bolts down by hand till they touch the head. Torque down using the correct sequence (will be on an insert with the gasket, otherwise in the manual).

Exhaust manifold gaskets are metalized, use no sealant. Combination gaskets ditto -- MB tends to use a metal plate on each side, with ridges on the manifold to bite in and seal the exhaust. May also be just flat, too. Use no sealant.

Separate intake manifolds usually have some sealant already applied to the correct surface.

Peter

gmask · #3 09-23-2002, 11:59 PM

Sounds good...

I guess anything plastic would make a good scraper? Do I want to use a scrub pad as well on the block or does the remnants of the old gasket usually come off easily?

Err.. I didn't get washers for the head bolts .. I have the old ones.. will it make that big of a difference?

ctaylor738 · #4 09-24-2002, 08:31 AM

If there is any deformity in the washers, replace the bad ones. It is also considered good practice to replace the nuts that hold the intake and exhaust manifolds, and the header pipes to the manifolds.

I would recommend checking the valve clearance as you install the ball studs and figure out if you need shims or different valve pads.

Ed Richardson · #5 09-24-2002, 10:39 AM

Did you get new head bolts? I did not see them mentioned. Ed

gmask · #6 09-24-2002, 12:10 PM

Quote:

Originally posted by Ed Richardson
Did you get new head bolts? I did not see them mentioned. Ed

I have new bolts but not I didn't get washers

leathermang · #7 09-24-2002, 02:36 PM

I don't know if this applies to your engine,, but I read somewhere about the factory changing to harder washers... might want to check tsb's ....
When I am cleaning something like a block I put on ear protection and turn on the shop vac and hold the hose next to where I am cleaning... everything falls up ....
Peter said " you might want to use a thread chaser"... I will be more blunt... Don't be stupid enough to risk all this work you have done , and the money, because you failed to take the 20 minutes it requires to run a tap into all your head bolts holes... Any excess ( meaning less than perfect, clean, lightly oiled, ) friction puts all your work at risk.... because it means you are not getting the hold down effect the engineers designed for ....
On a heavy head like yours the guide bolts are really really a good idea....they are really easy to get out if they are several inches longer than the originals... you can get a vise grip on them if they try to stick on you....
Take the torque up in stages, a little at a time, ( I use 10 lb increments ) going around the bolts in the proper specified order... then I think MB suggests before the last torqueing you let the bolt " rest" about 10 minutes.. I guess to let it stretch.. so your final reading is more accurate...

cth350 · #8 09-24-2002, 02:43 PM

When assembling the moving parts, use an assembly lube. It's basically good old fashioned white grease. Liberally coat the moving surfaces of the rockers, cams, towers, valve keepers, etc.

Like Fred said, all the paper and metal gaskets go on dry. The rubber gaskets get a layer of whatever they are sealing (ie oil).

The copper and aluminum crush seals get special treatment. They get tightened, loosened and then tightened again. Do not overtorque the hollow nuts. It is worth it to replace the two little ones between the head and the water pump. They rust from the galvanic issues between iron and aluminum.

Lastly, be sure to following the tighten specs as well as the pattern on the head bolts. You want nice, neat washers. Recycle the good ones. Thick washers are on the cam towers. Thin washers are on the cover pedistals. The head is torqued in stages. First get all the bolts hand tight, then to the first tightening spec, then the second spec. Then warm up the motor, let it cool and do the third round. I believe that round three is done within 500km of reassembly.

Important: When retightening the bolts, you loosen only the current bolt and then retighten it to spec. Only one bolt should be loose at a time.

-CTH

gmask · #9 09-24-2002, 02:57 PM

Quote:

Originally posted by leathermang

When I am cleaning something like a block I put on ear protection and turn on the shop vac and hold the hose next to where I am cleaning... everything falls up ....

Well I don't have a shop vac but maybe my regular vacuum will suck up anything that falls in to the cylinders? I could also put a neatly rolled piece of cardboard inside the cylider as a barrier with a spronge stuffed inside so that it presses against the cylinder walls and kepts anything from getting down there?

Should I try to block the cooling passages while cleaning?

Also when I clean the tops of the pistons I should crank each one to the top so that it is flush with the block?

I guess I get everything back together I should flush the cooling passages with a citrus treament? Can I get the stuff from an auto supply or is a MB only deal?

gmask · #10 09-24-2002, 04:03 PM

When I rebuilding the camshaft and rockers I want to put the least worn or newer parts on the cylinders that wear out th efastest.

I have the general impression that one and two tend to wear faster than others?

For example I have an assortment of ballstuds to choose from and I know some of them are too loose to to reuse.. for those cylinders that tend to wear out the studs.. The first cylinder seems to allways do this. I may wish to by NEW rockers and NEW ballstuds for C1 since all 3 heads I have gotten intimate with were all worn on cylinder one wether it was the rocker, ballstud or cam shaft. Metric Motors gave me some used rockers that they polished and said were fine. I know that about half the studs on the old head are loose. I'm not sure what the condition is of the ones that came off the junk head.

I don't want to buy all new rockers and studs if I don't have to as they are pretty darn expensive for a complete set... guesstimating around $300 24x$15

gmask · #11 10-28-2002, 12:58 PM

>>>>You may want to run a thread chaser down the head bolt holes if they are dirty. This will allow you to torque the head properly.

OK .. I've been fiddling around with a bunch of other stuff and now I'm ready to tackle the head. I cannot find a thread chaser for this diameter and thread pitch of the head bolts. I guess I may have a better idea of wether or not I really need to worrry about this once I get the head off. Do you know of a place online that has an infinite selection of thread chasers?