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  #1  
Old 03-25-2004, 05:33 PM
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Need help reassembling 4.5

I have some dumb questions, so please bear with me. I've never torn an engine apart like this so any little bit of advice is greatly appreciated.

Now that the head is at the machine shop, I need to clean everything up.

1. For cleaning the piston crown, may I use a gasket scraper with some carb cleaner to gently remove the crud?

2. Are these cylinder head bolts re-useable? They're not stretch bolts I think, but is there something I should check? Also, must they go back in the same exact spot like valve train parts?

3. There's probably a lot of gunk in the bolt holes in the block itself. Do I need a tap or dye, to get it cleaned out?

4. What is the correct stuff to apply to the head bolts when reassemlbing the head?

5. The head gasket goes on dry right? But, what about the intake and exhaust manifold gaskets?

Thanks in advance.

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  #2  
Old 03-25-2004, 10:33 PM
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You can buff the piston heads with a power wire brush. Don't get real agressive, you can scar the heads. If it doesn't come off with the brush try the scraper. If it still doesn't come off bung the piston back in the engine. If you can't get it off it won't come off in the engine.

In my experience with gas engines the cyp. head bolts can be reused. On my Diesel trucks they can be reused once. Cyl. head bolts do not have to go back into the same holes from which they came.

As for as cleaning the bolt holes you should take the block to an engine rebuilder and get them to clean it in their tank. Most modern shops have a machine that sprays the block with a very hot caustic solution. Remove all aluminum parts or the caustic will do it for you. The engine will come out much cleaner than you can get it and it will probably only cost you $20 or so.

Definately tap all the bolt holes, not just the cyl. head ones. Be careful when you blow the gunk out of the bolt holes. It comes out straight back into your face a lot faster than you can move out of the way. I understand that there are very few jobs for blind mechanics.

Thread lubrication is a much debated subject. Some people use ATF, some Never-Seze, some STP, and some just clean the bolt and hole and use no lube. Check with the local MB shop. I know that there are different torque tables for lubricated bolts than there are for dry ones. I think that clean, dry threads is the way to go.

When I started building engines in the late 50's we used to have to soak head gaskets in the bath tub overnight so they would expand and seal correctly. From what I have read in the gasket sets I use lately all gaskets go on dry. Again, check the manufacturer's recommendations. There is often a note in the gasket set that will tell you what to do.

If your heads are in the machine shop you might ask them to Magna-Flux them to check for hairline cracks.

I hope you have an engine stand on which to mount the engine before you start re-assembly. They are dead cheap at Harbor Freight and worth their weight.

Good luch
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  #3  
Old 03-25-2004, 10:39 PM
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AFAIK, Josh didn't pull the engine, it's still in his 108...

I would be VERY careful, when cleaning the pistons, to make sure you get all the **** out... if anything gets in the bore or between the bore and piston, it can really scuff things up.
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  #4  
Old 03-25-2004, 10:51 PM
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Thank you Kip.

The engine is in the car, so I'll be doing my best to clean it up myself.

I think you touched on all my questions, thanks a lot.

The engine manual for the 4.5 glances over things but I have a shop manual for the fintails that goes into much more detail. It is almost as if they expected DIY'ers to be doing a lot of the work, and make an attempt to cover some basics of automotive repair.
They do mention coating head bolts lightly with a graphited oil, but I have to check if that was for a 190D or 200D. I'll check with my local MB indy.

Amazingly, the cylinder walls look to be in great condition. There is cross hatching clearly evident. I really don't know how many miles are on this engine however.

The reason I pulled the head was because an exhaust guide broke when I was attempting to replace stem seals. The guy at the machine shop pointed out that it had been running that way for some time as the seat was Totally worn unevenly. The guide had to have been cracked and the valve must have been opening and closing crookedly. The stem seal was apparently the only thing keeping it from disintigrating.
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  #5  
Old 03-25-2004, 10:54 PM
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The gaskets go on dry. You can reuse the bolts. Clean them first they'll be gunky. Make sure the bolt holes are free of coolant. Lightly oil the threads of the bolts.

I tend to run a bolt through all the holes w/o the head in place just to make sure they are clean.

For the exhaust, replace the nuts that hold things down. They are deformed lock nuts and are not reusable. Make sure each one gets a washer under it.

-CTH
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  #6  
Old 03-25-2004, 11:46 PM
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Helluvalot easier pulling the head than replacing seals with cyl head on the engine, isnt it? For sure, doing the seals intact is toughest job any DIY owner can attempt.

They bawled me out on this forum when i mentioned using fine grit sandpaper to clean the short block surface on a 220Sb long time ago. Everybody agrees that dust and grit are public enemy #1 to bores.

You might want to replace exhaust manifold nuts as they tend to rust and seize. Also you should probably be careful about not overtorquing exh nuts. Have read alot about cracked manifold ears on this board.... on the 4.5 especially.
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  #7  
Old 03-25-2004, 11:46 PM
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Now is the time to get new studs for the exhaust manifold as well!

I am going to be replacing my left head because it's the easiest/cheapest way ($25) for me to do this with minimal downtime. New studs now mean you won't have to pull it in the future if/when one or more snap and it develops an exhaust leak!
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  #8  
Old 03-26-2004, 12:21 AM
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Helluvalot more work! Once I understood how the valve stem seals were supposed to be done, it didn't seem that bad. I would have been back on the road a long time ago if I only had to change those. The shop manual actually tells you which pistons are at TDC for different degree readings on the balancer!

The Ex manifold nuts were practically finger tight when I took them off. I wonder where ya get them new wuns.

Just to double check, can anyone tell me if the exhaust and intake manifold gaskets go on dry? I'm assuming that the head gasket was referenced before.
Also strangely, the torquing sequence does not seem to match what actually is there. It shows the inward bolts, what seems to be cam tower bolts and then a row of bolts on the outward side of the head that do not correspond to the 8 that are actually there. Ya know, the ones in and around the ex manifold. What's up with that? I thought those 10mm recessed coolant passage plugs were head bolts and jacked one up trying to get it out. Those 10mm's correspond to what's shown in the tightening sequence if you interperet it literally.

Fun stuff.

I've got to watch out for Might As Well Syndrome. I'll see if what the machine shop wants for new exhaust studs. I'm putting all this effort into what most would consider a parts car
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  #9  
Old 03-26-2004, 05:24 AM
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How I clean piston tops:
- Bring the piston to the top of the bore
- Push heavy grease into the gap between the piston and the bore all the way round
- Get a toothbrush and sharpen the handle to a chisel point. Use this to scrape off the carbon
- Use a vacuum cleaner to suck out the crud as you scrape
- When the top is clean, drop the piston 1/2 an inch down the bore and wipe off the grease that has caught the bits of carbon that otherwise would have gone down the bores.
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  #10  
Old 03-26-2004, 05:42 AM
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All gaskets go on dry.

You get the exhaust manifold bolts from the dealer.

Replace the rubber tubes between the intake manifold halves. It's out of the car so why not.

Make sure the head bolt holes are free of any liquid, oil or coolant. All threads need to be clean and lubricated.

Personally, I would use a razor blade scraper to clean the pistons.

Replace the chain guides, the heads are out so why not. It would also be a good idea to replace the chain tensioner and the chain while you're at it.

Cleanliness is next to godliness.

IMHO.
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Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

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  #11  
Old 03-26-2004, 07:08 AM
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Now is NOT the time to replace the chain, since you don't have any references to roll a new chain in. Do tha once you're reassembled and there is evident chain stretch.

Nothing wrong with getting practice on a parts car. You can always transplant the "almost good as new" motor into your next car if this one is retired.

The exhaust nuts are available from any competent foreign autoparts store. They are also used in VWs & BMWs. The short exhaust studs are common, and will cost about 1.50$ each. The long studs are NOT common. More than likely you can get them from fastlane. If you're lucky, the driver's side manifold of your 4.5 doesn't have them. A 3.5 has two.

Most definitely do not over tighten them. And again, make sure each one gets a washer.

-CTH
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  #12  
Old 03-26-2004, 11:39 AM
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cth: Yup, 2 long studs on the driver's side. I think there's 1 or 2 on the pass side as well.

I went to a local company that sells all types of nuts + bolts and picked up bolts to replace the long ones...
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  #13  
Old 03-26-2004, 02:42 PM
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I just ordered the guides, an exhaust valve, tensioner rail and one upper rail. I really hope I don't have to replace the chain and tensioner. Have you seen the price on that tensioner?!? From what I've read, broken rails are more the issue than a chain actually breaking. I would like to keep using some of the other slide rails. They are the original rubber coated ones and some of them have only light grooves. I wish it was possible to order the rubber coating. Does anyone have a lead on that? Dealers don't have it.

CTH- roger that on chain replacement at this time. Unless I wanted practive removing the timing cover. . .

neileg, that grease method sounds good.
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  #14  
Old 03-26-2004, 04:16 PM
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gimme a low-tech 240D
 
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Them old chain rails are what i call "retro-upgrade" to newer plastic ones. If they are only lightly worn and still have rubber on them, why replace them at all?

Torque sequence for nuts and bolts is always the same....... start with centermost 2 then jump to outermost 4, returning again to *next* centermost 4 working your way to outermost 4 and bounce back and forth from one side to the other and work diagonally too. Repeat this several times at varying ratchet pressure until you are ready to start measuring torque and you will seat the gaskets fine.

Cutting edge is NEVER loosening bolts as they are torqued equally.... the idea is that as each pull on the wrench compresses the gasket you want to sustain that pressure without backing off.

Awhile ago after college, I was doin parking lot brake work on my 190c and an old timer, my neighbor, walked by just as I was taking off the wheel. He saw me loosening lugnuts using the same sequential pattern as torquing bunches of bolts - loosening each gradually. Then he smiled and said it looked like i didnt need any help. This guy looked looked to be about 90 yrs old and knew alot of stuff.... so i offerred him a cold beer and suggested he could start on the rear brakes if he wanted to. Its an excellent habbit - both tightening and loosening ALL bunches of nuts 'n bolts according to the universal torque sequence system described above that's the same for all applications.

Hell yes - pullin cylinder head and haulin the head to machine shop where guides can be press-fitted and valves can be re-seated is piece of cake, isnt it? No doubt doin the other side the same way will be walk in the park compared with what can go wrong just replacing the seals with head in place.

Last edited by 300SDog; 03-26-2004 at 05:35 PM.
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  #15  
Old 03-27-2004, 12:06 AM
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240DieselDog,
I can only guess that you had a traumatic experience once doing valve stem seals. If by easier, you mean taking a head off is just a simple step by step process compared to the syncronisity of air hoses, spring compressors, magnetic retrievers and bungee cord restrained breaker bars on crank bolts, then yes. If you don't have one of the parts right, then you run the risk of having to pull the head off.
Now I'm confused, valve stem seal jobs are to be dreaded but only because you might drop a valve and then have to remove the head, which. . . uh, I guess is just a walk in the park

You know I'm just kidding around right?

But now I must admit that I don't plan on taking off the other head. (Heading for cover now) The plugs look fine, and unless I drop a valve doing the seals, I'm going to go with it. The next owner can pull that head if they want.

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2013 VW JSW TDI M6

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86 300E 5 speed
2010 VW Jetta TDI M6
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