I am getting ready to put the head back on my 1989 300TE with an m103 engine, I know there is a tool Mercedes has for cleaning the head bolt holes but I was wondering if I could use a tap? If so does it matter if it is a starter or bottom tap? and also what size should I get if it is ok to use one.

well, a tap is ok but i use an old head bolt. if you have the head off, you should have a box of new bolts. take an old bolt, cut a groove into the threads and use that for a cleaner. the groove allows the crap to come out. machinists have avoided taps for fear it might remove metal also. good luck, chuck.

If you use a tap get one with a flat end so it will clean all the way down in the hole.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I just completed a head job on a M104. What I did was buy some steel wire brushes (about $5.00 for a pack of 10) that had long wire handles. I then took a hack saw and cut the handles to the length I needed. I placed the cut-off brush in my drill and it worked very well, very fast too. I'd shy away from using a tap because if you get it off centered you'll end up cutting into your good threads, which is very easy to do with an aluminum head.

Get you some wire wheels to clean all the flat surfaces on the head, your combustion chambers and the block. You will also want to make sure that the flat surfaces are flat by taking a straight edge and placing in length wise on the bottom of the head. Then take a piece of paper and see if you can slide it under the straight edge. If the paper fits under the straight edge you will need to get the head surfaced. If not you should be OK.

I only use my fingers to clean the threads with a tap. ... No danger of damaging them that way.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Unfortunately I tossed the old bolts in the trash last week thinking what the heck am I keeping used head bolts for anyway (damn). When you say cut a groove into the treads do you mean cut a groove the length of the bolt so it go's across the threads.

Are these brushes that could fit into the head bolt holes, if so where did you get them from because I have never seen them that small.

Yeah, this is what I was thinking of.


I am not sure I am going to do it like this now but just in case no other alternative comes up I might have to go with this.

I bought them at Harbor Freight Tools. The pack of ten or so are different sizes some are steel and some are brass.

Gotta take issue with a few things in this post.
1. A sheet of paper is probably too thick to use to check for a warped head. It also isn't rigid and flat enough to reliably pass under the straightedge. You need a REAL straightedge (a machinist's straightedge) and you are checking for flatness of around .002" (depends on the manufacturer's specification). Use feeler gauges.
2. Do NOT use wire wheels to clean any flat aluminum surfaces!!! I cannot emphasize this enough! The wire wheels will remove aluminum and DESTROY the sealing surface. Even on an iron block you should use care with a wire wheel.
3. Careful use of a tap is fine for cleaning up threads in a block. (You wouldn't be cleaning head bolt hole threads in a head.) In fact careful use of a tap would damage the threads less and remove the junk better than a wire brush, although a wire brush might be "OK." If you use a wire brush you have to be sure no stray bits of brushes (pieces of wire) are left behind.

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1987 W201 190D

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I don't recall the MB spec, but I doubt it is over .004". It could even be .002". I'm glad the paper worked for you, but I think it would be far too easy to feel that a slip of paper won't pass through the gap just because it isn't stiff enough to do so. The right way is feeler gauges, without a doubt. Paper, matchbooks, etc, are adequate to set breaker points in a pinch, not to rebuild an engine.

As for the wire wheel on aluminum, again, I'm glad it worked for you. Unfortunately it is a well known way to ruin aluminum heads, and many manufacturers issue specific advisories against it. As I said it is OK on iron, but care should be taken as with everything when rebuilding an engine.

I felt it necessary to make my comments because I think someone without advanced skills or a sensitivity to the treatment of the parts could easily get into trouble using some of these methods.

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1987 W201 190D

Service Manual Diesel Engines 603, 602:
permissible unevenness of mating surface in mm

longitudinal direction 0.08 = .00314"
transverse direction 0.0

My .004 paper spec is bigger than the allowable 0.003149 MB spec.
Gosh darn, I'm going to have to pull my head and have it straightened then.

I'm not trying to be argumentative. Do what you want with your car, if it works for you and you are happy that's good. I'm glad you are posting the methods you've used, but I think it is imprudent to state potentially harmful methods without also discussing the approved or more generally accepted methods.

Obviously you aren't going to pull your head. (Unless it starts to leak again....) But using paper instead of a $5 set of feeler blades is just plain foolish. And without a set of feeler gauges one really can't know what their head's flatness is.

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1987 W201 190D

In my experience, wire wheels can do a good job or be too aggressive on the surface. It depends on the wire thickness. Wires with thickness ≤0.008" do a gentle job of removing deposits and polishing the metal.