1983 300D head job
 

started today. I think everything is fine but do suspect that it was time for a head gasket. I will get the head to the machine shop over the next week or so.

head bolts - notice the rust on the bolts that came out around the #4 cylinder.

And finally my favorite picture :)
Based on the deposits on the pre-chambers it becomes quite evident that I am using my Redline.
Basically, everything looks pretty good with the cross hatching being evident in the cylinder bores, etc... I suspect the head gasket to be weak around the 4-5th cylinder, I don't know - just trying to justify tearing it down :). I have seen no obvious mechanical issues so far.
Compared to the last one (non-running 240D) I tore down this one looks GREAT!!

My main concern is the amount of rust I am seeing in the coolant passages. I have been running the MB coolant since purchasing the car a little over a year ago and do run more water than coolant. I will probably alter my coolant/water mixture a little.

Nice pictures, Jim! BTW, a couple of the bolts were slightly corroded on my car too, between cylinders 5 & 6 - where the main cracks were, and also where the gasket was suspect. Mine's back together now but untested as I'm still waiting for brake pads (due this week, long story). Keep us posted on how things go. Make sure the machine shop does a thorough check, maybe with a magnaflux too?


Have fun! :p

I would look for the impression of the head gasket on the cylinder head and block to help with diagnosing a head gasket leak - in addition to the head gasket itself. If you have very clear impressions for the entire circle left by the head gasket on each cylinder both on the head and block, then there's a good chance the gasket was not leaking. On my old engine there was a very small gap in the impression between cylinders 3 and 4 only on the head side allowing hot combustion gasses to enter cylinder 3. Cylinder 3 had pot holes in the cylinder wall on the far side away from the leak and there were pot holes on the face of the valves - I can see where the damage was worsened when the piston tried to compress hot combustion gasses leaking from cylinder 4. The leak between cylinders 4 and 5 was much worse and the damage was very bad.

Did you do a compression check before the TDI? This would help with diagnosing a possible head gasket leak. Rust on the head bolts that are exposed to the outside is to be expected (the ones close to the injector nozzles). Rust on the head bolts that are inside the valve cover could indicate a head gasket leak - maybe not. The engine I replaced my old engine with had a couple of head bolts with rust on them and I know that head gasket did not leak.

I suggest using an Elring head gasket set when you assemble the engine. I've used the Victor head gasket on my old engine (my newly rebuilt engine has the Elring gasket) and I do not like the way it is configured to correct the known problem with head gasket leaks the 5 cylinder 300 engine is known for causing M-B to redesign the head gasket for 1979, using the torque to yield head bolts, and hardened head bolt washers. Victor makes the metal sealing rings larger in diameter, Elring has more metal in the area between cylinders in addition to larger diameter cylinder rings, Victor does not have a metal sealing ring around the return oil passage at the back of the engine, Elring does, Victor has larger openings for the coolant passages, Elring has openings closer to the size of the coolant passages, I liked the additional line of sealer run all around the outside of the gasket that Victor does not, and it seemed to me the sealing material Elring uses is better than Victor.

M-B spec calls for 55% antifreeze, 45% water for coolant. You can clean out the crud with citric acid from M-B after the engine is assembled.

Based on your picture the pre-chamber injector ports in the head need to be checked for build-up on the inside (the portion exposed to combustion with the white build-up on them in your picture). I used small drill bits to clean them out and restore the spray pattern. Have you cleaned the top of the pistons to see what the spray pattern looks like (my old engine with 300,000+ miles cleaned right up with a little soaking with WD40, the replacement engine I rebuilt only needed a WD40 soaked rag to clean the top of the pistons off)?

Since I did a complete disassembly and rebuild on my 300D, I may have some other info and suggestions you may find useful - let me know.

Good Luck!
Tom

I would recomend using a geotze brand head gasket and not an elring. over the last 15 years I've never had one fail under normal use.I've done many 103 gaskets for a second and even a third time. always elring. I know this is what the dealership uses but,it doesn't mean it's the best part.All the mb dealer techs I know won't use them on their own cars. just my h.o....Paul

I'll be doing my head next weekend
 

Great pictures and very helpful comments. I'll be replacing the head on my '85 300D with a rebuilt one this next weekend (as discussed in previous posts). I have a couple of questions:

1. I will be pulling prechambers from the old head and installing into new head. (I have proper tools and seal rings). What should I do to clean/inspect the pre-chambers...I dont really know what to look for. I havent bought any new ones as I expect to use the old ones...but I wont put in bad ones. If one is bad, should I replace all?

2. What should I look for on pistons or in cylinder bores...I'm not planning on doing any cylinder work....the head is going on no matter what, but I should be aware of any indications of damage.

thanks

Mark

MarkM,

1- Inspect the prechambers for cracks. Repalce any with cracks. You can clean then up with a wire brush, wire wheel, or bead blast them. Get them as clean as possible inside & out, with no residue left inside. The "spherical pin" inside should not be "burned or scaly" according to the manual. Don't confuse that with carbon deposits, though. Only replace bad ones - which you would do anyway, given the cost, ~$50/each aftermarket (nearly $100/each at the dealer!)

2- Pistons should not have visible damage. Carbon is normal. Cylinder bores should have pretty "cross hatch" pattern visible. Basically you're looking for obvious damage. Also look for water damage, where a leak caused the block or liner to get "eaten" by steam or corrosion. Not likely to find that, though.


HTH,

So, you took your head off just for the hell of it? Your my kinda guy!! :D

Yea, turbodiesel - it looks that way :):). I went in looking for a reason why it kept "pressure" on the cooling reservoir a day after running. Only thing I found that was not in order was the #5 injector seal washer was in backward.
I was "caught up" on stuff to do and the family was at the in-laws so I figured "what the hey" you know. The yard looks like crap but the head is off of the 300D :) - you have to have your priorities in order. The 300D tranny is on the list down there somewhere.
I'm going to try to get it broken down this morning and to the machine shop before I go on vacation for the next week. I'll get it back on over the next couple/few weeks. I am really enjoying the 240D :).

Just talked to the head man at the shop. Seems all it is going to need are new guides and seals. Valves, head, etc... look good with no problems.

Doesn't this look better. Got a couple/few things to do before putting it back on but I thought it came out pretty good.

The yard looks like crap but the head is off of the 300D - you have to have your pri
 

Ha, Ha!

I have the head off my 240, and my yard looks like crap too!
More fun to clean up my head than clean the yard.

I have decided to just lap in my existing valves.

Two shops I took the head to, said they don't work on diesels...

What the F...? Amazing...

I have not had time to work on it this weekend - too many soccor games right now.
Ya'll take a look at the enclosed picture. It shows misalignment associated wear on the guide rail "pin". I am considering going ahead with the guide rail replacement while I have it this far down.
Opinions, thoughts would be appreciated.