79 300d Head Removal
 

Good day, everyone. I've decided to challenge myself.

In an attempt to eliminate white smoke upon start and warm-up, I've done the following:
-adjusted valves
-diesel purge
-new fuel filters
-new rebuilt & balanced injectors

None of these were successful. The engine runs strong and can easily maintain 70 mph with cruise control. But that darn smoke. So upon returning from a 500 mile trip, I decided to replace the valve stem seals and perform a compression test just to verify the health of the engine (146k on the clock). When I pulled the 9th valve seal, the valve stem sleeve came with it! My heart dropped.

Today I started the process of pulling the head for inspection and send off for a rebuild. I've never done anything like this before but feel confident enough to push through it. Plus I have time and space to work slowly. But dang, today was a challenge and it took nearly 2 hours before I was finally able to locate and see the block drain bolt! Next is reaching it. To do that, I assume the intake and exhaust manifold should be removed? But to do that, I have to remove the a/c compressor mounting bracket. That looks like a booger. But somehow it was installed to somehow it can be removed.

After 5 hours of investigation and struggle I managed to drain the radiator; strip one radiator fan bolt; realize removal of the manifold bolt nearest firewall is going to interesting.

I do have an appropriate MB service manual but it does not really go into detail. The PP head gasket tech write up shows a different layout than what I'm looking at. Does anyone know of more appropriate head removal instructions applicable to the 1979 300D?

Sometime this week I'll work to remove the stripped fan bolt and remove the radiator. I don't think it is necessary but the coolant looked old and I'll go ahead and give it a flush. Plus, it will creat a bit more working space.

Any and all insights are greatly appreciated.

I have done many of these jobs, and it really is not all that difficult. You may find the most challenging part is removing the chain guide pin, but once you know how, and have the right tool, it is easy. Be sure to put the crank at TDC (0lT) on compression stroke for #1 (both lobes pointing up) before removing the cam gear. Once you have the manifolds off and the block drained, remove the bypass tube (front of engine-12mm). There are 3 allen head bolts (6mm) in front of the head, two inside the cam chain hole, and one outside (or maybe two outside? I forget). Either way, don't forget about these. Use a magnet for the two inside, so they don't drop down inside. I like to remove the cam follower assemblies next. Once the bolts (8mm allen) are out, just pull the assemblies toward the right side of the engine, and the followers will slide out from between the cam and valves. Next you can remove the upper chain guide (13mm bolt and pin). I use an M6 all thread bolt (35+mm long) and a nut and fender washer. You also need some sort of spacer that has a hole in it larger than the pin. Screw the nut all the way against the bolt head, and then screw the bolt into the pin (at least 10mm) with the spacer against the head, and the washer between the nut and spacer. Tighten the nut, and the pin will pull out. If your bolt is long enough, you can use a 3/8 drive socket as a spacer. With the guide removed, you can remove the chain tensioner and then the cam gear bolt (22mm). Be sure to put the crank back on TDC if it moved while loosening the cam gear bolt. Next, you can remove all the head bolts. They should be 10mm XZN (Triple Square). Of course all the injectors and wiring should have been removed at sometime before. Some injectors are in the way of removing head bolts. Speaking of head bolts, they are one time use only, so new ones are in order. Also, if you are removing the prechambers (if the head shop can't or won't remove them), I would suggest removing them BEFORE removing the head. These will need new seals as well. It is always best to surface the head if one is going through the time and effort to remove it, and the prechambers have to be out to do so.

If you have any more questions, this is the best place to ask them. Many members here have experience with this job, and would be happy to help......Rich

When you have the head off, double and triple check the combustion area of the head for cracks.

The symptoms you describe; white smoke can be coolant entering the combustion chamber and the loose guide lead me to suspect the engine was overheated at one time in the past.

http://www.peachparts.com/shopforum/diesel-discussion/332787-300d-overheated-blown-head-gasket-what-do.html

Post # 10

I will certainly do that.

I picked up the car from Las Vegas and drove it home to South Texas in January. Cold temps all the way and the engine stayed well within normal operating temps. This last trip was up to Dallas and back during typical Texas heat and mid-day driving. Coolant level remained constant and no appearance of it in the oil. The smoke had no hint of sweetness but could be described as strong exhaust. If I where to guess, I'd say a tight valve during that long trip from Vegas.

Another recent observation is some vapor in the valve cover. This is recent occurrence.

I'm hoping, if a tight valve was the cause, the piston is undamaged. But this is just a guess. When I finally get the head off, I suspect we'll have an answer.

I'm a novice mechanic so my guess could be way off.

Rich, thank you for the extra info and guidance. I'll be referring to it during Day 2 of my toil.

-John

Roll guy are you sure about reusing the head bolts. I would have thought the 79 might have the reusable ones.

I may be wrong, but allen head bolts might be reusable. I am sure the XZN bolts are NOT reusable. A stretch bolt is designed to have a sort-of "spring" to it while under tension. Once they are removed, that tension goes away. If they are reused, the tension won't be even, and one risks the chance of stripping the threads in the block. It's the last two 90 degree steps in the sequence that would cause an already stretched bolt to pull the threads out of the block.

The FSM gives acceptable lengths for re-use of the XZN bolts. If they are within the range specified, they're reusable. It's a good idea to replace stretch bolts out of habit, but it's not required if they're within spec.

That is good to know. Could you provide the length tolerance for the three sizes of head bolts for a 617? I have a bucket full of them, and it would be interesting to know if any of them can be reused. Thanks, Rich

If you did not mention it you ought to give Fuel Injection Pump timing a try. White smoke can be atomized unburned fuel do to Fuel Injection Pump trimming not being advanced enough (late timing).

I had this happen when I installed a Fuel Injection Pump wrong. I got billowy clouds of pure white smoke coming out of the tail pipe.
When I did the timing correctly that white smoke disappeared.

What about the Camshaft timing? Look up the 2mm Method

For the AC compressor and bracket... you’ll want to undo the bracket from the engine with the compressor still attached to the bracket. A few bolts through the front and a couple underneath the compressor. If it’s got a charge of refrigerant in it you can probably get away with just pulling it to the side and leaving the hoses attached to the compressor and compressor mounted to the bracket.

I don't have a copy of the 617FSM, however on the 603FSM it's in the section on bolt torquing in the head assembly procedure.

The bolts on a 603 are much different than a 617, so that does help for a 617.

Thanks for the suggestion, Diesel911. I've been thinking about the pump as a possible cause but won't address it until ruling out all other options. Lining up the shaft notches shows me to be +4 degrees, within acceptable limits. Once I have the head rebuilt, I perform the more accurate dial test. Having a broken/dislodged sleeve may be the cause of my cold start smoke. After she warms up, smoke greatly decreases.

I did a valve job on my old 85 300sd. The Factory Service Manual has all the information you'll need.
I ended up replacing all the long head bolts. The shorter ones were fine. But be sure to check length and verify it's within specification.
A few of my long bolts were on the line and they got replaced. You really don't want to do this again so don't cheap out.
BTW I concur with the guy that reported that late injection timing will cause white smoke.
Another point if the timing is very late then the cam chain might need to be changed. I'd also bump the timing from 15° After Top Dead Center (stock) to 12° ATDC to improve take off or low end torque. Makes a noticeable improvement.
But take your time and don't get into a hurry. The old adage haste makes waste is true.
Roddy

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There was a point in there where they went from conventional bolts to the stretch kind. I believe 79 would still be the old style bolts which I believe are reusable. The stretch bolts are necked down a bit and as noted can be measured to determine if they have enough stretch left to use safely.