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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #1
The other day I noticed that my delivery valves were leaking, and not just one. So, I decided that I would pull the intake manifold to make it a bit easier to gain access, though it's not required.



Once I had the intake off, I noticed a small coolant leak puddling up on the block beneath the port where the heater gets its source on the cylinderhead. The o-ring didn't appear to be leaking, so I just assumed that the headgasket had failed externally--which is an unusual failure mode for these things. Since I already had a headgasket kit on hand, I went on to just pull the head...but not before stripping one of the head bolts, which required me to burn through 7 drill bits before I could remove it--fun.



Turns out that the headgasket was fine, though I'm certainly glad to install the latest design in there for peace of mind. The source of the leak was a disintegrated thread-in adapter for the heater tube. It had turned to complete chalk, with only a few threads still left intact. I've never seen anything like it, and there were no other signs of unusual aluminum corrosion anywhere else on the head.



Since the head was off, I opted to pop the valves out and replace the stem seals. The guides and stems were in surprisingly good condition for 180k, though I had no intention of replacing them anyway. I like to play with my die grinder, so I also decided to do some mild port work, and then hand lapped the valve faces and seats. The valve faces and margins were great, with very little dishing and solid contact area...except for a weird pit that showed up in the exact same spot on every exhaust seat. When I pulled my original OM603 head with 200k on it, there was exactly one of those pits. I really have no explanation for these, as they're not even near a flame front--bizarre.











I'll update this thread with some more pics once I re-seal the delivery valves and pin the head back together.
 

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94 E320 Cab, 93 400E, 87 300TD, 92 300CE24 Sportline, 94 SL320, 92 500E, 99 SL600R, '02 CLK55
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33 Posts
I am about to pull the head on my 91 300D, and I'm interested in the head bolt stripping issue. Is there anything I should do to prevent that from happening, and what was your strategy to remove the bolt once stripped. I see that you went through 7 drill bits, and your picture looks like there's a phillips screwdriver engaged with the bolt - but what exactly did you do to get it out (in case it happens to me!). Thanks
 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #3
You'll want to clean the recessed heads obsessively. This one turned to butter as soon as I applied torque--dunno why.

I first tried to drill the opening up to see if I could pound the next size up version of the XZN drive bit in there--no go. Then I drilled a pilot and a series of larger sizes until I busted through a portion of the bolt head, then drove a Torx bit in there and it unscrewed nicely.

How do you plan to remove the two timing rail pins? I keep meaning to buy the proper tool for this, but I keep using long bolts and a series of washers to accomplish this task--very risky business.
 

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94 E320 Cab, 93 400E, 87 300TD, 92 300CE24 Sportline, 94 SL320, 92 500E, 99 SL600R, '02 CLK55
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33 Posts
Well, I am a little worried about the timing rail pins, but I figured I'd rig up or weld up some sort of tool to remove them, sort of as you describe. I was really hoping that I could get away with not removing them, but as I've never done this job before I don't really know - and I saw those strange tools in the manual.

Most of my work has been on Porsches and I'm not that familiar with working on Mercedes, though I now have three ('87 300TD, 91 300D and 93 400E).
 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #5
The head is now reassembled and ready to install, after I replaced the valve stem seals:



I've been prepping the deck to clean it prior to installation of the headgasket:



Next I tackled the delivery valves. This requires that the surface be extremely clean, so that accumulated detritus doesn't fall in the pump:















Cleanliness is really critical, so I used a vacuum cleaner throughout the process. I really think replacing the crush washers is important, but it's probably arguable that if you're already in there, it might be a good idea to also replace the springs. I think I'll stock up on some of those for future needs. My shop is now completely maxed out for projects, so I really do need to wrap this one up, asap.

 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #6
I finally finished this project, and it's resulted in a very satisfying outcome, though the scope increased substantially. Through my investigations I determined that the serpentine belt pivot bearing and tensioner pulley were both very close to seizing. Additionally, the power steering pump shaft had a lot of lateral play, which explains the noises it made at full lock.

I knew that the vacuum pump was of a newer design, 'cause I could see the external torx screws on the cover. Out of curiosity I pulled it to inspect the roller bearing and timing advance ramp for possible scoring. It all looked good, but when I compared the pump against one I had purchased a few years ago for my 603, I noticed that the newer design "caged" the roller bearing, which theoretically will keep the ball bearings in place should it fail. I opted to swap in the newer design.



Here you can see the new coolant junction compared to the old corroded unit that essentially necessitated this project in the first place:



One thing I recommend when pulling the head on these OM60X engines is to allow the lifter buckets to bathe in oil for an extended period prior to re-installation. This keeps them pumped up, and mine didn't rattle at all when I fired it up.



When I pulled the head, I thought I was being clever by also pulling out the exhaust studs with the copper nuts. This allowed me to keep the manifold and turbo in situ, which meant I theoretically could re-install the head and just thread the cleaned up studs back while avoiding extra work--wrong! I couldn't line up the manifold, gasket and head for the life of me, so I ended up pulling everything. This allowed me to snap a pic of the T2 turbo that I had previously converted from a vacuum-signaled wastegate actuator to a boost signal unit from my old 603 Garrett T3. You can see the washers I had to fit underneath the boost canister in order for it to clear the stock bracket.



I highly recommend this swap, as it allows you to bypass all the vacuum transducers and plumbing issues that vex owners of older high mileage 602 cars.

As I mentioned, now that it's all back together, I'm very pleased with the results. It's very smooth, starts right up, is quicker off the line, and more throttle responsive than before. The responsiveness is more than likely due to the fact that I tested the old ALDA and found that it wouldn't hold boost at all. I swapped in a unit that I had re-sealed a few years ago. The difference is nothing short of amazing.



Yesterday I drove it on a shake-down trip to Portland and back, and the engine performed remarkably well. My next project will be to take the cruise actuator apart and clean the internal contacts, as it has difficulty maintaining a constant speed, especially when the car is driving down a slope.
 

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94 E320 Cab, 93 400E, 87 300TD, 92 300CE24 Sportline, 94 SL320, 92 500E, 99 SL600R, '02 CLK55
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33 Posts
What a great thread - and especially timely for me as I am in the midst of changing the head gasket on my 300D.

I am having difficulty getting the metal header tube out of the thread-in adaptor; there doesn't seem to be enough clearance to allow its withdrawal from the adaptor. Any tricks to accomplish this?

Thanks, Gary
 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #8
I'm not sure what you're referring to when you say "metal header tube". Could you please provide some additional information?
 

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94 E320 Cab, 93 400E, 87 300TD, 92 300CE24 Sportline, 94 SL320, 92 500E, 99 SL600R, '02 CLK55
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33 Posts
I am referring to the fitting that mates up with the adapter that was extremely corroded on your car. I have removed the retention clip and pulled the coolant hose off the far end; the two (fuel?) lines are still hooked up. I have removed the bracket for the wiring harness that runs between the metal fitting and the oil filter housing and pulled back the wire run, but there doesn't seem to be enough room to pull the fitting out of the piece attached to the head.

Also having a very hard time with the lower slide pin for the timing chain rail. I removed the upper one with some difficulty using the slide hammer called for in the manual, but I can't budge the lower one. Also tried pulling it with a bolt, nut and socket arrangement and broke the bolt off in the slide pin. I have now removed the piece of the broken bolt but the pin won't move. I am contemplating ways of breaking the timing chain rail at that slide pin so I can get the head off.

Gary
 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #10
Ah...gotcha. That bit of coolant plumbing is a real bear. If I remember right, I had to un-thread the adapter while holding the pipe, with the head still installed. They were removed in one piece, which you can see in an earlier pic in this thread. I still had a hard time separating the two, even on my workbench. It's a way more complicated design than what MB used for the OM603 engines. Since I live in a temperate climate, I opted to bypass the fuel thermostat altogether, and simply sawed off the fuel pipes. This made re-installation a lot easier, and I don't have to worry about the inevitable fuel leaks from the thermostat.

I used the threaded bolt and shim technique for both the upper and lower pins. I tried the same technique in the past on my 603 and snapped off the bolt. The trick is to use the highest grad 6mm bolt you can find, which I believe is typically 10.9. Most metric bolts of that size come in grades 4.8, 5.6, 8.8 and 10.9. If you can't find a suitable length in that grade, then you'd best just buy the proper pin-puller. They're around $30
 

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190D Turbo
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Concerning the vacuum operated wastegate, I have a 87 190DT with the OM602.961. My understanding of the system is that a switchover valve allows ambient air into the injection pump when the boost reached 14.5psi which reduces the fuel flow. I don't have any vacuum hooked into my turbo, so believe my turbo is also boost actuated right? If I wan't to increase power with a simple mechanical boost controller (3Bar Racing) would I need to address the waste gate, the switchover valve, or both?
 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #12
Just directly plumb the boost line from the manifold to the ALDA on the injection pump. The bypass is for overboost situations that never really arise. Your wastegate is boost actuated. Until and unless you find some way to mechanically increase the fueling (big $) for the engine, I wouldn't bother trying to tweak the turbo boost output. These engines can be modified to produce huge hp/torque, but that takes injection pump mods and lots of work.
 

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190D Turbo
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14 Posts
Just directly plumb the boost line from the manifold to the ALDA on the injection pump. The bypass is for overboost situations that never really arise. Your wastegate is boost actuated. Until and unless you find some way to mechanically increase the fueling (big $) for the engine, I wouldn't bother trying to tweak the turbo boost output. These engines can be modified to produce huge hp/torque, but that takes injection pump mods and lots of work.
Thanks for the info! I will bypass the bypass, but not until I get my boost gauge hooked up. It will be interesting to see if anything changes.
 

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1991 124 chassis 300D 2.5 TurboDiesel 355K miles
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192 Posts
Zeitgeist,

With the ALDA, what sort of vacuum should it be able to pull? I will pull mine and test it during my re-build. Any trick to pulling it from the IP?

What luck did you have with cleaning your cruise actuator contacts? Did that fix your speed seeking problem? Mine varies quite a bit, especially down hill, and frequently disengages.

Well after re-build into a few months of running, I would like to ask you more about the turbo mod from vacuum to signal.
 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #15
A slight correction, the ALDA works off of a pressure signal, rather than vacuum. I use a big set of channel locks and a 27mm(?) wrench to remove the ALDA. I believe the test is to see if it will hold 10psi for a set amount of time. You can slip the eraser end of a pencil into the actuator rod and see if it moves when you pump it up. You'll want a MityVac that produces both vacuum and pressure--a very handy device for these diesel cars.

Yeah, cleaning the contacts completely cleared up CC problems I'd been experiencing. I also applied some dielectric grease to the contacts.

The vacuum to pressure wastegate actuator mod is just a swap of the actuator from an OM603--it's really that simple.

I still need to conduct some 0-60mph tests, but my seat o' the pants meter tells me that this engine is as quick as an OM603. I haven't even turned up the pump yet, but the head work I did seems to have produced some impressive airflow characteristics that I wouldn't have predicted.
 

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1991 124 chassis 300D 2.5 TurboDiesel 355K miles
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192 Posts
I'll get ahold of a MightyVac, sounds like a great tool for the Benz Diesel arsenal. Good note on pressure vs. vacuum - I phrased the question wrong, you did state boost previously. On the ALDA, will test to see if it holds pressure. For removal, is it threaded or pressed on?

For the cruise control, I'll crack mine apart, do the same, with dielectric grease as well.

I'll start the search for an OM603 wastegate actuator.

Did you polish both intake and exhaust ports on the cylinder head? I'd love to take the time for that, but these are my prime wheels. When I get backup wheels, time and resources, I'll do the turbo mod and pull the head again for some polishing. The performance increase sounds worth it.
 

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1991 124 chassis 300D 2.5 TurboDiesel 355K miles
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192 Posts
My cruise control is smooth and dependable now after following your procedure Zeitgeist, thanks.
 

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80 280SL, 85 300SD, 87 300TD, 90 300TE 4Matic, 90 300D 2.5 Turbo, 92 300D 2.5 Turbo, 92 300TE 4Mat
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Great job and great write up.
 

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1991 560sl / 1987 300TDT / 1995 E300D / 1994 S350D / 1993 300SD /Cummins Diesel PU /2 airplanes
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861 Posts
NICE WORK! EXCELLENT PHOTOS AND WRITE UP.

I'm building a S350D engine now. May I ask where you got the copper washers and 'O' rings?

I don't even want to think about how difficult it must have been to get out that broken head bolt!!!
 

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Cruise Control
'87 300TD/'90 300D/'94 Quattro/'89 Vanagon TDI/'01 EV Weekender VR6
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52,233 Posts
Discussion Starter #20
Try plugging these part numbers in at your favorite online retail site

Copper washers -- 004-997-45-40
O-rings -- 017-997-41-48

You DO NOT want to strip a head bolt. It was no fun whatsoever.
 
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