What is considered good compression for a W124 diesel? Local junkyard has one with 320/cylinder. Does a 1987 W124 sedan 6 cyl. diesel engine swap directly into a 1987 W124 300TD wagon? Does it require any modifications?

Five to ten miles after filling the fuel tank, I started seeing exhaust smoke; lots of it. I thought (hoped) "bad gas, water in the fuel". I pulled over, put it in park and hit the accelerator - a thick plume spewed out. It looked white, not blue, with hints of grey/brown. And it smelled burnt, not sweet like coolant. I drove a mile home in a cloud of depression. Next morning I popped the hood and squeezed the readiator hose, it was soft, not hard and the coolant was clean. I started it again, no smoke, and took it for a short ride and saw smoke after 200 yards, then started hearing a clack - more like a metal on metal drumstick. Pulled over, opened hood, no visible issue, but distinct clack from one of the 6 cylinders. Turned off engine, the smell of burned smoke lingered heavily in the air. I got in, started up, smoked a u-turn, accelerated to 20mph, cut the engine, and coasted back home.

Overall, the car is in very good shape. But with 289K miles I expected the head gasket or #14 head to go eventually. But I don't think it has. And I'm very certain that overheating did not happen.

So... what to do now... invest in diagnostics? Which diagnostics could provide value with these symptoms? Meaning: is there a chance in hell that with these symptoms something can be fixed?

Or... proceed directly to swapping in a used engine. (local MBjunkyard offers the 320/cyl from an '87 sedan for $1200 + $500 labor and probably a short warranty). Or do I find a reputable remanufactured engine (anyone know who has one with a non-#14 head? Or are there advantages to rebuilding with my old #14 head (valve job, resurfaced, new gaskets, rings?, etc. guestimate $4k+). Or...

Despondent and optimistic. What am I missing? I'd appreciate hearing from members who have experiences (pos and neg) to guide me through this stinky fog.

It could still be the head or gasket. To check for a cracked head, pressurize the coolant system and see how it holds over night. Be careful on starting the next day as it could be hydrolocked from a cracked head. If it leaks or locks, the head should be scoped out. I got a crate engine from MB dealer with 4 year/40K warrantee but it was expensive. Metric Motors has rebuilt engines for a little less. Smoke could also be caused by IP or injectors if they are the original with all those miles. It could also be timing chain stretch. Also has the ALDA been adjusted?

__________________
87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

A same year sedan engine is a direct swap for the the wagon engine.

320 psi is below ideal by 80-100 psi but it could be a result of technique and a cold engine.

With the engine clacking at idle, loosen the injector lines one at a time to see if you can isolate the clack to a cylinder. If you can, swap injectors (you should replace the heat shields) to see if the noise moves with the injector or stays with the cylinder.

There are a range of things to check but because this is a sudden rather than gradual event, I'd pull all injectors and peek into the prechambers to see if the bb at the far end is still in place. I don't know what that bb does but it causes problem when it shakes loose.

You mentioned smoke but not a word on performance. How does it feel? Does it shake more at idle?

Sixto
87 300D

Thanks for the input. I just started it up cold. sounded fine for 5 sec, then clacking began. I used a scredriver crammed to my ear to check listen to each cylinder by the injector, and to each IP injector. The #2 cylinder sounds like the one making the noise. After 1 minute smoke was pouring out of the tailpipe and wafting down the street.

Ref, the top radiator hose was-and-is soft squeezable, no pressure in the cooling system, and the coolant tank is still clear. I have not adjusted the ALDA or messed with the IP (though I have replaced "o" rings on a previous 124TD)

Sixto, performance may be a bit off, but I haven't really pushed it since this pretty sudden onset of smoking, and then smoking and clacking (I don't remember hearing the clacking right away, the radio was on). This TD used to do 0-60 in 10.5-11 secs.

So to look into the cylinder head pre-chamber, is the process to remove both injector racks , or just the one with the 3 that feed the #2 cyl? Do I remove them from both the IP and the cylinder injector? And after looking for the bb, should I swap another of thsee 3 injectors to #2 and then reassemble the fuel feed lines to test the injector itself in the new cylinder, and then listen to #2 to hear if it is still making noise? Is that the process? PS what is the heat shield?

Sixto, it doesn't really shake at idle. It sounds bad and smokes badly, but looks good. not a drop of oil, no visible coolant loss.

The prechamber is in the head. It's the thing the injector screws into. Nothing to do with the IP. There's something of a metal washer that seals the injector tip against the prechamber. That's the heat shield. You can fish it out with a hook or a magnet or crank the engine and watch it fly into oblivion.

Noises resonate througout these engines so I wouldn't trust ears. The clacking could simply be a serpentine belt tensioner damper Heim end that's worn out. Lots of folks have mistaken the noise for nailing or rod knock. Don't trust your ears! Loosen each injector line one at a time to see if you can isolate the noise and/or smoke. A full turn or two until fuel dribbles from the junction is all you need.

I performance isn't affected, maybe you lost an exhaust valve seal or turbine/hot side seal.

Sixto
87 300D

Sixto, after starting the engine, I loosened and removed each injector line starting at the front and dribbled/shot fuel spurts from each line and then looked for smoke. the car smoked fairly consistently. However, the sound did modulate louder and quieter. But the most significant thing I noticed, that sent me running back to my computer, was a consistent bubbling of some gas in the puddled fuel around the flat heat shield area where the #1 injector enters the head. Clearly there is some kind of air-exhaust gas leak from around the #1 injector. the other 5 did not have these bubbles. I tried tightening the #1 injector, but it was snug - and the bubbles kept coming.

I got magnifying glasses and lights and looked for a crack, didn't see it. I did notice a flec of aluminum coming off the very thin wall next to the injector, between the injector and the big torx bolt, where the head is milled for the torx indent. but again didn't see a crack. Turning the engine on, it looks like the bubbles are coming fron the IP side, from an area what looks like the opening of thick "c" clip, or it could just be escaping from that open area.

Where are the exhaust valve seal or turbine/hot side seal?

Hopefully the compression leak is inconsequential. I'd try a new heat shield for that injector (one per injector) -

http://catalog.peachparts.com/ShopByVehicle.epc?q=1987-Mercedes--Benz-300td-Diesel--Injection&yearid=1987@@1987&makeid=63@@MERCEDES+BENZ@@X&modelid=6235:MBC|1519:ED|10000096@@300TD&catid=240706@@Diesel+Injection&subcatid=240710@@Injector+Heat+Shield&mode=PA

If it's conclusive that cutting fuel to each cylinder didn't affect smoking, the smoke must be caused by an oil leak downstream of the combustion chambers. Each exhaust valve stem has a seal keeping engine oil from the head from seeping into the exhaust stream. The valve guide does most of the work serving also as a bushing to guide the path of the valve. The valve stem seal does the rest. There's also a seal between the bearing section of the turbo and the turbine section driven by exhaust gas. When that seal goes, oil leaks from the bearing section to the very hot turbine section and out the exhaust pipe.

We don't have conclusive evidence at this point so we're doing cheap diagnostics. I'd remove the pipe that connects the exhaust manifold collector and turbo. IIRC it's 2 nuts at the collector and 4 nuts above the turbo. All take a 13mm socket. It might take some blows with a soft mallet to release the connector pipe. If the inside of the collector pipe is coated with wet oil, the oil is coming from the engine. If it's dry, however sooty it may be, it's likely an oil leak within the turbo. You can idle the engine with the connector pipe off. Just be sure nothing falls into the turbo! Cover your ears then see if the same smoke you see out the tailpipe is coming from the engine upstream of the turbo. It'll be loud!

Sixto
87 300D

Those 13mm nuts on the connector pipe are hard to work in that confined space. I dropped the lower aft one and heard it hit the street. Reaching under the car to get the dropped nut, I found a small puddle of black engine oil covering 2"x1.5" roughly parallel to the back of the engine. I jacked up the driver's side and crawled under to look for the source. It is coming from the #6 cylinder at the exhaust manifold.

Sixto, This oil drip is new to the car, and the puddle appeared after the short time that the car was idling to test the fuel delivery to each cylinder. I'll stop trying to remove the exhaust connector, as this engine oil dripping from the rear-most cylinder area may redirect your guidance.

The same thing happened to gsxr with a new head which IIRC he attributed to a wrong or poor quality valve stem seal.





If so, a new valve stem seal might do it for you. Trouble is, you need a funky valve spring compressor to get to the valve stem seal and I don't think anyone in the tools forum rents such a tool (go check). Maybe Perf Products rents it. Or maybe you can configure a similar watercooled VW tool.

[Edit] - Oops, photos courtesy of gsxr.

Sixto
87 300D

Ayy ayy yie ayie. That is exactly what I see/saw. Powerful presentation of the pictures! Thank you GSXR!

So...with the right tool, can this repair be done without removing the head? (I could use a new valve cover gasket.) If so, anything else you recommend doing with the valve cover off?

Ironically, it's no easier with the head off.

gsxr recommends valve stem seals from the MB dealer vs even trusted manufacturer aftermarket.

And you need this type of valve spring compressor -



Sixto
87 300D

OK, the euphoria has phaded. (My calvin has been hobbled.) That last photo of a benched head with the spring tool looks like the entire overhead cam has to be removed. (Or do I entrust a MB master mechanic with the tool to romance the spring, remove the old valve stem seal and install dealer seal(s)).

What is the recommended best way to proceed? Should I consider doing just one seal? Are we (as a forum) recommending investing in refurbing #14 heads with 289k? (Most of us are runnig #14s - and lots of us are running them hard.) Are there other considerations or pitfalls to be aware of? Any ballpark estimate of the cost/hrs for these repairs?

By the way, this forum and you guys are great. Sixto, thanks so much for getting me to this point in the diagnosis so fast. (gsrx, thanks for taking those photos. They hit me with the strength of the Sunday comix, back in the daily days.) Looking back to my first post this morning, I'd assumed the engine was toast! Now, with a 'rita under my belt, the toast tastes like buttered lobster.

That's a VW head but representative of the 603. So yes, the cam has to come off. Did I mention there's a sequence to removing the cam towers? One wrong move and the cam can snap.

If it's the seal, I think it is but who can be sure, and it failed from age rather than some recent event (filling with bad gas won't damage an exhaust valve stem seal), I'd say replace all the exhaust valve stem seals if not all the seals.

At this time you haven't isolated the accompanying noise. Does it take a few minutes for the noise to start? Does the noise start when the smoke starts? If so you might have a problem with the hydraulic lash adjuster on the same valve. If the noise is unrelated, run the engine from bone cold with the serpentine belt off to see if it's something up front making the noise. Only for a minute or so! Don't trust the engine temp gauge when the water pump isn't circulating coolant. I think I already mentioned the belt tensioner Heim ends as suspects.

Sixto
87 300D

So, if you're recommending replacing all of the exhaust valve stem seals, and all other seals (and the head gasket and crack inspection with 289k on a #14 head?). Sounds like a rebuilt head is required.

Noise: started it up cold this morning and it sounds pretty normal for the first 5+ seconds, but it doesn't fully smooth out and purr, and smoke is evident almost right away. It continues an intermittant quiet clacking. If I hit the accelerator it smokes more and the clacking gets somewhat louder. Sometimes it clacks more loudly. It does not take "a few minutes" for the clacking to begin. does the valve job address the hydraulic lash adjuster(s)?

If the noise is unrelated: Heim ends look and feel OK, but I don't know how they fail. to I'm going to postpone removing the serpentine belt, as I may get an indy involved or help confirm the noise diagnosis. It is fairly ellusive and changing.

I can replace the water pump and Heim ends (inspect and clean the turbo/exhause man for oil. Anything else? replace timing chain?

By the way, the local MBjunkyard called to report the 87 sedan's engine ($1700 installed) has 254k miles and compression is 320, 340, 380, 360, 360, 320.