Based on all Ive read here in the last couple days, I'm fairly certain I have have a cracked head, but wanted to verify with the forum wisdom.

Its a 1987 300D with 190k mi. and the infamous #14 head. No trap ox.

Symptoms:

1. Thick gray smoke. Bad at idle, hard to know for sure, but seems to be less driving.
2. Engine is LOUD. Much louder than normal. No new frequencies, or off timed noises (pinging, or clanging), just normal sounds with more amplitude. Sounds like a full size diesel truck.
3. Oil pressure pegs at idle.
4. Slight power loss.
5. Slight water loss?? I have only let it run 15 minutes since the "event" but the water looked low in the overflow/reservoir after it cooled. Took a thermos full (16oz) of water to refill it to normal cold level. No evidence of oil in coolant.
6. Oil seems normal. Black, homogeneous. Nothing that seems like water in it. I pondered if it seemed to be higher than normal, hard to say as its parked on a slope...
7. Idles smooth, just more loud.

The "event":

I was driving to work, when someone was driving slow in the fastlane. I punched it to go around, a few seconds into passing I felt a power loss and the engine noise picked up.

Temp stayed put at low 80's, so I continued on to see what happens. As I pulled in to work, the temp was up a bit, mid 80's.

Parked with the engine idling is when first noticed how bad the tailpipe smoke was.

After work I checked the water, and added the 16oz. Didn't know to note if pressure was high on cap removal.

Started up no problem, noticed the oil pressure peg out while idling. That, with the engine noise increase, and smoke I opted to tow it home.

I started it once for 15 seconds to re-position it after the tow truck left it too far from curb.

History:

I am the 3rd owner. PO is a good friend that gave me the car 3 months ago telling me all he knew was wrong. The list was long, but small stuff. Brake lights, flashers, windows, cracked windshields, paint, leather, glowplugs, etc. He had owned it for 10 years and did the minimum to maintain it for the 2 mile commute he had.

In addition to some electrical work, in the last few months I have:

Refilled the AC with R12
replaced the fan clutch
replaced the radiator, t-stat
replaced serpentine belt

Unfortunately, these are all linked with a theme of getting warm to hot. The AC use accentuated the temp gain when going up hills or when sitting in traffic (95-100) This prompted the fan clutch change. Removing the stripped 8mm hex bolt was such an ordeal, I opted to only tighten the replacement T-55 bolt (no locktite). It was fine for a day, but came loose when I punched it (hmm a theme). The fan blade flew off and punctured the radiator. In the 2-3 minutes between hearing the noise of what later turned out to be the fan, and being able to pull off the road, temp got into the red.

In the hopes that the in red time was small enough to not make the head gasket fail, and knowing the radiator replacement was relatively easy, I did so.
(I used blue loctite on the new fan clutch bolt BTW. Single bolt, spinning with positive and negative torques. I should have known better than to heed the "just torque it down" proponents...)

I had been driving it somewhat gingerly for a week before the the "event" happened with no fluid mixing, so my concerns about damaging the head gasket were abating...


I have not landed on whether or not to fix it. If its a cracked head, i wont. If its "just" the gasket I might. The gasket seems like a pretty big task on its own, and has some uncertainty it will fix the issues, particularly with this #14 head. I'm also kind cranky from the poor driving to wrenching ratio of late (albeit somewhat self inflicted because of a few drops of loctite). But it sure drives nice when it does!

The head seem like too much. the cost of a head, the trouble to find one, the modification for the injectors, the time to do it all.

So do I have a gasket issue or a head issue? Can you tell from the symptoms? It there a relatively easy test to verify either way?

There is a way to test for combustion gasses in the cooling system, but that could be either from a crack in the head, or a gasket. The combustion pressure will take the path of least resistance. You could just pull the head and have it checked. If it does have crack(s), you can determine if you want to proceed or not.

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Grey smoke would be fuel related. The loud engine you describe sound like injectors that need nozzles replaced and balanced. The oil pressure should peg at idle when cold and will drop down to as low as .5 bar at idle when hot. Sounds like you need to look into injector and/or delivery valve issues.

The _ONLY_ reliable way to check for a combustion chamber to coolant leak is to pressurize each cylinder ( with both valves closed ) to about 100 PSI then look for bubbles / coolant to rise in the radiator cap.

There is a chemical test but this won't find those slight leaks nor will it point you to the cylinder causing the problem.

Definitely sounds more like an injector issue. With that being said it's easy to tell if it's a head gasket/cracked head issue. The coolant hoses will still be hard after the engine has sat over night.

And if it does turn out to be a head gasket I wouldn't reinstall the original #14 head. To much work involved to take a chance with the #14 head IMO.

+1

it's commonly known as a leak down test.

I highly recommend it.

Possibly injectors. Thats unexpected. I'll have to research this more in the morning.

What failure mode occurs with the injectors that leads to a loud engine and grey smoke. Is just one injector that failed under the high stress, or did they all go at the same time?

From my personal experience, a cracked #14 head failure is more catastrophic. While on a 200 mile round trip got stuck in some serious accident traffic. Knowing I had a #14 head of unknown history I always kept an eye on the gauge. Once moving again, my temperature gauge started swinging up and down. Then my heat would come and go. Uh-oh!

Made it back home with intermittent heat and a swinging gauge. Next morning the SDL was hydro-locked. Was able to slowly squeeze the radiator fluid out via a breaker bar on the crank.

Was then able to get it started with all sorts of foul smelling smoke and steam. The overflow tank exhibited obvious bubbles. The engine did sound normal.

If they are not popping at the correct pressure you will get nailing and grey smoke. You can try running a couple of cans of diesel purge thru it but most likely you just need to rebuild them.

I'm sorry about this happening to you...it sucks when were faced with a lot of labor to check for an engine failure. Less work then pulling the head, if you could get the prechambers out and snake in a scope (borrow one or buy a used Snapon on ebay, great to have in any event, about $3-500 used), you would see water drops on the piston or residue on the cylinder walls, even some rust if a head gasket was leaking coolant in there. Like others said, pulling the head is the only way to be sure if there is a crack or it was just a gasket. But the scope test helped me realize when my engine was toast.

This is my experience with OM603/1.

1) if head is crack bad. You wouldn't be able to drive the car without overheating. Also serious crack may leads to hydro locking of engine.

2) if the car runs and doesn't overheat then it is possibly a very minute leak. Check for stiff radiator top hose after standing overnight. It should be soft to squeeze and not rock hard.

3) #14 head is Ok. I would take a #14 head anytime. Issues with #14 head is overblown.

4) Pulling pre chamber is not easy on a 30+ years old car. So forget about putting a scope in there. Waste of time and money.

5) Pull injectors and pop test it to make sure they are within spec and check engine compression.

6) pulling head and replacing gasket is not as difficult as one may think. BTDT a number of times.

Good luck.

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The infamous test of leaving the car sit overnight. If the hoses are still hard next morning it is usually thought a cracked head. I have no ideal how good a test this is. Yet it seems to be used on the 603s.


For one if a cooling system where not tight the pressure could be released. Still if you were going to purchase one of these that is a test that is used. Why it would be specific to a head crack over a head gasket has always made me wonder.


Normally as the coolant cools the hoses go soft over time.

I have to agree about this test. Seems like its only good for coolant to exhaust cracks.

That said its an easy test. I'm less concerned about destroying the engine, so will plan on starting this test tonight. Just warm up it up to get the t-stat to open, check the oil pressure, then shut it and check the upper hose in the morning.

I have some prep to do tackle the injectors. Was thinking a moly lubro diesel purge or injector cleaner is also easy to do now, and then get more in depth with the injectors if that does not correct it. The injectors are uncharted territory for me so need to find a good thread for removal, testing and rebuild.

If this was caused by an injector.I do not suspect an attempt to rectify it with a chemical is going to be productive. Every 100K Mercedes recommended removal of the injectors and testing them.

If an injector tests good just continue to use it. For all we usually know they could have been done not long before we purchased many of these examples.

If you really believe you are losing coolant it may be better to follow that lead.

I did the top hose pressure test. Letting it warm up last night to operating temp, then checking top hose pressure this morning. Hose was loose and gurgley.

I did notice this pre ip filter though.

Looks like engine oil. Could that happen?

Was thinking of bypassing the tank and running from a container of diesel and letting the return go to another to what it looks like.

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