Alright, so I'm going to start out with the synopsis of my last few odd weeks, and then finish with a couple assorted questions that I could use a few answers to.

My first symptom showed up a few weeks ago. I was driving along and noticed a low coolant light. Before I could even get off the road to check the level, the light went out again. I opened the hood and the coolant was about an inch above the sensor in the expansion tank (Which was formerly full to the "kaltwasserstand" marking just like it's supposed to be). I thought that was odd but didn't want to open a hot system and needed to keep moving, so I just kept driving. I watched the temp like a hawk for the rest of the trip and it never even climbed past 100 at a stop light. (Summer days this time of year are hitting 92, 93 degrees outside.)

I gradually started to realize that my low coolant light symptom was only appearing under hard acceleration or during long freeway runs at relatively high RPM (3200+). That type of circumstances anyway. I'd punch it to get moving on an onramp, the light would come on, and by the time I could get merged out and start worrying about it the light was off again.

This behavior continued until i added coolant (1-3 cups, I'm guessing) to the tank to replace what was lost (to an unknown location; it's not showing up in the oil visibly yet). Now, I can STILL make the coolant in the tank drop from the cold fill line down to about an inch over the sensor for the light just by driving hard on a hot day. When I park in the yard and leave it idling after a hot run, the coolant is down to that level in the tank. When I shut the engine, I get a little bit of it back in the tank from somewhere.

HERE is the unfortunate part. When I open the pressure cap, the level instantly raises another inch or two back to somewhere close to my fill line (although still, for some reason, not quite to it.) The doubly unfortunate part is that from overnight to the next morning, if I leave the system closed - it's definitely holding pressure. The upper hose stays firm and when I open the pressure cap cold the morning after I drive the car, I get a long loud hiss of air under pressure (NOT vacuum) escaping along with a spew of coolant sometimes. Probably just a couple teaspoons launch out the top of the tank once the cap is loose.

I've repeated this about 3 days in a row.

The car has never in my time of ownership been overheated to 120 or above according to the gauge. Ever. It has, however, experienced anywhere from 4 to 6 events caused by two different problems in which the temperature climbed to what I would estimate at 114-118 degrees on the gauge before I was able to arrest the climb. So I'm assuming I could have cracked a head simply by all those temp flexes even though I have never in my life allowed it to hit or exceed 120.

So here's my questions.

1. Does the pressure in the cold overnight system indicate definitively that my head is in fact cracked, no matter how much I thought I wasn't mistreating it? Is there any OTHER place I should look for the reason for my morning pressure and for my disappearing and then reappearing coolant?

2. Where, geographically under the hood, can I read my head casting number, with the engine in place, mounted, everything just as it is when I drive it, to check if it's a #14 or something else, and likewise to check potential donors for their casting number? Is this information visible from a fully installed engine? If so, on what part, behind which other parts, near which widgets, etc, can I find this information?

3. Is it logical that I could have a cracked head, if that is indeed the problem, and have no oil contamination or antifreeze contamination? I know an oil analysis would show the presence of glycol that my eye can't detect, but the oil isn't going foamy, it doesn't look watered down on the dipstick, and I can find no evidence that the antifreeze has entered the crankcase. I can also find absolutely no traces of oil around the expansion tank area. I know a head crack and a head gasket failure are two entirely different things, but I see those symptoms mentioned occasionally in both contexts.

I'm just going to go from here with it. No doubt I'm at least partially to blame for letting it climb to 115 that many times without trying to make a more aggressive diagnosis of the problem, but that's water over the dam at this point. I'll worry about how it happened once I've got something else to work with, but for the moment, I'm more interested in what to do next. I've got no job this summer so I'll be driving it for a while until the symptoms get worse while I save up for whatever I have to replace, be it the head, the whole engine, or the whole car. I've got no problems with the engine EXCEPT these weird symptoms at the moment; it hasn't affected anything I can notice in daily driving yet.

The reason I say complete car replacement might be wiser than engine replacement is that if this is in fact a catastrophic engine failure, this car already has rust at the inside door surfaces even though the outside's clear, it's in very very desperate need of a complete repainting to deal with sun damage, it's got air conditioning troubles (SLOW freon leak plus control unit issues), it needs a new rear windshield at some point as the separating corners gradually get worse over the years, the upholstery, while intact, is just barely hanging on... this car has had a LOT put into it and is still very, very valuable as a source of good, already paid for parts for the next one, but I'm not sure how many of these thousands of dollars I ought to throw at a body with doors that are trying to fall off and in which half of the electronics are insane.

For the moment those 3 questions I posted are the ones I need answers to the worst at the moment. Thanks for any input on whether there's any chance my problem is something other than a cracked head. And, either way, is there any further diagnosing I can do and report back the results of.

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

pressure test your cooling system or have it pressure tested . i have a #14 head on the sdl as well and no signs of cracks or anything and it has over 200k miles on it. Also what color is your exhaust when go under hard acceleration?

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

If the car is the one in your sig then does it have a 617 or a 603 engine in it. I believe the #14 head issue only applies to the 603 engine. The 603's have an aluminium head , the # is found above the #2 injector on the side of the head. The format will be something like 603 014 00 00, hopefully your head has anything higher than 014. If you don't have a 603 engine then you don't have that specific problem. The rest I leave to other more knowledgeable members. Cheers Dan

__________________
It's always something simple
91 300D 603.960 (from japan) 194K
92 Toyota Diesel Landcruiser HDJ81-t 116K
02 Golf TDI new head courtesy of PO
87 300D
97 BMW 525 TDS Wagon 5spd
bunch of Onan and other diesel generators

It's a 1986 300SDL, the only Benz I've got, so yes, it has a 603 aluminum engine. That's one reason this was my first guess.

I've been watching for "white smoke" ever since I noticed I was having trouble, and have not observed any. When I drop the hammer, I just get the grey/black cloud of unburned diesel that I'm accustomed to.

thanks for the info about where to look for the casting number. I'll go out after supper and see if it's a #14 or higher. I suspect I'll find a 14, because I have a nagging suspicion I've read that number before and didn't know what I was looking at. But I'll post back.

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Firstly, I sense the trepidation in your words and I believe you should just take a step back and thoughtfully consider the possibilities. The vehicle can be driven perfectly well just the way that it is and you can carefully make plans for the future.

1. No, pressure in the cooling system does not definitively mean that the head is cracked. It's not a good sign, however, the sign can be a blown head gasket just as well as a cracked head. The fact that the engine is consuming coolant tends to reinforce that a problem definitely exists...........be it a head gasket or a cracked head.

2. Get yourself a small dental mirror or hand held mirror. Shove the mirror directly below the crossover pipe to that you can read the numbers that are directly above the #2 injector on the driver's side of the engine. That's the casting number and you cannot read it without that mirror unless your eyes are much better than mine. If it's the original head, it most certainly will be a #14 casting (group of two digits that are just before the final group of two).

3. It's unlikely that you will have a blown head gasket or a cracked head without some glycol contamination in the oil..........but, it's not impossible. You won't see the glycol contamination until the problem worsens. You don't want to wait until that point because glycol is a problem for the journal bearings on the lower end. Get yourself an oil analysis to improve the diagnosing capabilities. It's $20. well spent and we probably won't need to be making a bunch of guesses.

Post back on this thread with the results.

I'll send some oil off next change I get to see if any glycol is detected. I did just go out and check... with a bright flashlight I was able to just look through the hole without a mirror. It's definitely a #14 head. Which proves nothing but adds to our natural suspicion. I'll post back with oil analysis results.

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

How long does it usually take Blackstone Labs to get oil analysis results to new customers? I ordered a sample kit and finally, after 2-3 weeks, got it in the mail. Vacuumed out just enough of the oil to fill the container, sent it in over a week ago, and haven't heard so much as a confirmation email from them. Any idea if this is normal or if the wonderful post office messed me up or anything?

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Was it one of the small plastic containers that they expect you to apply postage to and mail it as-is? My local post office told me to always put those into a padded envelope and send it that way - that the size of the small plastic mailing jar they provide is just right to tumble out of their mail handling containers and get lost.

If it's only been a week though, give it some more time.

__________________
'98 E300 turbodiesel

I'm going to attach the oil analysis. Now that the 240 has arrived, I'm probably going to drive this one until it gets worse and then at some point after we're sure the other diesel is fit to make a regular driver, pull the head off the SDL and see what it looks like and THEN try to source whatever parts we're in need of. My interpretation of their interpretation of their findings is that we're ok for now but probably have trouble coming, just a matter of when rather than if. But not an emergency yet.

Attached Files

oilrpt.pdf (51.8 KB, 167 views)

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

They don't know what they're talking about.

The sodium and potassium levels are of no concern and are typical of what you'll see when you run Rotella syn. All of my analysis on both vehicles always show some sodium and potassium. Personally, I'm sure it's a byproduct of this oil.

Furthermore, for the presence of antifreeze..........they show ?. Did they run a test for antifreeze...........or not?

I'm no fan of this lab...........

Looks like there may indeed be some slight coolant transfer going on....seems to be fairly minor though.....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Chances are good that you'll find cracks in the head.

I is also as likely, that the cracks will be insignificant, and might not even be leaking. I've pulled apart a good engine for parts, didn't use coolant, had the head pressure-tested, also good, but there were two visible cracks in the usual areas. No need to pull it apart if it is asymptomatic or the symptom is minor enough to not affect reliability/driveability. Put a lower pressure cap on and water-wetter in the car.

__________________

Gone to the dark side

- Jeff

have a machine shop check the head out. A machine shop can do all the tests needed and will tell you what to do with the head.

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

I find myself in the same situation. I was not able to crank the car the other morning as one cylinder hydrolocked. I got the ratchet out and hand turned the engine. I could hear liquid being squeezed out of the cylinder. i also opened the cap on the expansion tank and it was pressurized from the previous evening.

So I have coolant leaking into the bore. :-(

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

Cannot believe the head cracked in the few miles that you've driven it. Must be a head gasket issue of some sort............