1987 300D odd symptoms....

[Marcb]

Hello,

Well, my trusty 1987 300D is acting very odd again. It's been having a little stumble and miss when I've been trying to start it cold (and sometimes warm) lately. I thought it might be a weak glowplug but the light comes on and it has been running well. The low coolant light has came on at least 4 times over the past several months and I've topped off the coolant in the expansion tank. Now, I haven't been worried about the coolant loss as I've noticed some air in the heating system since my indy flushed the system about 1 year ago. I haven't had a chance to get it purged yet...

Tonight, I drove the car about 50 miles and shut it off for an hour long dinner. Funny enough, the low coolant light illuminated as I entered the parking lot. It had been almost 3 weeks since it had done this previously. When I restarted it after dinner, the car was missing and there was a large amount of thick smoke coming out the back. I couldn't tell if it was coolant or diesel smoke or ...? It did this for a little bit and I shut it back off. I waited a few minutes and then tried to restart it and there was more smoke .... While it was smoking the injectors were nailing and it was very noisy... it didn't seem to miss, but the poor engine wasn't happy. The smoke finally went away and I topped off the tank and drove it back home where it is sitting right now. Does anyone have any ideas what in the heck is wrong with the poor 300D? It has 232k on it and we've been very faithful in the maintenance, good synthetic oil, etc. The temp gauge has never been in the "danger" zone and it wasn't overheating when it was smoking, etc. Even driving home the temp was right on 80C the entire time. Does anyone have any ideas? I have my fingers double-crossed that it isn't the head... I hope it may be a radiator cap, trapped air in the heater core, etc. Oh, I did notice that it seems to bubble in the expansion tank when I fill it up and I hope that isn't a *bad* sign. Please, please, please let me know your thoughts on this. I really hate to part with the car after all of the time, effort and TLC we've put into it. Heck, it even has new seats and seat covers!

[Motorhead]

Coolant consumption without ANY visable leaks is suspicious. If You see it smoking again on startup, try to get back by the ehxaust and see if it smells like coolant. If it is white, chances are that it has an internal water leak. Are you getting any black residue in the coolant recovery tank?

I know this is little consolation to you but I don't understand why manufacturers use aluminum heads on DIESELS!!

[C Sean Watts]

Is pressure in the cooling system.

AFTER you get it going (assuming it's up to temp) put on gloves and squeeze the top radiator hose. It should have some pressure but you want to be able to nearly pinch it together. It should NOT be as hard as a two liter soft drink bottle-much pressure & little yield.

ALSO (just a guess since I'm not there) have you blocked off your EGR and/or gotten rid of the trap oxidiser? Some 603s also have an under body catalytic converter looking unit that can become blocked and cause LOTS of backpressure.


JUST IN CASE
http://cgi.ebay.com/ebaymotors/MERCEDES-6-CYLINDER-DIESEL-HEAD_W0QQitemZ250037655256QQihZ015QQcategoryZ33617QQrdZ1QQcmdZViewItem

[Marcb]

Thanks for all of the great input and feedback thus far. When the engine was up to temp last night, I did try and squeeze the upper radiator hose together and it was very, very hard. It felt much more like a 2 liter pop bottle and when I opened the recovery tank, it relieved quite a bit of pressure. Interestingly enough, you can also see some moderate bubbling in the recovery tank. And, I did try and take a whiff of the exhaust last night and it smelled like diesel to me rather than a "sweet" smell. It definitely didn't look normal, however.

The trap was removed around 107k and we've put 62k on the car in the last 3 years.

One more thing, I haven't seen any residue at all in the tank and the oil looks great! I just knew something *odd* was up because it started using coolant all of a sudden and I could hear some sloshing noises in the heater core. Also, the "miss" on a cold and occasional warm start was something new too!

Thanks for the posting on the head too! If the car does need some head/headgasket work, it looks like my Dad and I are going to be busy.... I need to find an FSM first.

[Marcb]

One more update: I started it up this morning and it started just fine. I let it run with the expansion tank cap off and you can see this fine wispy smoke coming out of the tank. Any thoughts on what it might be? The exhaust smelled normal and there wasn't any "extra" smoke other than some slight unburned diesel when it first started. Please help and give me some direction. Thanks!

[Brian Carlton]

Originally Posted by Marcb

Thanks for all of the great input and feedback thus far. When the engine was up to temp last night, I did try and squeeze the upper radiator hose together and it was very, very hard. It felt much more like a 2 liter pop bottle and when I opened the recovery tank, it relieved quite a bit of pressure.

You were provided with erroneous information regarding this test.

The system is pressurized to 20 psi when it's fully warmed. The upper hose will definitely feel like a brick at this pressure.

After the engine sits overnight is the point where the upper hose is squeezed for the test. If the hose remains very hard, then you open the cap on the expansion tank. Now, if the hose is much softer, the internal pressure has been relieved. This is a sign that points to a head gasket leak or a cracked head.

If you find this sign, and the engine is consuming coolant, you've got two good indicators that you've got a problem.

Now take a sample of oil and spend $20. on an oil analysis. It will confirm glycol in the oil sample if you've got a coolant leak and then you've now got three good indicators. At that point, you've got your conclusion.

[michael cole]

dont panic.lumpy starts with the 603 engine are quite common.check for coolant leaks very carefully.chances are your coolant reservoir cap may be overpressurizing the system causing a small leak.

[retmil46]

From what I've read on the forum, your symptoms - especally the bubbling and "smoke" coming out of the coolant tank - point to either a bad head or gasket.

[Marcb]

Thanks again for all of your help. I really don't want to give up on this car as we really love it. In all fairness, the engine wasn't consuming much more than 1/2 qt every 5000 miles. We've always fed it synthetic oil and I replaced the vac pump, tensioner, etc on time as well. I went back through the PO's records (we have everything from day 1) and it looks like they R&R'd the cylinder head and replaced the head gasket in 1995 when it had 75,000 miles on it. I wonder if that stressed the head...? It now has 232k and has run perfectly up to this point. The hose test (at least 1 week ago) proved that the system was perfect in the morning. Very soft, no pressure, etc. I remember checking it right after we purchased the car and it would even pull a slight vacuum when it was cold. Any idea what the slight amount of "smoke" coming out of the reservoir might be?

And, thanks Brian. I think a test will be helpful and I hate to run the engine much until we get the problem corrected.

[psfred]

Check for another coolant leak.

That head, even the new one, is very intolerant of overheating, and will crack if you get it too hot. Then you get pressurized cool engines, coolant loss, etc.

First think I would to is replace the cap on the reservoir. A bad one, not holding pressure, will cause the coolant to "burp" out of the overflow tank under the fender -- usually leaves a puddle, but not if it happens on the highway only.

A pressure test of the cooling system will help locate a leak.

"smoke" in the reservior is either combustion gas or boiling coolant.

Peter

[Motorhead]

You can buy a chemical carbon monoxide tester that samples the "air" in your coolant recovery tank while the engine is running. The setup is about $30.00 I believe. I had a VW diesel Dasher wagon that I suspected a head gasket leak. It showed right up.
This gadget is like a big eye dropper that you fill with a blue dyed, carbon monoxide sensitive fluid. You put it partially in the neck of the radiator or coolant tank and squeeze the bulb on top. It sucks the air and any gasses from the tank. If carbon monoxide is present then the blue fluid turns green to yellow with alot of carbon monoxide.

[Marcb]

Funny thing... we have never overheated the engine in the 60+ k miles we've put on the car. I've been very careful with maintenance and it was primarily used for my wife's 110 mile commute. That is why I'm so confused. Other than some lifter noise, it still runs perfectly. The idle is "loping" a little bit, but it has done that for 20k miles or so and I attributed it to the coolant flush with some air still in the system. If it is a head gasket problem, I have my fingers crossed it is only the gasket! I wonder if I should buy the 18 head "just in case".

[Zeitgeist]

Marc, I suspect the loping idle could be associated with leaking delivery valve seals on the injection pump - easy, and cheap to fix.

If you can afford the extra $, I'd go ahead and spring for the #22 head-upgrade, if you're removing the old one for a gasket swap anyway. My engine exhibited the coolant loss problems for a while, until I replaced the reservoir cap. But that didn't fix the underlying issue, which for you is more than likely a cracked head.

I have a few pics here which show what I found when I pulled the #14 head off my engine with 212k miles. Note, mine had multiple head and gasket failure modes at the same time.

[Marcb]

Zeitgeist,


Hey, great to hear from you! Any chance you'd be up for helping me check out the car? PM me if you have some time and I can get your contact info!

-Marcb

[Marcb]

Well, I'm still investigating this a bit further. My wife told me that she's seen a small "trail" of water the past few weeks every time she backs up the car. That tells me that it must have been pushing water out of the recovery/expansion tank while on the highway or something. I'm not sure.... One more update - I'm also told that while trying to start the car it wouldn't start properly a couple of times. After glowing, the starter would engage and the car would act like it was "frozen"... i.e. wouldn't turn over, just dim the dash lights. After the engine was rotated via the belt a couple of times, it would start and run just fine. I hope this isn't another "bad" sign and simply a starter getting old! Any more thoughts?

I have a spare 603 engine on the workbench with 120k miles on it (per the seller) and I don't know if I should simply swap the 2. It also has a 14 head on it and I'm having trouble deciding. Heck, I don't know if I even have a real problem yet! A new 22 head is $1800 plus the cost of new lifters, etc. Please feel free to share any thoughts you might have. I really appreciate it! You guys are great!