1987 300D odd symptoms.... - PeachParts Mercedes-Benz Forum

Marcb · #1 10-14-2006, 03:58 AM

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 · #2 10-14-2006, 04:41 AM

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 · #3 10-14-2006, 08:45 AM

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 · #4 10-14-2006, 01:38 PM

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 · #5 10-14-2006, 05:15 PM

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!

michael cole · #6 10-14-2006, 06:54 PM

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 · #7 10-14-2006, 06:56 PM

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.

Brian Carlton · #8 10-14-2006, 06:51 PM

Quote:

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.