Greetings all. I have recently aquired a 1978 300D. The PO didn't drive the car very much and didn't do a lot of maintenance other than yearly oil changes. Now that I am driving it daily there are little issues that keep surfacing and need to be dealt with. I've been on half pay for months recovering from knee surgery, so I can't just hand the car off to a mechanic with a list, I need to do a bit at a time myself.

The car itself drives really well. Seems to have plenty of power, idles pretty smoothly. Has more power than the 75 300D I had ten years ago. Does not like going up steep hills, but I suppose that is to be expected. The car does not make any smoke, even flooring it up a steep hill I see nothing in the rear view.

Does not like starting in the cold, I have to leave it plugged in over night if I want it to start and it's below freezing outside. If it sits somewhere for more than 6 or 7 hours after it's last run I have to crank it for a solid 45 seconds to get it to fire. I double cycle the glow plugs, and let them run for 10 seconds after the relay light goes off. It seems like there is one "reluctant" cylinder that doesn't fire up as fast as the others. If the car is warm it fires up almost instantly.

I have had the car for two months now, it has been driven daily; short half hour in town stuff mixed with at least once or twice a week spending several hours on the highway. I have had to top the oil up once in that time. I can't give exact mileage because the odometre/speedo is the Canadian model and of course it stopped recording mileage almost instantly. It was at 330,000 km when it quit.

The car has blowby, it wants to push the oil filler cap off and puffs like a locomotive. Other than that though it idles smoothly and has good power.

So far I've replaced the injector return lines, which were starting to leak and so old they were like straws, and put in a new 850 CCA motormaster battery that cranks the car over with a lot of authoritah.

Here is the list of issues, which should I tackle first?

(1) The glow plugs are the old loop style. They are at least 12 years old. One plug was replaced 12 years ago, the others must be older than that. The relay light works as it should, and the zig zag glow plug wires get fairly hot; the one closest to the rad actually melted an exploratory pen cap. I want to do the replace with pencil plugs things.

(2) The alternator belt is loose and somewhat glazed. The car squeals if it's a "wet" (snow is melting) morning and I put the headlights on. If it's dry or I leave the headlights off it doesn't squeal. It charges the battery up (I never lack for amps no matter how much I crank or how many times I start the car in a day). I tried the soap trick and the squeal stopped for a while.

(3) The air breather elbow hose that connects to the top of the valve cover is leaking oil right where it connects to the valve cover. It's a fairly slow but steady leak down the passenger side of the engine. If I clean off the top and passenger side of the valve cover it'll be oily again after a day.

So how should I tackle this and which one should I do first? Any feedback or advice would be greatly appreciated, and have a good day everyone.

When was the last valve adjustment done? Tight valves will lead to hard starts when the engine is cold.

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'83 300D, 126K miles.

Last valve adjustment is "unknown". Would not surprise me if it was "12 years". I should probably add that to the list.

If I were you I would tackle those jobs in the order you've written them.

#1 needs to be fixed ASAP - you don't want an electrical fire. You don't really need to do the upgrade - you just need to make it safe.
#2 needs to be fixed soon so you don't end up with a flat battery.
#3 can be fixed later on - whilst you are figuring out what's gone wrong be sure to replace the valve cover gasket as well - these often leak as well.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

!! I thought those wires were supposed to get hot. That is good to know.

I had the plugs upgraded on the 75 I had and it made a HUGE difference, that's why I was figuring while I was replacing them I might as well improve it. It seemed like a job I should be able do myself as well; remove old plugs, put the "oversized" pencil ones in, attach new wires, don't reattach ground wire. Get the kit from m*source to idiot proof the experience.

Ya I was thinking of doing this first, even though the thought of lying on my back in the snow is not appealing. I'd rather have a flat battery than a bonfire though.

That could roll into adjusting the valves. Adjusting the valves myself is something I'm not sure I should do myself, it seems like it would be easy to screw up.

Welcome and congratulations on the car.

Overall for 330k kms on the odometer, assuming this is the original motor, it sounds like it performs well for a car that came out of the hands of an unenthusiastic owner.

The blowby is sort of to be expected... but I wonder if that is in part because it sounds like the car probably sat for extended periods. It's possible that the rings will come back to life a bit as you drive the car a bit more. I have purchased three cars that sat for long periods and on two there was a difference after a few months... the third never got better.

I didn't see a mention of fuel filters. If you haven't changed them yet, you should. A partial fuel filter blockage would contribute to the lack of enthusiasm for hills.

You do need to get the valves adjusted before you really know for sure how the car starts and performs.

If after the valve adjustment and fresh glowplugs it still doesn't like starting in the cold, you could consider doing the upgrade to manual preglow controller. Of course you can just do multiple glow cycles and achieve the same result, but I find the manual control more convenient (I have it on my '78).

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

If changing the Fuel Filters does not help swap the Position of the Fuel inlet Hose with the Fuel Outlet Hose. Make sure you have at least 1/2 Tank of Fuel because this bypasses the Fuel Tank Screen and draws Fuel higher up inside of the Fuel Tank.
If performance improves your Fuel Tank Screen is restricted. Only do this for the test as bacause the Fuel is being drawn higher in the Tank that means you will run out of Fuel sooner than your Gauge shows.

Also if the Linkages or the Throttle Bushing on the Fire Wall are really Sloppy the Throttle Lever on your Fuel Injection Pump will not move far enough and you will be slow.

With a cold Engine reach over and hold the Throttle Lever on the Fuel Injection Pump while someone steps on the Accelerator Pedal and watch how much Play is in the Linkages.


Things to check:
The Oil Cooler Hoses
If an Auto Trans; the Oil Cooler Hoses for that
The Drive Shaft Flex Discs
The Drive Shaft Bearing Support
The Rear CV Axle Boots (Mercedes fills them with Oil; if the Boot leaks all the lube comes out)
DIY Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum

PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles

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84 300D, 82 Volvo 244Gl Diesel

Generally speaking when plastic parts are melting that's not a good thing. To be sure about this I reckon you're best off posting up a picture if you can, just to make sure I haven't gotten the wrong end of the stick.

Adjusting valves is a pretty simple process so long as you take your time and use the correct tools. If you are nervous about doing this then make sure you have plenty of time - say as much as a weekend (which it shouldn't take) just in case. There's no point getting stressed. That's when things will go wrong and you'll spend ages adjusting an exhaust valve to the inlet spec - doh!

For the correct tools you'll be able to find many threads on the subject here. (If you get stuck searching for threads please let me know and I'll help - but it is better for everyone if you get to grips with searching for your self!)

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I would suggest upgrading to the pencil style plugs...the old may be fine but if one burns they all go and they are good for engines that are worn.

I would also suggest to get the wrenches and learn how to do your own valve adjustments.

What you will find out about the cars that sit a long period of time, is that they gum up and carbon builds up....you'll need to go in and adjust the valves probably every 1000 miles because they were never adjusted as they should be..

You will also want to do a lot of oil changes, you will see that the oil will become very thick because once the valves are in spec and you start driving it....the oil will do is job cleaning the gunk/carbon out of the engine..

On my car, the valves were all tight and to the point where the nut could barely break free...checking the valves and adjusting them ever 500 miles slowly freed up massive amounts of carbon....I would do an oil change every few month and the oil filter would weigh 20lbs....from sitting, not being driven at high speeds and not having valve adjust really clogged my engine up...plus the owner was using wvo which made it worse..

Would love to see photos of your car too!!!

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#1 sounds like normal operation for the loop-style glow-plugs. Isn't the zig-zag wire supposed to get hot? Why is that a fire hazard?

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DrDKW

Sorry yes the zig-zag wires do indeed get hot - I think I got fixated on the melted plastic bit of information...

...by the time I put up my second contribution to this thread it had me wondering exactly which bit was causing trouble. If there's something rubbing up against these wires that shouldn't be there for example then there could be trouble. That's why I asked for a picture - just to be sure. I'm still uncertain about which bit of plastic has melted.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

When the glow-plugs were switched on, the OP tested the circuit by touching the plastic tip of a pen (pen cap) to the zig-zag wire, so of course the plastic pen-cap melted.

Happy Motoring, Mark

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DrDKW

The alt belt slipping would be high on my suggestion list. That squealing sound.. How embrassing. Can be a bit of a PITA too with the toothed bolt design. You'll need three hands or you'll need to get a fine balance between loose but not too loose on the alternator bolts so that you can make the adjustment then get it snugged up right away. Just make sure you explore to operation of the mechanisim fully before you go a try to tighten up everything as to avoid potential damage to the toothed bolt. Also, plan on getting a new quality belt to avoid problems down the road.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Oh right now I get what was going on.

Sorry for any confusion I've caused.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Sounds like there may have been some polymerization of the oil from the wvo and it took some time to get it loose and all collected in the oil filters. Part of the unheated wvo can get to the walls of the cylinders and down past the rings accumulating in the oil over time.