Looking for some advice/help on a W115 240D!!

[Army-Ant]

Hello...I tried posting this in the "Vintage Section" and got no responses...hopefully this is the place to ask
Im new to the MB scene. Ive got alot of questions (some of them probably painfully obvious), but I am not the wrencher that some of you appear to be. So bear with me, please.
(Same story, new guy) I bought this 76' MB 240D W115 (115.117, D-4, fuel injected, auto trans.) a few days ago. It starts and runs OK...but there are some issues that I could use some help with.

1) It appears that oil leaks from the oil filler cap..not alot but enough that its noticeable...the cap looks aftermarket...it fits a little less than snug. The PCV valve does not appear clogged. What could the culprit be?

2)Can someone explain glow plugs to me in plain layman English?

3)While on the issue of glow plugs, the round thingy on the dash that is supposed to glow before starting...does not. When starting, I wait about 20 seconds before pulling the start knob...but it doesnt always start on the first try....it takes about 4-5 attempts holding the knob out for about 8-10 seconds...before it will turn over. Does this mean my glow plugs are bad or dirty? Should they be replaced? I read somewhere in here that someone cleaned them???

4)On replacing things...what should be done as far as maintenance? Change oil, oil filter, fuel filter (are there 2?), belts...what else?

5)The A/C still works, but makes a loud crunking noise only when idling, it goes away when accelerating...what could this be? Maybe a loose belt...Is the belt thats positioned the highest and farthest left (if looking at the engine from the front) the one attached to the A/C compressor? If so, it has about a 1/4 inch in play...should it be tighter? Could this be my crunking noise?

I'll stop here for now.
2 more questions...thats it, non mechanical...
Is there a place on the web that sells pre-cut carpet for this model Benz? Are the Haynes manuals any good?
Thanks in advance to all those that may reply. Any help is truly appreciated. I hope this is the right place to post my questions and that I can become a regular poster on your forum. Thank you.

Anthony
76' W115 240D

I'm not an expert on the W115 240D, but I can give you some basic answers:

1. The original oil cap was metal, but the replacements look like this:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ425G02GFSB&year=1976&make=MB&model=240-D-001&category=All&part=Oil+Filler+Cap

You can also replace just the gasket:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ425G02GFSB&year=1976&make=MB&model=240-D-001&category=All&part=Oil+Filler+Cap+Gasket

I find that putting a little grease under the cap also helps seal it.

2. Glow plugs are simply electric heating elements that pre-heat the air in the cylinders so the engine will start on compression. They do burn out, sorta like light bulbs.

3. Your car has glow plugs wired in series such that if one burns out, none will work, which is probably why the light is not coming on and the car is hard to start. The glow plugs look like this:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ425G02GFSB&year=1976&make=MB&model=240-D-001&category=All&part=Glow+Plug

You should be able to identify the failed plug(s) with a volt meter. If you search, there is a bunch of info here on trouble shooting glow plugs.

4. Regarding maintenance; Change oil/filter (normally 3000 miles for conventional oil or 5000 miles for synthetic - use a diesel rated oil), fuel filters (There are 2) that should be changed if you notice a lose of performance:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ425G02GFSB&year=1976&make=MB&model=240-D-001&category=All&part=Fuel+Filter

Belts and hoses (just like any other car), auto transmission fluid/filter (every 30K miles), adjust valves (every 15K miles), coolant (every 2 years with MB coolant or Zerex Z05), I'm sure I'm forgetting some.

5. The AC noise is not normal, start with the belt and see if you can locate the source of the noise (hopefully not the compressor).

6. These guys sell carpet sets, but you may find better prices elsewhere:

http://www.adsitco.com/category.asp?CID=1558&VID=

7. The Haynes manuals are "OK" for minor stuff and wiring diagrams, but no substitute for the actual factory manuals. It's probably worth picking up a Haynes (I have one).

This is the best place to post diesel related questions.

Hope that helps.

[Army-Ant]

Thanks Craig...I was beginning to think I was in the wrong place...again.

About the glow plugs...cant I just buy a set of four from Autozone and replace them, instead of trouble shooting them?
Do you have a preference for diesel motor oil?
Whats this about purging after changing fuel filters? I read something about it in the owners manual but dont fully understand.
Is there some sort of order of priority in which I should begin the maintenance? I guess...what should I do first...then so on....

Again...thank you for the advice and the links.

Replacing all the glow plugs is probably a good idea, buy Bosch or Beru brand. I would do that first.

There are lots of opinions on oil, but the most important thing is to use a diesel rated oil. If you want to use conventional oil, shell rotella 15W40 is good (maybe a little heavy for cold weather starting). If you want to use synthetic, Mobil 1 5W40 and shell rotella synthetic are both good. I would recommend changing conventional at 3000 miles or synthetic at 5000 miles (the cost will work out to be similar), again there are many opinions.

I would do the glow plugs first if they are not working correctly. I would also try to find out why your AC is making noise before something is damaged. Regarding maintenance, do you have any records from the previous owner? If not, I would change the oil first and then start working my way through everything else.

When you replace the large fuel filter, you have to "prime" the system with a small hand pump or the car will not start. I'm not certain where the pump is on your engine, look around the are of the fuel filters. It's also a good idea to carry spare fuel filters and the appropriate tools to replace them, you can get stuck if the filters clog.

[R Leo]

That knob is called a "Gorilla Knob". To start, turn the key to ON and pull the gorilla knob until you feel a little resistance and can see the idiot lights dim slightly. Hold at that positon until you see the GP indicator (salt shaker top looking thingy) above the steering column glowing. Pull a little further and she should fire off. I have to pull on mine for at least 45-60 seconds before I can see the glow in the dash indicator.

FWIW, in warm weather (>90°F) these engines generally don't need anywhere near that much glow time. On my 115 5-10 seconds usually will do the trick. If the engine is hot, I just yank it and go.

[Army-Ant]

Problem is, I dont see the glow at the GP indicator light. I plan I buying a set of GPs this afternoon. Any special advice/tips on switching them out. I bought the oil filter, will buy the oil later as well.
Im gonna try not to run the A/C until I can get it to a mechanic. Switching out belts is above my ability level.
Thanks for the input.

Pay attention to the order of the wires and insulators on the glow plugs when you remove them so you put the new ones in correctly. Small hands help.

[pdxwaker]

Originally Posted by Army-Ant

Problem is, I dont see the glow at the GP indicator light. I plan I buying a set of GPs this afternoon. Any special advice/tips on switching them out. I bought the oil filter, will buy the oil later as well.
Im gonna try not to run the A/C until I can get it to a mechanic. Switching out belts is above my ability level.
Thanks for the input.

This isn't necessarily a problem. If the car starts, the plugs are working (at least somewhat). Both of my 220d's have never had working salt shaker indicators though I've verified that they draw the proper current.

If you're going to the trouble of replacing the GPs anyway, I _strongly_ recommend that you upgrade to parallel style plugs. This will greatly reduce your glow time and give better starts by far. They incremental cost over buying new series plugs isn't much.

The parallel upgrade is pretty simple to do. Short out the salt shaker element w/a piece of 12 or 10 Ga solid romex. Replace the plugs. Replace the resistive elements between plugs with heavy Ga wire. Remove the grounding strap from the front-most plug. You shouldn't need a relay if you have the gorilla style starting knob. Do some searches on this upgrade but be careful to differentiate between relay based GP systems and gorilla knob style GP systems (there are 115s with both styles).

[R Leo]

Originally Posted by Army-Ant

Problem is, I dont see the glow at the GP indicator light. I plan I buying a set of GPs this afternoon. Any special advice/tips on switching them out. I bought the oil filter, will buy the oil later as well.
Im gonna try not to run the A/C until I can get it to a mechanic. Switching out belts is above my ability level.

I'm not being scarcastic but, if changing belts is beyond you then changing the oil/filter on this particular engine may be more than you want to get into.

Changing the oil filter in the older 616 engine is a gold-plated PITA.

[pdxwaker]

glow plug upgrade:

115 Glow Plug Upgrade

[Army-Ant]

Not at all R Leo. I have a 67 IH Scout with the canister style oil filter. Ive changed these many times. Unless the MB filter removal and replacement is completely different.
Thanks pdxwalker...but Im think Im just going to swap out the existing GPs.

The belts aren't really that bad either, just a PITA.

You may want to consider the GP upgrade for a future project, this is the upgrade kit:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ425G0TB09Y&year=1976&make=MB&model=240-D-001&category=All&part=Glow+Plug+Kit

[Army-Ant]

Any advice on replacing belts???

[KylePavao]

I own a W115 Ant, and they are fun to work on if you don't mind getting dirty.

I personally hate replacing belts. I have a mechanic who does it cheap, so I tend to bring it to him.

The oil filter is the canister under the area roughly where the injection pump is. Note: You will get dirty, and it will be black black oil.

I'd replace your four plugs with four new Bosch OEM plugs. I'd advise against upgrading to the new type, unless you also buy the relay; some may not agree with me, but the new pencil type plugs draw a lot more current, and the stock relay in my 300D would not handle it. If you want your dash light and original arrangement to work as it came from the factory, buy the OEM plugs.

Feel free to PM me with any W115 related questions.

Regards,
Kyle

[Army-Ant]

Thanks Kyle for the offer to PM you...I have lots of ?s.