Howdy,

I'm new to this forum, though i've read some very useful posts here in the past as a guest. I bought my 240D in 2007. I've been taking care of it myself since then just using chiltons/haynes and a few threads here and there that I've googled etc.

I regularly change the pre-filter (with oil changes) and the secondary fuel filter every 6 months or so. I've adjusted the valves every six months or so too. I run Rottella synthetic motor oil.

The previous owner had the trans replaced in 2005 by a mechanic that specialized in mercedes down in Miami... I and just recently changed the trans fluid and filter (though I couldn't get the torque converter drain plug alligned with the access hole so it was only a partial drain... long story but i'll probably just do it in my driveway rather than on the base with their lift and get the plug out [I'm in the service and we have hobby shops with lifts and lots of rules]).

I run regular petro diesel. The prior owner ran a petro bio mix. But no WVO that I know of. When I first got the vehicle my prefilters would clog when the tank got low. I bio shocked a few tanks of dino diesel and reguarly changed the prefilter and eventually the secondary filter and haven't had much trouble since beyond what I'd consider normal particulate accumulation in the prefilter. (my other cars are GM 6.2 diesel trucks) I have run a tank or two treated with Slick 50 "Diesel Cleen" every 4 months or so.

Any ways I've noticed since I've owned the vehicle that when it was cold and asked for more than idle power would knock, so I got in the habit of letting it warm up... it never knocked at idle... until lately. Over the last 4 years or so I've noted that the water temp it would need to get inorder to apply more than idle power has crept up from 100, then 110, then 120 etc until now it has to be at 175 or if I put my foot into it, it will knock. Also the other day when the temp was 40 deg and I started it, it knocked until it warmed some then settled.... but I had to get the water temp up to 175 for it to drive without knocking....

I've parked the vehicle until I can get this figured out.

I'm thinking the IP timing has been slipping, but am looking for advice. I just ordered a drip test 'dripper' and am waiting for it to arrive. I'm looking for advice on fixing a knock that goes away as the engine warms.

Also I brought up the automatic trans issue as it seems the trans pulls a lot at idle in drive, and shutters in reverse... Especially if I apply the brake or stop the vehicle. Since I changed most of the fluid and filter it has improved but its not totally cured... It did seem to run better as the car warmed up after the change. I'll probably run the mix of old an new fluid a while and then do a proper drain of the Tq converter and trans with another filter change and see if it helps (perhaps varnish has built up in the trans?).

Looking forward to your insight. I really appreciate all the help I've gotten in the past from just reading posts here. I ran a search but didn't find much on knocking that went away with warming up.

Thanks!

Tom

Sounds like injector nailing to me. Try starting the car cold, and let it run. Then loosen each injector line nut at the injector one at a time and rev it a little and see if the knock is still there or if the knocking changes. If no change. Then that injector it likely okay. Move to the next. If the knocking goes away completely with one injector then you know that injector is in need of work. If the knocking is lessened with a few injectors then you likely have several that are nailing. Though if one it bad then the others are likely not far behind, in which case you might think about some new Monark nozzles to put into your original injector bodies.

Nailing is when the injector's pop pressure has become too low and it's injecting fuel in too soon and the fuel is pre-detonating. Causing that hammering noise.

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Hello!
Welcome to the forum,
the noise you are describing sounds to me like injector hammer.
Pull the injectors, and have them pop and spray pattern tested, replace the leaker nozzle.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

You're on the right track. Check timing first. Once it is precisely set, if the noise remains, have the injector patterns and pressures tested.

Good luck and welcome to the forum.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Thanks for the good speedy advice... Any suggestions on finding a shop that can test the injectors? What is a ball park price I should expect for testing them?

It might be easier to use the broom handle trick one end against engine, other end on your ear, using like a stethescope) to locate the cylinder you hear the knock coming from!!!! Then throw in a junkyard injector, or two, until you find one that works without knock/nailing.

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1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002

Check the local yellow pages for a truck repair shop to perhaps find somewhere to check them.

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83 SD

84 CD

i just had a similar situation, it ended up being a bad injector- i did the test described above, found 1 injector that was the culprit and swapped it with a known working used injector and the problem went away. it was a quick $10 fix for now, til i can get all of them rebuilt with new nozzles and pop tested properly.
once you pull an injector, you will need a new heat shield for each one when re-installing it. so even if you pull yours and have them rebuilt, either get heat shields from the rebuilding shop or order some online so you have them when you put your injectors back in.

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k

Where was everyone when I lived in SoCal (Long Beach)??? I've been seeing the SoCal crowd coming out of the woodwork in the last few weeks!!!! Well, actually, I can't complain, because when I needed mechanics, I got my (very good) referrals from here. . . . one in Santa Monica, and another near Fredericksburg, VA.!!!! BTW . . . I have a very good mechanic for general stuff in LA, and he loves MBZs, and has a complete machine shop . . . should anyone need to know. He is weak on some of the specialty stuff . . . such as the HVAC systems.

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1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002

oh, and before you try to pull an injector, be sure you POP the wrench, don't use steady pressure to remove from the head. I've had Prechamber rings stick to the injectors before, and you do NOT want to deal with putting them back together...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Good to hear you have been changing the secondary fuel filter every six months on your 240d. If you install a pressure gauge to monitor the pressure in the base of the injection pump. It will tell you when the filter should be changed.

The total cost of this is approxamatly two secondary filters. So basically it is free if not saving money as well. There are several other benifits as well in having that gauge installed.

Also benifits to reduce the amount of filter changes by simply replacing the piston pressure spring in the lift pump with one from any junk 617 or five cylinders lift pump. This elevates the pressure out put of the 616s lift pump.

This way it can deal with filter restrictions much better delaying further the change intervals required of the secondary filter. You may find if the fuel is clean in your area that a filter may only be required every few years for example. Or if you pick up a load of really dirty fuel you need it now.

For many reasons you especially always want decent fuel pressure in the base of the 240ds injection pump. This is not expensive to have and monitor. Low pressure may result in paying a price you do not want to pay over time.

Those that only change fuel filters in 240ds when they are totally restricted or performance has droped off may pay too high of a price in my opinion. Plus without the gauge they either are not really sure why performance has dropped or are unaware it is substandard to start with.

Ok... Thanks for all the advice.

I called a mechanic and ask him where he'd get them tested. He recommended a local diesel shop that will test the injectors if I bring them in. Called that shop... He said a rebuild would cost about $60 per injector if needed. and if they didn't need it $8 per injector for the test. I'm wondering if he just swagged price based of a typical job... most stuff on this car has cost me more than the 'typical'

I'm thinking about removing all 4 and getting them checked and not even trying the loosening to find the bad one approach... figure it would give me more piece of mind. I doubt they've ever been rebuilt. Where do I get 'heat shields' if I need to replace them after a pull the injector?

Oh and I've got two freeze plugs on the passenger side of the engine weeping/leaking... any suggestions on where to get them and removing the old and putting new in?

For the parts you need, click on the "Buy Parts" button above.

There is a forum member here that rebuilds injectors.
http://www.peachparts.com/shopforum/members/c-sean-watts.html

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83 SD

84 CD

You know I tried that before I posted... and it didn't work... I couldn't find much of anything for my car... so you post to do it and now it works just fine, and i'm finding lots of little things I couldn't get out of the junk yard! Thanks again.

If you're going to be removing your injectors, it might be a good idea to check the compression of your cylinders while yer in there.

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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)