My 240D has a compression problem. #4 cylinder is good (320psi) and compression on cyl's 1-3 are a dismal, but identical, 200psi on the nose. before I rip the engine apart to R&R the rings, does anyone know of another explanation for this symptom? I just did a valve adjustment and i have verified the compression results through both the glow plug holes and the injector holes. Does anyone know of something else i can check before the rebuild to make sure it is necessary?

any help would be greatly appreciated!

jnewbold,

There are some techniques for determining where your compression is being lost. One is to repeat the standard compression test, except you add some oil to the cylinder through the hole you are hooking up the pressure gage to, and then repeat the procedure. If the compression gets better, it is because the leak was past your rings and they got sealed by the oil, temporarily. If the results are the same, the leak is either in the head, like valves, or the head gasket. Then there is a pressure leak down test where you pressurize the cylinder with poor compression results, and then listen for where the leakage is, like at the intake or exhaust, or the crankcase. A stethescope or some other device that helps you pick up barely audible noises may be helpful. I have never done the leak down test myself, so I cannot vouch for how audible the leakage will be or how distinguishable the sources are.

In any case it sounds a lot like you need to take the head off, and make some decisions based on what you find at that point. You can have the head checked for cracks, valve leakage and so on, while the cylinder bores can be inspected for damage.

Good Luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Dude I forgot about the oil trick, that's a good idea. I still think you have bad rings. What are the odds of leaking valves or head gasket that yield 200psi in 3 cylinders. You're better off wining the loto in 3 states on the same day. I bet you couldn't misadjust the valves to do that if you tried! Maybe see if you can secure a used motor and we'll swap it out. Should be done in a days work no sweat with the two of us working simultaneously.


Knarf

__________________
'82 300SD

Thanks jim! I just did the "oil assisted" compression test and it went right up to 340psi! Looks like its the rings for sure. Now i gotta look into my options for rebuild or replace. Does anyone know how much i should spend on a motor out of a boneyard?

-John

It's good to see you've come to terms with your loss, he he, not to laugh though. Seriously, check out your options and let me know what's up. Last I checked you could rent the hoist for about 35 bucks from Vista Equipment Rentals. We'll get 'er going.

Frank.

__________________
'82 300SD

Ask Engatwork, he's done it.

(Just search for his name in teh search, it'll show all his threads about the Engine rebuild)

__________________
2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/119226-1982-300d-sale-post852260.html

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP

John:

Just curious - how much mileage do you have on the engine? I just wanted to get a point of reference for what its been through.

Also, what symptoms prompted you to do the compression test? If there were no symptoms and you just did the test for the heck of it, I'd say continue to drive it. If its not using much motor oil you might get a lot of use out of it before an overhaul.

Ken300D

Hi Ken-
I bought her 6 mos ago with 175k on the odo. For a '79, i figured i would have a couple of good years before i had to deal with engine fatigue, based upon the track record of these cars. It was a little slow to start when i bought it, but nothing surprising. about a month ago i started to have real trouble starting it, giving it plenty of glow and cranking it a bunch, but only when she was stone cold. Warm, she ran fine and started right up (2 or three strokes maybe). I figured it was glow plugs , so i replaced them, no difference. I did a valve adjustment, which subsantially helped performance and smoothness, but did nothing for cold starting. I started to have to crank it more and more, eventually needing to jump it now and then. I replced the battery and voila, all good again.....

for about a week, then back to the same thing. I parked it about a week ago and the next morning - dead. I pulled the injectors and cleaned them up a little, checked them outside the engine for pattern - all good. checked the glow while the injectors were out and you could see it fine. Did another valve adjustment. meanwhile i consulted the BBS and ordered a compression gauge from S-sales (30 bucks, sweet deal - thanks to you guys). Comp test showed the results above. that brings you up to the start of this thread.

Its now at 183k and it sits...cold as my heart...on the street . . i just hope i can push it around enough to prevent myself from getting a ticket while i prep for the rebuild.

Anyone in SoCal out there have an engine hoist they are willing to lend out for a weekend?

John:

Just for the hell of it, go to K-Mart or Wal-Mart and get a bottle of Engine Restorer and dump that it and run if a while.

If you just have stuck rings, it may free them up and save you the trouble.

Ditto for changing to synthetic oil, which may also do the job unless the stuck rings have chewed up the cylinder walls.

And, if you aren't using a huge amount of oil, do one of the above and take a longish trip with your foot to the floor -- if your problem is stuck rings, they may free up and restore compression.

I'd be surprised to see three cylinders worn out and one in next to new condition!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thought I would pop in and ask a question. How did you do the compress test? How does it hook up to the engine? Never done one and have thought about checking it out on the SD.

Thanks.

__________________
1994 C280 204k miles

psfred-
Thats a great idea! If it doesnt work out, I am ripping it apart anyway, so im only out 5 bucks or so.
However, can the engine restorer work if i cant get the thing started? should i just dump it down the injector holes? Im pretty sure that putting it in the oil will do nothing, since the oil isnt circulating. likewise, the whole taking of a longish trip isnt going to happen, unless its on the back of a flatbed, and i get the idea that this isnt going to have the effect you are looking for.
One way or another, the ring sticking concept could help to explain the 3 really bad / 1 good phenomena and the sudden decay i experienced (i should point out that i went to a different filling station than my usual one about 2 days before my problems started)

Oh Heck, I guess that my next question for the concensus is:

How do you un-stick rings in a car that wont start?
Could i use something like WD-40 down the injector holes? can i bang on something with a hammer and/or rod? can i sacrifice a chicken to some diety of diesel? how about a virgin? on second thought, it would be easier to overhaul the engine than find one of those. I think i will try to soak the pistons in marvel mystery oil, much like engatwork in thread 24196.

Thanks psfred.

dwcasey-
this is how i did my compression test:
step 1: got the right gauge and adapters (i got it from S-s sales. )
Step 2: got new injector seals. Fastlane or performance products - 2-3 bucks each. These are needed on cars that actually have some compression when the injectors are re-installed. Got new ricirc hose and plug as well.
step 3: pulled the metal injector tubing contraption off (17mm open end wrench). put it somewhere clean (Larrybible recommends using a plastic bag, see '78 300D Injector R&R). i put a clean rag over the IP outputs too.
step 4: pulled out all of the injectors, using a 27mm wrench. took off all the little hoses too. left the seals in for the tester adapter to seat against.
step 5: installed the tester in each hole and crank the engine a few times.
step 6: repeated step 5 for all holes.
step 7: Mopped up the puddle of diesel on the ground. next time i will clamp off the recirculating hose from the IP.
step 8: got online and begged the world for help.

Hope you have better luck than i did. I also pulled out one of the glow plugs and tested through that hole, but it was more of a pain than the injectors due to location.


John

Easier to rebuild than find a virgin! Dude you're hilarious.

One thing to remember, while the decay may seem rapid as it goes from start to no start, the engine's decline was much slower. It started as you said with a little hard starting here and there. Then a month of battery probs...etc... then finally a merciful death. Oh the tradgedy of it all! Whoa, getting carried away there.

Anyway, 3 stuck sets of rings sounds odd. Think about that mechanism. All would have to stick and leak the same amount in your case, I don't think so. When you see uniformity like that, you have consistent wear and tear. As for the forth, if that injector was on the blink, for example, that cylinder would have run cooler and might not have worn so quickly.

Just get the head off, mic the cylinders, get the parts, I'll get some beer and off we go to rebuild the motor.

Frank.

__________________
'82 300SD

I should also add, my car had one cylinder go down. 100K miles later another one did and the motor was finished. The remaining 3 had uniform compression. It exhibited the same symptoms as Johns to the "T" except it took longer as it has an "extra" cylinder so to speak. It had bad rings.

Frank.

__________________
'82 300SD

I got your point about the mechanism frank. However, a gradual decay as you mentioned still doesnt jive with a 200 psi compression (to me). thats 2/3 of where it needs to be. Yes, the decay existed in some degree since i got the vehicle, but the last month has just been rediculous.

but all symptoms aside, there is a known issue with the rings, and itll be 3-4 weeks before i can pull the motor, so i think psfred has a good idea there. heck, the price is right and she is just sitting there. I can soak those things for days.

PV = NRT Once you loose enough P, you don't get the T. You figure your glow plugs are putting energy into the system to get it going. So you had to gradually put more and more energy into it in order to start it. At some point, you you can't put any more engergy into it as the battery and glow plugs have a defined limit to the engergy they can produce and it doesn't start. You likely hit that point and did so gradually over the 6 month period.


Frank.

__________________
'82 300SD