Finally did my compression test (sort of) - PeachParts Mercedes-Benz Forum

mikeyfev1 · #1 01-08-2011, 06:38 PM

Because of this forum I decided to do a compression test on my recently acquired 1985 300D KaliKar before getting serious with money and time. The results are:

#1 450 lbs
#2 ???
#3 400 lbs
#4 450 lbs
#5 450 lbs

The bad part is that I couldn't do cylinder #2

I was doing the "glow plug" method. Managed to rip the screw-tip off plug #1--the little nut was so tight and corroded on. BTW, has anyone noticed that little glow plug wire nut is SAE 5/16"? Not quite 7mm or 8mm.

As soon as I pulled out a nice new 5/16" wrench those nuts came off easily.

Anyway, I was using my new diesel compression tester from Harbor Freight. Gauge goes to 1000 lbs. Could not connect to cylinder #2 because I couldn't fit all the adapters between the head and a protruding box on the block-side of the IP. You install a glow plug fitting, which sticks out about as far as a glow plug, then a right angle fitting, which wouldn't fit on #2, and then click-on the gauge fitting.

So I'm going to presume for now that #2 is OK. The engine was starting quickly in the cold (well, in Houston cold

) but had a lot of off-throttle clattering (meaning like when coasting down to a stop from freeway speeds). The driver-side engine mount is squashed like play dough in a press, the right-side engine shock is missing and I want to install new injectors. I have performed 2 valve adjustments (second one a few hundred miles after the first to confirm). After all of that I hope the clattering goes away. What are the symptoms of a spun rod bearing?

Aquaticedge · #2 01-08-2011, 07:04 PM

How many miles? was the engine just rebuilt?

layback40 · #3 01-08-2011, 08:41 PM

Good numbers !!
What makes you think it has a spun rod bearing? You would hear it when stationary.
you may just have noisy injectors. If you do #2 & its over 400 I would not be doing too much to it. Does it have good oil pressure?
How is the vac pump?

mikeyfev1 · #4 01-08-2011, 10:05 PM

OK, so I will start with the engine mounts and oil lines. Will re-evaluate after that.

I forgot, its very possible that a very worn timing chain rail is causing the clattering. I did the simple stretch test for the chain (align the camshaft mark to the mark on the camshaft tower) and it showed 2 degrees on the crankshaft pulley.

Let me go check the car history that I have and see about engine rebuild/replacement.

mikeyfev1 · #5 01-08-2011, 10:34 PM

Original purchase was by a Houston, TX resident; but the car was purchased from Silver Star A.G. in Sherman Oaks, CA. There's probably a story there.

The records I have are the Mercedes Maintenance Booklet, from owners 1 and 2. Records extend to 8/12/2001 @ 180,365 miles. All what you would expect, oil changes, filter changes, a few brake services, a starter change on 12/14/1998.

So there were only 70K miles put on the car in the last 9 years. I doubt the guy I bought the car from did much of anything to it. He said he was using it as a work car. Drove himself and a few other blue-collar workers to/from work.

Oil pressure is good. When warm and idling, 1.5 bar, from 1800 rpm and up it pegs the 3 bar gauge.

Vacuum pump seems good; all vacuum functions work, but there is a leak somewhere; can't lock the doors after about 10 minutes after shutoff.

I worry about a spun rod bearing because of that d$*&^...darned clattering sound. Can clearly be heard over the engine noise.

Aquaticedge · #6 01-08-2011, 11:25 PM

Record the sound if you can. has the timing chain ever been done?

W124 E300D · #7 01-09-2011, 07:30 AM

Engine mounts are your top priority.

You can't really tell anything else for sure until they are done.

WHEN you have changed the mounts you will understand what I mean.

Spun bearing shells, on a running MB diesel with oil pressure? What you smoking dude?

funola · #8 01-09-2011, 09:16 AM

You may want to verify the accuracy of your HF gauge. Mercedes spec for a new engine is 22-24 bar (319- 348 psi), wear limit is 15 bar (217 psi)

If it is accurate, your combustion/pre-combusion chamber may be packed with carbon, raising the compression ratio.

Quote:

Originally Posted by mikeyfev1

Because of this forum I decided to do a compression test on my recently acquired 1985 300D KaliKar before getting serious with money and time. The results are:

#1 450 lbs
#2 ???
#3 400 lbs
#4 450 lbs
#5 450 lbs

The bad part is that I couldn't do cylinder #2

I was doing the "glow plug" method. Managed to rip the screw-tip off plug #1--the little nut was so tight and corroded on. BTW, has anyone noticed that little glow plug wire nut is SAE 5/16"? Not quite 7mm or 8mm.

As soon as I pulled out a nice new 5/16" wrench those nuts came off easily.

Anyway, I was using my new diesel compression tester from Harbor Freight. Gauge goes to 1000 lbs. Could not connect to cylinder #2 because I couldn't fit all the adapters between the head and a protruding box on the block-side of the IP. You install a glow plug fitting, which sticks out about as far as a glow plug, then a right angle fitting, which wouldn't fit on #2, and then click-on the gauge fitting.

So I'm going to presume for now that #2 is OK. The engine was starting quickly in the cold (well, in Houston cold

) but had a lot of off-throttle clattering (meaning like when coasting down to a stop from freeway speeds). The driver-side engine mount is squashed like play dough in a press, the right-side engine shock is missing and I want to install new injectors. I have performed 2 valve adjustments (second one a few hundred miles after the first to confirm). After all of that I hope the clattering goes away. What are the symptoms of a spun rod bearing?

chasinthesun · #9 01-09-2011, 02:59 PM

You can bring it by and compare it to some of mine ,these engines are not quite while idleing ,I like the clatter of a diesel motor ,it sounds like a tractor.Im near the woodlands.

chasinthesun · #10 01-09-2011, 03:04 PM

Oil lines are easier as your doing those motor mounts. The oil lines run up to the oil filter housing ,pre bent to hug the block in its travel to the housing.You dont have much room otherwise, it made a big difference when I replaced these pieces on my 300sd.

chasinthesun · #11 01-09-2011, 03:20 PM

The kit from HF should also do your #2 hole by taking the injector out and putting the right fitting at the injector.Remember to take the compression washer out with a stick magnet before trial.

leathermang · #12 01-09-2011, 04:16 PM

Quote:

Originally Posted by mikeyfev1

I did the simple stretch test for the chain (align the camshaft mark to the mark on the camshaft tower) and it showed 2 degrees on the crankshaft pulley.

The Factory Shop Manual specifically says those marks are for Initial alignment only... DURING assembly of the engine. They do not measure the chain elongation... lots of good info in the archives on how to do it correctly.

mikeyfev1 · #13 01-09-2011, 06:04 PM

Quote:

Originally Posted by chasinthesun

The kit from HF should also do your #2 hole by taking the injector out and putting the right fitting at the injector.Remember to take the compression washer out with a stick magnet before trial.

Yes, I will eventually do this. I don't yet have the tools to pull the injectors.

Its a 27mm deep socket, right?