cylinder head replacement - PeachParts Mercedes-Benz Forum

benzdude42 · #1 03-12-2013, 03:20 AM

I'm pulling the head on my 300d in about two weeks. my engine has been knocking/ticking from the day i bought it a year and a half ago. i've pen pointed it to piston 3 and 4 and am hoping that i just have a bad head. i was wondering what i should do and or get to prep for the project.

Stretch · #2 03-12-2013, 04:34 AM

If you want => I'd try and get some more advice concerning the type of knocking / ticking you've got. From the information you've given in this thread so far a "bad head" doesn't sound like a likely possibility to me.

But to answer the question about preparation for the project the first thing I'd do is read chapter 01-145 in the FSM

Simpler=Better · #3 03-12-2013, 10:15 AM

I'm 85% confident that your injectors are worn out and your timing is off. Send your injectors out to be balanced, get new nozzles. While the car is apart, measure and correct the chain stretch, replace the timing tensioner spring, and then set your Injection Pump timing. Once the injectors return to you put them back in and she ought to run smooth.

pinkfloydfan810 · #4 03-12-2013, 04:03 PM

Doesn't sound like a head. If you have access to a digital camcorder or digital camera with video compatibility (being the 21st century, most cameras do). The video might point us in a better direction. As I also believe it could be injectors, I recommend what was said above. Also, at this point I'd run injector cleaner through the fuel system to see what nastiness comes out if you do put in new injectors. Good luck and keep us updated.

dude99 · #5 03-12-2013, 04:48 PM

I'd do a compression test before I pulled the head off. It should be telling... I also assume that you've adjusted the valves?

Brian Carlton · #6 03-12-2013, 06:29 PM

Quote:

Originally Posted by benzdude42

I'm pulling the head on my 300d in about two weeks. my engine has been knocking/ticking from the day i bought it a year and a half ago. i've pen pointed it to piston 3 and 4 and am hoping that i just have a bad head. i was wondering what i should do and or get to prep for the project.

"Knocking" can be anything from a fuel injector to a main bearing. What it cannot be is the head, unless a valve is hitting a piston (highly unlikely).

You mention that you have pin pointed it to piston 3 and 4. Can you please elaborate on your diagnosis?

I agree with the aforementioned posts with regard to a sound byte of the engine prior to head removal. Many of us can separate the issue via sound if you get right up close and personal to the engine.

benzdude42 · #7 03-12-2013, 08:02 PM

i've rebuilt the injectors, run the cleaner through it and done the values 4 times. i'll record the sound tonight and upload the video to the website for you guys. pretty much at this point i'm thinking about taking the head off to see if its a bad piston and or head. where i live, its super hard to find a engine to swap in and i'm about ready to just do a basic rebuild(rings, sleeves, bearings, and timing). i've ran into other thread's with the same sound but different results, from a cam braking in 3 places after a year, to a piston slap gone wrong. i have this engine and another that came with the car for parts. i figure out of the two i can get 5 good pistons and a crank.

benzdude42 · #8 03-13-2013, 12:26 AM

the knock is coming from piston 4. today i removed the injectors and turned over the engine with out the injectors with no knock. although it didn't have any compression in the pistons at that point. then i put the injectors back in tell the knock came back. then i switch the injectors and the knock was still there in piston 4. i pored thick oil into the piston and the knock was still there, wouldnt this mean that the values in piston 4 were bad?

dude99 · #9 03-13-2013, 12:33 AM

its possible, I'd run a compression and leak down test

benzdude42 · #10 03-13-2013, 12:45 AM

Mysterious 1985 Mercedes 300D Engine Knock - YouTube
theres the knock.

whunter · #11 03-13-2013, 02:34 AM

Quote:

Originally Posted by benzdude42

Mysterious 1985 Mercedes 300D Engine Knock - YouTube
theres the knock.

I am going to assume:
# The cam lobes look good on #4.
# You inspected the #4 pre-chamber, and found the ball undamaged.

Swapping the injectors removed them as direct cause.

At this point there are few (general) possible causes:
#1. Damaged: Cylinder head, valves, guide or gasket.
#2. Damaged: Injection pump delivery valve calibration.
#3. Damaged: Rod bearing, rod, wrist pin, piston skirt, ring, cylinder wall.

Or stated another way:
* Head related.
* Injection pump related.
* Engine short block related.

Of the three options a failed head gasket or cylinder head is IMO cheapest.

Please read this thread:
The sound is identical to what my 240D was 1980 240D CRACKED cylinder head + cavitation damage
Please note the (now twice removed) previous owner rebuilt this 240D engine roughly 3000 miles before I touched it, and did not notice the cracks.
IMO: Absolutely zero blame for missing the cracks, I spent hours cleaning the suspect areas before finding them.

The good news is that after replacing the 240D head, MPG and power improved so much that I bought the car.

SOLD: 1980 Mercedes W123 240D – China blue

If it was my personal car, the head would be coming off for inspection.

You may want to read this thread, it took him serious cleaning to find these cracks on a single cylinder. Post# 12 of this thread has further examples of what you may find.
300D overheated and blown head gasket...What to do?

This entire thread will interest you, but post #44 and #49 show another example of cracks on one cylinder. Post# 144 details the cleaning used to find the cracks.
1985 300TD head gasket repair
1985 300TD head gasket repair

Diesel cylinder head issues thread

.

Stretch · #12 03-13-2013, 04:58 AM

@benzdude42

Make sure you read this bit!!!! =>

Quote:

Originally Posted by whunter

I am going to assume:
# The cam lobes look good on #4.
# You inspected the #4 pre-chamber, and found the ball undamaged.

...
.

benzdude42 · #13 03-13-2013, 10:47 AM

yep cam looks good and the per camber is still here(cleaned them when the injectors where out). i just ordered the 12 point star to remove the bolts is there anything else i might need other than the basic tools one would have working on other engines? i'll be sure to post pictures about what i find as i find it. there are alot of 300d's with this weird knock.

Simpler=Better · #14 03-13-2013, 11:23 AM

No other special tools, maybe an engine hoist to pick the head. Don't forget to remove the regular allens up front when you pull the head.

You will want to buy a box of 3M blue (aka soft) rotary scrubber pads. They make removing the old headgasket a dream. If you have air a HF 1/4" rotary tool is great (~$20), if not a regular drill works too.

EDIT: a 1/4" air grinder thingy, NOT a 1/2"

benzdude42 · #15 03-13-2013, 01:44 PM

thanks man, i'll pick some up. at this point i just want to know what that noise is. i know its not going to blow up anytime soon(been driving it like this for 10k miles or a year and ahalf)but the noise haunts my dreams!