I didn't kill my motor after all. Maybe - PeachParts Mercedes-Benz Forum

C.Doner · #1 09-20-2012, 03:11 AM

It was just tired already, but its running better after MMO in the cylinders for days.
well here is the low down
this is an engine from a 81 TDt that was wrecked. Rolled over.
I thought it was dead. it may still be, but it runs like it always has since i have had it.
I changed the oil recently and only got around 5 quarts maybe a little less out of the engine.
The engine started running rough and i figured it was just a clogged fuel filter, or the valve lash was off. well both of those needed fixing. I figured I would repair my oil leak at the oil filter tower to block seal. I did all the work in the same job.
Once i got it all back together, valve lash done and the fuel bled. I start it and it runs horribly. Worse than ever. Its shaking all over the place and smoking. So I check the basics like air in the fuel and valves adj. No avail.
I decide to check the compression and bummer only like 180 on #5 and 230 on #4. i put a tablespoon or so of oil in and compression went up. Extra bummer. After checking those problem cylinders i just got bummed and gave up.
Since i was using a POS Hfreight compression tester I decided to let a trusted indy do a leakdown test. On Cyl #1,2,3 compression was good 4 and 5 had approximately 75 % leakage.
I'm bummed thinking i ran it out of oil. It never lost pressure though as far as I know. Indy tells me to put MMO in the Cylinders and let it sit for a few days. I put one bottle each cylinder #4 and 5 and come back to blow it out by cranking without injectors, and nothing comes out. It went into the crank case.
Well I drive it for a bit and nothing is better. then i give up since I had shoulder surgery coming up.
So six and a half weeks later i go start it and it smokes a bunch. I take it for a drive and it runs smoothly no missing. I'm thinking well its probably just the biodiesel making it smoother. so I put in diesel #2 and still runs good
I decide to check compression. I check only #5 which was the worst . It was pretty much dead. So i have the compression tester hooked up, I crank it, the motor sputters for a few seconds because the other injectors are hooked up and the compression goes all the way to 420 Psi. I check it again with no sputter and its back down to 180 or so.
I check the other good cylinder #1 and it goes all the way to 500 or something with the same type of sputtering of the engine.
So I believe this may be the same testing method i used when i first tested the engine making me believe it was a like new motor when really it was tired.
Well none the less, it is back to the same running condition that it was when i installed the engine. The idle is a little shaky but it is clearly running on all cylinders. I loosen injector lines to check.
One other thing is the lack of major blow-by. I take off the oil lid and it barely moves. If i remove it all together some blow-by is apparent but nothing major. Oil does not come out when it is idleing with the cap off.
So I'm going to take it out on a long drive after changing the oil to get the MMO out. Maybe It is not over after all. What do you think.

C.Doner · #2 09-20-2012, 03:30 AM

The engine power seems quite fine. I get up to 60 mph or 100 kph as my speedo reads in around 12 seconds on a very mild upslope.
this is the 300dt 4 speed manual. My sig is a little confusing.
thanks you all.
BTW the shoulder is getting better. I can now help my left hand out a little with projects. I'm right handed which is the one injured. I guess I need a right hand man to help me work on the car.
Peace

t walgamuth · #3 09-20-2012, 04:07 AM

Well of course you will get a higher compression reading with the engine running than just cranking it with the starter.....how much I am not sure.

Testing with all the other cylinders open is the standard way to do it.

But the real reason to check compression is to determine overall engine health. A low cylinder does not mean you cannot drive it and enjoy it. A dead cylinder is another matter.

A five cylinder will always hop around more than a four or six at idle.

A five with the heavy five cylinder flywheel though idles very smoothly, almost like a six cylinder.

Simpler=Better · #4 09-20-2012, 09:13 AM

If it runs, change the oil regularly and drive it forever

My gas DD makes terrible terrible noises on startup & when cold, but I plan on spending more time driving it and less time worrying (with regular fluid changes)

Diesel911 · #5 09-20-2012, 09:18 AM

I soaked the Cylinders of my Volvo Diesel that had been putting out hazy gray Smoke all the time (the Car had sat for 1 Year and after it was running I found I had been driving it with a Thermostat that was opening too soon) and I guessed it was stuck Piston Rings.
Besides changing the Thermostat I changed to one that also had a higher temp and that did not help the Smoke issue.

I was skeptical that the MMO would work but it was cheap. Soaked 1 week and rotated the Engine and soaked again for 3 days. Wanted to soak longer but had to get the Car on the Road.

I did change the Oil before taking it out on the Freeway for some serious driveling. Over the course of 3 Days the gray Smoke cleared up.
So for the Volvo the MMO worked.

I tried the same on the Mercedes to see if it would reduce the Blow-by but I could not see any difference afterwards.

Another Member used the MMO and it raised his compression and reduced the Blow-by but several Months later He had the symptoms He started with. I am guessing His Rings carboned back up; perhaps His Piston Ring Grooves were worn.

When I had that rough idle after the Engine was hot issue after a Valve Adjustment rebuilding the Injectors is what had the biggest effect on reducing that issue.

C.Doner · #6 09-20-2012, 11:01 AM

Well i'm hoping it will get through the winter. I do have another vehicle. I am more worried about it sitting too much. At least this way ill be able to drive it to keep it from rotting from the inside.
i dont expect much from this MMO trick. the engine was quite carbon crusted,so its worth it to drive until I find a decent engine replacement and have the time to do the work.
Things are still up in the air as to what I am going to do for an engine.

barry123400 · #7 09-20-2012, 11:15 AM

I would investigate this a little more before assuming anything. At least inject compressed air and listen for where it is escaping on the back two cylinders. If the rings are as bad as indicated I would expect more blowby.

C.Doner · #8 09-20-2012, 11:51 AM

Well il try some synthetic oil. Its expensive though. its pretty hard to spend more $$$ on this motor. At like $9 per quart it adds up. i guess its worth a try though. Hopefully its not in vain.
I just changed the oil less than 500 miles ago just before this started. Should i put in a new filter too.

Simpler=Better · #9 09-20-2012, 01:35 PM

I wouldn't, but I'm cheap.

Maybe a rudimentary alcohol setup?

C.Doner · #10 09-20-2012, 01:46 PM

Quote:

Originally Posted by Simpler=Better

I wouldn't, but I'm cheap.

Maybe a rudimentary alcohol setup?

what do you mean.

StaggerLee · #11 09-20-2012, 02:14 PM

Do the compression test RIGHT so you know what you are working with.

Simpler=Better · #12 09-20-2012, 03:23 PM

It's rumored that if you spray a mist water or alcohol into the intake it will steam clean the engine from the inside out. I only ran a couple gallons here & there on my engine, and them removed the system and ran it another 10k before pulling the head, so I can't say if it helps or not.

C.Doner · #13 09-20-2012, 03:30 PM

I am pretty much limited to one hand wrenching so that wont be happening for a month or so. Until then i'm just going to drive the hell out of it. we'll see then.

Junkman · #14 09-20-2012, 03:42 PM

Quote:

Originally Posted by C.Doner

Well il try some synthetic oil.

I just changed the oil less than 500 miles ago just before this started. Should i put in a new filter too.

Why? You just changed the oil. It has likely run for miles on dino oil. Have you done anything to corrupt the oil that is there now? You don't know what the issue is or how long you're likely to run the engine. Spend the $$ on diagnostic equipment if anything.

C.Doner · #15 09-20-2012, 04:10 PM

I put 8 oz of MMO i put into each suspect cylinder # 4 and 5. When i cranked with the injectors out nothing came out of the injector hole. Maybe it went out the exhaust.
Actually my oil level did not seem to go up, so i dont really know where all the MMO went. Maybe my assumption that it went into the crank case was wrong. All this was 6 weeks ago so its hard to tell.
But yes you are right its time for a good compression tester. Forget the HF POS.