1985 300D engine rebuild - Page 2 - PeachParts Mercedes-Benz Forum

psfred · #16 09-09-2002, 11:03 PM

Jim:

If you decide to rebuild, check the pistons by getting a set of new rings (you only need one set to check with) and check oil clearance on each ring groove with the new ring. If the clearance is OK, you can reuse the pistons. Most likely you can, since the bores have just been polished out. Certainly if there is a minimal ring ridge, the lands should be good. Any evidence of piston wear (scuffing or scoring, ridges at the ring lands, excessive oil clearance on rings), replace.

If the pistons are worn, you have the choice of new pistons (oversized) with a bore and hone, or new pistons (standard size) with new sleeves and bore and hone. Oversized pistons will give you a bit more horsepower, too.

Piston and ring set is about $110 each, more for the turbo, I think. Sleeves are $35 each, plus whatever it takes to remove/replace and bore to size. You have a wonderful machine shop there, so no worries on that front!

Peter

Cap'n Carageous · #17 09-10-2002, 09:28 AM

What kind of engine was the one at Cassidy's? I'm sure if it would fit you would have already thought of that!

engatwork · #18 10-20-2002, 07:26 PM

It was finally cool enough to get out and start getting into the 300D engine today. I got the intake/exh and turbo off and was in the process of taking the timing chain apart when just for the heck of it I started turning the engine over looking at where the marks lined up on the cam and crank. I turned the crank to line up the cam mark and looked at the crank indicator and IT WAS ABOUT 20 DEGREES off - past top dead center!!! This was all with the tensioner intact. I don't have a clue how it got this far off. Anyway, I moved the chain one tooth over and now the marks line up like they are supposed to. Now, I'm wondering where in the world the fuel injection pump is timed at so when I get back out there on it I will do the old "drip" test and see where it is set for start of delivery. The last "major" job I did on this engine was a head job back around April of this year. I will say it has not run right since that time (rough idle, hard to crank and excessive smoke - but once it got up to speed it would run out good and the fuel mileage was around 25 mpg). I have a heckuva time believing it has been off one tooth all that time but I guess it has because I don't think they will "jump time" one tooth with a healthy tensioner. After resetting the chain one tooth I did turn it over manually for quite a few revolutions to confirm it was lining up properly. I will probably do another compression test after getting the intake back on just to see where it really is.

psfred · #19 10-20-2002, 09:09 PM

Jim:

They will run that late on valve timing, but the compression will be pretty low and it will make LOTS of smoke. At high rpm, the valve timing "catches up" -- the rule on valve timing vs power is that the power is still there, just at higher rpm. I don't know if this applies fully at 20 out, but you will get better power and less smoke wound out than at low speed with late valve timing.

You probably dropped a tooth when installing the cam gear. I cannot imagine when else you may have done so -- unless the chain got loose on the driving side and pulled out when you started it. Funny things can happen, I know you are a meticulous worker and would have checked before buttoning her back up!

If you didn't remove the chain retainer on the injection timer, the injection pump timing didn't change -- it's a real pain to get THAT part of the chain to jump!

Button her back up if the compression is good -- I'd wait until the oil consuption got out of control to rebuild!

Peter

engatwork · #20 10-21-2002, 06:23 AM

Thanks Peter - I think that is what I will do. I am about 99% sure I confirmed the timing when I put the cylinder head back on but who knows - I am still scratching my head over this one. Oh yea - It did make LOTS of smoke when it was running - so much so that I could have "fogged" for mosquitos.

slowmoe · #21 10-21-2002, 10:35 PM

engatwork,

Not to change the subject, but I need to ask these questions, even at the risk of being on the receiving end of the " here we go again reply..."

First, for how many miles have you owned this car. Secondly, how often did you change the oil, and... you guessed it...what kind of oil did you use in this engine.

engatwork · #22 10-22-2002, 06:23 AM

I've owned it a couple years - purchased it with 217,000 miles on it and no records. Found it on ebay and the guy lived about 5 miles from me. Paid $1500 for it and it needed a brake job. It does not use oil so I figure it has had oil changes pretty regular. Since purchasing it I have changed the oil every 3k miles with Delo400. In April of this year I pulled the cyl head and installed new guides and seals. I installed new timing chains and guides right after I purchased it. I guess I got the timing off when I re-installed the head in April - I can't imagine it "jumping timing" although I have run accross people in my life - broke down beside the road - that have stated their car "jumped time" and left the stranded

. On acceleration it is in high gear by the time it gets to 40 mph and I have yet to figure out what is causing that. Based on additional reading I am starting to suspect the vacuum control mechanism located on the upper rear of the fuel injection pump. The vacuum control signal that it puts out to the tranny is pretty much a 45 degree slope curve from 20" to 0" and 0-100% on the throttle. Based on my reading the curve is supposed to be pretty flat till right at the end where the vacuum is supposed to drop off rather abruptly. After I get it going I may try to mess with this some more.

engatwork · #23 11-03-2002, 03:42 PM

I finished putting it back together today and it no longer smokes and it cranks better but it does not idle as smoothly as the 300TD. I suspect it is because of the "weak" #5 cylinder. While I had the intake/exhaust manifold off I took the liberty to crank up on the turbo wastegate some and am now getting 11 psi of boost which resulted in the car accelerating MUCH better. It actually runs pretty doggone good once you get off of idle.

On cranking up the boost - there were initially 4 threads showing above the lock nut, now there are 7.

suginami · #24 11-03-2002, 03:56 PM

Good good good.

So now you're back on the road.

Does the poor engine idle bother you enough that you're still going to do a rebuild, or are you just gonna live with it.

Or, plan "C", sell the car, and "invest" the money into upgrades for your wagon or the 240D?

engatwork · #25 11-03-2002, 04:16 PM

Man I don't know. The wife wants me to sell something

. I have been thinking about pulling the 300D engine, rebuilding it and eventually putting it in the 240D. On the same hand I may put it on ebay and see what happens. It has way too many new parts to get rid of it on ebay though. I don't know - hopefully I will come up with something over the next few days.

leathermang · #26 11-03-2002, 04:44 PM

Somewhere I got the impression that you replaced the chain without compressing the oil powered detent chain tensioner... is that true ? If so I think that is the cause of your timing difference....

engatwork · #27 11-03-2002, 04:51 PM

Leathermang - I don't know. I have done a head job on this car since replacing the timing chain. I guess I missed something when putting the cylinder head back on is about the only thing I can figure.

I have considered your offer and doubt if you can afford the payments

.

leathermang · #28 11-03-2002, 05:04 PM

You are probably right....

suginami · #29 11-03-2002, 08:10 PM

Quote:

Originally posted by engatwork
Man I don't know. The wife wants me to sell something . I have been thinking about pulling the 300D engine, rebuilding it and eventually putting it in the 240D. On the same hand I may put it on ebay and see what happens. It has way too many new parts to get rid of it on ebay though. I don't know - hopefully I will come up with something over the next few days.

LOL Jim.

What's the deal with your wife?

You have been given a 3 car limit? If so, man, one has got to go.

It's hard to get rid of any of them, especially considering the condition of the cars, not counting the time and money you've "invested" in the cars.

You have a couple of sons, don't you? Maybe you can negotiate this with her so that one of the cars will be driven by one of your boys.

My wife watches Dr. Phil at home everyday, and he has repeatedly brought up the concept that marriages are a negotiated relationship. One spouse ought not get his / her way dictatorialy, but rather a give and take needs to take place.

Just something to chew on....

engatwork · #30 11-03-2002, 08:42 PM

LOL - you ain't met my wife

. Negotiate is not a term she understands.
I'm going to try ebay for a week and see what happens. If it does not sell then I will just pull the engine, rebuild and store it and eventually put it in the 240D.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1871896403