84 300 CD suddenly making HORRIBLE noises and running VERY rough - Page 8 - PeachParts Mercedes-Benz Forum

rcounts · #**106** 10-17-2008, 12:54 AM

Well, I've been working pretty steady at it for two days now (about 14 hours so far) and it STILL isn't quite ready to go back in. Seems that the numbskull who pulled this motor out is VERY fond of his wire cutters. Every electrical cable and vacuum hose has been cut, and I'm having to swap just about everything but the IP over from my motor to the replacement. While I have it out I pressure washed the engine bay (after closing all the open hoses etc. with baggies and rubber bands) and then I pressure washed the relacement engine.

So far I've got the motor mounts, all the AC hoses, the injectors & lines, the cruise module, and last but not least the turbo swapped over and installed. I made the decision to swap the turbo because the oil drain-back tube was crushed nearly flat about 2 inches above where it enters the oil pan, and the turbo itself had a fair amount of oil in it. I'm think that the oil wasn't draining fast enough and backing up pressure to the bearings to the point that it was causing the seal to leak. I know my turbo is good so I figured I'd be best off swapping it while the engine is out of the car.

I'm at the point now where all that's left is swapping one set of vacuum lines, and the GP harness, and I'll be ready to put 'er back in. If the good Lord gives me another dry day tomorrow I'm hoping to have it running by dark.

BTW, what is it with Mercedes engineers and those 5mm socket cap screws? Somebody must've got a killer deal on a whole warehouse full of them so they decided to use them for EVERYTHING!

rcounts · #**107** 10-17-2008, 05:31 PM

OK, new issue. What the hell is this plug on the side of the IP

and how do you take it off?

It looks like it is just secured with two screws, but even after removing them it doesn't unplug

It goes to a 3-prong male plug that plugs into a 3 prong female that is fastened to the firewall right above and behind the valve cover. Naturally mister clipper-happy cut the end off, so I thought I would just unscrew the two screws and swap the one off my motor's IP. Doesn't seem to work that way.

Advice needed ASAP please....

bgkast · #**108** 10-17-2008, 06:05 PM

Must be an '85 engine. That is a rack position sensor, for the EGR computer. Just ignore it for your car.

barry123400 · #**109** 10-17-2008, 07:00 PM

Three hundred to three twenty cold compression numbers sound not bad on your replacement engine. It is really nice they are all fairly equal as well.

Will watch for your thread from time to time to see what you find in the old engine if you get into it. Curiosity has got me.

rcounts · #**110** 10-17-2008, 08:54 PM

Quote:

Originally Posted by bgkast

Must be an '85 engine. That is a rack position sensor, for the EGR computer. Just ignore it for your car.

Ummm, you sure about that? Mine is definitely an 84 (01/84 mfg date) and it has the sensor on the IP and the other end was plugged in. The engine I'm swapping has it too and the wrecker said it came out of an 84 300SD...

rcounts · #**111** 10-17-2008, 09:15 PM

Well, its in. Not all reconnected and running yet, but its sitting on the motor mounts and bolted to the tranny. The oil filter housing ended up being more of a PITA than expected. I thought I could just swap the plate where the oil pressure sensor (on the SD motor) and the oil pressure line (on the CD motor) attach. Of course that isn't how it works, so I ended up swapping the entire assembly. And wouldn't you know it, that also meant swapping the oil cooler lines AND brackets. They made just about everything on the outside of these two motors JUST different enough that you have to swap it all!

Having encountered this little issue of the rack position sensor (or whatever the heck it is) I pulled the GP harness off both motors, but didn't get the one from mine installed on the temp motor. Should be finished and running tomorrow though, for sure...

BTW, I have to say PRAISE THE LORD! I asked for dry weather and despite all the predictions of a better than 60% chance of rain, it was dry all day and only started sprinkling a half hour AFTER I packed it in for the day!

I'm thinking I may just cut and splice that connector onto the clipped cable and call it good enough - especially if on an early 84 it truly doesn't do anything...

bgkast · #**112** 10-18-2008, 02:12 AM

Pull the passenger kick panel that would be next to the passsenger's right foot, is there a computer box in there?

rcounts · #**113** 10-18-2008, 02:31 AM

Quote:

Originally Posted by bgkast

Pull the passenger kick panel that would be next to the passsenger's right foot, is there a computer box in there?

Dunno, guess I'll check that tomorrow. But, since my EGR is blocked off (still installed, just with a block-off plate in place of the gasket - so as not to alert the emissions inspectors), I guess it will be pretty much a non-issue either way, eh?

rcounts · #**114** 10-20-2008, 12:06 AM

Well, it is in, and its running. Sounds great. Blowby looks to be even less than the original. The oil pan that was on the replacement engine was pretty caved in on the bottom, so I decided to swap that too. Good thing. The PO put the oil pan on with about a half a tube of RTV and no gasket. Naturally all the stuff that squished to the inside had broken up into chunks and the pickup screen was about 3/4 blocked with the pieces.

So I pulled the screen off but the center "sleeve" was all warped out of shape, so I decided to use the screen off my original motor as well. When I pulled it off and pulled the center "sleeve" out of mine, looky what I found...

So, the mystery is solved. At least one rod bearing is gone, and by the quantity of metal flakes and pieces, I'd say probably more than one. When I checked it before, I drained the pan, and strained the oil. Then I removed the pan and looked in it, and examined the screen with a flashlight but I didn't remove it. I figured that since I could see the screen and couldn't see any metal pieces, there weren't any. I didn't know that there was a removable rubber "sleeve" in there and apparently the metal pieces all went up over the top of the sleeve and settled in behind it. You can see in the picture how it is all around the outside where it would be hidden by the "sleeve", but still pretty much nothing in the middle - and that is even after my messing with it and disturbing it.

So, I'm up and running again, and I know exactly where to start with tearing down the original engine for the rebuild...

johnathan1 · #**115** 10-20-2008, 02:56 AM

Glad to hear you're up and running again. Any way this damage could have been caused by the bad fuel?

rcounts · #**116** 10-20-2008, 05:13 PM

Quote:

Originally Posted by johnathan1

Glad to hear you're up and running again. Any way this damage could have been caused by the bad fuel?

Well, I can't think of any other explanation. Like I said in the first post...

1) It had been running great with only 210k-220k miles on the clock.
2) The tank was empty, and I bought 5 gallons from the diesel pump at Shell.
3) It ran fine for ~15 miles from the station to Harbor Freight.
4) Started up fine at Harbor Freight and in the <5 miles from there to my house it all went to $h!t. Knocking, no power, smoking, missing.
5) Took the filter off and there was a strong odor of gasoline. Sniffed the tank filler neck and it also smelled strongly of gasoline.
6) Three days later I got a sample from the same tank at the Shell station and it STILL had a gasoline smell - not as strong as what came out of my tank, but who knows how much more diesel had been pumped into the tank (or what had been pumped out of that tank) during the 3 day interim.
7) Either the rod or main bearings in my motor appear to be shot.

While it is true that I had run half a dozen tanks of 50/40/10 blended D2/SVO/RUG through it in the last couple of months, I had run it down to 1/4 tank or less and filled it up with straight D2 three times since the last time I put any blend in the tank. PLUS the tank was below Reserve - almost bone dry - when I bought the fuel at Shell.

Draw your own conclusions. I'm completely convinced it was the fuel...

rcounts · #**117** 10-22-2008, 05:59 PM

Well guys, this may be the last post in this thread for a while - at least until I get around to tearing down the old motor to find out exactly which bearing(s) went south on me.

I've driven it two days now and the replacement motor I swapped in seems to be a really good one.
It starts easier
It has more power and pep - even though the ALDA has never been tampered with
It doesn't seem to be leaking a drop of anything
It doesn't smoke - except a little puff of gray/white at startup and a little haze of black when I romp on it hard enough at 60 to make it drop down to 3rd gear

It has better oil pressure - about 2-3/4 bars minimum when warmed up, and it pegs at 3 bars before it even reaches 1000 RPMs
It runs quieter - about all I can hear at freeway speed is a faint turbo whine, and I can't even hear that if the cabin fan is on.
It runs cooler - in fact it may be running a little too cool (~60*C), so I'm thinking the thermostat might be stuck partially open.

About the only issue so far is that it had a case of the hot-idle-shakes the first couple of times out, though that seems to have pretty nearly gone away.

So I spent $350 on used motors, $100 on new parts, and 25-30 hours work, and my baby is running better than ever. PLUS I also have LOTS of good used engine parts now AND two spare automatic transmissions.

This wasn't exactly how I wanted to spend my last week of vacation for 2008, but all in all, I guess it didn't work out too bad. Thanks for all the help and advice.

barry123400 · #**118** 10-22-2008, 07:05 PM

You might borrow a heat reading gun or any other ideal you can come up with and read the engine temp. Chance the temperature sensor has gone out.

One of my cars sitting idle for a year had its sender drop out. Beats changing the thermostat. Then the sender afterwards. Only a possibility. Or for the limited effort involved. Use your last working one as a substitute. Unfortunatly I just rejected my thoughts.

Your hot oil pressure is higher than normal because the engine is cooler. You cannot win them all.

Happy the new engine was good. It always does not work out this well with used engines. Not nearly as happy for this outcome as you are though.

rcounts · #**119** 10-23-2008, 05:48 AM

Quote:

Originally Posted by barry123400

You might borrow a heat reading gun or any other ideal you can come up with and read the engine temp. Chance the temperature sensor has gone out.

One of my cars sitting idle for a year had its sender drop out. Beats changing the thermostat. Then the sender afterwards. Only a possibility. Or for the limited effort involved. Use your last working one as a substitute. Unfortunatly I just rejected my thoughts.

Your hot oil pressure is higher than normal because the engine is cooler. You cannot win them all.

Happy the new engine was good. It always does not work out this well with used engines. Not nearly as happy for this outcome as you are though.

Yeah, I'm 99.9% sure the temp reading/sensor is accurate. The slightly elevated "hot" oil pressure is one indicator that it is running a bit cool, and fact that the heater is only blowing lukewarm is further evidence that it isn't getting all the way up to "proper" operating temp.

But if the only thing "wrong" with this replacement motor is that it needs a new t-stat, and everything else about it is better than the one I pulled out, then that's such a small thing as to be a non-issue in my book. I mean, a t-stat replacement is what, $20 and less than an hour's work...?

I can live with that.

87tdwagen · #**120** 10-29-2008, 09:02 PM

Quote:

Originally Posted by Brian Carlton

I'm sure it was gas in the diesel tanks..........a certain amount anyway.

Remmber, you might get some injector knock for a bit after you put it back together..........the 603 did this with a new #6 fuel line...........took about 300 miles to completely disappear. Very strange.............

Brian,
I hope you are right on this, I just replaced my no. 6 line on my OM603 and am getting that strange knocking you describe from no. 6 injector. Only got 50 miles on it so I hope it goes away soon. Sounds like a Singer above 900rpm but knocks loud at idle.

Bill