Konstan's 1982 300D Engine Out Thread - Page 7 - PeachParts Mercedes-Benz Forum

konstan · #91 03-26-2010, 11:50 AM

It's been nice outside, I had to spend some time with the 240D that I have sitting outside. I think it needs rear suspension sway plastic things. Also other cars have been neglected... so, I had a break from the 300D motor.

I got plastigage but have not done the measuring yet. Also going to pull the pistons and inspect.

The head is soaking in biodiesel, the garage smells really nice. Soybeans.

KCM · #92 03-26-2010, 01:59 PM

I really don't think Plastigage is going to show you anything. If it was knocking that bad, you would find a spot in a bearing where the silver is worn off and the brass underneath would be showing bigtime.

After looking at the photos and seeing the amount of carbon, could the knocking simply be because of too much carbon build-up? The distance between the head and piston is not that much due to the high compression, so if the engine uses oil, or you are burning veggy oil, that could cause the carbon to build up and compress hard. Too much build-up and that will cause knocking as the carbon can only compress so tight. This has been known to happen to any brand of engine. Usually the carbon breaks up and exhausts out on its own, but sometimes it doesn't.

konstan · #93 03-26-2010, 03:01 PM

I don't think so either, but I am trying to not skip any steps. I.e. I don't expect to see an excessive clearance in the bearing.

After I check the clearance, I will take the pistons out.
While doing that, I will replace the valve guides and seals in the head.
Maybe replace the rod bearings, they are cheap.
Maybe replace the piston rings.
Replace the crank seals.
Put it back together!

layback40 · #94 03-26-2010, 08:13 PM

If its a nice day you dont want to be stuck in a shed playing with a motor!!
Rod bearing shells & piston rings are a good idea given you have it in pieces.
I havent bothered with valve guides as they can be a PITA to remove & install. Unless the valves feel loose in the guide, I leave them. Soaking in bio is a good idea.
Have Fun !!!

btrapr · #95 03-26-2010, 10:15 PM

This has been a very interesting and educational thread for me! BUT I do have one question?

Can someone please explain the following_________________
"The only problem found so far is excessive end float in the timing device."

Thanks in advance!
and good luck on your endeavor!

jt20 · #96 03-26-2010, 10:58 PM

it means that, along the axis of rotation of the Timing Device, there is 'play' or free movement

layback40 · #97 03-27-2010, 12:03 AM

Or in rough terms; if you grab the TD you can pull it out & push it in a bit, & it goes clunk clunk when you do it.
The idea being that when the motor is idling, the timing chain and so the TD can vibrate around a little & so the rattle, as the motor revs up the load on the timing chain increases & so the TD doesnt rattle in & out..
While I have never heard of it before, nothing else has been found yet that would cause it (the noise).
I think it is fair to say we would all like konstan to find something more tangible as a cause of the noise.

KCM · #98 03-29-2010, 11:07 AM

Quote:

Originally Posted by layback40

If its a nice day you dont want to be stuck in a shed playing with a motor!!
Rod bearing shells & piston rings are a good idea given you have it in pieces.
I havent bothered with valve guides as they can be a PITA to remove & install. Unless the valves feel loose in the guide, I leave them. Soaking in bio is a good idea.
Have Fun !!!

+1

Before you install the rings, you will need to hone the cylinders to take out any glazing and add some cross-hatching to make sure the new rings will seat. I would also have the valves and seats ground (though not 100% necessary) and install new front and rear main seals. At least going this route you will have a basic overhaul job.

Something like this can really snowball. If you are that far, might as well replace the timing chain and guides. And replace the pistons and sleeves too. I guess it just depends on you budget and the condition of the car.

vwkess · #99 03-29-2010, 11:11 AM

Quote:

Originally Posted by layback40

Or in rough terms; if you grab the TD you can pull it out & push it in a bit, & it goes clunk clunk when you do it.
The idea being that when the motor is idling, the timing chain and so the TD can vibrate around a little & so the rattle, as the motor revs up the load on the timing chain increases & so the TD doesnt rattle in & out..
While I have never heard of it before, nothing else has been found yet that would cause it (the noise).
I think it is fair to say we would all like konstan to find something more tangible as a cause of the noise.

Is there a spec for this?

layback40 · #**100** 03-29-2010, 11:18 AM

There is a spec for the endfloat, it is given back further in the thread.

vwkess · #**101** 03-29-2010, 12:42 PM

Quote:

Originally Posted by layback40

There is a spec for the endfloat, it is given back further in the thread.

I looked, but did not see... checked again and still don't. Could you point out post #? Thanks!

DeliveryValve · #**102** 03-29-2010, 12:43 PM

Quote:

Originally Posted by konstan

I don't think so either, but I am trying to not skip any steps. I.e. I don't expect to see an excessive clearance in the bearing.

After I check the clearance, I will take the pistons out.
While doing that, I will replace the valve guides and seals in the head.
Maybe replace the rod bearings, they are cheap.
Maybe replace the piston rings.
Replace the crank seals.
Put it back together!

I don't think your knock is in the bearings also. But a plastigauge will tell you if your bearings are out of spec, and if you need a crank reground and need to go to an oversized bearing.

If you disturb/remove your pistons, rings should always be replaced. You will need to measure the ring lands for spec to see if the piston is still serviceable as well as checking for cracks on the skirt, tops and etc.

And as mentioned above hone the cylinder if the cylinder is still in spec and not have an out of spec taper.

.

layback40 · #**103** 03-29-2010, 08:14 PM

Vwkess,
Sorry its not this thread. konstan had a thread before this one about the knock. its in there. Do a search on his threads & you will find it.
Sorry

konstan · #**104** 03-29-2010, 11:57 PM

It's' right here... the knock that started it all (for me)

Troubleshooting my engine knock (long-ish) 1982 300D

jt20 · #**105** 03-30-2010, 11:50 AM

Quote:

Originally Posted by konstan

I don't think so either, but I am trying to not skip any steps. I.e. I don't expect to see an excessive clearance in the bearing.

After I check the clearance, I will take the pistons out.
While doing that, I will replace the valve guides and seals in the head.
Maybe replace the rod bearings, they are cheap.
Maybe replace the piston rings.
Replace the crank seals.
Put it back together!

I am not concerned about your bearings and there is certainly ZERO material missing from your crank. Replace the bearings since the engine is open and they do wear.

Concerning valve guides; it does not make too much sense to replace them and not match the valve seats.. you will lose compression.

Certainly replace the rings, I am deeply regretting not doing so when I had the chance. Honing / deglazing is something you need to read up on for yourself. There was a member here (jonL) who was an engine designer and mentioned some research about deglazing not being necessary. I am sure there are limits involved, you need to educate yourself about that.

You can have 40 different members tell you 30 different things, but you are the one with engine in your garage staring you in the face, if you know the limits and what needs to happen, you can make the decision based on what you see and what the engine is telling you.

crank seals... ALL seals