Konstan's 1982 300D Engine Out Thread

[konstan]

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]

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]

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!

[DeliveryValve]

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.

.

[jt20]

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