I have a 933 11A with D311 engine. Have done numerous projects to it including remove and replaced Pre combustion chambers. I have removed the radiator and had it redone (had leaks) to like new. During that process I did have a event of it getting hot from a air pocket in the head while refilling the radiator. I have since put in a drain valve (vent) at the Port going to the Pony engine. I have a electrical system with a starter. (factory installed). A few days ago I started it after it sitting idle for about two weeks and it overheated, it blew coolant out of the pressure relief at the radiator cap. This was just in the low idle while warming up. I stopped the engine, temp no higher than 180 on gauge, and opened my vent at the rear of the head and just air came out. I restarted and filled up the radiator with coolant till it came out of the vent without air bubbles. The engine runs good and starts great. It has been about 32 degrees here and it starts with one minute of glow plug.
It is possible that I just didn't completely fill up the radiator as I did not check it after it was run and worked. Oil is clean and new. The engine was degreased and power washed after the radiator work was done. Here is a link to two videos that I took tonight after I pulled it into the shop. I did hear a bit of pressure at the radiator cap after shut down and I removed the cap. Was not hot as I just brought it in from the cold to park out of the coming snow storm. Also, in the video is a black tar coming out of the exaust. There is a bit of something at the cylinder head gasket location on the exaust side as you can see in the video.

I sure could use some suggestions.
Thoughts that I had were to retighten the cylinder head, replace the cylinder head gasket, remove and replace the pre combustion chambers again to see if there is anything obvious there.

I believe there is a vent on the top of the pony to vent the cooling system, This would be the high point and a natural air trap.

I would proceed under the assumption that you had some trapped air but watch for a slow leak now that you have it inside.

The gaskets and such look pretty normal to me. Unless you want it to be ready for parade or display those seeps aren’t going to hurt anything. The best solution to them was to coat the head gasket with the brush-on type gasket maker like Permatex 300. As you know, the ferrules and grommits seal all liquid penetrations through the head base and block deck, but adding the gasket maker adds another layer of protection against seeps. The only area not to be covered by the stuff is the fire ring area around each cylinder where the surfaces of the gasket, head and cylinder sleeve must be clean and unpitted.

Unless you have a cylinder misfiring which is pretty obvious on a 4 cylinder, the “tar” is just incompletely burned diesel and motor oil mixed with carbon that is going out the exhaust. Short term solution is to work it hard making sure the thermostat allows it to get up to temp or nearly hot. Might have to slip some cardboard in between fan and radiator to block a little of the surface are if you can’t get it up to temp.

Long term solution to the slobbering as it’s usually called is working it hard and avoiding idling, operation with coolant not up to normal temp etc. If it gets too bad, and the working hard and hot won’t stop it, then it’s usually time for an overhaul. Usually folks avoid that until there are other problems like excessive oil consumption, low power, poor starting etc.

There used to be a procedure to use a limestone powder (BonAmi) dusted into the intake to help seat rings after overhaul if the usual procedure didn’t result in normal oil consumption. I have heard of this being used on old slobbering engines, but I doubt the (good) effects would last long. Probably just hasten the necessary overhaul.

UPDATE:
I started up with the loader in the cold shop. Did not start right off with the glow plugs. Needed a little squirt of ether. Just shortly after starting the radiator pressure relief valve started spitting radiator coolant. I checked the level of the coolant prior to starting and it was visible just below the cap and the vent on the head had no air in it just coolant. While the tractor was running, I unscrewed the radiator cap and there was a lot of bubbling. Head gasket was my assessment of the problem. I was also getting a bit of a miss, not sure exactly what cylinder. This is the first time that I have ever heard a miss in the engine. It was about 20 F in the shop. I pulled the head with the assumption that the bubbling in the radiator was a sure sign of that being the problem. After sleeping on it, it could also be a seal on the pre combustion chambers. Head is off and I have a few videos of the condition of the head and block with the gasket still on it. Just for reference I did replace the glow plugs, pre-combustion chamber seals and o rings last summer. I would be grateful if you guys could look the videos over and give me your assessment. There are a few seals that look a little suspect as well as a few of the brass sleeves that insert in them that look like during the last installation might have gotten beat up. I don't know when/if this head was ever replaced or any history on the engine. The stamp on the head is 7F8308 and the stamp on the head gasket is a 4F2789 VICTOR.
Here is the video of the Block with the head gasket on it just as it looked after head removal:

Here is the video of the head:

Here is the video of the head gasket:

I will be ordering a new gasket.
Will it come with the seals or are they separate part numbers?
Based on what you see and have experienced, would it be recommended for this head to be gone thru and resurfaced?
Do they ever warp?
Can you tell from looking at the face of the head if there was leakage at the precombustion chambers?
There is still cross hatching in the cylinders. I am assuming that the coolant in the 4 cylinder got in there when I pulled the head....it was tilted that way when I lifted it out with my a frame hoist. I have many pictures if they would be useful to see. I also noticed while removing the head nuts that they were not all equally tight. I would love to read your insight on this project of mine.

Here is another video of the engine block after gasket removed.

I also read in the D311 engine service manual that the head gasket can be reused more than once is there is no sign of damage. Not showing any signs of cracks or blow by. Do you guys recommend to replace it or reuse it? Also, what type of tool would you use to clean up the recesses for the rubber seals?

Seems you kind of jumped the gun pulling the head so soon.
I don't see anything glaringly amiss with the gasket sealing but pictures are not the same as actual witness.
Anyway, things to check:
Liner protrusion should be in the range of 0.002 to 0.005"
Head warpage is not usually a problem but you can check for daylight under a straight edge.
Pre-combustion chamber seals and seal surfaces can be combustion source leaks.
Worn valve guides can be a contributor to engine slobber.
Close check for any cylinder head/block cracks.

By all means replace the head gasket with new and coat both sides with "Permatex 300" gasket sealer.
Ferrules and seals are purchased separately
That head number doesn't match the info I have, Should show a 7B0596 casting number (7B3068 part number)

Couple of parts diagram pictures for the D25Uxxxx head, same as the 933 11A

I did some more cleaning up and better photos. What do you think of the carbon on these two cylinders. Also, a photo of the casting number on the top of the head. I did notice another stamping on the end of the head but I didn’t get a photo. Could be the part number possibly?
Is the carbon deposits thru the edge of the ring able to pressurize the radiator? The seals on the pre combustion chambers did not show any obvious signs of carbon bypass but surfaces are a bit rough. Here are some photos of them.
In the third cylinder (picture with the carbon at the bottom) I think the carbon came from the removal process. Blew off after I took the picture and the seal ring didn’t have any carbon on it.

That would be the head casting number 7F8308. Could be a later version.
The seat for the chamber in picture #11 does not look good.
Seat in picture #10 looks rough.
The chamber tip in picture #7 has pitting like the type of damage that occurs when there is water introduced along with combustion.
What is that at about the 4 o'clock position (just above the part number) in picture #1. Is it cut/eroded through the fire ring of the gasket?

Hi rehpig,
after the last head fitment did you re-tension the head after the first run to operating temperature??.
These multi layer gaskets must be re-tensioned after the first run in our workshop, and again after 100 to 125 hours by Cat recommendation in Service Magazine Aug 23 1961

Usually clients noticed oil seeping and may be bubbling of the oil if the heads were not re-tensioned--re-tensioning usually stopped the issues.

This may or my not be your cause as you need to check also the subjects others have listed above.

Cheers,
Eddie B.

I will follow those instructions when reassembling/running.