Yesterday I thought I should check my coolant level and when I removed the rad cap under the seat there was about 1\4" of sludgy oil on top, not good. I added water slowly to allow the oil to overflow out. I checked the dip stick and the inside of the oil filler cap, both look normal, so I don't suspect any coolant in the oil. I am thinking the only way oil can get into the coolant system is through a blown head gasket or crack in the head. Engine runs totally fine, so I am not sure. I am at 121k kms on it now. Any ideas?
If you have a compressor, buy a cylinder bleed down tester. https://www.amazon.com/JIFETOR-Cyli...inder+bleed+down+tester&qid=1638865901&sr=8-5 Not recommending this one, but it is inexpensive at $30. They start there and go up to Snap On crazy. You warm up the engine if it is running, and then pull the plugs and hook it up to cylinder 1, and rotate to close both valves. then apply the air pressure. And listen for the air. If air is coming out into the crankcase and then out the oil cap, your rings are bad. It you hear it in the intake manifold the intake valve seal isn’t good. Same for the exhaust side. If you get bubbles in the radiator, your leaking into the water jacket, normally a bad head gasket. With the engine cooled off the rings will have shrunk, increasing the ring gap, and allowing more air into the crankcase.
I am going to just pull the head and replace the gasket. Suspect oil pressure has found its way into the cooling jacket. Being oil is higher pressure than the coolant it would be a one way direction and explains some of my oil consumption. Do you know if these are torque to yield head bolts?
Yeah, usually a cracked head will cause water in the oil or excess pressure in the coolant system. I think head gasket is more likely. I would run a compression test before I did any work though.
After completely dismantling another Sambar engine I am working on, I am pretty sure what happened. Was running 20 50w oil to deal with some engine oil burning (blue smoke when cold) and came to find that the manual says not to run heavier than 30w. The way the oil travels from the block into the head is very strange, not a straight path, in fact it travels through a section of the head gasket to an opening in the head to lube the valve train. I think the heavier oil having more resistance to flow pushed its way into the cooling jacket of the head through the gasket. Oil can flow into the coolant, but not the other way because of the pressure difference. The head bolts are only torqued to 21 ftlb, crazy. A lot of blabbing there, but I am 99% sure it is the head gasket as a result of using wrong engine oil. I will post up some pictures when I open up the engine.
I am not sure what manual you are looking at, but the original Owners Manual specifically calls out a number of oils including 15w40. Running slightly thicker oil than that will not damage the head gasket. Now I know you are looking at the "English Service Manual", by James Danko. That book cannot be trusted, as there are numerous translation problems, and a large amount of flat out missing information. Somehow, he decided to consolidate about 900 pages of the original books down to about 200. Obviously, a lot was lost in doing that. I wrote up an "addendum" to his book specifically about the head bolt torque problem. I emailed it to jdmfdm, and they host it besides the rest of his book. Here is a link to it: http://jdmfsm.info/Auto/Japan/Subar...anual/Subaru Sambar Head Torque Procedure.pdf
That is hugely valuable information. How the hell did that get screwed up??!! I just installed a head on an engine I am rebuilding (different truck) and can easily adjust. I thought the torque order was strange, opposite to what I am used to, and not as tight. Much appreciated!
Well finally finished replacing the head gasket as well as new valve seals and machining the head. No more issues. No question the oil was getting past the seal into the water jacket between head and block. Anyone who has taken these engines apart and analyze the way the oil travels will know how strange it is designed. Further, if you see pictures of the top of the block you will see how the seal slowly eats into the block and head until it fails.
