Oil leak around head

[Vev]

I've just completed a 50hr maintenance programme on my Jab 160.

 

I noticed a very small amount of burnt oil around the bottom head bolt cap, not sure where this oil has come from ... any thoughts out there?

 

By the way, leak down and comp test are all good, which I'm thinking it suggest there is no head leak... The engine is running fine and no noticable loss on power.

 

Cheers

 

Jack

 

 

[Vev]

Found the problem ... it is the rocker box breather vent hole.

 

It is misting a very small amount of oil out through the vent... oil when runs down through the water drain hole which goes though the head ... this allows the oil to make it's way to the bottom head bolt.

 

I spoke with the guys from Jab at Temora who confirmed the source of the oil.

 

All good and no issue ....

 

Cheers

 

Jack

 

 

[derekliston]

I currently have the same problem with cylinder 4 on my engine. It took me a while to figure out where the oil was coming from and it is not a massive leak but it is a leak and I'd like to fix it. Anyone know why only one cylinder is doing it, what causes it and how to stop it. I have to say that I haven't found the factory particularly helpful. Hoping that someone on here knows the answer. To paraphrase an old TV ad "Not happy Jab!" This engine has done 25hrs since a rebuild by the factory to nil hours after a prop strike. In that time I have had to fit two new distributor caps a new (one mag) set of ignition leads and this persistent oil leak!

 

 

[John M]

I've just completed a 50hr maintenance programme on my Jab 160.I noticed a very small amount of burnt oil around the bottom head bolt cap, not sure where this oil has come from ... any thoughts out there?

 

By the way, leak down and comp test are all good, which I'm thinking it suggest there is no head leak... The engine is running fine and no noticable loss on power.

 

Cheers

 

Jack

Found the problem ... it is the rocker box breather vent hole.It is misting a very small amount of oil out through the vent... oil when runs down through the water drain hole which goes though the head ... this allows the oil to make it's way to the bottom head bolt.

 

I spoke with the guys from Jab at Temora who confirmed the source of the oil.

 

All good and no issue ....

 

Cheers

 

Jack

Found the problem ... it is the rocker box breather vent hole.It is misting a very small amount of oil out through the vent... oil when runs down through the water drain hole which goes though the head ... this allows the oil to make it's way to the bottom head bolt.

 

I spoke with the guys from Jab at Temora who confirmed the source of the oil.

 

All good and no issue ....

 

Cheers

 

Jack

Skypics234 here:

 

I had a problem with #1 head on my 2200. It was leaking around the head/jug seal. Looks like the head was not properly sequenced at my 1195 hour overhaul. It had burned the aluminum at the seal so I had to fork out almost $700 for a new head. The new head that was sent was for an older early hyd lifter engine when there were issues with the pressure in the crankcase not allowing the oil to exit the rocker boxes down through the push rod tubes. This caused the oil in the rocker box to coke up and eventually affect the valve guides and valve stems.

 

However, my engine (3239) has the deeper oil pan and so this problem was eliminated.

 

So I had oil leaking from the new #1 head and had removed that head 5 times. Each time I checked the rocker rod and push rod tube O rings and all were good.

 

Finally we noticed that besides the oil holes in the rocker box that lubricate the valve guides and stems, there was a hole up in the middle between those oil holes and we found this to be an air vent hole leading to the outside of the engine between the fins. This hole was Jabiru's fix for the coking oil issue. My friend and I just drilled tiny holes in the top of our rocker box covers and had no problems.

 

I had to place some high temp RTV in between the fines where the hole exited. My oil problem is fixed.

 

Since then a friend found a way to place the head on his lathe and he resurfaced the small 3 thousands

 

divot in the head seal so I have a usable head that will fit on #1 or #4 if anyone should need on and don't want to pay close to $700 for a head. This one does NOT have the air vent hole.

 

John M

 

 

[derekliston]

Thanks for the responses. If in the space of 8hrs I can find two other people with the same problem then it beggars belief that the factory is not aware of it because if there are three of us with the same problem then I'm sure there are more. Why the manufacturer isn't, or isn't admitting to be, aware of it I couldn't say.

 

 

[jetjr]

The factory is well aware, isnt that why South africans developed different setup for drain on side of case, now seen on latest models I think

 

 

[derekliston]

I don't know about South Africa, I just don't find them particularly helpful which grieves me because I defend Jabiru engines against all comers! Anyway, since I am not willing to live with the problem having thought about the problem I have come up with a small mod in the form of a short tube fitted with a slight interference fit. I think this should work provided the oil level in the rocker box isn't too high when the engine is running. I am a retired LAME but confess I have no idea of that particular. Does anyone on the forum know the answer to that? I will find out fairly quickly once I run the engine. I will try to upload a couple of pics shortly.

 

 

[derekliston]

Couple of photos once I figured how to get them here!