low oil pressure ?

[tx_swordguy]

I am looking at a jabiru 3300 equipped sonex and the owner has been very forth coming about any issues he has had, so much so that I have agreed to buy it. He mentioned a low oil pressure issue he had in the past and just recently replaced the oil pump. In reading the web I have found that this may not be so uncommon. In my research there was some mention as to high oil temps being related and I was wondering if anyone has put a larger oil cooler or a stack of oil coolers on a Jab sonex? It gets quite hot in texas most days and I was thinking I could install some kind of flap to close off partial oil cooler air flow during the winter but allow for more cooling flow in the summer. According to the owner the problem is not currently there but if it truly is a high temp oil breakdown issue it would make sense in hotter climates to add additional cooling to the oil. Just trying to get as educated as I can. Not trying to re-invent the wheel if this has been looked into, just haven't found much on a larger oil cooler talked about.
Thanks Mark

[peter anson]

Hi Mark, I'm assuming the engine is already fitted with a cooler because they can't run without one. My very early model engine came with a single layer cooler that wasn't big enough (I think it might be the type recommended for the 2200 engines). I replaced it with a larger multi-layer cooler that I bought from Jabiru Australia I can't remember the model off-hand but I'm sure there are plenty of people who can recommend suitable types. If the aircraft you are looking at has a similar cooler it should be fine.
Peter
Sonex 894 Jab 3300, 353 hours

[DCASonex]

Mark,
If using the "Standard" oil pressure port which is the one on the 45 degree angled upper surface of the crankcase, you will be reading pressure from the pump, the port facing forward directly below that is the one that will show actual pressure being feed through the engine, after it has passed through cooler and filter, and is the port I prefer to monitor. If reading low pressure in forward facing port, temporarily move sensor to upper port to help locate the problem.

In addition to what Peter mentioned, make sure that the fittings in the oil cooler adapter have been up-sized to at least 1/4" NPT.

I know of at least one 3300 where the washer that Jabiru calls a seat for the PRV (Pressure Relief Valve) had worn its pocket in the crankcase to the point where it flopped around so much that too much oil was simply bypassing around it. Making new thicker seat seemed to cure that problem.

At worst case, low oil pressure may be due to fretting between the case halves which can require major machine shop work to fix so worth trying to get a handle on the problem before purchase.

Strongly recommend that you join the JabCamit forum on Yahoo for support for that engine. Lot of knowledgeable folks on that, and a lot of Sonex drivers.

Would also get the serial number of the engine. There was a period referred to has early hydraulic engines, that are prone to several problems. The very early solid lifter engines have a good reputation, and the more recent series (hollow push-rod and then the roller lifter types) seem to have addressed most of the problems.

Hope this purchase works out for you. A good 3300 in front of a Sonex provides more fun than any other option.

David A. Jabiru 3300, and now CAMit 3300.