Jabiru – Oil leak ..sorted

The ongoing issue of the oil seepage has kept me grounded for a long time now …. The plugging of the rocker breather holes in each head (now I’ve conveyed to solid lifter from hydraulic) has certainly helped see the wood for the trees with only small but positive amounts of oil showing at the base on the rocker guide tubes on ground runs

Each ground run, where I let it get up to 50 degrees then push to as much throttle as the small heel brakes will hold .. usually around 2,300 rpm …at those revs the brakes are starting to squeak and object … but you can get short bursts of higher and accept the move forward if clear.

The option I did in the summmer … tying the tail to the hangar metal upright girder .. I’m not so happy about now .. his was after reading an Australian post on a Jabiru site about having Jab 2200 in taildraggers and excessive ground running NOT being good .

The reason sighted for this was possible oil starvation of the front cylinders, rockers due to the significant slant of the body

So I don’t do prolonged hot ground runs .. if I can avoid it.

Anyway .. to the fix

Having spoken with the engineer I decided an ‘in situ’ fix in a cold dusty hangar wasn’t ideal and to whip the engine out, pop it in a boot and strive up to Yorkshire was probably the far better, sensible, solution !

Engine out Friday, marking all ancillaries and safely supporting the exhaust … carb body status in situ so you don’t d disturb choke and throttle … and it’s craned out and in the boot in just over an hour

Drive to Yorkshire Sunday, work on it Monday, Back Monday night, reinstall Tuesday, Ground run Wednesday !

WORK

The engine was mounted on a sturdy bench … nose down … bolting 3 bolts through the prop driver plate through the table … this made a really easy working environment and the engine was easy to rotate

Given the photos I’d sent ..we looked to remove the rocker push riot tubes from one side first and investigate … rocker cap off, rockers undone .. pin removed … head slackened in turn …and tubes slid out of position

The alloy tubes sit in small alloy cups that then mate into the sump body. The place they insert has a rubber ring in the sump body, the allow tube has a rubber ring … the cups should be quite stiff to remove … but weren’t

This was repeated for all 4 tubes on one side and all cups were relatively slack

These were thoroughly cleaned and de greased and then new rubbers, Vaselined up and a dab of heat proof silicone for surety … and popped back in place .. this was related both sides of the block


Kevin had pre drilled the rear of the backplate – Spider to allow easy (regular) torque checking of the new flywheel bolts vs the big in situ strip.down I had to do when replacing the bolts and nordloc washers last time 👍

Ongoing investigation …oil

Having now plugged the oil vent holes in each rocker head and waited for the massive cold snap to go …and the rains that followed to ease …I’ve finally managed to get out and get 2 ground runs in to check for ongoing oil leaks.

Block and surrounds all degreased and dry I run her up to 50’ then 60’ oil temps .. then ranges from tickover to 2,000 rpm then up to 2,300 before the brakes creak at me that they can’t hold on the wet grass.

Taxy back from the power check area and whip off the now warm cowls to check

3 of the 4 cylinders are showing signs of oil smears and even drips starting at the base of the push rod guide tubes .. on checking the Jabiru maintenance manual these have a double line of rubbers as they locate into the block .. rubbers 11 and 17 in the diagram below as it exits part 13 .. the adaptor

It’s cold outside ….

I have noticed how much colder it is living up in the winter wilds of Norfolk … and the engine doesn’t burst into life as rapidly as she used to … ok it’s still within say 6-8 revolutions … but used to be 1st or 2nd

Ok .. it has been really cold … but this coupled with reading how Jabiru engines configured in a tailwheel aircraft ..mean that at low revs and cold startups .. the oil is sitting in the rear of the sump and may not get ‘efficiently’ to all the parts that it should

In fact an Australian article went as far to say that the front rockers may not get much lube at all in the initial stages of starting and warm up

Ever, and now MORE conscious of the engine (following the rebuild), I’m keen to be aware of more than I was before and so invested in a heater I saw on Machine Mart to allow pre warming of her in these cold cold months

You know that problem .. you look at something in a picture .. expecting it to be much smaller in real life .. heater duly ordered and delivered and it’s way bigger than I’d planned ! … I’d planned to make a neat little hanger and cowl to hook on the prop and direct nice warm air directly to the sump base and fins.

He heater is about 15” diameter and pretty chunky ! Great for warming me whilst I do the rocker cover removals but not quite petite enough for the ‘hang and blow’ design … will resort to plan B .. the Oratex heat gun in a cradle and running low speed

Anyway – following long discussion with my engine specialist .. we have decided to block off the pre drilled rocker breather holes (these were a mod when hydraulic lifter valves were in use)

I’ve moved from hydraulic to solid lifter … so one suspects you probably need to reverse the mod ! And… after 4 shortish flights … that’s what I’m doing …. Stop spraying oil and electrics with oil over the bulkhead !

The small grub screws were provided and the special Loctite Si gasket cement ordered and then warm the hangar up .. degrease everything and apply and screw in place

Each head has a small hole angled upwards and egress into the fin heads
Not bad at about £9 for the tube .. small self tappers provided
Job done
Next .. test what effect this has .. ground run followed by circuit up to 3,200-3,300 rpm

The useful see through rocker cover will let us run it and see exactly what the oil is doing inside the cover …it’s good to make sure they are getting fully lubed and the return flow …not under pressure, goes back down the pushrod guide tubes into the sump.

Short trip before the weather changes – Beccles

Will .. my middle son,who is frustratingly waiting for a combination of aircraft and weather window to complete his qualifying cross country suggested we get the Ranger out and pop to his training base at Beccles for breakfast.

2 pax and full fuel does take her close to limits and the grass was pretty wet at Priory but the base is also pretty firm … even though it was pretty cold and damp he engine warm up was fairly quick .. to 50’ oil temp ….so backtrack to take the 19 southerly take off and then head for the Suffolk coast

Beccles asked for us to extend the landing and miss the grass as pretty waterlogged .. touching down on the tarmac … still need to practice turnarounds by unloading the tail and blipping throttle

Great welcome by super friendly team at Beccles and free coffee as flown in ..

Keeping an eye on Parachute Caravan and canopy drops before getting the “all canopies down” clearance … then Caravan out straight away and we have around 15 mins to get out and off before they drop again and circuit and departing have to wait … seems to work …

One of these nights. …

Not the Don Henley Eagles version … but an evening in the hangar .. sun long down … and a few things to do …

expect to get one , maybe two done … but … to come away with ALL done … great 😊

Now the permit is done … time to clean, tidy and get this little niggly things worked on …

2 more mini screen bolts to drill out and fit … Done

2nd inspection ring under port lower wing needs the proper ‘layered’ inspection sandwich of material with plastic ring in between… the existing hole is one of two in a section between root and first rib. So patching over, with an oversized panel may not easily take … and leave the rest of the panel … some 50cm x 60cm slack

The freshly cut ring, pre glued took really well the the fresh glue around the outer ring of the old inspection hole. As it was so cold in the barn the heat soon dissipated meaning I could lightly shrink it … beautifully tight .. so ready for the next layer of glue to be applied ready to seal in the inspection ring.

Then, my ongoing intermittent click in the radio … whilst working on he engine reinstall, I realised I had BOTH mag leads running almost parallel to 3 dedicated direct earth leads (secured to the engine block) .. one of which is probably the dedicated earth for the Trig radio and Transponder

The slight irony … is that retracing these mag leads … they end up running down an engine mount tube and then end up going vertically up the bulkhead and into a dedicated blue loom … So when I installed I obviously wanted these to stand out and BE separate.

It may makes things better … now diverse routed … but good to continue neatening the general wiring and routing

Flight test and LAA paperwork

Doing something different to the day job ….

Having spent a few days on Teams and QA bits and automation it’s the time to get out and do a full Test Flight Schedule … a 14 page document to be completed for the authorities after any ‘significant’ work … an engine refurbishment is classed as ‘significant’ …

so it’s powered, timed climbs, logging pressures and engine and exhaust temperatures and climb rates …

stalls .. ie basically closing the throttle and waiting for it to slow right down and stop flying ..3 of those …

then dive at full speed … then pull out (ideallly) … and put her sideways with crossed controls then let go of the aileron … do that both ways and log what happens … then setup for landing and put full power and climb away and then down to land

Now try all of that with a biro in your mouth whilst noting the facts and figures and effects … in an open cockpit …

All in a (exciting) days work 😊

Admission … flying takes a chunk of your brainpower as you focus on the various normal tasks …. Now add the slight overload of a flight test .. which raises the stakes a little …ie you have done ‘bits’ that, by their nature, need testing …. Then add the capture of all those measures like oil temp and press … CHT 1 and 2 and EGT 1 and 2 .. and ASI .. and cloud base of the extended climb … and lookout …. And omitted one thing …..

..so, was that Tibenham below … oops no … it’s Old Buckenham …. The drift at 3,500 was appreciably more than I’d planned … they probably wondered who his loon was stalling and diving and turning around !

One of the ‘new’ post flight jobs I’ve got to get used to now in the U.K. … is wiping the muddy bottom post landing 😊 a nice job ..after a lovely curving approach down to Priory grass ..

Evening work – New front screen and oil filter

Loads of strip lights in the barn make it very easy to get the old oil filter off and a new one part filled and tightened up against the TOCA unit.

Then don’t forget to wire lock the drain plug and tie off

Then remove the 8 or so very small polished hex bolts and nylocs from the front screen… the one that I very carefully cleaned with brake cleaner !

The old screen was out in around 15 minutes so a quick clean up of the area and then e move some of the protective covering on the new screen before drilling the pilot holes.

Love using clecos … such a simple and useful tool

Using a narrow metal rule to prevent the drill overrun going through the cockpit coving … like it did 6 years ago ! Rookie error 😊

Front screen removed

Bolts out … screen just lifts out…amazing when the new one is in … so clear it’s like nothing is there !

High speed ground tests

Post the engine refurbishment I needed to conduct some (final) high speed ground runs to check for oil leaks under high RPM

The brakes on the Ranger are basically bike cables so wont really hold her much above 2,300 and I need to get to 3,200 and even 3,300 … without the need to chain her to a hangar !

On both these high speed runs, I’d intended to stay on the ground .. but she just always wants to fly … probably something to do with all that lift area and chucking a load of air over them !

Jabiru .. oil flow to the rockers

Having had the much improved refurb of the engine it looks like we have too much oil getting into the rocker boxes … it’s good to have them lubed …but not over lubed

The pipes from the sump route oil up to the rocker boxes and it then drains back down the alloy pushrod tubes …

If the feed is too great then 5e exit back down into the sump can’t keep up … so the rockers fill and, eventually, it reaches the old vent drilled hole that allows venting to the head fins

To confirm all this I’ve now got use of a converted rocker box head … that has had the centre cut out and a glass inspection panel sealed in place. This will allow us to run up to speed and eyeball exactly what is happening

If we find the oil supply is too great … then it’s probably a simple switchover of the oil feed pipes … it seems the ones in place now are high capacity feed

Update .. late September … looks like it might have been user error. I replaced the oil cooler matrix with a new slightly larger one … and, on refilling with oil, I was over generous allowing for the new EMPTY matrix … by about 750ml ! This had nowhere to go .. except out through the breathers …lesson learned 😊

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