CHT EGT lost on 1 and 2 - 500hr exhaust replacement

[paulmilo]

Hi Steve,

In your thread subject you state 500hr exhaust replacement. Where does it state that the exhaust must be replaced at 500hrs, I understand it requires ongoing inspections and if cracked, replacement, but I have not found anything mandating replacement at 500hrs, although you are the second person I have seen imply that is a requirement in Australia. I’m hoping I don’t have a large bill around the corner!

Cheers,

Milo (Melbourne, Oz).

[SteveHarding]

Email from my LAME update

We have check all the EGT, CHT & fuel injector wiring and checked the resistance.
Reading thru the manual & the trouble shooting section Chapter 77-40 Page 34 of 34
“Any of the following indications absent or erratic : RPM, Manifold Pressure, EGT, CHT, Fuel Flow. (FADEC Health Status Annunciator Normal).
It gives 2 options
1st Interconnection Fault = Replace interconnection cable between FADEC & connector VM-04 on DPU or
2nd DPU= Replace DPU (Data Processing Unit) Part Number We have check all the EGT, CHT & fuel injector wiring and checked the resistance.
Reading thru the manual & the trouble shooting section Chapter 77-40 Page 34 of 34
“Any of the following indications absent or erratic : RPM, Manifold Pressure, EGT, CHT, Fuel Flow. (FADEC Health Status Annunciator Normal).
It gives 2 options
1st Interconnection Fault = Replace interconnection cable between FADEC & connector VM-04 on DPU or
2nd DPU= Replace DPU (Data Processing Unit) Part Number 4010083.

We have checked the cable with no faults showing.
So I think the DPU may be out problem as the engine is running fine which tells me the FADEC is working OK & we have no lights.

It just cant get the data to the screen.


We have checked the cable with no faults showing.
So I think the DPU may be out problem as the engine is running fine which tells me the FADEC is working OK & we have no lights.

It just cant get the data to the screen.

[SteveHarding]

The Exhaust replacement is 1000 hours not 500 which I have just reached.

[paulmilo]

Are you servicing under Schedule 5 Steve? If so, I’m not sure you will need to replace the exhaust. Same as the engine, under the Discovery Maintenance Schedule you will need to overhaul that now (12 years), but under Schedule 5 you can run on condition. I assume the exhaust would be similar (?)

[SteveHarding]

Hi All - update as follows. Yes I am running the engine on condition ( schedule 5 ) and the exhaust has been removed and checked. With regard to to my EGT and CHT on 1 & 2 we tried the DPU replacement which was not successful. With the help of another Liberty owner who my LAME also does the work on we were able to swap out one FADEC unit and the problem is solved with all faults being removed and display on VM1000 correctly showing EGT and CHT on 1 & 2.
The question now is do I order a new FADEC unit from TCM or try my hand a a 2nd hand unit.
Another pressing question is how is it possible that no fault indication lights occurred with a suspect fadec unit ?

[paulmilo]

Lucky you had a ‘spare’ aircraft to do the fault finding! I’d be very interested in the cost you end up paying if you could share.

Cheers,

[SteveHarding]

So a quick update on the EGT and CHT on ZLY. After swapping out the RHS fadec unit with another liberty owners aircraft and all issues resolved on cyl 1 & 2. Considering the cost of a new unit it was decided to open up the unit and have a look inside.
this took some time considering the sealant used but once open the circuit board and connecting pins was cleaned throughly and reinstalled and sealed. Problem now resolved without spending $6500 US.

[N645XL]

Outstanding!

[paulmilo]

Well done. Did you do that yourself or use a LAME? Would be good to have a contact in Oz

[frfly172]

The exhaust requires inspection at twenty five or fifty hour intervals. The hours depend on what model exhaust was installed. That and the prop torque can usually be done with the oil change.