Low oil pressure TLS/Bravo

[Robg]

I have a 91 TLS with the Bravo conversion done in 1997.  Recently seeing oil pressure that decreases at high power and increases at low power.  My mechanic called Lycoming, who recommended we check to ensure that the correct lower exhaust valve seat was installed.  1700TT with about 900 since the conversion.  Three cylinders pulled and reworked/overhauled since that time, one by a prior owner, two since I've owned it.  I've owned approximately 3 years.

Apparently, the wrong part number is installed for the valve seat and the correct ones are $200 each.  Question to those knowledgeable about this marque:  Does the Bravo conversion come with all new cylinders, or is it a kit to modify existing ones?  I'm trying to figure out how the wrong part number would have been installed on cylinders that have never left the engine (assuming logs are accurate and I've had no occasion to think otherwise since I've owned it).  Second question, if the part number that's installed is for the -AF1A engine, would that cause the symptoms I'm seeing now?  (Oil pressure is confirmed accurate, since the factory gauge matches the OP on my JPI that uses a different transducer).

Appreciate any insight from those familiar with this engine.  Thanks, all.

[Skywarrior]

Not an expert on this at all, but my '91 Bravo has Oil pressure at the top of the green after engine start, then it drops to the bottom of the green after climbout. It started doing this after an MSC installed an oil pressure sensor with a stronger spring than the original one. (at least, that's how I understand it)

The valve seat notion doesn't make any sense to me, but as I said at the beginning...

Chuck M.

[LT4BIRD]

Oil should be 80-100 cold and as the temp increase's the oil will thin to 50 -80lbs.

What type of oil are you running?

I don't see valve seats  affecting oil pressure.

[thinwing]

I think you have a warrenty issue...The Bravo cylinder heads were a lycoming designed and supplied part with them being shipped complete with the new oil ports to the valves installed.I believe valve seats would have been installed at factory along with valves inplace.If wrong part # was installed (Valve seat from af1aversion)at the factory ,than this is a defect with no limitation on warrenty  re the low oil pressure...not directly related,but I bet  you end up with new jugs one way or the other...kpc

[drmarkflies]

I have a 91 TLS with the Bravo conversion done in 1997.  Recently seeing oil pressure that decreases at high power and increases at low power.  My mechanic called Lycoming, who recommended we check to ensure that the correct lower exhaust valve seat was installed.  1700TT with about 900 since the conversion.  Three cylinders pulled and reworked/overhauled since that time, one by a prior owner, two since I've owned it.  I've owned approximately 3 years.

Apparently, the wrong part number is installed for the valve seat and the correct ones are $200 each.  Question to those knowledgeable about this marque:  Does the Bravo conversion come with all new cylinders, or is it a kit to modify existing ones?  I'm trying to figure out how the wrong part number would have been installed on cylinders that have never left the engine (assuming logs are accurate and I've had no occasion to think otherwise since I've owned it).  Second question, if the part number that's installed is for the -AF1A engine, would that cause the symptoms I'm seeing now?  (Oil pressure is confirmed accurate, since the factory gauge matches the OP on my JPI that uses a different transducer).

Appreciate any insight from those familiar with this engine.  Thanks, all.

RoBG... my response in neither timely nor do I have a solution yet. All I offer now is affirmation that I have the same oil pressure problem and will report back.

 

I have always had the same reduced oil pressure indication at cruise since I put in a new zero time Lyco TIO-540. Just barely in the green (40 psig) at high MP (32). At start up pressure is 80. Lower MP (27) puts the needle back at 55-60 psig.

 

Now with 50 hrs. on the zero time, oil burn in #2 and #6 has never resolved with break-in. I can tell by coking around the exhaust expansion joints on the manifold.

 

Unrelated, but, I also had oil seal failure on two brand new turbos, both failures identified by oil in the exhaust pipe on pre-flight rather than in flight.

 

My $50K Lycoming engine is a pain, but so far Lyco has paid for warranty issues. Now working with Lyco Authorized service center on oil burn problem an low pressure problem (related?)  Will definitely look into the possibility of an incorrect valve seat as mentioned, but I think oil could be making its way around the rings.

 

I will report back causes with oil burn and low pressure when they become clearer.

[MB65E]

As for the oil pressure spring, I had a shop tell me to use P/N LW-18085 oil pressure spring on the Bravo I took care of for awhile. This was changed to prevent low oil P at altitude above 13k. I changed the spring and remember the issue being much better. From my recollection, all the true Bravo conversions recieved a new data plate indicating TIO-540-AF1B. "B" being the key to the mod... Not sure why you still have the "a".

Great airplane and engine combo, if you can keep cylinders on it!

Hope this helps.