TSIO-360-MB boost weirdness

[geoffb]

This morning on my climb out at maybe 8,000, full power,I had a sudden drop in manifold pressure. About 3 inches loss.  Lasted 3-4 seconds I’d guess and returned to 36 inches.  A couple minutes later, it did it again.  I got up to cruise at 11,500 and 65% and everything seemed normal for the rest of my flight.  I was keeping my eye on it and the pressure would vary some, but less than 1 inch of wander.  Don’t know if that’s unusual as I don’t usually get fixated on the manifold pressure in cruise.

This afternoon in the return home, same deal.  Full power climb on my way to 10,500 and twice got a dip in MP of 3-4 inches.  It’s enough to get your attention.  Only last seconds and returns to normal.  Cruise at 10,500 normal behavior, made boost, no unusual temperatures, oil pressure steady.  Even during the incident oil pressure was steady.

anybody had this happen before?  Reading the description of the pressure controller it seems unlikely that the poppet could just unseat.  Are the pop off valves known the get lazy?

I’ll inspect all the exhaust tomorrow to makes sure there’s no issue with the stuff that will kill you, but I don’t see how an exhaust issue could give these symptoms.

[Z W]

When ours did this, it was the wastegate sticking.    

Showed up like you described, slowly got worse, until MP maxed out around 28".  

Mousemilk lubrication was the answer.  It's recommended in the service manual every 100 hours, and it's on Mooney's 100 hour/annual checklist, but seems to be commonly missed.  Ours gets a few drops at every oil change now.  Cheap and easy place to start.  If yours is lubricated and/or this doesn't help, I'd suspect the wastegate itself, the turbo controller, and/or the turbocharger itself.

 

[LANCECASPER]

The most difficult part of doing this is getting the mouse to hold still so you can milk it. 

[anthonydesmet]

Had this happen before.  Could be wastegate but also might be water in fuel.  Sent my data off to SAVVY and they said most probably due to water droplets in fuel which was weird because obviously I sumped before flights pretty well.  I remembered a few days prior I was refueling and towards end of filling up it started to mist.  I am told that sometimes water droplets can get trapped behind some of the tank ribs and dislodge especially during climb out.  They recommended putting some HEAT in the tank.  Only happened on the tank I filled up during misting conditions.  When I switched tank no issues.

so does it happen on both tanks, was it raining during refueling?  Airplane sit outside?  Last time you changed fuel cap o-rings?

just thoughts.

[Fly Boomer]

8 hours ago, geoffb said:

I’ll inspect all the exhaust tomorrow to makes sure there’s no issue with the stuff that will kill you, but I don’t see how an exhaust issue could give these symptoms.

Post above by @anthonydesmet is a great application of Occam's razor, but many say the Mouse Milk treatment should be on regular rotation if it isn't already.

[Pinecone]

4 hours ago, anthonydesmet said:

Had this happen before.  Could be wastegate but also might be water in fuel.  Sent my data off to SAVVY and they said most probably due to water droplets in fuel which was weird because obviously I sumped before flights pretty well.  I remembered a few days prior I was refueling and towards end of filling up it started to mist.  I am told that sometimes water droplets can get trapped behind some of the tank ribs and dislodge especially during climb out.  They recommended putting some HEAT in the tank.  Only happened on the tank I filled up during misting conditions.  When I switched tank no issues.

so does it happen on both tanks, was it raining during refueling?  Airplane sit outside?  Last time you changed fuel cap o-rings?

just thoughts.

I had this happen on one flight.  We did get fuel and the airplane was out overnight.  But sumped fine.

I wonder if there was some dissolved water and the temp (14,000) caused it to come out.  It stopped after a short while and has not happened again

[anthonydesmet]

It was just a thought.  Obviously good advice above for wastegate health and I also change out my fuel cap rings regularly. Probably just me but want to make sure nothing gets in there especially if I’m in the road a lot. I also carry a couple bottles of HEAT.  If I sump and find water, sump until it’s gone, sump the gasculator and also add a bottle for peace of mind….I might be overreaching but MP surge or loss especially at night or IMC brings be back mentally to days of night catapult shots…..I’m to old and gray for those these days……hah!

[geoffb]

Thanks for all the responses.  I'm not 100 hrs from annual yet, but will try a little rodent milk.  Don't suspect water at this time.

My normal routes take me over the cascades with about 30 minutes of unpleasant terrain.  So, yes, it gets your attention.  Will report back.

[Will.iam]

Check your boot to naca vent on lower cowling make sure it’s not loose and or partially collapsed. Also check to make sure alt air source is not opening in flight especially under high demand loads like climb out. 

Edited April 26, 2023 by Will.iam

[geoffb]

Will do.  Hadn’t considered either of those

[geoffb]

Application of the rodent milk immediately following the advice and a second application after this weekend's oil change seem to have all functioning as normal.  Thanks again for pointing me in the right direction.

[Will.iam]

On 5/13/2023 at 5:55 AM, M20Doc said:

Be sure to apply it to the wastegate and exhaust slip joints at each oil change.

ok I see from the above picture diagram posted earlier to apply mouse milk on the butterfly shaft and control arm, is there a picture of the exhaust slip joints? are these were the v-bands that have to be replaced if you loosen them are?

[kortopates]

ok I see from the above picture diagram posted earlier to apply mouse milk on the butterfly shaft and control arm, is there a picture of the exhaust slip joints? are these were the v-bands that have to be replaced if you loosen them are?

no but at each joint where one piece of exhaust tubing insets into another slightly larger OD piece. the entire exhaust has one separate piece for each cylinder plus the cross tube in front with 2 sections from memory and then a lower section for the wastegate. capillary action will suck in the mouse milk as you apply it around the seams of each junction.


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[Z W]

I'd never heard of applying it to the exhaust slip joints.  Will start doing that as well.  Thanks Clarence.

[Will.iam]

6 hours ago, M20Doc said:

 

Thanks doc, wholy cow that’s alot of slip joints. Didn’t realize there were so many of them. 

[kortopates]

Thanks doc, wholy cow that’s alot of slip joints. Didn’t realize there were so many of them. 

Still only takes a mere minute or two to catch them all and the wastegate shaft. But remember an oil change is not merely an oil change but part of a ~25 hr inspection which should have you looking up below each cylinder anyway to make sure the engine hasn’t shed any exhaust nuts and there isn’t any exhaust leak stains as well, plus lubrication of all the engine controls, inspecting that V-band clamp etc. etc.


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[RoundTwo]

On 4/25/2023 at 7:52 AM, LANCECASPER said:

The most difficult part of doing this is getting the mouse to hold still so you can milk it. 

For me, it would be getting my big fingers around the tiny little…never mind.

[RoundTwo]

On 5/13/2023 at 6:55 AM, M20Doc said:

Be sure to apply it to the wastegate and exhaust slip joints at each oil change.

Does that apply to all models, or just the K’s?

[geoffb]

There's a shocking number of slip joints in the -MB exhaust, I assume to deal with thermal effects.  The Mouse Milk keeps them moving and not binding to prevent stress and cracking?

Now that I can change a cylinder like a NASCAR pit crew changes a tire, I've become pretty familiar with the exhaust.

[RoundTwo]

3 minutes ago, M20Doc said:

Your J has slip joints at the muffler, they also benefit from Mouse milk.

I guess it’s time to find a cooperative mouse.

[RoundTwo]

35 minutes ago, M20Doc said:

Don’t pick the one in Florida, I heard he’s not too happy lately.

Uh oh. I need to learn more about this mouse milk stuff. I assumed I needed a girl mouse. Yuck!

[KSMooniac]

I hit my J/Knisley exhaust slip joints with Mouse Milk too at annual, and maybe every other oil change.  I'm still using the bottle I purchased 15 years ago.  It is good practice on our exhaust systems and especially those with turbos to keep them freely moving!