252 Turbo loss - exhaust gasket failure

[carusoam]

Piggy back on the existing CHT probe is way better than a probe/gasket for the spark plugs...

The gasket style probe just doesn’t take the punishment, and it is measuring the wrong place, when consistency matters...

For a really hot measurement a probe closer to the exhaust port would be better for analysis.  But we’re not necessarily that interested in the hottest points...

We have taken a convenient point to measure, and associated some rough limitations around them... 380°F using this spot here... or Red Line from the same spot....

PP thoughts only.

Best regards,

-a-

[kortopates]

After my last post I felt a little remiss about not mentioning the safety issue of continued flight. Thirty minutes is a very short flight that probably most would be tempted to continue. But recognize a loss of MAP as experienced here is very significant. A small leak, whether induction or exhaust, will not typically cause a significant loss of MAP. A large leak is more likely with significant loss of MAP, and consequently if its exhaust the threat of fire is very real and there is no more time critical emergency than fire. All this adds up to the need to divert to a nearby field before things get much worse. Maybe it turns out to be a minor induction leak, but you just never know.

 

Luckily these kinds of turbo related issues are pretty rare, but we need to diligent about getting down if and when they do occur.

 

Sure don’t mean to be critical of Bryan in this instance, this was really meant for others that have yet to experience such an emergency. Hopefully very few will.

 

 

 

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[kortopates]

Figured so, that is why I want to go to the EDM900 to be able to remove the factory probe and gauge. My current setup shows #2 with 50* above the others normally, this with brand new baffles. JPI says I can move the spark plug to the top cylinder but figured I would start with a new probe.

The piggyback adapter probes work pretty well for CHT. But the real issue IMO is that your 730 is just very limited. You really need a full up engine analyzer that includes FF, MAP, RPM, oil temp & press and that is integrated with your GPS for alt etc. all that data is critical to interpreting what’s going on with the engine at altitude. The EDM 900 is my choice, but if need to for budget, you could simply upgrade the display to the 830 and add the few additional sensors and be much better off.


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[kortopates]

You will likely see just the opposite in temp readings although not too much.
Putting the piggy-back thermocouple on will read slightly lower than the other cylinder temps.

We see it go both ways at Savvy. But the piggy back is quite close. But the spark plug gasket probes are terrible and they can go either way too.


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[N201MKTurbo]

I have had my compressor side pop off valve fail and cause a sudden drop in MP like this. 

A $700 fix as opposed to a $3000 fix.

[L. Trotter]

On 3/31/2018 at 4:05 PM, Bryan said:

I have a sensorcon CO2 sensor in my cockpit and pretty low (normal) readings today. It’s right in my face so I would notice higher CO2 readings. I will de-cowl and take a look. 

Thanks for the input, will get someone to look for leaks around the turbo and V-Band clips; no idea on their last inspection. The plane has a fresh annual.

Just to clarify for others understanding......

Carbon Monoxide (CO) that would enter the cockpit through the heating system (and thus raise CO levels on a sensor) would occur from a leak with in the exhaust heating shroud. A leak from a turbo charging unit (turbo charger case or V-band attachment points) would blow 1500+ºF exhaust gas inside the cowl (not associated with the heating shroud) which would exit with the normal flow of cooling air. This "leaked" gas would not likely enter the cabin. Therefore,  a CO sensor will NOT detect a turbocharger system leak. The hot gas will acted as a blow torch with in the cowl and likely burn something up.

[jlunseth]

I see some stuff in this thread about getting data.  Fine, if you can get the data without flying the aircraft again.  But please don’t go up again even for a short flight in the pattern until the problem is diagnosed, because it does look and sound like an exhaust leak.  George Braley tells a story about these (v-band failures).  I will shorten it up.  His brother flew a light twin with turbos, saw suspicious reading on the engine monitor, knew what they meant, and made a rough emergency landing with some damage to the aircraft.  The NTSB agent said he was glad to talk to him.  George’s brother was apologetic about the landing.  The NTSB guy said, you don’t understand, I have investigated several of these and you are the first pilot I have been able to talk to.

The exhaust temp is pressurized and in the vicinity of 1700 dF.  Whatever you do, don’t fly it again even to test it, unless you know to a certainty you do not have a leak.  White powder or soot is a sign of exhaust leak or crack in the turbo.  

You had at least some turbo working for you.  Pressure at 18 k is a half atmosphere.  If atmosphere is 30” (29.92) then a half atmosphere would give you a MP of 15”.  1ATM=14.7 PSI  times 2.036 - 29.92 .  At 15k you would have had somewhere around 17” if no turbo.

Don’t fly it please.

PS During pre-flight, every flight, you should open the turbo inspection door and check for two things.  One is white powder, actually its more like gray, and usually it coats the outside of the turbo. Two is take the end of the exhaust in your hand, try to move it, and check to see if there is any movement at all in the turbo or exhaust system.  You don’t want to put a ton of force on the system obviously, just see if you can make it move.  If it moves, don’t fly.  

You could do that check on your aircraft right now, I bet you will see movement.

Yes, it could be a controller or wastegate issue, but the soot is telltale of a leak.

Edited April 1, 2018 by jlunseth

[231LV]

Absolutely agree, have your mechanic inspect regarding the turbo and all associated lines, gaskets, etc. Also, tell your mechanic to run a compression check on all 6 jugs....my 231 exhibited similar characteristics as you described, though more subtle which lead me to believe I had a turbo problem. Turned out I had lost all compression on 1 of my jugs....it was still firing and looked normal on the JPI but wasn't putting out any power.

[Bryan]

UPDATE:  Was able to go out to the plane today after a great Easter Holiday with the family and inspect the issue. After reading your comments, I am very thankful to be able to be here after what could have been bad.

I first removed the inspection panel but nothing visible we could tell besides the soot aft of the access panel on the cowl as shown in the picture above.  We continued to remove the cowl and my mechanic just happen to stop by the airport to drop something off to a hanger neighbor.  Great timing!

We got the cowl off and no visible signs of anything on the inside of the cowl - nothing burnt or discolored as evidence of anything - to the cowl.

After a quick look at the turbo and V-Band clamps, all is tight and no indication of leaks or cracks which also confirmed my pre-flight check at the beginning of the day.  All was very solid and in-tact. 

Following the exhaust up, we found the source pretty quick - it was the exhaust gaskets blown on #3 and #5.  In fact the outboard exhaust stud and nut was missing from #3 completely.  #5's outboard nut was backed out and not tight at all.  It appears that these exhaust gaskets were the "no-blow" style as they were still in-tact but will not be re-used.

Very lucky to not have caught fire or worse!

We are ordering all new NUTs and Gaskets for all 6 cylinders even though we might only need to replace 3 sets of them and at least several studs to replace the missing ones and the ones that need to be replace for removal of the system.  I have the part numbers for the Gaskets (630365) and the Nuts (22022) - "using two gaskets per exhaust port, concave sides together" per the Continental SB14-8.

I need to find the replacement stud part number.  Anyone have that manual digital for the TSIO-360-SB they could PM me?  Or a link?

My A&P that happen to be out at the airport on Easter Sunday and gave me an hour of his time to take a look said he has the manual in his office and could get it tomorrow.  He said after replacement of these parts we would pressure test the exhaust system for leaks and compression check the jugs.

I have learned some very good lessons in this deal and hope someone else does, too.  Engine monitors are invaluable - trust what they are telling you and process the information to stay as safe as possible. 

Thank you everyone for your help in the opinions and insight into the possibilities of what could have been a lot worse.

 

[jaylw314]

Holy smokes!

FYI, here's the link for the USB-to-serial adapter I use for EDM-700 series.  $27 at Amazon. 

I use one of those Windows hybrid tablet/notebooks.  They're cheap, light, have USB ports, and will run the JPI software fine. 

Also FYI--the CO monitor will only detect CO, not CO2.  When you run lean, you make far less CO than if you were running rich.  A such, you'd be less likely to detect a CO leak (either through the firewall or the exhaust heater) if you were leaned out in cruise than during climb.

[kortopates]

Boy, i was right on with it being the #3 gasket.
I believe what you refer to as #6 is actually your #5.
Unfortunately, you can’t assume you’ll need the standard stud, you may need to go oversize. Your tech will know when a new one is screwed in if it’s not tight. Loctite should be used too.
But before it goes back together make sure the aluminum exhaust port is cleaned up from any erosion caused by the leak - otherwise it will continue to leak. i.e. it may likely need to resurfaced to be perfectly flat if the leak burned away aluminum as it often does. There are tools to do this in-situ if needed so that cylinder doesn’t need to be pulled.

BTW, it’s not uncommon for these engines to shed exhaust bolts which is why it’s so important to inspect these with every oil change.


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[Bryan]

@jaylw314, thanks for the link. I will try to get one ordered.  And yes, I said "CO2" but mean "CO" earlier in the post.

@kortopates Yes, you are correct - not #6 but #5 - my two odd (co-pilot side) exhaust gaskets had blown.  These will be added to my oil change checks.

My mechanic did mention that we might have to helicoil the missing stud hole but would examine when we drop that exhaust side off; won't know until we get a closer look.  Same for the re-surfacing of the exhaust port.  I think I found the replacement stud part number: (TCM 402044P003)

[wpbarnar]

While you are at it,  take a close look under the heat shield on the exhaust cross over tube in front.   On my TSIO 360 SB, I found the mounting standoff for the heat shield, chafing into the exhaust tube.

Bill

[carusoam]

Got to love the power of MS...

Thanks to all that contribute...

Nice catch, Bryan...

How are you feeling during your steep learning curve?

I am a bit surprised about the CO monitor... dumping a bunch of exhaust in front of the firewall has a tendency to find ways into the cabin.

What make and model monitor are you using?  You may want to make sure it is working as expected...

If it is the Sensorcon unit, there is a method of testing and calibrating...

Best regards,

-a-

[jaylw314]

1 hour ago, Bryan said:

@jaylw314, thanks for the link. I will try to get one ordered.  And yes, I said "CO2" but mean "CO" earlier in the post.
 

Oooh, dang, I should point out that the serial cable to the JPI plug needs to be ordered from JPI for $39 unless you happen to have it in the box of goodies your seller left you...  I suppose if you were good a pinning and soldering, you could make one yourself, but I don't know how it's wired...

[kortopates]

1 hour ago, Bryan said:

TCM 402044P003

My recollection is the P003 suffix refers to the 3 thousands oversize. You'll want to start with the standard size and only go to the over size if the standard size fits loose.

[jlunseth]

1 hour ago, wpbarnar said:

While you are at it,  take a close look under the heat shield on the exhaust cross over tube in front.   On my TSIO 360 SB, I found the mounting standoff for the heat shield, chafing into the exhaust tube.

Bill

Same here.

[jackn]

The first thing that I would do, is to look in the logs to see who installed this engine. I would have somebody else look this engine over with a fine tooth comb. also, look to see if they did any other work on this plane.

[Marauder]

UPDATE:  Was able to go out to the plane today after a great Easter Holiday with the family and inspect the issue. After reading your comments, I am very thankful to be able to be here after what could have been bad.
I first removed the inspection panel but nothing visible we could tell besides the soot aft of the access panel on the cowl as shown in the picture above.  We continued to remove the cowl and my mechanic just happen to stop by the airport to drop something off to a hanger neighbor.  Great timing!
We got the cowl off and no visible signs of anything on the inside of the cowl - nothing burnt or discolored as evidence of anything - to the cowl.
After a quick look at the turbo and V-Band clamps, all is tight and no indication of leaks or cracks which also confirmed my pre-flight check at the beginning of the day.  All was very solid and in-tact. 
Following the exhaust up, we found the source pretty quick - it was the exhaust gaskets blown on #3 and #5.  In fact the outboard exhaust stud and nut was missing from #3 completely.  #5's outboard nut was backed out and not tight at all.  It appears that these exhaust gaskets were the "no-blow" style as they were still in-tact but will not be re-used.
Very lucky to not have caught fire or worse!
We are ordering all new NUTs and Gaskets for all 6 cylinders even though we might only need to replace 3 sets of them and at least several studs to replace the missing ones and the ones that need to be replace for removal of the system.  I have the part numbers for the Gaskets (630365) and the Nuts (22022) - "using two gaskets per exhaust port, concave sides together" per the Continental SB14-8.
I need to find the replacement stud part number.  Anyone have that manual digital for the TSIO-360-SB they could PM me?  Or a link?

My A&P that happen to be out at the airport on Easter Sunday and gave me an hour of his time to take a look said he has the manual in his office and could get it tomorrow.  He said after replacement of these parts we would pressure test the exhaust system for leaks and compression check the jugs.
I have learned some very good lessons in this deal and hope someone else does, too.  Engine monitors are invaluable - trust what they are telling you and process the information to stay as safe as possible. 
Thank you everyone for your help in the opinions and insight into the possibilities of what could have been a lot worse.

 

Thanks for the update. In 1993 while on an IFR Flight in IMC I had the same thing happen to my non-turbo. One of the studs broke and the other nut vibrated free resulting in the entire exhaust stack falling into the cowling. I had an engine analyzer (a GEM 602) and saw the loss of EGT but the remaining CHT. It also sounded like I was on Harley.

There was a follow up with the FAA and the determination was the stud failure was due to over torquing the nut.


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[Bryan]

My Sensorcon Inspector unit is less than 6months old from molex by recommendation here.  I think it is working because normally at a climb i show 11-15ppm and maybe saw 20-25ppm this day on the climb but when I realized the problem and pulled back for level flight it went down to below 10ppm and never alarmed over 30 (or 50), I forget.

On the ground, with the door seal deflated and the door cracked, I did notice it higher but nothing off the charts.  In fact, normally, in cruise, when I pull my cabin heat it goes from 5-9ppm down to 1 or 0ppm (normally).

Again, more information (even the firehouse method) is better than no information.  Thanks all.

[FBCK]

 I look down and my MP is near 36” instead of the normal WOT (wide open throttle) 39” (Encore 252 )

 

Shouldn't the max for a 252 be 36 inches?

[LANCECASPER]

On 4/2/2018 at 3:17 PM, FBCK said:

 I look down and my MP is near 36” instead of the normal WOT (wide open throttle) 39” (Encore 252 )

 

Shouldn't the max for a 252 be 36 inches?\

Page 1-4 of the Encore (220 hp -SB engine) POH says 39" MP at 2600 rpm.

[FBCK]

Thanks, I guess that's where the extra 10 hp comes from.

[thinwing]

On 3/31/2018 at 3:26 PM, milotron said:

BTW it looks like you have a data logging serial port for the JPI up and to the left from the display...or am I mistaken?

 

 

It looks like the same port as mine..and yes you can download from that port...get one from jpi but it is not USB ..it's an rs232 ..you will need an older lap top but the data is there

[Bryan]

@jaylw314 pointed out that there is a serial-to-usb adapter that works with the rs232-to-serial cable from JPI.  Amazon delivers mine tomorrow:
"link for the USB-to-serial adapter I use"

 

Over the weekend, I got all the new parts in and my A&P got them installed without too much issue.  Here are the part-numbers in case anyone needs them:

TCM Exhaust Gaskets: 630365
TCM Studs: 402044P003  (yes, the P003 designates the oversized by three thousands but these are nice and tight - replaced two.)
TCM Nuts: 22022

Note: the oversized studs are colored red probably to denote the over-size.

He checked and re-torqued all of them before we ground ran the system to ensure nothing leaked before the test flight - all good now.  MAP is back up to the normal 39" at WOT.  Thanks guys! 

We did find a couple more that were not super tight and confirmed all are torqued according to the SB referenced above.  This will become another check during my 30hr oil/filter changes.