Need some advice for Mooney 231 with CHT acting up

[Jrob]

Good morning all, 

I have a '81 231 with about 1500 SMOH, LB engine with a JPI 700.  A couple of flights ago, just after oil change, I noticed that #5 was showing CHT LOW.  EGT was normal range, engine was running smooth and I as out in the sticks so I finished my trip (150NM) and just before landing, the CHT was reading normal again.  Two days later, plane started fine with no rough idle or morning sickness (OAT 25F) and everything read normal.  Flew home without a problem. Last trip home, CHT did the same thing with a LOW indication and EGTstill normal.  Probe registers inline with the others before start up and engine runs smooth.  I'm taking the plane in but wanted to get some opinions as I think the mechanics often jump to worst case scenarios (ie pulling the cylinder and checking for valve issue).

The JPI was installed with zero slack on the wires so I cant reach the #3 wire up to #5.  Would anyone say replace the probe first? Any thoughts are appreciated.

Judge

[Andy95W]

Check and clean all the connections first, and you might as well swap that probe to a different cylinder.  That way, if the problem follows the probe, you'll know it's bad.

If the problem remains on #5, then it is most likely a dirty connection at the d-sub connector at the back of the instrument.

Edited March 30, 2016 by N1395W

[MARZ]

A while back I was flying from Dallas back to Houston, I happened to look at my egt gauge only to find out one was indicating stone cold - first thing I thought was I had lost a cylinder - I was sure of it - heck I even thought the engine was missing and I had a vibration... after dialing up the closest on my 430 figuring out how far I could glide when the engine shot craps and picking a good landing spot in case I couldn't glide to the nearest -   I reflected a bit and cross checked a few things - my airspeed hadn't dropped, in reality the vibration was the same ole familiar drone, broke the seal on my headset to listen to the engine - all normal - telling me I had fallen pray to the technology trap!!

75 dollars later and a new probe in place all was back to normal.....

But it sure was a good what if exercise, though somewhat unnerving.

[carusoam]

A fun way to exercise your JPI skills...

Download the data and post it on MS.  Try to capture the issue on a page.

If there is something unusual, it may be recognized by an MSer.

There is also a service that you can upload the data to.

Best regards,

-a-

[Jrob]

Thanks for the input. I went and opened up the cowlings and moved the air box but realized I didn't have my "plug sockets" so I'll have to tackle it this weekend. Wife says I have to mow the yard tonight. I started looking around and found my flexible exhaust pipe looks terrible. I had the oil changed last time (15 hours ago) and am certain it wasn't there when I changed it 45 hours ago. Any ideas on what may have happened. Don't mean to highjack the thread but I started it anyway. Any thoughts on replacement product?  The "aerodux" that is in place seems really brittle.  Again, thanks for any help

 

[carusoam]

Is there a penalty for high jacking your own thread? 

Aircraft Spruce had that kind of material.  Diameter an length will be needed for the proper order.

Best regards,

-a-

[Guest]

Aero duct Scat 12 for the broken the duct.  You should also remove the 2 Tyraps from the steel tubes before they damage it, and the damaged Adel clamp with the missing rubber.

Clarence

[grami-air]

Just curious.  What does the OEM CHT gauge show when your JPI CHT is indicating a low CHT?  That is unless the #5 OEM CHT probe was removed and the cluster gauge marked "INOP"

[Jrob]

M20Doc- thanks for the visual overhaul based on one picture. That was like finding the hidden picture game. I did notice lots of zip ties to the frame. Do all of those need to be phased out and replaced?  Any thought on SCEET v SCAT? I've heard that SCEET can work loose easier but I also had some serious gouges in the oil pan and MERLIN caused by the wire in SCAT hose. 

The OEM gauge was reading normal but I didn't realize it was on #5 and as I said before EGT was normal and the plane ran smooth and otherwise normal. Thanks again for yalls help. 

J

Edited April 1, 2016 by Jrob
Typo

[Guest]

7 hours ago, Jrob said:

M20Doc- thanks for the visual overhaul based on one picture. That was like finding the hidden picture game. I did notice lots of zip ties to the frame. Do all of those need to be phased out and replaced?  Any thought on SCEET v SCAT? I've heard that SCEET can work loose easier but I also had some serious gouges in the oil pan and MERLIN caused by the wire in SCAT hose. 

The OEM gauge was reading normal but I didn't realize it was on #5 and as I said before EGT was normal and the plane ran smooth and otherwise normal. Thanks again for yalls help. 

J

I do look carefully at all the pictures people post here to see what I can spot.  Its a skill which seems weak in the current crop of maintainers.

Adel clamps are safer than Tyraps in your engine compartment.  Accepted standards for tube damage is 10% reduction in wall thickness, that means 0.003"- 0.005" for a typical mount tube and a dent equal to 20% of total diameter of the tube.

Clarence

[Steve Dietrich]

Hose looks like it has been rubbing on something .  Look at the inside of the lower cowl to see wuzzup

Also look at the white deposit  on the turbo oil return line just below the turbo to make sure that it is not an exhaust leak.

Edited April 1, 2016 by Steve Dietrich

[Jrob]

Looking in through the cowl flaps before removing it, I didn't see anything rubbing .  Do you think the white deposit on the turbo return line would be from this hose opening up? It's a SCAT HOSE from pilot exhaust manifold to the copilot side. What would you see/smell/hear in the cabin or on the JPI if you had an abrupt exhaust leak?   Would you lose power due to less exhaust going to the turbo and if so, how much?  On the last flight, plane ran fine and nothing seemed out of the ordinary except the #5 CHT reading LOW. 

Edited April 2, 2016 by Jrob

[Steve Dietrich]

There is a connection and probably a  gasket where the exhaust enters the turbo,  I would look very carefully around the turbo .  It might just be white spray lubricant but exhaust leaves a dull white deposit ( lead )   anything with the turbo plumbing is critical.  Also while you are in the hood check the clamps holding the checkvalves on the turbo supply and return oil lines.  The integrity of the rubber on the clamps is VERY critical as the clamp will wear through the valve body in short order.

 

I can not tell if the scat tubing is the heat system or the tubing running from the alternate air intake to the turbo side of the motor.

 

The black on the scat tubing indicates it was rubbing on something   may have been the cowl

 

 

Edited April 4, 2016 by Steve Dietrich