Author Topic: Failed compression on #4 jug in TCM IO-360ES (Read 486 times)

Wolfala · « **on:** June 24, 2007, 01:47:10 AM »

Did a 100 hour today for 13 hours with my teacher. Had mid 70s all around, and then we hit jug #4. 10 PSI - what the ****. I put my head down to the exhaust and felt air comming out. Hoping its a piece of carbon built up on the exhaust valve and it just has to be staked, but the failure mode of this wouldn't be pleasent. There were no indications in flight of roughness on the ground or in flight and no vibration.

What else could it be if the valve wasn't sticking? The hobbs has 784 hours, which if tach adjusted is a little over 625 hours actual engine time.

Wolf

Roscoroo · « **Reply #1 on:** June 24, 2007, 01:56:23 AM »

stuck , burnt, mushroomed, carbon on valve . or a broken /weak valve spring.

worse case is a dropped valve seat .

Maverick · « **Reply #2 on:** June 24, 2007, 10:29:43 AM »

May not be a problem at all. Take it out, run it hard (at least 75% power) for an hour. (I am assuming the plane is back together.) Then do the compression check again. If a piece of carbon is stuck on the valve seat that should remove it. Staking only seemed to work in about 10% of the cases we tried. It's better to "scope" the jug first. If the scope shows the valve burned you know you are stuck with a top on that cylinder anyhow.

if it is still soft after running you can pull the jug and have it rebuilt. You might even get away with just lapping the valve if everything else is ok. You'll still have to pull the jug but if the mechanic is ok with you doing the labor it won't cost you much to try.

P47Gra · « **Reply #3 on:** June 24, 2007, 01:49:18 PM »

This is common with the IO 320 and 360. I would do a run up and lean out the engine while at 1800rpm. Lean it out to the point it is about to quit and then adjust the mixture 50 degrees back on the EGT. Or if no EGT gauge then three clicks rich. Run it like this for a few minutes and re do the compression check. If it does not do the trick you have a burnt valve or week spring.

Jugs are fun in pairs!!!!

Wolfala · « **Reply #4 on:** June 25, 2007, 04:37:17 PM »

OK this is the update. My teacher and I pulled the exhaust manifold off and examined the valves from the other good cylinders. As thought, the valves of the other cylinders were seating correctly, but on #4 it was seated about 1/2 inch low for being top dead center. To make sure, we hooked the air hose up and sure enough, it was blowing straight through.

So the remediation is to R&R the jug with a repair only to the exhaust valve. Checking to make sure the valve is not bent, and if it is good to reface the valve and the seat.

R&R to remove the jug and get to the valve is about 6 hours - 7 if they pad the number. Odd thing is, and I didn't realize it till yesterday, we could only tell that the jug was leaking when the engine was at idle - and then only at shutdown did it make the wheezing sound.

Wolf

LePaul · « **Reply #5 on:** June 25, 2007, 05:57:42 PM »

Ouch

That sounds like an expensive process.

If you have that much work to do to it, would it be worth while to do a complete annual/1000hr check?

Toad · « **Reply #6 on:** June 25, 2007, 06:08:00 PM »

When that happens on a Ranger, you pull it through until the exhaust valve is supposed to be closed (you can figure valve sequence from TDC on #1 and pull to the appropriate cylinder) and shoot 2 ounces of marvel mystery oil in the cylinder. Let soak over night.

Fly hard for 1-2 hours.

Recheck comp; brings it up nearly every time.

Wolfala · « **Reply #7 on:** June 29, 2007, 03:19:27 PM »

Final update. Pulled the jug and found a burnt exhaust valve. Makes compression now.

A few photos.

Maverick · « **Reply #8 on:** June 29, 2007, 04:16:06 PM »

How was the seat and valve guide?

Wolfala · « **Reply #9 on:** June 29, 2007, 04:23:18 PM »

Ground the seat and laped the new exhaust valve then put it in.

Maverick · « **Reply #10 on:** June 29, 2007, 04:26:21 PM »

Did you do the labor or have it sent out?

Wolfala · « **Reply #11 on:** June 29, 2007, 04:28:21 PM »

6 hours labor - I could've done it but needed the plane up for the weekend for trips customers we're booked a month in advance for. Valve was 250, gaskets about 10 bux. Labor is always the big 1. Just couldn't take any time off work to do it - no PTO left.

Maverick · « **Reply #12 on:** June 29, 2007, 04:42:50 PM »

I was curious as I liked doing engine work. I had a leaky exhaust valve on my Comanche. Not severe but it would end up leading to a burned valve later. My IA helped me pull the jug and check the valve. We ended up lapping it the old fashioned way like I did on an old car I used to have. That jug had the highest compression after that.

Later on when I bought a 172 with a couple partners we had to do the engine. I did the tear down and build up. We sent out the components for service. When everything came back and it was running I did the break in flight. There is something very interesting about flying behind an engine you just built. Especially for the first flight for break in.

Wolfala · « **Reply #13 on:** June 29, 2007, 04:53:01 PM »

Yea, first flight your hyper sensitive to the slightest tick or vibration. Where did you do the tear down?

Maverick · « **Reply #14 on:** June 29, 2007, 05:03:05 PM »

Tucson (TUS) is where I lived and I had a good relationship with my IA. I ended up working for him for about 2 years before the wife retired and we hit the road.