Exhaust manifold leak?

Skyjunky · Post by **Skyjunky** » Mon Dec 04, 2017 8:25 pm

My exhaust manifold (IO-540) was showing signs of blow-by where the manifold connects to the cylinders. I replaced the gaskets but exhaust is still leaking from the attachment area. I also have a Piper with a IO-540 and it doesn't have this issue. On the piper the manifold attachment lobs are much thicker. Does anyone have any suggestions on how to stop the exhaust blow-by? Thanks.

Post by **andy** » Tue Dec 05, 2017 6:25 am

I have a MX-7-180 with a Lycoming O-360-C1F and this happened to me when I flew to Idaho last summer. The maintenance shop in McCall ID "re-formed" the pipe with some kind of compression tool/clamp. The pipe had elongated slightly due to movement over time and I was getting a lot of exhaust blow-by from the forward end of the pipe. Worked great after they did the work and would have been a fairly inexpensive repair, but they also found several exhaust weld cracks and had to re-weld. Over the almost 20 years that I've owned this airplane, exhaust weld cracks have been the most frequent problem that I've experienced. There are several threads on it in this forum if you search. 6-cylinder engines run smoother than 4-cylinder engines and are usually less of a problem but it still happens.

Skyjunky · Post by **Skyjunky** » Tue Dec 05, 2017 9:26 am

Thanks Andy. When we put the new gaskets on we did notice slight warping on the lobes. I wonder if anyone has a technique for leveling the connection area of the manifold.

Post by **andy** » Fri Dec 08, 2017 6:29 am

As I recall, you're pretty limited in what you can do to level the connection of the pipes to the headers because of the slip joint brackets. Also, you have to watch out for small angular errors at the top of the muffler pipes because they make for big errors at the bottom of the tailpipes where the hangar straps connect. it's been a while since I messed with this, so maybe Jeremy or someone else can weigh in.

VA Maule · Post by **VA Maule** » Fri Dec 08, 2017 9:31 pm

Skyjunkie:
If asking about where the pipe attaches to the cylinder jug ex.port ? Then yes the cylinder ex.port face can be resurfaced, and it can be done without removing the cylinder from the engine . The resurfacing jig plate & cutter mandrill mount to cylinder's intake port studs and is powered by a 3/8" drill. Just did this to a Apache twin ( yes both engines all 12 ports)

Skyjunky · Post by **Skyjunky** » Sat Dec 09, 2017 6:40 am

Thanks VA Maule. Which tool do you recommend? I'm looking at the exhaust port resurfacing tool on aircraftspruce. It looks to be a hand crank type. Also did you grind the exhaust manifold at all? Thanks again.

VA Maule · Post by **VA Maule** » Sat Dec 09, 2017 9:27 am

That's the one but it's not a hand crank the knob is for the preload/ advance the cutter. No grinding was needed pipe flanges were good ( Apache) , but weld can be applied( little at a time time so it doesn't get too hot and warped more

) than ground off, sanded down, filed, and straightedged. Straightedgeing needs to be done with the ex. Port nipples in the header pipe assembly to prevent binding of the slip joints. The exhaust system on our Maules needs to be loose fitting but secure in all joints ( jiggly) except the nipples that attache to the cylinder these need to be tight & torqued.

AndrewK · Post by **AndrewK** » Sun Dec 10, 2017 7:11 am

FWIW - A few years back I had a crack in one of my manifolds and totally forgot about possibly welding it and just ordered a new one from Maule. The one they sent me had a much thicker flange than the one it replaced. Perhaps closer to what you have on your Piper and hopefully not as likely to warp.

Skyjunky · Post by **Skyjunky** » Sun Dec 10, 2017 9:04 pm

That's interesting AndrewK. I wonder when Maule went to a thinker flang on the manifolds.

Exhaust manifold leak?

Exhaust manifold leak?

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