What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Leaking Exhaust Slip Joint

JokerF22

Member
I've flown my RV-14A five times so far and have seen somewhat consistent, but minor, fluid leakage out of the #2 exhaust slip joint (1st pic below). The substance blows out of the joint and a little gets on the cowl, but most of it leaks down the pipe. I found one other thread on the issue and it seems like it could be just a misshaped pipe that isn't sealing quite right. If so, my plan would be to get a pipe expander to make sure the pipes fit well. Different thoughts here? Is it oil?

My first few flights have gone fine, other than my #2 cylinder running a little hot as compared to the others (2nd pic). Stabilized CHTs end up with about a 70 degree spread between #2 and #1/3 (390 vs 320). Could the higher temperature for #2 be related to the slip joint leak somehow? Thanks for the help.
 

Attachments

  • image2.jpg
    image2.jpg
    293.9 KB · Views: 558
  • CHTs.JPG
    CHTs.JPG
    101.9 KB · Views: 365
Did you let #2 get above 440* at any point?

During break in, the cylinders burn a good bit of oil and it is expelled out the exh port. Not overly surprisiing that this oil could leak past the slip joint (I had oil leaking past the sparkplug threads during break in). It should stop once broken in, unless you glazed the cylinder. In which case it will always burn oil until addressed. Glazing usually happens in the first hour, if temps get too high (somewhere around 440-450) and can be seen on the walls through the sparkplug hole. Bottom plug is typically very wet from oil in this case.

Larry
 
Last edited:
The pipe may seal due to carbon buildup. Only two choices, fuel or oil. If it ain't tinted blue...

Not the question you asked, but the CHT spread seems excessive. Several possibilities for the hot #2.

The most likely is pressure loss in the area of the left inlet. Check the flap seal positions and seal quality. With the 14, the sealing around the front governor is a particular problem.

Your baffles came with a nice bypass duct for #3. The same problem (no fin depth on intake valve side) exists at the front of #2. Might want to mod there for a bit of airflow.
.
 

Attachments

  • Cyl2.JPG
    Cyl2.JPG
    92.6 KB · Views: 374
  • Cyl3.JPG
    Cyl3.JPG
    92.5 KB · Views: 374
On another thread where we discussed RV14A CHT #2 is always hotter than the rest. It is improved best by making sure the baffle has a good seal outboard. There is an area forward and inboard of the prop governor that is hard to seal too, but all my attempts permanent and temporary to close that off didn't change temps. In my opinion this is because the filter/snorkel arrangement makes putting a small bypass to the #2 lower fins impractical, so one lives with less cooling there. The little square offset shown in the baffle pic is akin to putting a washer on the front of older system's baffles to create that gap in front of #2.

These temps can be from run-in, since that is higher. Or from electronic ignition advance too early in run-in. But what is different is that for most of us 3/4 are coolest, 1 a little hotter than 3/4, and 2 the hottest. That isn't what is seen here.

A careful inspection for baffle and gap sealing is wanted, including a check that the baffle seals fold correctly under the cowling. Also need to make sure that the baffle seal on the front intakes is on top of the ramp and not under. When the engine is new it sits high and the seal could be shoved under.
 
I also notice in your blog the wheel pants aren't on. If you are speed-limited and high-power for your run-in you might not have as much cooling flow? Or are these number with wheels in fairings?
 
...this is because the filter/snorkel arrangement makes putting a small bypass to the #2 lower fins impractical, so one lives with less cooling there.

Doesn't require much space. This is all the bypass I run on #2, a "duct" depth is 0.125" or so. Cyls #1 and #2 run within five degrees of each other, usually two.
.
 

Attachments

  • Intake Fin Builtup Duct Parts.jpg
    Intake Fin Builtup Duct Parts.jpg
    202.7 KB · Views: 352
  • Intake Fin Builtup Duct.jpg
    Intake Fin Builtup Duct.jpg
    284 KB · Views: 350
  • 28 vs 23.jpg
    28 vs 23.jpg
    102.9 KB · Views: 333
Did you let #2 get above 440* at any point?

During break in, the cylinders burn a good bit of oil and it is expelled out the exh port. Not overly surprisiing that this oil could leak past the slip joint (I had oil leaking past the sparkplug threads during break in). It should stop once broken in, unless you glazed the cylinder. In which case it will always burn oil until addressed. Glazing usually happens in the first hour, if temps get too high (somewhere around 440-450) and can be seen on the walls through the sparkplug hole. Bottom plug is typically very wet from oil in this case.

Larry

Temps were high on the first flight, close to the range you mentioned. This was mostly due to my error in pulling the throttle back instead of the CS prop. My first flight was only 0.5 hours, but I flew too slow during that period and kept pulling the throttle more to manage temperatures. My last four flights have been faster, airspeed wise to gain cooling flow, with obviously better cooling performance. Based on my poor engine management, I'm concerned that I may have glazed #2, but need to due some more investigating to try and see if that's true. I'll check the bottom plug as you mentioned in addition to looking into the cylinder.

The pipe may seal due to carbon buildup. Only two choices, fuel or oil. If it ain't tinted blue...

Not the question you asked, but the CHT spread seems excessive. Several possibilities for the hot #2.

The most likely is pressure loss in the area of the left inlet. Check the flap seal positions and seal quality. With the 14, the sealing around the front governor is a particular problem.

Your baffles came with a nice bypass duct for #3. The same problem (no fin depth on intake valve side) exists at the front of #2. Might want to mod there for a bit of airflow.
.

Thanks. Since the first flight, I've re-attacked the inter-cylinder baffles with RTV and saw significant cooling effect as a result. I'll keep checking with a flashlight to see if I missed any areas. Your numerous posts on this subject have really helped, so thanks for that, Dan.

On another thread where we discussed RV14A CHT #2 is always hotter than the rest. It is improved best by making sure the baffle has a good seal outboard. There is an area forward and inboard of the prop governor that is hard to seal too, but all my attempts permanent and temporary to close that off didn't change temps. In my opinion this is because the filter/snorkel arrangement makes putting a small bypass to the #2 lower fins impractical, so one lives with less cooling there. The little square offset shown in the baffle pic is akin to putting a washer on the front of older system's baffles to create that gap in front of #2.

These temps can be from run-in, since that is higher. Or from electronic ignition advance too early in run-in. But what is different is that for most of us 3/4 are coolest, 1 a little hotter than 3/4, and 2 the hottest. That isn't what is seen here.

A careful inspection for baffle and gap sealing is wanted, including a check that the baffle seals fold correctly under the cowling. Also need to make sure that the baffle seal on the front intakes is on top of the ramp and not under. When the engine is new it sits high and the seal could be shoved under.

I've had the cowling off after each of my flights so far. The baffles are tending to fold more and more inward, so hopefully no issues there, but I'll keep checking. Thanks.

I also notice in your blog the wheel pants aren't on. If you are speed-limited and high-power for your run-in you might not have as much cooling flow? Or are these number with wheels in fairings?

Thanks again, Dan. The first three flights were with wheel pants off just to make sure there were no issues with brake lines etc. My last flight (which the data above is from) was with pants on. I got the 15 knots extra speed, but no major difference in the numbers between the fourth/fifth flights. The biggest gains were from adding RTV after the 1st flight. I agree with you that a baffle modification is required forward of #2. What are you thoughts on the inlet air dam installed there? Remove it altogether? My brain says that it should be removed, especially if I'm going to add the mod you pictured right behind the dam.
 
What Dan did to get the 1/8 extra clearance is a good mod, like most things Dan does! If I ever pull the snorkel and dig in there I might make that change.
 
What are you thoughts on the inlet air dam installed there? Remove it altogether? My brain says that it should be removed, especially if I'm going to add the mod you pictured right behind the dam.

Here's what I've been running 10 years now. That's a 1/2" 6061 angle across the front of the cylinder, meaning a "dam" about 3/8" high.

Note the upright dam in the baffle kit has a standing tab in front of the injector nozzle. It's there with an eye toward blocking turbulent flow around the nozzle, i.e. preventing pressure variation at the nozzle air bleed. Probably should keep that. Mine doesn't have one because I'm running turbo nozzles...piped bleed air from the tube the foreground. It's an attempt to boost bleed air pressure.

The second photo is the #2 cyl bypass slot on a Grumman Tiger, basically the same concept as in the previous post.

.
 

Attachments

  • Cyl2 Inlet.jpg
    Cyl2 Inlet.jpg
    107.4 KB · Views: 319
  • Grumman Tiger LF.jpg
    Grumman Tiger LF.jpg
    92.7 KB · Views: 369
Back with some pictures and thoughts.

I pulled four spark plugs today, both on #2 and the top ones from 1/3 to compare and look inside the bores. The plug pictured is from the bottom side of #2, so it does appear as though there's still significant blow through there that's making the bottom plug wetter than the others, which are dry. I'm hoping the ring just hasn't seated yet, since I've only got about 4 hours on the airplane. I'll keep running it hard per Lycoming's recommendation.

The other pictures are the best I could get inside the bore of #2. I still see good scoring on the cylinder and couldn't make out any glazing, but I'll admit that I don't know exactly what I'm looking for. The inside of #2 looked identical to the other cylinders as far as I could tell.

Anyone care to pass judgment on these pictures? I'm very curious what you all think.
 

Attachments

  • IMG_2129.jpg
    IMG_2129.jpg
    193.3 KB · Views: 337
  • IMG_2133.jpg
    IMG_2133.jpg
    128.8 KB · Views: 342
Back with some pictures and thoughts.

I pulled four spark plugs today, both on #2 and the top ones from 1/3 to compare and look inside the bores. The plug pictured is from the bottom side of #2, so it does appear as though there's still significant blow through there that's making the bottom plug wetter than the others, which are dry. I'm hoping the ring just hasn't seated yet, since I've only got about 4 hours on the airplane. I'll keep running it hard per Lycoming's recommendation.

The other pictures are the best I could get inside the bore of #2. I still see good scoring on the cylinder and couldn't make out any glazing, but I'll admit that I don't know exactly what I'm looking for. The inside of #2 looked identical to the other cylinders as far as I could tell.

Anyone care to pass judgment on these pictures? I'm very curious what you all think.

How many hours now on the engine? Likely a glazed cylinder 2. You need to look at the whole cylinder wall area. Glazing often only happens on limited areas. It also is more common on the mid to lower areas of the wall and not the very top. Translucent light brown coating vs shiny metal is glazing. Use flashlight and lok from both plug holes. Unlikely for only one cyl to not break in. Also, break in alone won’t typically cause that much oil ro get on a plug.
 
Last edited:
How many hours now on the engine? Likely a glazed cylinder 2. You need to look at the whole cylinder wall area. Translucent light brown coating vs shiny metal is glazing. Use flashlight and lok from both plug holes. Unlikely for only one cyl to not break in. Also, break in alone won’t cause that much oil ro get on a plug.

I have about 4 hours on the engine. I’ll have an A&P take a look at the cylinder.
 
I am having a similar problem with oil leaking from the #2 cylinder exhaust slip joint and I am curious how you resolved your leak?
 
What I’m seeing on my RV14

I believe the residue you see on the exhaust is from the nickel anti seize.

I noted the same occurrence when taking my exhaust on and off and each time I would reapply the anti seize it would run out the joints and stain the area.

Also it’s easy to oil foul those bottom plugs early in the break in due to the amount of that is still seeping by the rings.

My #2 is my hottest however not by much. I did the Dan mod during my build and also built me a smaller air dam to really only shield the injector but allow air down the frontal area. My #2 is only 15-30 hotter and I never see over 330-340 on hottest day climbs. My engine runs to cool….they tell me.

Also as previously mentioned in the other post, the governor is an area that needs to be looked over good for possible air leaks which could induce poor cooling on#2.

* as a side note, I never was able to get my right ball joint to stop leaking. Vans recommend exhaust cement, and that would work for about 5 hours. Since this was a bandaid approach I asked for new exhaust,(another RV owner said he had the same problem and got new parts) however, they said no to me but that I could send it in for repair. So I did, They re worked the ball flange area and shipped it back. It still leaks just like it did from day one. I should have escalated this up to Greg for a better resolution but I was reluctant to go down that path and decided to live with it. For now I just built a shield and used fiberfrax and aluminum tape to protect the engine mount.
 
I am having a similar problem with oil leaking from the #2 cylinder exhaust slip joint and I am curious how you resolved your leak?

On a good running, broken in engine, there should not be enough oil coming past the exhaust port to collect and leak out of slip joints. If your are getting oil out of the exhaust port, you likely have an issue with the ring / wall interface in that cylinder (glazed walls would be most common). If a new engine, it could be glazing or just not having rings fully seated yet. It is common to get oil past the exhaust port during ring seating, but that is usually complete in 5 hours.

Larry
 
Good suggestions from everyone regarding the spread and air leakage around #2 cylinder though #1 and #2 are typically the hottest and #3 nearly always the coolest.
As a reference my spread is around 12 degree and #1, 2, and 4 are within 2-3 degrees and #3 making the largest spread.
For your baffle, take a good look at the in-let area of #2 both left and right side. My baffle on this area would easily flip outward by the airstream on the outer side. Once fixing that and removing the dam on #2, it brought the temp within a couple of degrees to other cylinder.
 
I am having a similar problem with oil leaking from the #2 cylinder exhaust slip joint and I am curious how you resolved your leak?

I don’t have a great answer for you, other than to say that it resolved around the 8-10 hour point on its own. I haven’t seen any issues since that time. Patience was in short supply, but it worked out in my favor. Best of luck to you as well.
 
Back
Top