Intake Leak

BGF_Yankee

BGF_Yankee

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BGF_Yankee
I have been chasing a power loss issue for a little while in one of the engines on my Seneca II. Finally got around to pressure checking the intake system. There were a few tiny leaks getting through where the clamps hold the intake hoses on. Those were easy enough to fix by tightening the clamps up a little bit, but we also saw this:


It is leaking around the two rivets holding on the data plate, as well as around a seal on the side of the assembly.

I would imagine that even with little leaks, on a turbocharged system, they all start to add up. Would this be considered a decent leak?

I've already pulled the part and sent it out for overhaul, and should have it back in a couple of weeks. Just wondering if others have had similar experiences?
 
My opinion, based on working in an engine test lab with 100% of the engines being turbocharged, that isn’t a major leak. It is worth trying to get things as sealed up as is realistic however, but not to the point of mental obsession.

I’d say your power loss will be found elsewhere, especially if the manifold pressure created is where it is expected to be.
 
nrpetersen said:
How much pressure are you putting on the system?
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Just the amount coming out of a shopvac, so not a lot.

mondtster said:
My opinion, based on working in an engine test lab with 100% of the engines being turbocharged, that isn’t a major leak. It is worth trying to get things as sealed up as is realistic however, but not to the point of mental obsession.

I’d say your power loss will be found elsewhere, especially if the manifold pressure created is where it is expected to be.
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I'm seeing maybe a 1" difference on the ground at idle with this engine showing higher MP than the left engine. I'll be checking for exhaust leaks this weekend as well, although I feel like it's harder to check for this when the exhaust has slip joints. Maybe I'm wrong. The engine is far from making critical altitude though; however, I do get 40" MP on the ground for takeoff easily. The MP just drops off a lot faster than it should in the climb. It has a fixed wastegate which can be adjusted on the ground, but presently, it is where it should be according to the service manual to start making calibrations.
 
I'd fix that leak, what a stupid way to put a plate in. I would guess you are not getting much more than a few psi of pressure, if that. As the pressure differential got bigger I would expect a higher flow through those leaks, that would drive me nuts knowing they are there.
 
BGF_Yankee said:
I'm seeing maybe a 1" difference on the ground at idle with this engine showing higher MP than the left engine.
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1 inch at idle wouldn't have anything to do with leaks on the turbo side of the throttle body since you are not boosting - that is where these leaks are, right?
If the leaks are on the engine side of the injectors, then you have a problem.
If you have a power difference due to these leaks, it would show up as a loss of manifold pressure when you have the throttle open wide, but given the volume of air being pushed through the system, this doesn't seem to be much of a leak. And, there are more likely causes of loss of boost.

Warning: I ain't no A&P.
 
A shop vac doesn't create the pressure of a turbo system by about an order of magnitude. My guess is this loss though isn't the source of your problem, but it seems like some very tacky manufacturing etc. Also not an A&P, but an ME.
 
nrpetersen said:
My guess is this loss though isn't the source of your problem, but it seems like some very tacky manufacturing etc. Also not an A&P, but an ME.
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You think that's bad, you should see their cylinder QA. :D
 
Capt. Geoffrey Thorpe said:
1 inch at idle wouldn't have anything to do with leaks on the turbo side of the throttle body since you are not boosting - that is where these leaks are, right?
If the leaks are on the engine side of the injectors, then you have a problem.
If you have a power difference due to these leaks, it would show up as a loss of manifold pressure when you have the throttle open wide, but given the volume of air being pushed through the system, this doesn't seem to be much of a leak. And, there are more likely causes of loss of boost.

Warning: I ain't no A&P.
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Neither am I, but I'm trying my hardest to educate myself more on it. Previously I would've agreed with you, but then read this article, focusing specifically on the section regarding intake (then exhaust) leaks:

https://www.avweb.com/ownership/troubleshooting-the-turbo-system/
 
BGF_Yankee said:
I have been chasing a power loss issue for a little while in one of the engines on my Seneca II.
Click to expand...
Curious. Have you performed any of the service manual performance checks or troubleshooting steps and compared results between engines before your induction leak check?
 
meh....if it's a turbo those leaks could affect your service ceiling....other than that it would not be noticeable. The waste gate is going to regulate and hold as much pressure as needed to deliver desired MP.
 
Checkout_my_Six said:
meh....if it's a turbo those leaks could affect your service ceiling....other than that it would not be noticeable. The waste gate is going to regulate and hold as much pressure as needed to deliver desired MP.
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The “wastegate” on this application is a fixed orifice, as mentioned in an earlier post.
 
BGF_Yankee said:
Neither am I, but I'm trying my hardest to educate myself more on it. Previously I would've agreed with you, but then read this article, focusing specifically on the section regarding intake (then exhaust) leaks:

https://www.avweb.com/ownership/troubleshooting-the-turbo-system/
Click to expand...

All I’m going to say, is consider the source of that article.

The small bubbling leaks in your video are not gross leaks. If small leaks like this were that paramount, engine manufacturers such as Lycoming would not utilize two piece intake plenums with no gaskets between the sealing surfaces. Further, if small leaks were such a problem we’d never be able to successfully take bleed air off the compressor to pressurize a cabin and keep up with all its air leaks.

I know that your engine is not a Lycoming and that the Seneca is not pressurized, but I’m trying to paint a picture here. You May still have a vacuum/boost leak significant enough to cause trouble but I don’t think it is at the joints you posted a picture of. Keep looking and take a methodical approach. I’d probably start by treating your two problems as separate issues, although you may find one thing that cures both.
 
I would fix those leaks, it's just dumb having leaks in an intake manifold and as the pressure differential becomes greater so won't those leaks..... or you could start replacing and adjusting other things.
 
I'd be curious to see the result of a leak test on the good engine.
 
mondtster said:
All I’m going to say, is consider the source of that article.

The small bubbling leaks in your video are not gross leaks. If small leaks like this were that paramount, engine manufacturers such as Lycoming would not utilize two piece intake plenums with no gaskets between the sealing surfaces. Further, if small leaks were such a problem we’d never be able to successfully take bleed air off the compressor to pressurize a cabin and keep up with all its air leaks.

I know that your engine is not a Lycoming and that the Seneca is not pressurized, but I’m trying to paint a picture here. You May still have a vacuum/boost leak significant enough to cause trouble but I don’t think it is at the joints you posted a picture of. Keep looking and take a methodical approach. I’d probably start by treating your two problems as separate issues, although you may find one thing that cures both.
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Oh, I am aware. But as stated above also, I found 4 additional leaks around the intake hoses that were bubbling like this that we sealed up. I would imagine 7 small leaks all add up to an issue if not sealed up.
 
Checkout_my_Six said:
no different.....what MP is it reading?
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It absolutely is different. At some point a wastegate can completely close, directing all exhaust gas through the turbo. You will never have that with a fixed orifice.
 
mondtster said:
It absolutely is different. At some point a wastegate can completely close, directing all exhaust gas through the turbo. You will never have that with a fixed orifice.
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Nope....wrong. If it's making MP....the only thing different is the service ceiling.
 
BGF_Yankee said:
Oh, I am aware. But as stated above also, I found 4 additional leaks around the intake hoses that were bubbling like this that we sealed up. I would imagine 7 small leaks all add up to an issue if not sealed up.
Click to expand...

We do emissions testing in the engine test lab and have leak checkers to insure all the air is accounted for. Small leaks are going to be hard to quantify. They will add up and as you close the gaps the remaining leaks will appear to get worse. But at the end of the day, all those little leaks have never led to a measurable decrease in power or increase in emissions. Pressure is pressure, and if you’re getting the desired amount you’re not going to see a difference as long as the rest of the engine is healthy.

It is always easy to tell when you have a gross leak. Your shop vac testing should reveal something of that nature.
 
If it's not making full power and MP is fine....more than likely it's a fuel flow issue.
 
Checkout_my_Six said:
If it's not making full power and MP is fine....more than likely it's a fuel flow issue.
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Which could still be an air leak issue, if the upper deck reference pressure line for the injectors is chafed through.

And now we’re going in the direction I think this discussion should be headed...
 
mondtster said:
Which could still be an air leak issue, if the upper deck reference pressure line for the injectors is chafed through.

And now we’re going in the direction I think this discussion should be headed...
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was that blowing bubbles?
 
mondtster said:
We do emissions testing in the engine test lab and have leak checkers to insure all the air is accounted for. Small leaks are going to be hard to quantify. They will add up and as you close the gaps the remaining leaks will appear to get worse. But at the end of the day, all those little leaks have never led to a measurable decrease in power or increase in emissions. Pressure is pressure, and if you’re getting the desired amount you’re not going to see a difference as long as the rest of the engine is healthy.

It is always easy to tell when you have a gross leak. Your shop vac testing should reveal something of that nature.
Click to expand...

OBDII in cars can make intake leaks a big deal. There's a test to make sure your catalyst is there and working, it works by richening then leaning or vice versa, I don't remember at this point, but the downstream O2 sensor needs to show a reaction within a certain amount of time from this test, an induction leak is one of the causes of this failure. I had a 2008 Jeep grand Cherokee with a hemi that kept failing that test tripping the MIL. 2 dealers and 2 independent mechanics could not figure out what was going on, smoke tests, leak test, whatever, they couldn't find it. The car had about 70k on it and I suggested the PCV valve, each one of them told me no, that can't be it, in fact, neither dealer stocked it and it was a 2 week delivery. So hundreds of dollars lighter in the wallet and the Massachusetts emissions test due, I finally ordered one through amazon. It came few days later, I installed it, within about 3 minutes of driving the light went off.
 
PaulS said:
OBDII in cars can make intake leaks a big deal. There's a test to make sure your catalyst is there and working, it works by richening then leaning or vice versa, I don't remember at this point, but the downstream O2 sensor needs to show a reaction within a certain amount of time from this test, an induction leak is one of the causes of this failure. I had a 2008 Jeep grand Cherokee with a hemi that kept failing that test tripping the MIL. 2 dealers and 2 independent mechanics could not figure out what was going on, smoke tests, leak test, whatever, they couldn't find it. The car had about 70k on it and I suggested the PCV valve, each one of them told me no, that can't be it, in fact, neither dealer stocked it and it was a 2 week delivery. So hundreds of dollars lighter in the wallet and the Massachusetts emissions test due, I finally ordered one through amazon. It came few days later, I installed it, within about 3 minutes of driving the light went off.
Click to expand...

I’m well aware of some of the concerns. However, OP’s engine is not and as already discussed, slight air leaks may only affect the critical altitude.

As far as your cars are concerned, the leak you had must have been pretty significant. Most of the ECUs I’ve worked with will trip the light for a fuel correction in the 20% range which is pretty significant. Even cars on which I’ve disabled the entire PCV system haven’t gotten far enough out of whack to trip the MIL.
 
mondtster said:
I’m well aware of some of the concerns. However, OP’s engine is not and as already discussed, slight air leaks may only affect the critical altitude.

As far as your cars are concerned, the leak you had must have been pretty significant. Most of the ECUs I’ve worked with will trip the light for a fuel correction in the 20% range which is pretty significant. Even cars on which I’ve disabled the entire PCV system haven’t gotten far enough out of whack to trip the MIL.
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It's not fuel correction, it's a test that was added to stop people from pulling out the catalyst, but anyway, it will be interesting to see what the OP discovers.
 
PaulS said:
It's not fuel correction, it's a test that was added to stop people from pulling out the catalyst,
Click to expand...
There is both. You set codes if the closed loop correction gets too big due to leaks / fuel pressure / whatever, and you have diagnostics for catalyst activity. (I wrote a fair bit of that stuff.)

Back to your regularly scheduled program, already in progress.
 
Capt. Geoffrey Thorpe said:
There is both. You set codes if the closed loop correction gets too big due to leaks / fuel pressure / whatever, and you have diagnostics for catalyst activity. (I wrote a fair bit of that stuff.)

Back to your regularly scheduled program, already in progress.
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Yes there is, but the trim was fine, it was the catalyst test that kept failing. Any who.
 
Checkout_my_Six said:
If it's not making full power and MP is fine....more than likely it's a fuel flow issue.
Click to expand...

Just the opposite. Making a full 40" on the ground and throughout the first few thousand feet of climb, but not all the way to critical altitude. Legitimately, I need to have SID97-3G done, but I'm trying to ensure everything else is tight first. No sense it doing the SID unless I'm confident all is in working order. That would be a lot of time wasted. I did leak check the opposite engine intake and it was tight as a drum. Did not have these same leaks from the throttle control assembly.
 
BGF_Yankee said:
Just the opposite. Making a full 40" on the ground and throughout the first few thousand feet of climb, but not all the way to critical altitude. Legitimately, I need to have SID97-3G done, but I'm trying to ensure everything else is tight first. No sense it doing the SID unless I'm confident all is in working order. That would be a lot of time wasted. I did leak check the opposite engine intake and it was tight as a drum. Did not have these same leaks from the throttle control assembly.
Click to expand...
Necropost reply here, but since am having similar issues with my Seneca thought I would see what the end cause and solution was.
 
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