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Intake pipe blow-by

chepburn

Well Known Member
Hi all,


My engine has 50 hours SMOH, and I changed the oil last night and noticed that there is some blow-by on the intake pipes up by cylinders #2 and #4. I think this is pretty recent, as I have had the cowls off before the change.. within the last 10 hours or so and I didn't notice the accumulation before. There doesn't seem to be a lot of accumulation but...its there.

I am getting about 6 hours to a quart right now on the engine, and maybe this blow-by is a signal. I have attached a pic of the intake pipe on #4. Its seems to be originating at the flange to the cylinder....I find it hard to believe that the gasket is gone already.

Should I be worried? The bolt torques on the flange seemed to be OK.

picture of intake pipe on #4 is here:

open


Thanks for any hints
 
First I'd get a pack of gaskets (cheap). Then pull that tube, inspect the thin flange on the tube for warps and reinstall with a new gasket. Slide the hose up onto the tube out of the way so it doesn't affect the flange seating. Snug the flange/tube/gasket sandwich and make sure the tube is in the counterbore recess evenly. Slide the hose over the sump nipple and final torque the flange. Then do the hose clamps. Your oil consumption is high. What level do you run and have you been throwing the airplane around?
 
I had the same issue...

I had the same issue few weeks ago. My engine has ~200hrs. I've noticed blue stains along 2 of the 4 intake pipe. This is not oil leaking, but 100LL.
If you look closely, you'll probably see that the gasket is broken.

Very easy to change and quite cheap as well. You can order those gasket from ACS Canada. I have an extra set. I think they are the same for any 0-360 engine. If you're in a hurry, you can take mine (i'm in Gatineau).

BTW, I've also put a layer of TiteSeal, as advised by few people on this forum. Should help. ACS also have this in stock

Michel Roy
RV-7A
Gatineau
 
I had the same issue few weeks ago. My engine has ~200hrs. I've noticed blue stains along 2 of the 4 intake pipe. This is not oil leaking, but 100LL.
If you look closely, you'll probably see that the gasket is broken.

Very easy to change and quite cheap as well. You can order those gasket from ACS Canada. I have an extra set. I think they are the same for any 0-360 engine. If you're in a hurry, you can take mine (i'm in Gatineau).

BTW, I've also put a layer of TiteSeal, as advised by few people on this forum. Should help. ACS also have this in stock

Michel Roy
RV-7A
Gatineau

Thanks Michel,

I'm pretty sure its oil... I've got an IO360A1B. I have been chatting with Aerosport today, and they have told me to keep an eye on it, and try replacing the gaskets.... if there are more issues, they are standing by.
I'm just going to order some gaskets from ACS today.



First I'd get a pack of gaskets (cheap). Then pull that tube, inspect the thin flange on the tube for warps and reinstall with a new gasket. Slide the hose up onto the tube out of the way so it doesn't affect the flange seating. Snug the flange/tube/gasket sandwich and make sure the tube is in the counterbore recess evenly. Slide the hose over the sump nipple and final torque the flange. Then do the hose clamps. Your oil consumption is high. What level do you run and have you been throwing the airplane around?

Thanks Dave,

I'm about to order a set of gaskets... and ya, I think my oil consumption is a bit high too. The engine was test cell run for it's first 9 hours, so , I'd hope that the break-in was good...but I guess you never know. I don't throw the airplane around, but I do cruise at 2450 to 2500 most of the time...its an IO360A1B, so I have a pretty wide RPM restriction band with the Hartzell. I'm going to put a few hours on the new oil and pull the cowl again. If I have more leakage, Ill replace the gaskets on those two pipes and check them out.
 
If your not already, try running a few hours at 6 quarts and see if you notice a change.
 
If your not already, try running a few hours at 6 quarts and see if you notice a change.
- I usually run the engine between the 5 and 6 qt marks.

Went up for a 30 min test flight yesterday, landed, and pulled off the cowl. Lots of oil on #3 pipe.(I misspoke in the earlier post...its #2 and #3 leaking)

Pulled the pipe, and there is a lot of oil contamination in the intake chamber. I guess I know where my oil is going now. Gasket at the top wasn't obviously damaged, but the "let go" torque was less than 85 in-lbs on the hold down bolts on the collar. So I guess its time to look for the source of oil in the chamber...I have to check my oil return line for blockage and my oil breather to see if Im pressurizing my case...after that, I guess its pointing to my rings in that cylinder or the valve guide. ....dont have an extra O-Ring for the bottom of the tube so the plane is AOG this weekend (and a long one to boot...darn)
 
dont have an extra O-Ring for the bottom of the tube so the plane is AOG this weekend (and a long one to boot...darn)
I didn't pay enough attention to your picture...IO engine, duh. Anyway, I think your in hot pursuit. You might only show oil leakage there, but could have it in all 4 intake ports. If so, its most likely your ring/bore fit somewhere.
 
When you put the intake pipes into the flange that bolts to the head, it's real easy to get them ever so misaligned, and no amount of torque will fix what will be a leak. (Hold the intake pipe with some pressure away from the flange and move the pipe around a little and you'll feel the pipe sort of snap into the correct position. You can also see visually whether there is a uniform space between the pipe and the flange all the way around.)

It sounds like you could have had it slightly off, then it chugged into place so that when you removed it the torque seemed a lot less.

Just another $.02.

Dan
 
Leakage

After you'e cleared up your gasket leak, and if you're getting a lot of leakage out of your sniffle valve, check to see whether you might have excess valve guide clearance.

What's happening in that case, is that oil from the rocker box seeps past the valve stem and guide into the intake chamber where it is diluted by fuel that is boiled off from the injector lines. It then goes through the spray nozzles into the intake chamber. From there it drains down the intake tube to the air plenum then out the sniffle valve.

A little bit is natural and that is what the sniffle valve is for.
 
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