Leaky Intake Seals
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Joined: Aug 2013
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From: Lafayette, LA
Leaky Intake Seals
I'm trying to replace the intake seals on my 08 FLHX. Disassembly and reassembly was pretty straight forward, with some modified allen wrenches to get to the intake flange bolts. The problem I'm having is I've done it twice so far and it still leaks! The first time I re-assembled it, started it up and then sprayed some throttle body cleaner around the flanges. The leak was still there. I was able to kill the motor with a moderately heavy spray.
So I took it apart and tried again. This time I greased up the seals with silicone grease. Put it all back together and it STILL LEAKS! This time it's less of a leak, but I can still affect the idle by spraying around the bottom of the flanges.
I am making sure that when I re-install everything I only hand tighten the bolts until everything is lined up, then I alternate between the top and bottom flange bolts until they're all the way tight, and then lastly I tighten the filter plate bolts.
I know this is a tricky job but what in the world am I doing wrong here? Anyone have any ideas?
So I took it apart and tried again. This time I greased up the seals with silicone grease. Put it all back together and it STILL LEAKS! This time it's less of a leak, but I can still affect the idle by spraying around the bottom of the flanges.
I am making sure that when I re-install everything I only hand tighten the bolts until everything is lined up, then I alternate between the top and bottom flange bolts until they're all the way tight, and then lastly I tighten the filter plate bolts.
I know this is a tricky job but what in the world am I doing wrong here? Anyone have any ideas?
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From: 40.2444° N, 75.6419° W
Only thing I am thinking is, take it back apart, make sure the gasket isn't 'rolling" or tearing, after that the intake is aluminum is it flat or warped, cracked?
also be conservative with the grease, I think I may have used a "light" coat of silicone grease on mine when I did it, just enough that they aren't dry. Not saying this is it, but its what comes to mind.
also be conservative with the grease, I think I may have used a "light" coat of silicone grease on mine when I did it, just enough that they aren't dry. Not saying this is it, but its what comes to mind.
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From: Lafayette, LA
Yes. Once I get the flanges in place with the screws hand tightened I line up the bracket and insert the bolts into the head and tighten them down so the whole assembly doesn't move. Then I evenly tighten the flange screws.
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From: poway
Some things to think about..
1. Make sure you are using the right intake flanges. I can't remember when MCR heads were made but heads made before 2006 use a different flange than 06-up. Bolt the flange up and make sure it centers on the port.
2. Make sure that your manifold has some space between the heads where it can float front to back a few thou (5 to 10). With different heads it may need trimming. Bolt the manifold on without the seals to check.
3. If the heads are early and you have the early flanges, you might need to clearance the intake for the cam side screws if using a late manifold..
4. Make sure the leak isn't at the Map sensor or some of the spray is getting sucked into the intake.
1. Make sure you are using the right intake flanges. I can't remember when MCR heads were made but heads made before 2006 use a different flange than 06-up. Bolt the flange up and make sure it centers on the port.
2. Make sure that your manifold has some space between the heads where it can float front to back a few thou (5 to 10). With different heads it may need trimming. Bolt the manifold on without the seals to check.
3. If the heads are early and you have the early flanges, you might need to clearance the intake for the cam side screws if using a late manifold..
4. Make sure the leak isn't at the Map sensor or some of the spray is getting sucked into the intake.
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Joined: Aug 2013
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From: Lafayette, LA
Ok, thanks for all the advice. I ended up getting it.
The flanges are the stock flanges. I bolted them up just to check and they are centered on the ports. And the intake plenum did have a tiny bit of clearance front to back. And I checked the map sensor for leaks each time and it never appeared to leak. I also checked the flanges on a flat surface and they were perfectly flat. No issues there.
I made sure everything was immaculately clean. Including the mounting surface on the heads. Then I re-greased the seals, assembled the intake, flanges and seals, and inserted the whole thing onto the left side bolts. Then I put the right side bolts in and made them snug and the breather / mounting bracket bolts and made them snug. Next I made sure the plenum was centered as possible between the flanges. Once it was I tightened the bracket bolts to hold it in place. Next, per the service manual, I tightened the left side bolts all the way, then finished off the right side bolts. Put everything back together and that was it. All good.
Not sure which thing I did worked but I think it was a combination of the cleaning, centering, and the tightening sequence that did it. Wanted to post this in case someone else goes looking for the same answer. Maybe it'll help them!
The flanges are the stock flanges. I bolted them up just to check and they are centered on the ports. And the intake plenum did have a tiny bit of clearance front to back. And I checked the map sensor for leaks each time and it never appeared to leak. I also checked the flanges on a flat surface and they were perfectly flat. No issues there.
I made sure everything was immaculately clean. Including the mounting surface on the heads. Then I re-greased the seals, assembled the intake, flanges and seals, and inserted the whole thing onto the left side bolts. Then I put the right side bolts in and made them snug and the breather / mounting bracket bolts and made them snug. Next I made sure the plenum was centered as possible between the flanges. Once it was I tightened the bracket bolts to hold it in place. Next, per the service manual, I tightened the left side bolts all the way, then finished off the right side bolts. Put everything back together and that was it. All good.
Not sure which thing I did worked but I think it was a combination of the cleaning, centering, and the tightening sequence that did it. Wanted to post this in case someone else goes looking for the same answer. Maybe it'll help them!
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