I am new to this forum and would like some advice. I have noticed that the bushing on the variable intake leakage is rattling and leaking unmetered air into the intake.I cant afford to replace the intake at $400 on my salary. Would it be cheaper to have a machine shop replace or repair the bushing? Is there somehow i can fix it by tearing it apart? How does the linkage seal into the hole at the front end of the intake? I assume it is just real tight tolerance. I know i could unplug the vacuum hose on the dashpot, but it seems like more unmetered air comes in when i do that.I would appreciated any advice.

What rig / motor are you talking about? Maybe the 3.5 DOHC? Maybe the buttefly valve on its intake?

Yeah...

I had to click on his user name to find out he's got a 95 SR.

@akmikek,

It would be really helpful if you could put it in the post or in your sig. <img src="/forums/images/graemlins/kewl.gif" alt="" />

The "real" fix is to buy a new plenum from the dealer. Some have made their own bushings, but you have to consider that if you're bushing gets sucked in... what it's gonna do to valves, and pistons. Also some have removed the butterfly valves, and welded the holes up. If you do that, you'll be done with the problem forever.

Sorry about forgetting the engine, and thanks for such a quick reply. The engine is the 3.5L V6 DOHC. The bushings that i am refering to are the ones in the center intake plenum. I cant afford to spend the $400 on a new intake plenum on a military salary so i was looking for alternatives. Has anyone ever pulled the shaft and just replaced the bushing at the front of the manifold? I could not find a parts diagram for the intake ( not even in may service manual)to see if repairing it is possible.I am sure a machine shop can press a bushing in place of the old one for less than $400. Has anyone ever just repaired the intake by pressing in a new bushing.If i disconnect and remove all valves and secure hole, what will it do to the performance and fuel economy or lack thereof? Thanks again for the advice.

Nice long thread for you to read HERE debating disabling/removing the butterfly valves in the intake and its pros/cons. If that is what is going on with your engine, I strongly recommend doing something about it asap. I lost an engine due to the butterfly valves getting sucked into the engine. MUCHO $$$ if that happens.

It's not just the front bushing that gets worn, the ones between runners get worn, too.

I have had new bushings made for mine and I have the schematic, parts measured down to the ten thousandths, that a machine shop used to water-jet cut the new parts from an aluminum-bronze alloy. Seems to work just fine, but I was unable to stop a small leak at the front of the plenum. You can't make that part fit too tight or the shaft won't turn and I haven't taken it back apart to try again and to check on the condition of the replacement bushings.

I could tell a difference, having fixed it. Others will disagree. I feel confident nothing is going to fall off into my engine. My small remaining air leak only makes the idle a bit rough, but off-idle, it runs like a champ.

If you do plan on putting the contraption back together, use loc-tite on the butterfly valve set screws and find a screwdriver that fits those screws as perfectly as possible.

I was planning on repairing these on an exchange basis, but my source for the replacement bushings has not responded about cutting more for me. For now, I'm hanging on to the schematic for the parts, since we did the R & D on this end, but that could change if more time goes by.

The aluminum-bronze we used was chosen as the fabricator was making parts with it for an aerospace project and the machinist felt it was a suitable material. If I had access to Delrin, I probably would have picked that, but I can't ask for much when it's free.

John B.

I had the plenum off last week and the butterfly valve rod didnt seem loose except for the front where it exits the manifold. I may pull it apart again this weekend to double check the valves and look at the nylon fitting on the front.

Having taken a couple of these apart, there's virtually NO way the bushings can be sucked into the engine unless it cracks apart. It rides on the shaft and is sandwiched in place in the casting between butterflies and at the front and rear of the casting.

What is FAR more likely is that the set screws on the butterfly valves will loosen and fall out, then the valves themselves go in. That would ruin things in a hurry.

If you disable the two stage aspect by removing the valves and shaft, then welding up the hole in the front of the casting, you certainly would be rid of the problem forever, but you'd also be without the (potential) benefits of said system forever as well.

John B.

Both of the ones I had in my hands were more worn at the rear bushing than at the front, and a couple of the middle ones were non-existent. Check carefully by lifting the shaft all along its length.

You can see more by taking out the butterfly screws and sliding the shaft out, which you might as well do at this stage anyway. Put something temporary over the front hole in the casting for if/when we get a better resolution so you can revert back if you want.

You just really don't want that stuff bouncing around in there.

John B.