ElMartillo

The photo may not fully show it, but it’s a rather large tear in that rubber coupler. Of course I would expect there to be a difference. It wasn’t manufactured with this opening in the vacuum system. Fixing or circumnavigating that leak may not resolve all my issues, but it should make a difference.

If you can’t offer constructive advice or thoughts, please refrain from commenting.

Thanks.

4.3L XJ

OK, up to you. But I have been offering constructive advice. Maybe not the advice you want to hear, but helpful anyway. Have fun

5-Speed

I think what 4.3L is trying to say is that the line is going to be pulling vacuum whether or whether not its connected and/or has a cracked connection. The difference is that with it connected, it pulls air from inside the engine. When its not connected, it pulls air from outside. Either way, its still going to be sucking the same amount of air but from different locations. The only way it would change the way the engine runs is if gets capped off.

cruiser54

Why is intake measured in vacuum and exhaust measured in pressure?

Try this. Drill a small hole in your exhaust manifold. Tap it for a pipe thread. Screw a metal vacuum T into the hole. Leave one end of the T open to the atmosphere. Connect a vacuum gauge to the other nipple. Start it up and monitor the amount of vacuum reading on the gauge.

5-Speed

Where you going with this question? I know you already know the answer to it so there is another reason you are asking.

cruiser54

Just a thought....Try it.

5-Speed

That's a horrible answer haha.

cruiser54

Why? It could prove a point.

5-Speed

What point are you looking to get to? That the exhaust pulse has both pressure and vacuum?

Edit - you lost me when you said to leave one side of the tee open. Its would then be then venting to the atmosphere and not read much.

cruiser54

Nope. Only pressure.

5-Speed

Where are you taking the reading from? Collector or primary tubing? Primaries you get a pulse thats goes into vacuum(using electronic sensors. Looks like the pulse of an o2 sensor). Collector, ehh not so much. Greatly depends on exhaust systems though. Equal length header makes a huge difference in the readings.

cruiser54

Try it.

5-Speed

I have tested. Thats why i am asking the location you tested at. There is a big difference from testing each primary tube to testing at the collector (and not all collectors are created equal). And on top of that there is an even bigger difference when testing near the muffler.

RocketMouse

hey.. not to go off on a tangent...but since it kinda went the direction it has in this thread..... how much of a PITA is it really to do an exhaust manifold gasket replacement on a 99 XJ?
I'm taking it that the intake has to be completely removed to do this on the I6?

5-Speed

Sorry man. I thought cruiser and I were having a somewhat related peaceful discussion. We can take it elsewhere though. On a 99 its not too bad to do. On a 00+, it sucks. There is just no room.