My motor has been off for about and hour now and I have the UIM off and was going to replace the gaskets. My question is that I hear a distinct hissing sound from the motor. I think it is comming from underneath the LIM. I don't smell gas or exhaust from there. I guess it could be the LIM gasket could it. Any ideas? I do have a vaccum leak somewhere that makes the motor idle high and could this be the leak that I am looking for, I have inspected all of the vaccum lines and havn't seen any broken or damaged. Any ideas? 89 2.8 RS

 

did u hook the egr tube back up?also check the rubbe rplug that goes into the back of the throttle bodie,and on the drivers side of the motor near the front behind the ac compressor is 2 more vacum lines

 

Right now I am at the fuel rail and will take it off in a few minutes. I was wondering if I need to do anything before I disconnect the fuel lines. I disconnected one and the other I pulled off and some fuel was comming out and I put it back on.

The hissing wasn't as strong as before but I have the UIM off and it was still there and sounded like it was comming from somewhere the fuel rail.

 

could be a bad injector o-ring

 

Thats true. Those don't cost much do they? Also when I try to unplug the fuel line gas gets sprayed everywhere. Does the line have one of those ball valves that plugs it when I unplug the line completely? Also the hiss has become a really faint whistle now. I can barely hear it.

 

Does it hiss when the engine is not running?

 

Yeah that is the only time I can hear it. Its really faint.

 

i also had the same problem... when i took off my UIM i could hear a hissing noise coming from inside the mainfold.

I replace all the gaskets and o-rings and it solved the problem...

while you have the engine ripped apart make sure you replace everything that could fail..

i've had to take my manifold apart 2 times since then and have to do it another time to fix my FPR

 

I'll have to replace them next weekend then. I suppose that they don't cost much then?

Also I have a problem with one of my plug wires. I pulled it off to replace the header gasket and the wire came off but the metal clip that is on the end of the wire came off. I just clamped it back on. Should it be OK?

 

the manifold gasket kit is about $30 for the full set. the injector o-rings and FI o-rings and about 10bucks for those.
big job so be ready.. do the valve cover gaskets too.

if you have the money to get a new set of plug wires... do it.

if not then goto a junkyard and put one if your pocket i guess

 

I got the whole manifold gasket set for $17, the valve cover gaskets have been replaced as of last sept. The gasket set came with EGR and every manifold gasket that I need plus some that I have no clue that they do.

 

The hissing could be the check valve for the brake booster leaking. When it is making the noise pull the check valve out of the booster and see if it goes away.

 

whats the brake booster check valve?

 

i believe its the little plastic insert and goes into the brake booster..?

and those extra gaskets are for a 3.1 or 3.4

 

The gaskets are for a 2.8. I got gaskets for the whole top end of the motor practiacly plus some that I don't knwo where they go. I did plug the brake booster line and the idle could go much lower than what it has to sit at now. I inspected all of the other vaccum lines and they are all in good shape. Also the hissing is real loud when the fuel primes. I had the hood up and could really notice it.

 

Could bad injector o-rings cause a vaccum leak?

 

Did you relieve the fuel pressure?? There is 41psi on you fuel line that must be relieved before you disconnect the line from the fuel rail..If not it sprays everywhere. That could also be the hissing you hear...notice its going away each time you disconnect the fuel line.
As for the plug wire..Do Not try to reuse the broken one..It Will Miss.

 

I agree 100% with Ron- you should depressurize the fuel system first.

But, something else- there's no need to unhook the metal fuel lines from the fuel rail! Take a good look at the metal fuel lines as they run to the rail. They're held to the motor with a few clips and bolts. Remove all those screws and you can get the entire length of metal fuel line free from the engine.

Then you just lift the rail out of the intake manifold with the lines still connected, and swing it out of the way. It'll "hinge" on the rubber fuel lines that go between the driver side of the motor and the frame.

Much easier- and that way, you don't risk stripping the threads of the fuel rail. The fuel rail is aluminum and the fuel line's tube nuts are steel, which can ruin aluminum threads easily.

YES bad injector o-rings can cause a severe vacuum leak. Never re-use them. A new kit is about $8. If the local parts store doesn't carry one for a 2.8/3.1, get one for a same-year TPI 5.0. The difference is the v8 kit has four extra o-rings. Lube the o-rings with regular motor oil before installing them so they don't tear. If your old injector's pintle caps crack and you can't find replacement caps, no big deal, your injectors will work without them. Carefully remove any torn bits of old o-rings from the holes in the intake manifold to make sure you get a good seal with the new o-rings, and of course, be careful nothing falls into the motor.

Mark all the injector connectors so you put them back on in the right order. You may have to pry up on the fuel rail to get it to come out of the engine; those old injector o-rings will be holding on tight.

 

I have taken the fuel rail off to put new valve covers and seals on them. To depressurize the system I just full the fuel pump fuse and let it die right.

 

That will work, or if you have a fuel pressure gauge it will have a bleeder vavle to relieve pressure.