'89 GT Upper Intake Leak - Pics (HELP!)

Need some help. What is causing this leak? What all do I need to take apart to replace these gaskets that appear to be leaking (if they are not gaskets, what else is going on here)? I have 4 Mustang books (Haynes included), but cannot seem to figure out where I need to look. Nothing is helping too much.


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How do you know the upper intake is leaking? Have you used a vacuum gauge to determine if there is a leak? Have you squirted motor oil around the gasket mating surfaces with the engine running and seen the oil sucked into the gasket?

The upper intake manifold has 6 bolts that secure it to the lower intake manifold. There are 2 bolts at each end and 2 more hidden under the plate that says 5.0 HO. You need a torx bit screwdriver to remove the plate to get access to the bolts under it. The gasket isn't expensive and the whole job can be done in less than 30 minutes.

Finding vacuum leaks

Revised 04-Aug-2011 to add pintle cap, PCV grommet & power brake check valve grommet to checklist.

There is no easy way to find vacuum leaks. It is a time consuming job that requires close inspection of each and every hose and connection.

Small vacuum leaks may not show much change using a vacuum gauge. The range of "good readings" varies so much from engine to engine that it may be difficult to detect small leaks. The engine in my first Mustang pulled about 16.5" of vacuum at 650-725 RPM, which I consider rather low. It was a mass market remanufactured rebuild, so no telling what kind of camshaft it had. Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM. The only sure comparison is a reading taken when your car was performing at its best through all the RPM ranges and what it is doing now. Use one of the spare ports on the vacuum tree that is mounted on the firewall near the windshield wiper motor.

Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent, and no eyebrows is not cool...

The vacuum line plumbing is old and brittle on many of these cars, so replacing the lines with new hose is a good plan. The common 1/8” and ¼” vacuum hose works well and isn’t expensive.

The PCV grommet and the power brake booster check valve grommet are two places that often get overlooked when checking for vacuum leaks. The rubber grommets get hard and lose their ability to seal properly. The PVC grommet is difficult to see if it is correctly seated and fitting snugly.

Fuel injector O rings can get old and hard. When they do, they are prone to leaking once the engine warms up. This can be difficult to troubleshoot, since it is almost impossible to get to the injectors to squirt oil into the fuel injector mounting bosses. If the plastic caps on the fuel injectors (pintle caps) are missing, the O rings will slide off the injectors and fall into the intake manifold.

Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $3-$4 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:
http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/

Most of the links above have store locators for find a store in your area.

Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber. Heat the pintle caps in boiling water to soften them to make them easier to install.



Diagram courtesy of Tmoss & Stang&2birds
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Vacuum leak due to slipped lower intake manifold gasket...

Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.

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Plus 1 for are you sure its leaking? When is the last time you cleaned that area off. Some purple power or simple green and a garden hose should get most of that residue off . Then if it comes back in a short time I would worry about leaks. There really is no oil of fuel flowing thru that part of the intake, if you have a leak you should see a problem with vacumm like the previous post states.
 
I am not 100% positive that anything is leaking, but by the looks of it..???

So, do I put on simple green under there and spray away?

I will say that I have had the following problem that I have yet to get rid of:

In the last year or so, my RPM has stuck at 2K idle for a minute or so. This has happened only twice I believe. It was pretty bad but went away.

When I am driving, and I throw the car in neutral and coast, the car will idle at 1,200 RPM or so for a bit and then finally drop to 900 or so. Not sure if this has anything to do with that residue. The car only has 24K original miles on it.
 
I am not 100% positive that anything is leaking, but by the looks of it..???

So, do I put on simple green under there and spray away?

I will say that I have had the following problem that I have yet to get rid of:

In the last year or so, my RPM has stuck at 2K idle for a minute or so. This has happened only twice I believe. It was pretty bad but went away.



When I am driving, and I throw the car in neutral and coast, the car will idle at 1,200 RPM or so for a bit and then finally drop to 900 or so. Not sure if this has anything to do with that residue. The car only has 24K original miles on it.
Simple Green will probably work OK. I use motor oil because it's already inside the engine and another bit of it won't hurt anything.

See the "Surging Idle Checklist” for help with all your idle/stall problems. You can guess at the problem and throw parts at it, or you can use the checklist to help you find the problem quickly and inexpensively. It’s free and doesn’t cost anything: at last count there were more than 103,000 visits and still climbing

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the fixes & updates. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.
 
I ran codes a year ago and only got a code that meant there were no problems. I may have to try that again (I spent countless hours on this so I have to muster up the courage to start messing around with it all again). The idle problem is not bad at all so that is on the back burner for now. I am really wondering what all this buildup is. Maybe this problem has to do with my idling.