Need Help With Intake Manifold Problem

[RRoller123]

I was checking the torque on my intake manifold bolts and one of them immediately snapped off, at low torque, must have been prestressed at some point in the past. Does anyone have one of these? The threads start about 2.5" from the head. It is the long one that goes in the throttle plate heater position, also shown below. Here below are 2 pictures:





I also will probably have to take the intake manifold cover off to repair this and it looks like I need to depressurize the fuel lines. I understand that there is a vacuum pump for this but I have never done it. Harbor Freight Tools has one I think? Where do you hook up the vacuum pump? It seems that any pressurized fuel connection that is undone to install the vacuum pump will spray fuel around. Admit some confusion here.

Pete

[manoa matt]

I have all the bolts, and even the gasket that goes between the two halves. I'd remove everything first as you might/could break another bolt in the process, but you will have to remove the top half of the intake plenum to remove the one broken bolt. If part of it is sticking above the surface use a dremel and a cut off wheel to make a slot in it, then try to back it out with a flat blade screwdriver. Soak it with penetrating oil first.

I'm not a FI guy, but most FI systems have a pressure relieve valve. It should be on the fuel rail and looks like a tire/bicycle valve.

[narfire]

To de-pressurize the quick way... wrap a rag around to fuel line to the cold start injector and undo the clamp. Good idea to disconect the battery (positive) first.
I have broken a bolt there as well. You might get lucky and be able to extricate the stub with just the top of the intake off. Try that first before mucking about with the whole intake. See if it has broken flush or if there is a stub try and file 4 two flat edges each side and use vice grips to undo. You'll want to put some shop towels in the intake runners to keep anything from falling in.(don't have anything, you'll be taking the whole intake off... )
If it has broken flush, perhaps try and drill out a bit and use an easy out. A lttle bit of heat first sometimes helps.
I can buy replacement metric bolts at a jobber store near me.

[RRoller123]

Thanks you guys for the quick responses. I like that quick depressurization technique. I think I will try that, battery disconnected for sure! How much fuel comes out before the pressure drops? I would expect an ounce or two is all?

I think there is a stub available for an easy out or slotting, as there are only a few threads showing on the broken off end. I may just replace all the bolts, as it is likely that somewhere in the past they were all overtorqued. A couple of others felt a little soft as I was torqueing them, and I stopped before a second one broke. Such is life.

One last question: I assume that the manifold cover gasket can be reused if it is in good condition. This isn't a one-time only use only gasket I assume?

Pete

[burlybryan]

A few ounces of fuel. A little from the pressured line, but mostly leak down from the rail.

Get new grade 8 bolts.

The manifold gasket is paper or felt. It's not sealed, but it might be stuck to one or both surfaces. I'd replace it if you can pair it with an additional purchase (to help with shipping). If it's only a few years old, it will be fine, but if it's 30 years old (like mine was), it's shot. With the car down anyway, pull the intake and see if the gasket makes it.

[So Cal Mark]

no reason to take the intake off, that's just a plenum bolt that broke

[RRoller123]

But need to depressurize the fuel line to get the plenum off, need to remove the cold start valve, yes?
I think I will paint it while I am at it.

[RRoller123]

Well I was able to repair it today and replace not 1 but 2 broken bolts.

I have an observation that may help those of you who need to take the intake plenum off. There is no need to depressurize the fuel system if you take the Cold Start Valve/Jet out complete. I struggled getting the hose off initially, then decided to see if I could just get the CSV Valve/Jet out whole. The CSV connector hose gets in the way of the bottom allen bolt, but I went and bought a 5mm Ball Head Allen wrench and was able to get it out. The 5mm Ball just barely gets enough grip to loosen the bolt, you get about 25 degrees of side play with it.

[RRoller123]

@burlybrian:

Thanks for the response on the fuel and the gasket. I was able to reuse the existing gasket as it was fine, but I sealed it to be sure. No fuel leaked since the CSV can come out in one piece. This is a lot safer than letting even a little gas out, so I like this approach.

CSV Valve complete after cleaning:



Mess of a throttle plate: Talk about gunked up.



It took 3 cans of carb cleaner to clean the mess inside and outside the plenum. 32 years of junk I expect, but odd that the gasket was in such good shape.... Not sure what grade bolts I got at ACE, but they fit and torqued down fine. Off to the Millis Cruise Night and the trip went well and no problems! (for a change.) The car is a big hit at these shows, I get plenty of questions and comments, with an occassional doofus who demeans the brand. But the doofus' are rare. Most people love the old FIAT cars.