I have a passenger side exhaust manifold leak on my 1996 f350 4x4 7.5l 5spd. It seems like every year or so it starts leaking out the back side of that cylinder head to manifold connection. I have installed gaskets, torque bolts, warm it up, re torque bolts, cool it off, torque bolts again, and just doesn't seem to stay tight. Anyone find a reasonable repair for this? loc tite, little serrated washers that keep from backing off, lock washers, anything? maybe a locking bolt of sorts? drill and safety wire? stud and nut? If it is repairable, I bet you guys have found the way. Any suggestions helpful.

 

Is the bolt actually loose when it starts leaking again or is the gasket just blowing out

Had a work truck with a 460 in it got tired of the exhaust leak so I got some aluminum gaskets for it they didn't match up perfectly so I modified them on the press

Look around if you can find copper or aluminum gaskets for it they work better than the paper ones maybe stage 8 makes locking header bolts for it

Also check your manifold make sure it's not warped

 

On the 1996 460 (7.5L) the exhaust manifold gasket was only used on the California engine. The 460 sold in the rest of the states did not use a gasket.

I do use high temp silicone on the mating surface when I put the manifolds back on and I have had no problems with leaks.
The factory did not even use that on them.

The 1996 Ford shop manual says:
Apply light film of Premium Long-Life Grease XG-1-C or -K or equivalent meeting Ford specification ESA-M1C75-B to right exhaust manifold or left exhaust manifold.

 

this is the first thing i would check.

and i agree with using the copper or aluminum gaskets as well. the nice thing about those are they are reusable. i would however put a thin coat of ultra copper rtv on both sides of the gasket to aid sealing.

 

The gasket isn't blowing out, if I tighten the bolts the leak stops. I have done gasket and silicon, but not silicon without gasket. Yes, I was aware no gasket from factory, so I guess the issue is hoe to keep the bolts from backing off?

 

I'm a fan of safety wire, but finding bolts that are pre-drilled and the lack of space make that difficult. I don't see why lock washers wouldn't work. And they make locking fastner kits for this application.

 

I had to have my manifolds milled to get rid of the warp. I put them on with gaskets and a year later they where leaking badly. I took them back off and cleaned them and the head surface put them back on without gaskets. Used grade 5 bolts with antiseize and lock washers. 2 years now no issues.

 

Lock washers won't continue to work after repeated heat/cool cycles. They loose their tension. I'd be looking at a warped manifold.

 

Thanks for the info, I was not considering conventional lock washers,but the little barb deals that bite and keep bolt from backing off, they work well in places where lock washers aren't desired, I think I will try those first, and if problem persists, manifold needs planed. Thanks.

 

I literally just did mine on monday,I had a slight tick with the gaskets on,I just took the gaskets off and tighten them back down,I don't have any leaks now.

 

Also try to make sure that its leaking between the block and manifold. My 97 FSuperduty leaks between the pipe and the manifold. It sounds like a manifold/head leak when it gets loose. I think the crossover pipe has been bent at some point is the reason it loosens up on me.

 

You can add another for a warped manifold.

Get it milled flat and do NOT use a gasket. Also, get NEW bolts

 

blue loctite.

 

What wrench are you able to use on your bolts? If the head is too big for a box wrench to fit, need to get some 5/16 head grade 8 bolts and beast em real tight....the glory of cast iron is the ability to do so.

This is after you check it for warping of course.

 

OK, we went on a strict regiment this morning; At 0700 hours we proceeded to analyze issues at hand. Issues finalized: Exhaust leak on starboard side, at rear of exhaust manifold. Appears to be able to remove manifold bolts, (preferably by unthreading all the way out) and proceed exhaust headwaters removal, inspection, repair, and reinstall.


One bolt was already falling out, near front. "How nice, easy fix." WRONG. Rearward most bolt twists off in cylinder head. Air pump bolt (3/8 6 point) won't budge. I remove all fasteners from engine, remove clamp and hose from air pump tubing, and proceed to remove manifold from chassis. It won't come out. With the tube attached it wants to stay in vehicle. Repair is necessary to have manifold out, and on bench. It is now 1100 hours. I have run fresh out of coffee. It is tooearly to drink beer. I need to remove inner fender well partially to remove manifold. I swore and I sweat. I get manifold out and on bench. I straight edge it, It is slightly high on the 2 port back and 3 port back. Not a total failure, but not flat. ThisIcan Work with.
Now, Thereis still one bolt taking up residence in the cylinder head, and let's face it, if it ain't paying rent, It's gotta go. I get the left hand drills, It laughs at me. I get my 1/8" carbides in a 20,000 rpm air die grinder, It laughs louder. I get my round tip carbide and I proceed to bore into the guts of the 3/8 bolt. It makes a nice provision now able to initiate broken bolt extractor. I insert extractor and it giggles and rounds the sharpies off of extractor set, 2 times over. I now go for 1/4" left hand cobalt bit, It bores into the bowels of bolt, quickly. Now, I go back to the carbide and slowly start my way forward, into the final invasion of the bolt's shattered kingdom. I start to see threads. I stop. I radio for back up, the cordless Makita and left hand cobalt grab the wreckage and thread it out, never even touching threads on cylinder head.


Now for the rebuild. I file the manifold, until my arm is about to fall off, then I file some more. I take the high points down slowly. Where there was rust and scale is now shiny and polished, from wearing down my file. I think this manifold might be an outer space prototype of a material slightly harder than diamond or carbide, possibly 150,000 psi Ductile Iron. Some WWII relic found in Japan that underwent a nuclear chemistry alteration from the nuclear holocaust. Not of ordinary composition. The perfect material to build a space shuttle from that can withstand multiple re-entries into the atmosphere without even a slight malfunction.


It is now time for reassembly, New bolts, cleaned manifold, clean cylinder head, Blue Loctite and orange hi-temp permatex. I retorque fasteners to 40 then 50 then 55, and button her back up. No leaks, and no gasket. I will repost if leak comes back in any tome frame less than the usual 2-5 years or the bolts keep backing off. Pull out of shop under own power 1345 hours. Quiet, healthy sounding big block, keeping the gas companies in business once again.