98 F250 5.4L 120k miles

Hey all,

Finally got the jumping misfire to go away. I noticed there was liquid around cylinder #1. Turns out the bottom of the thermostat housing's gasket is leaking. Also appears that part of the housing is moulded to the top of the intake manifold, in which I have to take that entire top piece off to operate. Researching this leak it appears it was quite common for a few years around 96-98. There's a plastic internal gasket holder I guess that fails. 99 and on they released a fixed version of the manifold.

Has anyone here tried to do that? It seems relatively straight forward, but curious if any traps to watch out for.

Also, looking on parts websites I can't find the name of the top of the intake manifold, the parts with the tubes on top, where the housing is in front of, just above the valve covers if I'm explaining it right. I can only find the lower intake manifold, not sure if I'm searching wrong. Thanks again for your time and thoughts.

Matt

 

Thy are referred to as , upper intake and lower intake manifolds.

 

You may need to be looking into salvage yards. Bet that is going to be hard to find.

Could you post a link to the video that you found on it?

 

Hey bismic,

Here's the link to the video of the upper assembly gasket replacement. Seems straight forward based on my throttle/upper plenum(?) surgery recently (to drill press broken bolt from EGR housing &#128566.


Here's the link to the guy about JB Welding a retaining structure with more detail about the failing inner retainer. He doesn't show how of course, just that he's 9/10 on average. It's scary, but worst case scenario I may be able to take my time with appropriate JB and Epoxies to create the new gasket channel (kinda like making a form and pouring concrete? Which I haven't done either ha).


Apparently there are no aftermarket uppers for my model. I've found car-part.com that have versions of my manifold. Scary getting one shipped that may already have same problem, or close to it. Since I never overheated, just the small leak, I'm hoping it's just the gasket and not the inner plastic. Tomorrow my plan is to disassemble everything and investigate after work. I'll update. Any thoughts on self-repair would be appreciated.

Matt

 

Make sure you replace the grommets on the bolts that secure the manifold.

 

Thanks for that heads up hanky! I wasn't planning on the valve cover gaskets but since I'm doing the intake gaskets, and just watched a video on it, I'm nearly there with the disassembly already. If I'm that far, is it smart to install a timing kit? I don't think it needs it, previous small idling changes could be host of other issues I've fixed/replaced. Can I just visually determine if the major front components are intact? I want to keep this truck as long as possible so I'm trying to head off future issues. Thanks all.

Matt