Nicholas Fluhart

October 3, 2012

2002 F-150 4.2L Intake Manifold Gaskets

Filed under: Daily Driver,Day to Day — Nicholas Fluhart @ 3:36 pm
Tags: , ,

Well, after ten years of trouble free service, my check engine light came on. I ran the codes and found that the intake manifold gaskets were apparently sucking air and causing a lean condition. The truck ran fine, but the problem was enough to trip the light. After doing some research, I learned that this is a common problem with the 4.2L engine. Alldata had a technical service bulletin on it. Fortunately, the problem is not the lower manifold gaskets between the manifold and the heads. However, it’s the upper manifold gaskets and the two-piece plenum gaskets along with the isolator bolts. In and of itself, that’s not too bad to fix, but the engine is partially under the firewall of the cab which makes access to the upper manifold very limited.

I was able to use a series of universal joints and a range of extensions and remove the upper plenum half without too much hassle, but it wasn’t easy getting to the rear bolts. Once removed, I saw no sign of leaks…yet.

So then I ventured lower. Once the upper half is off it gets pretty easy. I removed the isolator bolts and the bottom half comes off easy enough.

BINGO! You can see where the old gaskets were leaking. Also, the rubber (or what once was rubber) seals on the isolator bolts were as hard as concrete. No one had the isolator seals in stock, but Ford had the entire bolts which were expensive, but I was able to get them the day of the repair so I went with it. In the photo below you can see the difference in material in the seals on the bolts.

Now it’s just a matter of cleaning up the manifold parts and installing the new o-ring gaskets. Then it goes back together the same way it came apart.

Now is also a good time to clean the throttle body and idle air control assembly, and if it needs it, it would be easy to route plug wires at this time. However, I’ve only got about 20K miles on this set of wires, so I’ll let ’em ride. And back together it goes…

That’s pretty much it. It was challenging to start the engine, mainly due to all the carburetor cleaner I had sprayed into the ports had partially fouled the plugs I think, but once it cranked she cleared up and ran great. Now it’s ready to go…and no more check engine light!

Until next time…

Create a free website or blog at