86 F-0250 with a 6.9.
I was replacing my glowplugs and decided to replace the return lines and o-rings while I was at it. All the GP's were dead. autolites were replaced with motorcraft/Beru's.

The truck has what I thought was a blown exhaust manifold gasket. As the truck is running everything is fine at first. When it reaches the operating temp max it starts to make a sound like a pop on one cylinder. After its parked and cools down the noise goes away till the temps rise again. About to the R on the stock temp gauge.

As i was working on the truck it was very evident that the screen over the intake was very dirty. And the area of the intake manifold was filthy as well. i have only had the truck since January and I only drive it on the weekends at this point because of the hard start issue it had with bad glowplugs and having to use ether to start it in the morning when I do get to use it

So as I started the truck to do a visual on the return lines I noticed that the thumping is coming from the intake manifold. I have really bad hearing and this noise is not evident to me with the air cleaner on and the hood closed and in the cab driving. There is not any performance issues noted while driving the truck either cold or as it warms up and make the exhaust noise. The start up when I noticed the noise was after abou 6 hours from shutdown.

So do I have a bad intake valve? I can't get to the repair till the weather cools down out here but i would like to gather parts and figure out what I need to do.

 

on the underside of your air cleaners cover their should be a bowl shaped thing on it. The only purpose that serves is to dissipate that thumping noise. Mine makes the same noise that your describing and always has as long as I can remember. Its not something I would worry about.

 

OH and as far as the dirty intake goes, take a look at your CDR. Its the tuna can looking thing on the back of the intake. It needs to be cleaned periodically.

 

x2 with what boggs said...i would do the same thing.

 

thanks for the replies. How does the CDR come off to clean it. Or is it cleaned as it sits.
Started the truck yesterday after a nice long cold soak. starts perfect. I guess 8 working GP's starts better than 8 dead ones. LOL

 

Its held on with two small bolts. Just run those out and give her a lil tug to get it out of the rubber tube. Let her soak in some gas for an hour or so to break some of the gunk loose. Dont be afraid to kind of swash it around in there too.

 

thanks. That will be an easy fix. I'll take it off tonight and start it to soaking

 

Ive cleaned my CDR a few times, but something that still baffles me.. most people speak as if they get plugged up with gunk, sludge or what have you. Yet everytime i pull mine off it crystal clean inside, albeit covered in shiny black oil. But always clean, clear and seemingly in working order, FWIW it had never been off until i pulled it, i cracked the paint around the bolts the first time after 286k+

 

that's good. the inside of the engine should be just as clean.