99 F250 LD 4X4 W/ 5.4L and 202k miles.
I recently cleaned the TB ( it was filthy) and
noticed the plenum was also. I was considering
running some seafoam through the system and
wanted to get some opinions from you folks.
How hard is it on a high mileage truck. The o2
sensors, catalytic converter, plugs , etc.?
Does it work? I've heard pros and cons about
doing it . Thanks for the input.

 

What do you expect it to do for you? It will not clean out the intake plenum because it will never get in there.

Modern gasoline has a bunch of detergents in it already. There is no benefit to running seafoam through a truck like yours. If it was 30+ years old and carburated, I would say go for it, you might loosen up some junk in there.

It is a snake oil fix. I am sure plenty of experts will chime in and tell you how great it worked on thier trucks, but unless it is some sort of magic, there isn't much science behind what you are contemplating.

 

This is for the air plenum. According to the directions you remove the air intake hose from the
throttle body and place the spray tube 1/4" from the butterfly and the replace the hose back over the throttle body. Start the engine and spray 2/3
of the can directly into the plenum. I don't know if it works or not. Just wondering how to clean that
air plenum.

 

I think Seafoam is a wonderful fuel stabilizer, as for actually cleaning anything with it I don't think so. If you want a true cleaning you need much harsher chemicals. On the fuel side BG44K is good but really only worth it if it is used with a motorvac, for the air intake side I think disassembling and hand cleaning is the only way you are going to see true results. Also running an oil separator in the PCV lines will help keep the crap out of the air intake side of the engine.

 

I was kinda thinking that. Thanks

 

I have used Seafoam to clean the intake in half a dozen cars and trucks, 3 outboard motors, and 1 inboard V-8 boat motor.
On some of the cars/trucks the vehicle idled much smoother when I was done. On some of them I didn't notice any effect other than neighbors pissed off at the smoke, but even that was worth it !

 

Seafoam is not magic but it does work if used correctly.

For cleaning the intake and upper part of the motor you need to get it into the motor as quickly as possible (manifold vacuum). Then shut the motor down.

Leave it shut down for 20 minutes. The reason is so it can saturate and soak the carbon/oil deposits. If you keep the motor running the entire time you will only burn the Seafoam - not the deposits. Think paint remover here - you can't just pour it on and wipe the paint off - it needs time to work, too.

Now fire it back up and let it run a while. Sometimes you get a LOT of smoke and sometimes you don't - depends on the amount that was allowed to soak and what it is burning off.

Again - it's not magic but it will help you clean things out.