Whats tube for

[Wilcox]

Ok im stumped on this one the flat tube that comes off the heat shield on the passenger exh manifold. Is it suppose to be flat and what is its purpose??

 

[superj]

i bet its not supposed to be flat. i don't know what its for though.

 

[gaz]

I can't make out what you are identifying .(

 

[Wilcox]

Ya. I would not think so either. Has to be there for a reason dose anyone know. Thanks guys.

 

[dvdswan]

What are the two ends that it is connected to? 1 side looks like some type of canister that seems to be the size of a fuel filter. The other side looks like it connects somewhere on the lower side of the engine block.

Maybe jack up the truck and take a picture from underneath.

 

[Curious Hound]

Hard to see in your photo.

I THINK you are talking about the preheater tube for the intake. It is only used when starting the engine in cold temperatures. A thermal switch would activate a vacuum operated damper that would draw warm air from around the exhaust manifold and send that air to the intake. It helps the engine warm up faster. I live in South Carolina and removed all that years ago with no detrimental effect to engine operation. In real cold climates, it can be helpful.

 

[Wilcox]

Yep that makes sense. Zoom in and you can see the flatend tube on top of pic. Can't see from under truck very well. It dose connect to the heat shield over the passenger side exh manifold. Have not pulled battery tray to see if it ties in to air box, but what you are saying make sence. Tube must be just gone to be so flat. Thanks guys.

 

[superj]

i was wondering if it was a preheater. i thought those went away with carbs though? is that truck carbureted?

 

[Curious Hound]

i was wondering if it was a preheater. i thought those went away with carbs though? is that truck carbureted?

My 93 is fuel injected and had that. Intake air temp is still important whether carb or FI.

 

[superj]

hmm. crazy. i thought those away. well, i guess they went away after tbi? i do remember seeing them on tbi engines but not on anything since tbi


maybe i just don't work on anything anymore to see that kind of stuff

 

[Wilcox]

Yes its an 1988 2.9 fi. Will be taking to eastern wa. Roads are very dusty. Think I should cap off in air box and eliminate the tube?? Have not had any problems with cold start especially when tube is flat, must not have been working anyway.

 

[superj]

ha ha ha. i guess you could since its been flat for who knows how long. might also be easy to just put another hose on and see if it makes any changes?

 

[Uncle Gump]

I'm pretty sure it's the pre heat tube too.

Just cap off the the tube on the filter housing. Any air that enters there gets filtered prior to going to the engine... but capping it off will prevent hotter engine compartment air getting into the engine.

EDIT... Chances are the thermal vacuum switch doesn't work anyway.

 

[Rimjam]

Not easy pulling the battery tray, it's spot welded to the inner fender (& maybe the radiator support).