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Discussion Starter · #1 ·
Help me figure out what this hose is for on the intake manifold.

My gas mileage sucks! after my first full tank I only got 214 miles out of it so I did the seafoam treatment, added a K&N panel filter and I'm gonna do seafoam in the gas tank when I fill her up. Found this hose with a kink in it and it looks like whoever worked on this last used a straight, off the shelf heater hose and I'm sure it should be molded with the appropriate bends.

I'd like to know what it's for and where I can get one. Thanks in advance!



I'm gonna try shortening it to see if I can get the kink out.


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If you take it off without draining some coolant you'll spill coolant all over because that hose directs coolant to the highest point in the system for bleeding purposes.


See that bolt above the hose on the intake manifold? That's actually a plug, and you remove it to bleed the system when you fill the radiator. Once the coolant starts pouring out of the hole youve bled the air pocket and you put the plug back, then you run the engine with the heater on full blast and radiator cap off. You keep filling until it starts to come out of the radiator cap and you've got a bled cooling system

The hose serves no other purpose than routing coolant to the bleed screw so that won't be the cause of your bad fuel mileage
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You need to calculate your actual mileage. 214 miles on your last tankful but how many gallons did you use?
 

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Discussion Starter · #4 · (Edited)
You need to calculate your actual mileage. 214 miles on your last tankful but how many gallons did you use?


Don't know what features you 2ng gen guys have, but I tested it from roughly 2 miles into the low fuel light to low fuel light.

I'll calculate the MPG with this next tank under similar driving conditions. The seafoam proved to be a smokebomb as always, and cylinder heads were noticeably cleaner after the treatment.

After this next full tank I'll go ahead and change the spark plugs as well. It's a really clean truck and my brother took good care of it, but I need to figure out this consumption problem soon.


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If you take it off without draining some coolant you'll spill coolant all over because that hose directs coolant to the highest point in the system for bleeding purposes.


See that bolt above the hose on the intake manifold? That's actually a plug, and you remove it to bleed the system when you fill the radiator. Once the coolant starts pouring out of the hole youve bled the air pocket and you put the plug back, then you run the engine with the heater on full blast and radiator cap off. You keep filling until it starts to come out of the radiator cap and you've got a bled cooling system

The hose serves no other purpose than routing coolant to the bleed screw so that won't be the cause of your bad fuel mileage
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Saw the bolt after I posted and figured it out. Trimming the hose removed the kink and I "burped" the system afterwards.


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VG-powered, Nissan trucks were always known for their durability and reliability, but never for their good gas mileage. Usually a combined mileage of 15-16 MPG for a 4x4 model is not uncommon and sometimes a little less, depending on one's driving style and type of driving. Those with the supercharged VG's see even worse fuel mileage and have to run premium. 2nd gens have a little bit of an advantage due to a more efficient engine and transmission package.
 

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Discussion Starter · #8 ·
That's terrible! This 2wd version for a a considerably small V6 is a pig on fuel. Got considerable better after the k&n replacement filter, seafoam treatment and seafoam additive to the fuel tank. At 244 with a quarter tank left.


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Well, most small trucks, even new ones, don't get very good gas mileage. Considering the Frontier weighs close to two tons, has low rear end gearing, is not very aerodynamic and that the VG engine is a fairly old engine design (it first showed up in the US in the 1984 300ZX), it's pretty understandable. Even a brand new Frontier V6 is rated at only 15/21 mpg...and that's 13 years newer than when the last 1st gen Frontier rolled off of the assembly line.
 

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Averaged 18.36 (all combined) on mine since I purchased my 2017 P4X in December with 1 mile on it. On the highway I'll get up to 22 if I stay out of it...
 

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Discussion Starter · #12 ·
Well, most small trucks, even new ones, don't get very good gas mileage. Considering the Frontier weighs close to two tons, has low rear end gearing, is not very aerodynamic and that the VG engine is a fairly old engine design (it first showed up in the US in the 1984 300ZX), it's pretty understandable. Even a brand new Frontier V6 is rated at only 15/21 mpg...and that's 13 years newer than when the last 1st gen Frontier rolled off of the assembly line.


I understand that it's not the most aerodynamic thing on the street. I also understand it's age. I'm not new to cars/trucks, and I'd like to think I can handle just about anything related to upkeep and repairs. I usually have manuals for all of my vehicles, but being a strictly Toyota guy for my whole life, I asked the question here for quick feedback (but saw the bolt as I reviewed my picture and figured it out on my own).

Regardless, in the same driving conditions and the same "test", I got 317 miles from full to light. Wish I did the filter and both seafoam treatments at different times to see which affected gas mileage more, either way it was $67 well spent in my opinion.

The trucks in beautiful shape for an 04, but 211 miles on a rather very sluggish engine was just unacceptable for me. Next is spark plugs and fuel filter changes, then going full synthetic oil (huge royal purple fan), and a radiator flush. as I'm sure the last owner didn't do any of that on a regular basis. Everytime I tinker she runs better and better, so I'm happy with it so far.


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The previous owner had retarded mine so bad that I think it burned out the catalytic converter and it was causing the crank sensor to throw a code. Really sucks because the rest of the truck is in such good shape.

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Discussion Starter · #16 ·
No codes on mine. After the seafoam treatment I've been getting better than excellent gas mileage and climbing after he second bottle into the fuel tank. Last tank from full to gas light lasted me 362 miles.

I did change the spark plugs, cap and rotor also. I'm sure everything I've done helped collectively. Needless to say, I'm still a huge believer in seafoam now.


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Discussion Starter · #17 ·
Alright, another round of name that hose!!! Except this time, let’s play name what vac lines go here! Went to take a peak in the light trying to find a vacuum leak and found a rigid line with no hoses attached on either end.

Hope you guys can help! Thanks!






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There may not be a vacuum hose that goes to it. Nissan often had metal vacuum line assemblies on their engines that not always had vacuum hoses go to them. My guess it was a "one size fits all" part the what metal tubes were used depended on the vehicle options and emissions certification. Usually, if there was a hose on it for some time, you'll see the discoloration on the end of the metal tube were the rubber vacuum line used to be. If you don't see that discoloration, then there was likely never a hose on it.
 

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Discussion Starter · #19 ·
There may not be a vacuum hose that goes to it. Nissan often had metal vacuum line assemblies on their engines that not always had vacuum hoses go to them. My guess it was a "one size fits all" part the what metal tubes were used depended on the vehicle options and emissions certification. Usually, if there was a hose on it for some time, you'll see the discoloration on the end of the metal tube were the rubber vacuum line used to be. If you don't see that discoloration, then there was likely never a hose on it.


I thought the same thing, but on something this old and me not being the first owner I couldn’t be sure how long something’s been off so discoloration would be out if the question.


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I would just take a good look around the engine compartment to make sure there aren't any disconnected vacuum hoses laying around (which you probably have already done) and then start the engine and listen for vacuum leaks. If you don't find any loose hoses nor hear any vacuum leaks, I wouldn't lose much more sleep over it. If you wanted to go the extra mile, you could get a vacuum diagram for your vehicle from the FSM and double-check all of the vacuum lines, or, try and fine the other end of the metal line. To help you find the other end of the line, you could cut a length of vacuum hose and stick it onto the metal tube and either blow through it and listen for the other end or spray a liquid through it like WD40 or spray silicone and find where it comes out.
I don't know when Nissan started the practice of installing metal vacuum tube assemblies and not using all of the lines, but I do remember then doing it on E-series motors in B11 Sentras back in the early-80's, so, they've been doing it a long time!
 
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