Hose under the fuel pump?

[Bosshog]

There is a short coolant hose under the fuel pump of my 73 620 that I need to replace.  It feeds the carburetor heater.  It is two different sizes.  How is the best to go about replacing?   Thanks.

[datzenmike]

It connects the coolant line from the intake and the thermostat by pass back to the lower rad inlet. Warms the intake air (not carb) in winter and cools the air in summer. When the intake air is closer to a constant temperature during extreme hot and cold weather the engine runs better.

 

Yes the lower rad inlet is larger than the metal rube that connects it to the intake and thermostat. (I know, why do they do this?) What I did was get a hose that snugly fits the larger tube and just put two gear clamps on the looser end.

[ggzilla]

Actually it warms the bottom of the intake manifold for better atomization of fuel. The alternative is the old heat-riser manifold, which is less accurate.

 

Nissan ATC (air cleaner) is what warms the air, so that the a/f ratio is constant even during extreme hot and cold weather. And also prevents carb icing at 40° F.

[Bosshog]

Thanks for the replies.

[DanielC]

Is it the hose with a 90 degree bend in it?  If so, go to a Nissan dealer, and order hose A4056-32001.  I got one literally just last week.

[SadieD]

I used two hoses, one larger than the other, and a brass barbed hose reducer.

[red13]

i just ordered 3 from nissan last week as well. 14056-23001

[HOGIE]

i just ordered 3 from nissan last week as well. 14056-23001

 

Is it the hose with a 90 degree bend in it? If so, go to a Nissan dealer, and order hose A4056-32001. I got one literally just last week.

Two part numbers for the same part?

[ggzilla]

Yes, Nissan sometimes changes part numbers.

 

This page explains it

http://www.nissanpartsdeal.com/parts/nissan-hose-water~14056-23001.html

[datzenmike]

A part that was designed for use on the 68 510 L16 will still fit the '80 720 L20B but many things can happen over these years. The original may be rubber and have a woven covering. Later synthetic rubber and a better manufacturing method is found that is cheaper to make that is both stronger and lasts longer. The two parts are still interchangeable but the older one is then said to be obsolete and is superseded by the newer one.   .

[red13]

Your best bet is to order the number I gave you.it is the proper diameters you need. The l20b line sits differently.

[DanielC]

Here is the newer hose on an L-18.

[red13]

the question really that hasnt been answered is what motor?

[Cardinal Grammeter]

I really need some help on this one - and this is exactly the thread.

 

What I have:  EDIT:  1974 620 L18

• "Under the Fuel Pump Nipple" blocked off
• Small Bypass Hose from Thermostat Housing to Intake Manifold more of less in front of carb base (while standing in front of truck, facing engine compartment.)
• Complicated 360* bend w/90* end from Long Straight Pipe coming from engine under intake, snakes towards the firewall, then up, then forward to intake nipple on the EGR extension manifold.

I saw the pic just previously of this post which showes a 90* hose from the UtFPN to what appears to be a metal pipe that is horizontal and perhaps loops around the front of the valve cover - but if it does, I don't know where it goes.

 

Oh, and that LSP also has a Blocked Off Little Nipple that splits off right where the big hose attaches.

 

So I'm left with 2 orphan nipples:

• Heater Hose sized  UtFPN
• Tiny Bypass sized BOLN

Trying to find these routings in the parts manual - maybe check pollution controls...

 

...and yes, I found some answers:  EDIT:  1974 620 L18 parts diagram

 

 

So I'm completely missing Pipe #12 w/nipple that goes to Hose #13 which leads to THE QUESTION:  Where does hose 13 go?  The thermostat housing?  The hose on my thermostat housing goes to the intake where hose #17 appears to go - but my hose looks like its molded and proper EDIT:  doesn't look molded and proper.

 

???

 

Confused and missing parts - why should I be surprised.

[banzai510(hainz)]

13 goes to the lower stat housing. its like a bypass.

There was 2 versions on L16s that I have seen. 1 with a bypass(needs#13) and one with out which goes just straight to the intake manifold to heat. So there will be 2 versions of #12

 

 

 

2 versions of the stat housing (with hole and 1 w/o)

[datsunaholic]

You're missing parts, or you have mixed parts.  The metal pipe was the coolant bypas (recirc) pipe that  bypasses the thermostat.  Helps the engine warm up properly by passing warm water around a cold closed thermostat.    It teed off between the intake and lower rad hose to the thermostat housing.  It then runs to the intake to prevent carb icing. 

 

The 2 versions Hainz refers to never blocked off the lower hose- it went either straight to the manifold (in that case, the thermostat itself has a bypass and jiggle valve, which most replacement thermostats have) or via the method above.  The hose shouldn't just go straight between the thermostat housing and the intake manifold.  It wasn't designed that way.  Later (75-77) ones omitted the intake coolant loop (used a stovepipe setup via the exhaust manifold instead) so the coolant ONLY went between the lower radiator hose mount and the thermostat.

 

 

The "complicated" hose under the intake and to the EGR extension is the PCV hose, not a coolant hose. 

[Cardinal Grammeter]

OK, let's see if I get this right:  (EDIT:  forgot to mention I have a 1974 620 L18)

 

QUESTION:  If that "Complicated Hose" is PCV, where is the other coolant hose out of the manifold? - we have the bypass tube going to the manifold, but there should be another hose of passage to complete the circuit.  (Is there a water port at the intake manifold gasket?)

 

I have a thermostat housing with small nipple.

 

So I need the #12 tube w/T'd Off Small Nipple as shown in the diagram.

 

The #13 hose goes from that T'd Off Small Nipple to the Thermostat Housing Small Nipple.

 

The #12 pipe goes FROM the large nipple next to the large nipple to the heater core, under the fuel pump, TO the intake manifold fitting at the base of the carb.

___________________

 

Just when I thought I had all my pipes (!)

 

Oh..... I can't wait until I try to connect all the Emissions Control piping including the Combination Valve - even the air cleaner and carb are so not obvious.

 

THANKS

 

EDIT:  Here is a pic of the L16 with the 2 styles of bypass tube:

 

[red13]

#13 is NLA i have looked for it.  also what most people do is either run a rubber hose to the intake or just go get some metal line and make a line from the water inlet to the carb add a T to go to the thermohousing.

[datzenmike]

You CANT run from the thermostat to the intake!!!!!!!!!!!!!!!! This is totally against what is needed. Coolant flows out of the intake AND the thermostat housing and join and then go down to the lower rad inlet to the water pump. This water MUST circulate in this direction..

[datsunaholic]

QUESTION:  If that "Complicated Hose" is PCV, where is the other coolant hose out of the manifold? - we have the bypass tube going to the manifold, but there should be another hose of passage to complete the circuit.  (Is there a water port at the intake manifold gasket?)

 

 

The water connection at the manifold is under, to the front of, the carburetor.  It's #5 on the diagram.  The hose goes over the manifold's #1/2 runner.

[Cardinal Grammeter]

The water connection at the manifold is under, to the front of, the carburetor.  It's #5 on the diagram.  The hose goes over the manifold's #1/2 runner.

OK, I see #5 - that is what the #13 pipe goes to.

 

But my question is, #5 is one passage into the intake under the carb.  But there has to be another source of water so there is flow.

 

I don't see any other coolant fittings to this under carburetor coolant so is there a coolant port into the head via the intake manifold gasket?

_______________________

 

On a lesser note, I'll be silver soldering a T-fitting for the thermostat port:  1/2" barb X 3/8" barb X 1/4" pipe.  I am not looking forward to this.  (I should plug off the thermostat port and run the circuit from the water pump fitting underneath fuel pup to the manifold - I'm assuming that would work like the pre-72 L16's.)

[red13]

[datzenmike]

 

Water flows out of the head into both pair of intake runners. This the the front ones.

[Cardinal Grammeter]

Got it.  Thanks!

 

Let's see if I can post my fabbed fitting and hose routing pics....

 

...nope, I paste them to the edit window - they are inserted - but when I save, they disappear.

 

Found My Media but couldn't find how to upload to My Media.

 

Rrrrr....

 

Bit the Bullet - updated my PhotoBucket