2012 Coolant Overflow Bottle Has Two Caps?

Alstann

I noticed something peculiar when I was looking at engine photos and whatnot.

Before 2012 it seems, the overflow bottle has only one radiator cap, whereas my 2012 MY has two:



Only one of them is a pressurized radiator cap, however. The other one seems to just be a cap.




Any thoughts on why the change? I figured because of the oil to water cooler, but whatever. Don't really understand the reasoning why.

wheee!

That is indeed very different...

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VQStryker

same thing just different cap and position

takjak2

Though from the OP's images, I would think your caps are backwards. The overflow shouldn't be the one with the pressure cap.

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1slow370

check owners manual will probably have it it very well could be the pressure cap is supposed to be on the reservoir to change the system to a fully sealed one. that would explain the clamps on the overflow line and thicker plastic

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Alstann

EDIT: I just realized having after switched them round to what I thought would be correct, the cap without the pressure rating states to not put it on the overflow tank. So, I guess the pressure release point is now changed to the overflow tank.

wstar

Just noticed this. Anyone picked up the newer tank + cap from Nissan and retro-fitted on an existing car 2009-2011 car? My 2009 overflow tank is cracking a bit at the bolt holes anyways (off and on too many times with a little too much torque I guess), and I almost always get a little spill-out from the plastic cap at the track too. Figure this is worth a shot as an upgrade.

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ChrisSlicks

The plastic cap in the 2009-2011's sucked, always leaked out of the cap instead of out the overflow. This setup looks much better, would consider switching if I can get the parts for a reasonable price. Just going by a cursory glance at the pictures it looks like a bolt in replacement but hard to say for certain without a close comparison.

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*NOTE*
The following refers to 6M/T only. The 7A/T may differ on some part numbers.

FAST shows the following main differences:
1) Three part numbers for '09-'10, '11 and '12 radiators.
2) Two part numbers for '09-'11 and '12 cylindrical tank assy on radiator.
3) Radiator fan/motor assy has different part numbers for '09-'10 and '11-'12, BUT '11-'12 part number can be used on '09-'10 according to FAST.

Part numbers for upgrading to '12 parts:

21710-JK90B - '12 reservoir tank assy (hoses and possibly reservoir cap included)
21430-C991A - '12 radiator cap
21430-7995A - '12 reservoir cap
92131-JK20A - '12 cylindrical tank assy (maybe not needed?)
21481-JK600 - '12 radiator fan/motor assy (maybe not needed?)

Jerggy13

I would assume the change is due to the new engine coolant based oil cooler. Just an idea.

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wind.zero

Sorry to bounce an old thread but I purchased the overflow reservoir to convert a 2011. The 2012+ bottle has a hose on the bottom.

Those that converted to this setup, what did you do with the bottom hose?

esfourteen

you need to connect that bottom hose to the coolant hard pipe above the driver side manifold. I ran mine to a reducer and into the connection where the factory throttle body coolant lines returned (I deleted mine)

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Nixlimited

Interesting, what is the purpose of this connection, though? Is the overflow designed to return coolant to the system? And what prevents it from coming up from that line (e.g. a one-way valve somewhere?).

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wstar

The two systems (pre/post- 2012) work quite differently. You can see the differences pretty clearly in the Service Manuals (which are on the forums here in PDF, somewhere).

Basically, the earlier model has a non-pressurized overflow tank with a plastic screw-on cap, a metal pressure-relief cap on the water outlet (with just two thin hoses; waterneck -> tank -> ground). On these earlier models the outlet pipe on the driver's side of the engine (hard metal pipes with coolant hoses attached, can't miss em - Service Manual calls it the Heater Pipe) has only 3 connections on it: two fatter ones for the bypass flow to the rear water outlet and for the heater circuit, and a thin one poking out the top for the throttle body coolant lines.

In the new design, the non-pressurized overflow tank is replaced with a pressurized expansion tank (which is a much better design in many ways). The water-outlet cap is now a fixed cap (only remove for filling the system), and the pressure-relief cap is on the new expansion tank. The expansion tank has one more connection to it than the old overflow tank - the line from the bottom which goes to a new connector on an updated version of that metal Heater Pipe assembly on the driver's side of the engine (so if you want to convert factory-style, you need to update that Heater Pipe as well). The updated Heater Pipe, in turn, also has another new connection which goes to the new oil cooler down at the oil filter - so if you just wanted to update the expansion tank setup + pipe but not add the 2012 oil cooler, you'd want to block off that 4th connection. If you did want to add the cooler, then you'd also need to sort out the connector pipe for the other side of it, which is another separate piece. esfourteen's connection to the TB coolant connector is probably the easiest route to take, assuming you don't need the TB lines (don't live/drive in a cold climate).

The expansion tank is part of the real cooling system and runs full pressure, unlike the earlier overflow tank. The two connections (to the front/top water outlet area and to the side Heater Pipe) are what let air bleed over into the expansion tank where it should be, and let's the liquid sit in the tank at the correct level to use it as a gauge, but you won't see a lot of actual flow through them (since the connectors are perpendicular (or in the stock setup, backwards on the big one) from the normal flow).

Keep in mind if you run that connection to the TB coolant connector to route the line low - if you let it arc up in the air higher than the tank, bubbles won't make it to the tank as well (because the hose rather than the tank is the high point).

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Jordo!

That's what I was thinking too.

Then... is this just a revision to improve cooling overall or specifically to deal with the extra pressure and fluid in the system shared with the oil cooler?

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