Datsun-240z Vs Fairlady-z432

[kats]

Once water cooled down, the tube has air in it . I found it . 

Why does the car have the bottle for ? 

I thought to keep the water in certain level . 

Any input appreciated .

Kats

[HS30-H]

2 hours ago, kats said:

Once water cooled down, the tube has air in it . I found it . 

Why does the car have the bottle for ? 

I thought to keep the water in certain level . 

Any input appreciated .

Kats

Kats, the S20-engined cars had the tank/bottle acting merely as an 'overflow' catcher. There is no return path to the radiator as the coolant/air can only move in one direction so it's not the same as a 'header tank'. Generally speaking, it was a characteristic of high rpm/high performance engines of the period for them to cavitate their coolant somewhat, and the tank is simply a way of avoiding the slightly embarrassing scenario of, er, uncontrolled spillage... 

Nissan called it a "reservoir", but as far as I can see the only way that it can be used as such is if you manually pour the coolant caught by the "reservoir" bottle back into the radiator when it has cooled down. 

[kats]

Thanks Alan !

I learned , Overflow catcher , yes that is suitable for the bottle. 

So I think If I want dual path of the coolant, I should place the bottle as high as the radiator neck . I should make a bracket near the front shock tower . But I don’t think I would do it for my car .

Kats 

 

[Patcon]

48 minutes ago, kats said:

Thanks Alan !

I learned , Overflow catcher , yes that is suitable for the bottle. 

So I think If I want dual path of the coolant, I should place the bottle as high as the radiator neck . I should make a bracket near the front shock tower . But I don’t think I would do it for my car .

Kats 

 

I believe to have the coolant flow both ways the bottle and the line will have to be able to hold pressure the same way the radiator cap does. Also the radiator cap will have to be able to allow the coolant to flow into the radiator versus the current set up where it simply allows over pressure discharge

[HS30-H]

16 minutes ago, Patcon said:

I believe to have the coolant flow both ways the bottle and the line will have to be able to hold pressure the same way the radiator cap does. Also the radiator cap will have to be able to allow the coolant to flow into the radiator versus the current set up where it simply allows over pressure discharge

My (early) version of the bottle - which came with a radiator-type pressure cap - would theoretically be suitable for that type of setup, but I just can't see a scenario where the pressure in the 'reservoir tank' is higher than that in the engine/radiator - allowing coolant to flow back? 

Here's the factory parts list showing the 432/432-R system:

 

If you look at the radiator cap, it seems to be a simple sealing cap with no pressure relief valve. In this setup, the pressure relief cap is on the 'reservoir' tank. I think this would allow overflow/cavitated coolant to pass from the radiator into the reservoir tank, with excess pressure and/or coolant to be vented via the drain tube. The pipe connecting the radiator and the reservoir is radiator hose type quality, pressure resistant and with proper clips.

Nissan clearly did away with this system later, using a simple cap on the 'reservoir' (it has a small hole in the top to vent air) and a normal pressure relief type radiator cap. The later GT-Rs were like this too. My KPGC10 has a slim, unpressurised overflow catcher tank next to the radiator.      

Edited August 17, 2018 by HS30-H
pressed submit before finishing...

[Patcon]

12 minutes ago, HS30-H said:

My (early) version of the bottle - which came with a radiator-type pressure cap - would theoretically be suitable for that type of setup, but I just can't see a scenario where the pressure in the 'reservoir tank' is higher than that in the engine/radiator - allowing coolant to flow back? 

Here's the factory parts list showing the 432/432-R system:

 

Normally the way a system like this would work, is the air would collect at the radiator neck and be burped to the bottle when the pressure rises in the radiator. It comes into the bottle from the bottom. When the radiator cools and causes a vacuum in the radiator, liquid is drawn back from the coolant reservoir. This keeps the cooling system purged of air

[Patcon]

In the scenario in the diagram above, the cap at the radiator would be a cap with no disc or spring attached at the bottom. The overflow tank would then have a standard pressure radiator cap installed on it

[gnosez]

This is what was done on the L-series race engines built by BSR.

The radiator was tapped to run to the "T" fitting welded on the thermostat housing which was plumbed to an expansion tank which then had a line to an overflow bottle. The expansion tank has the pressure cap.

The radiator tap, the thermostat T and the expansion tank are all positioned as high up as possible.

I doubt you want to ruin your Z with these modifications and I show it only to illustrate how some folks tried to keep these engine from overheating.

[HS30-H]

38 minutes ago, Patcon said:

In the scenario in the diagram above, the cap at the radiator would be a cap with no disc or spring attached at the bottom. The overflow tank would then have a standard pressure radiator cap installed on it

I think we are on the same page there. 

But for Kats' installation on his blue HLS30U, he is using the later type reservoir bottle and that means an unpressurised bottle, one-way system. It looks to me as though Kats is getting quite a lot of coolant in the reservoir bottle. More than I would have expected. Japan has been pretty hot (to say the least!) lately, so maybe the cooling system is struggling to keep up?

Kats, is the pressure rating on your 240Z's radiator cap quite low?

[kats]

Let me explain , I learned and confused, and found something may not correct on my Z432 !

Thanks Alan, Patcon, gnosez.

Kats  

[kats]

For the early "a metal cap with a push botton" type reservoir tank,  

What I am confused is, seeing the manual , to my understanding, the  manual is saying "pressure relief valve is on the reservoir tank , not on the radiator "  . OK,  However, I can not see any specific part number for the radiator cap which should be put on the radiator. I mean , in this set up,

the radiator cap must be a simple "non pressure regulator " type.

BUT , ,, We only have a single part number for the Z432 radiator cap , from the beginning to the end, that is 21430-E4201 , this is the biggest question to me. 

From Jan 1970 , simple plastic cap (21516-C0500) began to be applied on the reservoir tank, if the manual is correct, this means

the radiator cap must be replaced by pressure regulator type, to achieve keeping good coolant temp in the water cooling system.

But there is no new part number for the radiator cap when this new cap was applied. 

We only have a single part number for the cap on the Z432, "21430-E4201" ,

so , I guess Z432 is different from the manual in terms of  radiator cap set up ...I will hold of my conclusion until I see the "non pressure regulator " type cap on the Z432 radiator.

I will upload some pictures.

Kats

[kats]

If my guess is true, the early set up on the reservoir tank ( push botton cap ) is useless. It becaomes "over flow catch tank " like Alan said.

I need to see other early Z432s as much as possible to clear my question.

Kats