Ae95 Cooling Issues

[Hiro Protagonist]

Explain why the bottom hose is always the hottest and why the thermo fan switch opens when the water is released from the thermostat which is between the thermostat and radiator.

 

It is not a commodore Ian.

 

Thermofan switch opens at a hotter temperature than the thermostat (93 compared to 82), so if the fans are on then the thermostat is open, thus it doesn't matter what side of the 'stat the switch is.

 

And I never said it was a Commodore. I just said that conventional wisdom (and essentially every single application of a vertical flow heat exchanger) says that flow will go from top to bottom, and the layout and flow pattern of the system (whilst the opposite of a lot of cars when it comes to thermostat location) has been stated by 3 of the most knowledgeable Toyota modifiers I know of (Bill Sherwood, Phil Bradshaw and Jason Purcell), and aligns with Toyota's own EPG for both RWD and FWD setups.

 

As a final note, take a look at the layout of the water pump - being a compressor-style impeller pump, it receives water axially and outputs it radially, like the compressor on a turbocharger - the radial outlet of the pump goes straight into the block, NOT through the thermostat.

 

Anyway, this is getting off-topic as the OP has a 4AFE, not a 4AGE, which means the layout is completely different - 4AFEs have the thermostat bolted to the side of the block on the end of the lower radiator hose, whilst the top radiator hose exits from the top of the head

Edited October 6, 2010 by Hiro Protagonist

[Trev]

Anyway, this is getting off-topic as the OP has a 4AFE, not a 4AGE, which means the layout is completely different - 4AFEs have the thermostat bolted to the side of the block on the end of the lower radiator hose, whilst the top radiator hose exits from the top of the head

 

You have a RWD water setup in your head.

 

FWD 4age water setup is the same as the 4afe.

 

If the 4a FWD system sucked the water in from the bottom then as soon as the thermostat opened it would be quenched by cooler water making it close which would limit the cooling affect.

Edited October 6, 2010 by Trev

[Hiro Protagonist]

You have a RWD water setup in your head.

 

FWD 4age water setup is the same as the 4afe.

 

If the 4a FWD system sucked the water in from the bottom then as soon as the thermostat opened it would be quenched by cooler water making it close which would limit the cooling affect.

 

The FE water setup is different to both the FWD and RWD 4AGE setups, and more akin to the 20Vs. In the FE setup both the inlet and outlet of the radiator (no matter which direction the flow is) are on the gearbox end of the block/head, whilst the waterpump is still in the same spot as the GEs.

 

And there is no sudden cool rush through the thermostat anyway, thermostats don't open like a floodgate at a particular temperature, they progressively open (like the wax pellet valve in the cold-idle valve, not that the revs slowly drop as the valve progressively closes with coolant temp increase) which allows time for the flow from the radiator to mix in. 4AGEs (and 7AFEs, and 4AFEs) also use double-valve thermostats - there is a bypass system so there is still some hot coolant flowing from the engine into the back of the thermostat as it starts to open, along with the jiggle valve which also lets a small amount through. As the thermostat fully opens, the secondary valve closes the bypass circuit.

Edited October 6, 2010 by Hiro Protagonist

[Trev]

The FE water setup is different to both the FWD and RWD 4AGE setups, and more akin to the 20Vs. In the FE setup both the inlet and outlet of the radiator (no matter which direction the flow is) are on the gearbox end of the block/head, whilst the waterpump is still in the same spot as the GEs.

 

Forgot how the 4af was, I was thinking of the 4ac system.

 

And there is no sudden cool rush through the thermostat anyway, thermostats don't open like a floodgate at a particular temperature, they progressively open (like the wax pellet valve in the cold-idle valve, not that the revs slowly drop as the valve progressively closes with coolant temp increase) which allows time for the flow from the radiator to mix in. 4AGEs (and 7AFEs, and 4AFEs) also use double-valve thermostats - there is a bypass system so there is still some hot coolant flowing from the engine into the back of the thermostat as it starts to open, along with the jiggle valve which also lets a small amount through. As the thermostat fully opens, the secondary valve closes the bypass circuit.

 

I know they don't open like a floodgate.

 

All the tests I have done with the 82 cooling system suggested to me that they flow in at the top and out the bottom but after thinking about what you have said I have started to think otherwise as it makes more sense and if I am wrong then I happily accept that and will cop it sweet.

 

The reason I say it makes more sense is:

 

1. Thermo switch is before the thermostat to detect hotter water entering the engine turning on the fan to allow cooler water to enter.

 

2. Temp sender will detect water coming from the engine and not into it.

[Hiro Protagonist]

Forgot how the 4af was, I was thinking of the 4ac system.

 

 

 

I know they don't open like a floodgate.

 

All the tests I have done with the 82 cooling system suggested to me that they flow in at the top and out the bottom but after thinking about what you have said I have started to think otherwise as it makes more sense and if I am wrong then I happily accept that and will cop it sweet.

 

The reason I say it makes more sense is:

 

1. Thermo switch is before the thermostat to detect hotter water entering the engine turning on the fan to allow cooler water to enter.

 

2. Temp sender will detect water coming from the engine and not into it.

 

It's a confusing system, I'll give you that. As for the thermoswitch being before the thermostat, like I said before because it opens at a higher temperature than the thermostat (which makes sense, as there is no point having the thermos on if there is no real flow through the radiator) then it can be before or after.

 

As for temp senders sensing inlet or outlet temperatures, it doesn't really matter as long as everything is gauged correctly. Generally inefficiencies in the cooling system come from the radiator itself rather than water galleries etc, so you'll pick up high temps from the radiator not functioning correctly before it goes into the engine rather than waiting for the engine itself to start to overheat (which would soon follow)

[Womble1972]

Edited

Edited October 12, 2010 by Womble1972

[JedzWagn]

Edited

 

Womble - back to your original post. I drive the exact same model as you, summertime assertive driving half way is normal or lots of stop starts in moderate weather.

 

When I run the air con it's stable at around the 2/3rds point (I use the economy air con setting to help keep the engine cool)

 

Freeway driving you should be below halfway

[Womble1972]

Womble - back to your original post. I drive the exact same model as you, summertime assertive driving half way is normal or lots of stop starts in moderate weather.

 

When I run the air con it's stable at around the 2/3rds point (I use the economy air con setting to help keep the engine cool)

 

Freeway driving you should be below halfway

Jedz It looks like mine runs alot like yours i have done 8000kms in mine now it seems to be no issue.

Thanks for your help & reply