Thermostat on rwd 4agze..why the $&#$% cant I get it to work!

[~SlideWays~]

I've tried putting it in the bottom hose with two back to back housings. The best I could get that was running at 'about' operating temp but on the track it overheated.

Now I've tried it in the top hose straight from the head (the hottest place I would have thought). I was told the the spring should be on the hot side (pointing towards the head). When I tried this it got up to temp pretty fast but then started over heating on a short drive. Then I thought wtf i'll try it the other way around with the spring poing towards the radiator, now this gets to temp at a stand still but literally metres down the road the gauge goes to rock bottom!!!

What am I doing wrong???? I know 4a engines all seem to have the thermostat in the bottom hose but this doesnt work for me because its a fwd 4agze and cant get the housing close enough to the engine (the heat).

Someone must know how I can fix this! All I want is for it to hold a steady temp for everyday and also the track (or even a blat up a hill).


I thought I'd finally fixed the problem!

[mike86ze]

I have mine on the top hose. spring toward the engine. works fine.

take it apart. check nothing looks susp, like it could be sticking or whatever,

check the thermostat works by chucking it in a pot of hot water >80º or boiling/simering.

therm shouldnt affect temp dropping that quick unless something gave way in a big hurry. what do mean by this?

[Mr Revhead]

maybe check gauges and connections?
airlock?

[matt dunn]

airlock?

That would be my guess.

Run it from cold at idle with the radiator cap off til the gauge reads too hot or for a good 10 mins after it reaches normal temp. Then put the cap on and try it.

Matt

[KinLoud]

I will probably be proved wrong, but...
I think that you might need to plumb in a fwd 4age thermostat housing pretty much the way that it is installed from the factory.
My reasoning follows:

My understanding is that you need some bypass water passing over the actual cylinder that moves the valve part of the thermostat. If you have the thermostat halfway along a radiator hose it might never get enough warm water near it to begin to open.
I'm sure most toyotas are set up this way -
When the engine is cold the thermostat is closed - the water circulates through the engine and back to the waterpump via bypass hoses and part of the thermostat housing. The bypass hoses etc. are fairly small diameter so don't flow heaps of water.
As the engine warms up the warm water flowing through the bypass and begins to warm up the thermostat. When the thermostat is warm enough it starts to open. This lets cold water flow from the radiator into the water pump and so into the engine. The thermostat balances the amount of cold water entering the engine against the water flowing through the bypass and so does it's best to keep the temp constant.
In some (maybe all) toyotas the thermostat closes off the bypass when the thermostat is fully open - this ensures maximum cooling.
Any comments/corrections on my theory?
Good luck

Ken
Hamilton
021 408 863

[matt dunn]

I will probably be proved wrong, but...
I think that you might need to plumb in a fwd 4age thermostat housing pretty much the way that it is installed from the factory.

Ken
Hamilton
021 408 863

Not meaning to shoot holes in your theroy but,

FWD thermostats are normally mounted to the gearbox and are basically a remote mount inline type anyway are they not?

I presume that this is what slideways is using?

Matt

[KinLoud]

Matt - Yes fwd 4age toyotas have a remote thermostat housing that sits on top of the gearbox.
This is what my AE92 FXGT has:

The bypass hose brings hot water from the engine to the back/spring side of the thermostat. The bypass water then goes back to the engine via the water pump. This is so the thermostat knows what temperature the engine is.
As the thermostat warms up, it begins to open and let cold water from the radiator flow to the engine via the water pump. This keeps the engine temp fairly constant.
On some/most/all? toyotas the bypass is blocked off by part of the thermostat when it is fully open - this means all of the hot water from the engine flows through the radiator.
NOTE -the water passes through the block then the head. It leaves the head at the cambelt end of the engine. There are 2 pipes/hoses. One is a big diameter hose that goes to the top of the radiator. The other is smaller diameter, this is the bypass hose, this goes to the back of the thermostat as per the picture.

~SlideWays~ If you plumb up your cooling system like this, using a bypass hose, I am sure it will work ok as long as you bleed all the air out of the cooling system. You might need to block off the hose that comes from the heater if you haven't got a heater fitted.

Ken
Ham
021 408 863

[gdsup]

mine is set up like the above diagram, bar the fact of no heater core so out the back of the head goes straight to return from heater core, seems to cool fine, note that i have larger twin core radiator, also drop vent in bonnet seems to work great, no signs of getting close to overheating since that has been installed and the car has copped some absolute hiddings

[matt dunn]

Matt - Yes fwd 4age toyotas have a remote thermostat housing that sits on top of the gearbox.
Ken
Ham
021 408 863

Ah yes I see what you mean.

You are are correct.

matt

[Stealer Of Souls]

Sorry to go a little off topic/hijack post...

Has anyone got/can anyone put up a picture of how the water flows normally in a RWD 4A-GE. Preferrably some sort of block diagram showing, radiator, thermostat, block, head, heater and any bypasses...