[Rice86]

Hi all, please take some time to read through the below if your interested in trying to help out

Car - Ae86
Engine - JDM 16v 4age bigport for AE86
Comments - Long story short, thermostat wont open AND water temp will not heat to operating temperture

Long Story -

Ive posted this on another corolla 4age related forum and got a few response, looking for a bit more knowledge if possible

My AE86 was running perfect, water temp showed 85-90 on my external water temp gauge
1 week ago my external Water Temp gauge then showed the temp to be only at 30 degree *lowest temp on gauge* while driving from home to work in the morning *1hour of driving*
So to me the car must of been cold all morning
On the drive home, the water temp showed only 70degree since it was a hot afternoon, again it should be 85-90 hot or cold weather
Next day drove to work again, didn't think much of it, water temp showed at 30 degree again, this time driving home in hot weather again, temp stayed at 30dgree

My water temp gauge starts and ends at 30deg-180deg so reading this, the water temp must of been 30degree or colder and this was suspicious

Troubleshooting done since.
i have bought a brand new Thermostat since and installed it
checked the water pump by pulling it off, the water pump is still looking brand new, no sign of wear or damage and fins in great condition
external water temp gauge is broken, put the sensor in hot boiled water, no reading on the gauge
the standard water temp sensor on the water outlet on the head of the 4age is dead too, not working with standard temp gauge on my dash/cluster, no temp reading

after the brand new thermostat was installed, put everything back in, bled the whole water system best to my knowledge and let it warm up
the top water outlet hose to the top of radiator got hot as it should, but still not hot enough
the bottom water inlet hose from radiator to was considerably colder then the top water hose
i then held down the throttle to rev the engine to about 3000 rpm while holding the bottom water hose, and there is pressure building as the engine was rev higher...but the thermostat still wont open upon pressure AND still the coolant temperature would still not get hot enough.
I can still stick my finger into the radiator to test how hot the coolant was and i still did not get burnt, this was after the car had been on ideal for over 15min
i test drove the car after all this, car had lost power as thermostat would not open to allow water flow...after driving the car, water temp still not hot as i believe it should be, i could still dip my fingers into radiator

after all this frustration, i am now running with no thermostat, ive gained back my engine power, but the car will not heat up, the engine on ideal after 1hour of driving is still acting like a cold-start, sits at 1500 rpm
when everything was working it sat flat on 1000rpm

external water temp gauge is dead
standard water temp sensor dead
brand new thermostat wont open when installed due to coolant wont heat up to operating temperature with and without thermostat installed

anyone know what else i could try?
i have boiled hot water and placed the brand new thermostat into a cup with the water, it did not open, i will boil water on a stove and test again after work today

i only ever had 4age overheat on me, but never once a 4age stay so cold, any help/thoughts are appreciated

[Rice86]

have double check thermostat since, both old and new is working perfect when in boiling water on the stove

installed thermostat in, again lost power and thermostat wont open, took it out, got 90% engine power back, engine wont heat up, coolent gets very warm but not considered HOT op temp...

will again sus it out over the weekend

[allencr]

Do these thermostats have that little extension & disk on their bulb to sense the bypass flow coming from the back of the head into the pump inlet? That piece of metal stays in the hot flow & keeps it from closing almost as soon as it opens for the coolant coming from the radiator.
Get the highest temp thermo. available, 90-92C or even adjust yours if it has a threaded rod on it. Use a kitchen thermometer to check it out. Opening in boiling water is a good test, but not very specific for what you need.
These things run cold, especially a well broken in & worn engine, and those with replacements for the plastic radiators.
I use cardboard to block off 1/3 of the radiators air flow in the winter & most of the summer if not sitting in traffic.