6G Celicas Forums

i recently noticed, that my gauge reads hot sometimes and then drops quickly, first time it did that i checked the coolant, was a little low added water,

and then it does it randomly, coolants level is good. however when i turn the blower on (with temp to hot and AC button on) the needle comes down.


i also noticed the first day, that its leaking from where the bottom radiator hose connects to the engine, above the transmission area.
but yesterday when i was filling up gas, (it wasnt over heating or anything, i just checked) i saw its not leaking from there, but its quit wet under the coolant reservior and it was bubbling.

im guessing its the thermostat, but any input from you guys? how do i diagnose a thermostat, other than taking it out and puting it in a hot pan?

i dont think its the thermostat. i think you have blockage in the system. you need to do a good flush.

I had an issue with intermittent over heating. It turned out the fans were not coming on. Not entirely sure why. After checking the system, apparently a loose wire was no longer loose and it was fine after that.

Well I was just going to post the EXACT same thing mine was doing today! On a st. with the 7A. Im going to flush coolant and replace the thermostat. Im also going check the cooling fans as mentioned and the temp sensor.

would u suggest i replace my thermostat anyways and then just temperarely fill water and take it for a flush? i mean i saw diy videos on youtube but i think it should be professionally done? any input?

its about 100 average where i live

Hey man I just ran to the autoparts store and bought a thermostat for like 6 bucks and some antifreeze. Came home and I removed the two main coolant hoses and the thermostat housing which is two 10mm bolts on the left side of the 7A. The old thermostat looked crappy. I then took my garden hose and flushed water through all lines, the radiator and the block. I also removed the line that runs to my heater core and flushed it til it was clear. Put everything back together. Filled with fresh coolant. ran it till it got warm and that's all the further it would go no overheating! In fact its cooler than it was running and my heater works better now too. It only took about 1 hour at max to do it! Its worth a shot and itll save you money instead of going to a shop!

First thing you have to do is identify and correct any leaks. The coolant system operates under pressure, to prevent the coolant from boiling. If the system is leaking you not only lose coolant, you lose pressure. Without pressure, the coolant can boil, creating bubbles. These bubbles then get trapped, randomly blocking coolant flow.

The thermostat is only testable in a pot of water, though it's simple enough. The leak you mention at the lower hose, if it's between the engine block and the metal sleeve which holds the thermostat, could be due to the thermostat gasket failing. Even if your stock thermostat is still good, you'd want to use a new gasket. I'd agree with Smaay, it doesn't sound like your issue is the thermostat. They either fail to open, causing your temperatures to rise and stay high, or fail to close, causing your temperatures to stay more or less normal except when driving or running the cabin heat.

thank you. it making sense now, its actually leaking from where the hose connects to the housing. ill try to snap a picture next time i see some dripping.

I got a chance to work on if today, when my brother came back from the parts store, I noticed that not only the overflow valve was pouring water out due to boiling water/coolant; but my hoses were sucked flat. Like they were pressed flattish...

Now the cars cool I notice water is low (obviously) so the question is:

should I replace the thermostat gasket and flush the system myself, and if so HOW EXACTLY

UPDATE: I lifter the car to drain the water out, saw that this one hose was open. From my understanding its for the automatic transmission cooling. Correct me if I'm wrong as I couldn't find any other hose that could connect to it. So I thought maybe this Is where it was leaking coolant from. So without plugging it, I added 2 liters of water , nothing leaked. Radiator was fill. I started the car with rad cap off. Bubble came out. Let it reach normal temp. Drove it to get gas. So the car was over hearing again about 3/4 way up. Got home didn't see any leaks other than a lot of smoke and bubbles from the coolant reservoir place.

(Also I see some green stuff on my conpressor, I'm guessing it sprayed out from that hose)















I'm waiting for the car to cool, so I plug that hose thing and add water if necessary and drive it again and see what happens

Any suggestions? Please


This post has been edited by Malhar95: Mar 3, 2013 - 2:44 PM

need help guys any ideas what i should change/check?
it still heats up even after plugging that hose. water is also still boiling in the reservior

It could be your hoses that are collapsing are weak and need replaced. that would also cause overheating. I think you should still check that thermostat also.

The green oily residue is refrigerant leaking from your a/c compressor. and those lines are a/c lines.

Yea I was thinking I should just replace the thermostat anyways. But the thing is, a few weeks ago my buddy's camry ( 5sfe) did the same thing. We replaced hoses thermostat and the radiator, did the radiator burp thing and he still has the problem from time to time. I worry it won't solve the problem and just waste money.

what's going to make a car heat only when the heater is off. needle stays at half when the heater is on, but as soon as I turn it off, a few seconds later it starts to rise. Then it back in it drops immediately

Replace the thermostat anyways, if it'll help at all, and for $6 you really can't go wrong. It'll be a step in the right direction at the very least

I had this very same problem but mines a 5sfe. I swapped out almost the whole cooling system but still having the problem. I'd recommend you use a infrared thermal scanner thingy. The laser thermal thing. Lol. Sorry don't know the name of the tool. But yea use that to determine how hot the engine block is, upper rad hose, bottom rad hose, and the rad. Make sure they're reading at the right temperature. The reason I said that was because when I had this problem. I took it into a shop and they told me I have a really good cooling system in my car. Looked at them crazy and they said I had a faulty ECT sensor(the dash one). So it was "lying" to my dash that it was overheating when it wasn't. So in other words. Check your electrical components too.

This post has been edited by ILoveMySilly97: Mar 8, 2013 - 11:33 AM

Ok you know your car is overheating due to coolant boiling out of the reservoir. so its not a faulty sensor. The reason it goes cooler when you turn the heat on is because its acting as a mini radiator under your dash. there is something stopping your coolant from flowing through the engine. If your fans are coming on those are good. The things it could be are the radiator is blocked, hoses blocked or weak and collapsing, Bad thermostat not opening to let coolant flow, or water pump not circulating coolant good enough. theres really not much to a cooling system.

Makes sense. The hoses look fine, ill replace the thermostat just cuz. The dealership has a drain and fill for 40$ with pressure test. I guess I'll just replace the thermostat and take it there and see if the pressure if good. If not start from a flush and then rule out a bad waterpump?

yep sounds like a plan.. I hope its an easy fix for ya!

Regarding thermostats and gases:
I had an Olds Cutlass that began to run hot on the highway, with the needle dangerously close to red. I had an extended warranty, and took it to a shop. They replaced the radiator, and flushed the system. I took it out on the highway, and it wasn't long before the temp guage shot right back up. I returned to the shop, and that said that's normal. This car's temp guage was always pegged at the halfway point once it warmed up. After doing some reading, I found that Volvo and some other european car makers were using thermostats with an 3/16-1/8 inch hole along the edge. These cars were having problems with trapped gases, and thermostats don't open for hot gases, only liquids. The hole allows the gases to pass by the thermostat, and have a constant coolant flow. I pulled out my thermostat, drilled the hole, and enjoyed watching the guage pegged at the halway mark.... until my son totalled it in an accident a few months later.

This post has been edited by FrankB2: Mar 9, 2013 - 8:49 AM

That's why Toyota thermostats are equipped with a jiggle valve, and why they are quite specific about the orientation of the thermostat when installing it.