Need some help with 5S, Not a Celica, but still a 5S Options

[d3ath2009]

Update: It lives!! thanks for all the help. Issue turned out to be timing. Thought I had everything in time, but when i turned the crank to take the slack out of the belt, I was jumping it ahead about 5 degrees. Temp gauge is still hit and miss though. one night it read right about mid-range the whole 15 mile drive (even after sitting at idle for half an hour) and the next it decided to read up near the hot mark after just a couple of miles. Temp would go back down to mid almost instantaneously if I made the car downshift or just upped the RPMs revving in neutral. Wondering if that sensor is bad and may have been the real problem the whole time. (Although I'm sure timing belt and water pump needed changing anyway just due to the miles on it)

[slavie]

Have you bled all the air out of the cooling system? It can take a few heat/cool cycles. Do you get heat in the passenger compartment? Put the heater on max, and you'll feel the air getting hotter with the coolant, if that's really the case.

I believe you should have two temp sensors - one that feeds the ECU, another that feeds the instrument cluster. I guess this is a safety conscious design where if one fails you can still read the other. Hook up some kind of OBD2 reader and read your Engine Coolant temp as read by the ECU, and check it against what you see on the dash.

Also, when was the last time the thermostat was changed? Those go bad, too.

[d3ath2009]

Have you bled all the air out of the cooling system? It can take a few heat/cool cycles. Do you get heat in the passenger compartment? Put the heater on max, and you'll feel the air getting hotter with the coolant, if that's really the case.

I believe you should have two temp sensors - one that feeds the ECU, another that feeds the instrument cluster. I guess this is a safety conscious design where if one fails you can still read the other. Hook up some kind of OBD2 reader and read your Engine Coolant temp as read by the ECU, and check it against what you see on the dash.

Also, when was the last time the thermostat was changed? Those go bad, too.

It definitely has heat in the cabin, it'll roast me out with no problem at all. Didn't bleed the system, as there is no bleeder that I can see. I guess i was under the assumption that air would work its way out and through the overflow tank in time. The one I believe to be faulty is the single wire coming in to the instrument cluster, but both could be failing with the miles that are on it anyway.

Great idea on hooking up the scanner, never crossed my mind to check it that way. I've got a wifi unit from amazon that works with my phone; if you don't have one, they are well worth the $15-$25 that they run.

Thermostat was replaced when I did head gasket, timing belt, and water pump (i.e. this job that was causing me headaches).

[Box]

Put the car where the front is higher than the rear, either by parking on an inclined surface or raising the front onto jack stands. Then take off the radiator cap and let it run for a while, if you have one put in a no spill funnel and fill it with a little coolant and you can watch for air bubbles.

There are two coolant temp sensors, one for the ECU and one for the gauge. The ECU one is probably more accurate since the ECU needs an exact temperature read to run its best, whereas the one for the gauge not so much since it's a dummy gauge and really isn't an exact representation. I can't remember exactly, but I want to say the two wire one is for the ECU and the one wire one is for the gauge. Any kind of OBD-II scanner will go off the sensor for the ECU.

This post has been edited by Box: Jan 8, 2018 - 6:08 PM

[trdproven]

^ i believe you are correct on the wires, for sure at least for the gauge.