6G Celicas Forums

I've still got some cooling issues on the BEAMS.

Here's the deal, I've got a new radiator, new OEM thermostat, new hoses, new water pump and new temperature sensor. (I want this swap to run for quite a while).

Still have some cooling problems though where it'll run hot, and the temperature gauge will behave somewhat erratically. I hooked up OBD to it and the ECU reported around ~95C with the needle close to the red. Of note, I tested my 82C thermostat and it opened, but maybe a bit higher than 82C (it's not the most accurate thermostat in the world) but it still seemed maybe a bit strange?

I'm pretty confident the system is completely bled, and heat works. The top radiator hose gets hot but the bottom one less so (though, shouldn't the coolant going into the engine be pretty cold anyway?)

I ran the engine briefly with no thermostat and just water and it also got surprisingly close to operating temperature (I didn't drive it though) on a maybe 90 degree day.

Thoughts?

The only time I've seen something like this was when the coolant wasn't fully filled.
Did you let the car idle for a a good 15-20 min while topping of the coolant until it was filling up in your funnel, and periodically rev the engine to get the bubbles out?

Actually...

I just checked, 95C is about 200F. That type of temperature shoudn't peg your temp needle. Normal operating temp is about 185F while the car is moving and and it goes up to 200F at idle. Once it reaches 200F, the radiator fans should kick on and bring the temp down to about 185F.

Sounds like there is a problem you the wiring or the coolant temp sensor for the gauge cluster. Most people forget that toyota uses to temp sensors. One is for the ecu, and the other is just for the temp gauge.

The wiring is a consideration of mine - mostly because I did it. (Extending the harness anyway). So it sounds like in general it should report a bit higher than what the thermostat is rated for? (Makes sense, it's coming right off of the engine block).

It's definitely filled, I've filled and bled the thing quite a few times with the same results. The radiator fans are triggered by the coolant radiator sensor at the bottom of the radiator, which given the fact that my radiator seems to be doing a good job of cooling, I wouldn't expect it to still be 200F at the bottom of the radiator.

The BEAMS only uses one coolant temp sensor with three wires, so your gauge cluster gets the same signal that your ECU does.

Matt, have you tried plugging in your 5S gauge cluster to see of the temp gauge in it behaves the same way as your SS-III gauge cluster? It could be a faulty resistor or something inside your new gauge cluster, or it might be a faulty coolant temp sensor.

Isn't the BEAMS three wire in the same way as the original one wire and two wire sensors? A la, one goes directly to the cluster and one goes to the ECU?

Nonetheless, I've actually got the 5S cluster's gauge in there, so when some bad weather dies down I will try putting in the BEAMS temp gauge/fuel part of the cluster and go from there.

Yeah, the BEAMS CTS is three wires. If your stock gauge is acting up, I'd wonder if it isn't an issue with the sensor itself. Or even an issue in the grounds. The BEAMS is a very electronic motor and grounds are very important with it. Are the four grounds on the back of the head secure?

I'm not talking about that sensor. I'm talking about the readings taken from your engine temp sensor.
On my megasquirt EMS, I see temps in the 185-200ish once the engine is at full operating temp. At 200F ENGINE TEMPERATURE, the cooling fans turn on. During this whole time, the temperature reading on my gauge cluster stays in the middle and does not move at all.

If yours shows similar behavior at idle with the scan tool, then the problem is just with an incorrect gauge cluster reading and not an engine cooling issue.

Ok, a few gained insights:
1) I've got a very, very small coolant leak in the throttle body heater pipe.
2) Radiator cap doesn't seem to hold pressure

And on the electrical side, there's a few things that might be strange? I would be super-appreciative if one of you guys could confirm some resistances for me:

Temp connector ground to battery negative: 101 ohms (seems a bit high... Odd though that this connects to the E2 on the ECU though. Maybe I could just fork this so that a part of it grounded to the block as well or directly to the battery)
ECU connector to battery ground: Infinity (this seems good)
Gauge to Battery ~40? (definitely nonzero, I forgot to write this down)
Connector ground to gauge: 40 ohms
Connector ground to ECU: Infinity


I'm most curious about what the connector/battery ground to gauge is. I believe it should be nonzero as the gauge needle will have some passthrough, I'm just curious what it is.

As far as the connector ground to the battery ground, I have yet to check the grounds on the back of the engine, but I'm pretty certain they are good (mostly because I forgot them the first time I tried to turn the car on).

Thanks!

A quick update - I think I may have found the problem.

The ground for the temp/fuel gauge is ~60 ohms to battery ground, compared to a svelte sub-1-ohm for the rest of the grounds that make their way to the cluster. Since temperature is measured as resistance between ground, I'm going to go ahead and try to bridge that cluster's ground to one of the other grounds on the cluster.

Hi,

the beams uses a 3pin sensor, two pins are for the ECU coolant temp, and one pin is for the cluster (both uses different typ of resistance), that pin makes the resistance to ground so that the cluster can read the temp
you can find the values in the engine manual


greetz