defi gauge acting funny

[supra88gr]

so my defi water temp gauge keeps on playing around it goes from being really hot to really cold it never stays at a constant temp like the stock gauge. whats wrong with it ? what should i check?

Thanks

 

[MK3Brent]

Check to see if you have air in your coolant.

Then check the sensor, the wiring, and the installation.

 

[Mr. Sinister]

As in it constantly swings from cold to hot? Or does it stay a temperature (90C), and then goes up to 110-120C for a little bit, then goes back to 90? The latter is normal behavior as your thermostat opens and closes. It won't stay in one place after the engine has warmed up like the stock gauge.

 

[supra88gr]

As in it constantly swings from cold to hot? Or does it stay a temperature (90C), and then goes up to 110-120C for a little bit, then goes back to 90? The latter is normal behavior as your thermostat opens and closes. It won't stay in one place after the engine has warmed up like the stock gauge.

it goes from like 60-70c and then when i full throttle the car it hits 110-120c or so like it almost over heating then back down

 

[Mr. Sinister]

it goes from like 60-70c and then when i full throttle the car it hits 110-120c or so like it almost over heating then back down

That could either be normal or an air in your cooling system as said earlier. Try this. Go WOT, have it hit 110-120, then wait for it to go back down to 60-70. Then, immediately go WOT again. If it hits 110-120 again right away, then you most likely have air in your system. If it stays at 60-70 for a while and then goes to 110-120, that should be normal.

BTW, 60-70 at normal operating temp is low. The stock thermostat is supposed to be 90 I believe. That could also be part of the problem.

 

[MK3Brent]

In stead of doing that, just see if you have air in your cooling system.

Get a pressure tester, or bleed the system.

 

[Mr. Sinister]

In stead of doing that, just see if you have air in your cooling system.

Get a pressure tester, or bleed the system.

Because the way the gauge is behaving might be normal. Doing the test I described hurts nothing, is easy to do, and gives us more information to determine if it's a problem or not.

 

[figgie]

stock t-stat is 86-90c for opening.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=CO&P=8

Unless you are in sub freezing temps, the coolant should stay relatively close to the opening temp of the t-stat and increasing when the power increases.

 

[MK3Brent]

Because the way the gauge is behaving might be normal. Doing the test I described hurts nothing, is easy to do, and gives us more information to determine if it's a problem or not.

I was more mentioning, doing this before having to run around wot on streets. It'll teach you the same things, but in your garage.

 

[supra88gr]

thanks guys for all the info i am getting the car ready for this spring now anyways so i was going to flush the system anyway. i just didn't think it was normal for the temp to jump that high

 

[Mr. Sinister]

I was more mentioning, doing this before having to run around wot on streets. It'll teach you the same things, but in your garage.

Pressuring the system will only tell you if there's a leak. It won't tell you if there's air in it. Sure you could try bleeding it, but I'd rather floor it in 1st a few times than jack up the front of the car, drain a bit of coolant so it won't overflow, then warm the car up to see if there are bubbles.

Besides, air in the system usually causes the temp guauge to peg, not stop at 110-120. And, it typically happens at idle when the water pump isn't moving enough coolant causing the bubbles to accumulate where the temp sensor is installed. I still think that his thermostat is opening too soon and that the guage is behaving correctly.

supra88gr: Is your stock gauge still hooked up? If it is and it also goes up when the defi does, then you most likely have air in the system. If not, I'd test the thermostat.

 

[MK3Brent]

Pressuring the system will only tell you if there's a leak. It won't tell you if there's air in it. Sure you could try bleeding it, but I'd rather floor it in 1st a few times than jack up the front of the car, drain a bit of coolant so it won't overflow, then warm the car up to see if there are bubbles. .

I have a bleeder behind my thermostat, so that's just the way I do it.


Oh and when I had lots of air in my cooling system, it did exactly what he's explaining.
It would be fine... then all of a sudden start fluctuating terribly.

 

[Mr. Sinister]

I have a bleeder behind my thermostat, so that's just the way I do it.

Damn. Fancy!

 

[supra88gr]

Besides, air in the system usually causes the temp guauge to peg, not stop at 110-120. And, it typically happens at idle when the water pump isn't moving enough coolant causing the bubbles to accumulate where the temp sensor is installed. I still think that his thermostat is opening too soon and that the guage is behaving correctly.

supra88gr: Is your stock gauge still hooked up? If it is and it also goes up when the defi does, then you most likely have air in the system. If not, I'd test the thermostat.[/QUOTE]

the stock one does not go up like the defi.

 

[Mr. Sinister]

the stock one does not go up like the defi.

I'm putting my money on the thermostat then. Normal behaviour should be that the gauge will read 90 once the car warms up. It will occasionally go up to 110-120 when the thermostat opens up, then will go back down to 90 (or to whatever your radiator was able to cool the coolant to). My guess is that your thermostat is opening/closing too often causing the swings that you're seeing.