Cooling line to the TB burst. Fun! After finding what line was leaking I replaced it. Filled it back up with a 33% mix. Let it run a bit watching temperature, topped it off. Drove is around a bit, topped it off again and so on and so on.

It’s been about a week now, and I haven’t needed to top it off in the last 3 days. The temperature used to rarely ever go above 94C. I was hard pressed to get it to 96C. Only time I would see it reach 98-100C would be after about 3 hr’s at 80+mph in Texas summer heat.

Now it will fluctuate from 94 to 100C fairly easily, and this is even in cooler weather. Driving for about 15 min at 60mph will yield 100C easy. Come to a light and before it’s green it will be at 94-96C.

What gives? Why is it now so touchy? What could have changed? I could be wrong, but I seem to remember the fans came on at 96C before. Now letting it sit and idle, they wont turn on till 100C. Then it drops it to 94C and turn off. Could there still be air in the system? Seems like it would have worked it’s way out by now. Thermostat dead?

Cooling mods are Pettit AST and Koyo Radiator. Both fans do turn on.

 

Keep burping the system. A lot of people like to burp the system or bleed it with the TB line off until all the air from that location is removed.

 

IMO it's the only way to "bleed" the air out of the system effectively and quickly. Good luck!

 

Just so I get the facts right. What's the proper way to burp or bleed the system useing the TB line disconnected?

 

one method of doing this is as follows:

when the car is cold, disconnect the tb hose but point it upward so stuff doesn't just spill out. then fill with coolant/water at the water pump neck till it comes out the tb hose. reattach hose and tighten it up. then (while the filler cap is still off) 'burp' the system by gently squeezing the coolant hose that comes from the radiator to the water pump (it is easier to get to if you remove the stock air box). you should see some bubbles kinda like when you rip one in a tub or pool.

repeat the next day and check the level regularly.

 

You'll get a lot more air out than that by using one of these tools: I removed a TON of air from my system, even after flushing and refilling slowly with the TB line open:

Coolant Burping Tool/ Radiator Cap Funnel
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/radiator-cap-funnel-eliminate-air-bubbles-342309/

Another reason that your temps are fluctuating could be due to a different water/coolant mix. If you've got a higher percentage of water than before, it could be absorbing more heat from the motor and transferring it to the temp gauge. Worst-case scenario you might be experiencing nucleate boiling.

Conversely, it's possible that you don't have enough water, and the 33% coolant mix is not as effective at transferring heat from the engine to the radiator. Coolant is cheap, you might want to experiment with this if you can. Please post the results here, if you don't mind.

Do the temps rise and drop quickly, or is it a slow steady increase?

-s-

 

The temps are a steady rise. Just as if it was warming up, never really spiking or jumping, just keeps going up to 100C.

I played around a lot with mixes when I put the new radiator in. I found that the 33% coolent mix is the most effective for my conditions and is what I had in before the line poped. Used to do 50/50, but I found less antifreeze is more effective in my system since I don't have to worry about freezing. 33% mix is good down to 1 degree F yet seems to cool better (well used to) However this could explain why on the rare event I had to go on a long steady high speed drive, temps would end up 98-100C after 3 hrs or so. Didn't have water wetter before either, going to be putting that in this time however. That might correct that problem.

Didn't get a chance to really dig into it last night, had about 30 min to play with before I had to run out, couldn't get the damn new hose off the TB, heh.

Thanks for that link, never seen that before. Totally badass idea.

Oh, the temps will actually drop faster then they go up, unless cruising. IE if I stop at a light, it will drop to 94c usually before the light turns green

 

Honestly if you havent changed your thermostat in a while then i would do that first. Then fill the system back up with a different antifreeze/water mixture.

 

The symptom of getting hotter at high speeds, and cooling off at traffic lights sounds to me like either something in the system is causing slow coolant flow (thermostat, as previously mentioned or bad water pump or loose belts?), or some of your radiator tubes are plugged and there is not enough radiator capacity for the heat that is generated in high-speed driving.