1990 electric fan diode?

[cherokee4fun]

So,
Local shops have a OEM radiator for about $110 and the good one at radiator barn is about $240, so that is a option.

What is the best way to get rid of air in the radiator?

When I took off the sensor in the radiator, I removed the the upper radiator hose from the thermostat and poured coolant down the hose and waited for the tube to fill, and then put the hose back on, filled the expansion tank.

When I do a complete flush, I usually back the Jeep up on ramps, fill through the upper hose, then remove the temp sender on the head, and wait for coolant to come out of there, as I fill the tank.

I can always use advice on what is best. The coolant that came out when I replaced the sensor looked clean, and I have not had any issues with this rig, and have always ran cool.......

Thanks again for all your help
Bob

 

[cruiser54]

I seriously doubt there is air in your system. You've done all the right things. I just loosen up the temp sender with the Jeep parked in my garage. Never had an issue.

 

[Ecomike]

I seriously doubt there is air in your system. You've done all the right things. I just loosen up the temp sender with the Jeep parked in my garage. Never had an issue.

Have you ever actually checked the top half of the drivers side of the radiator temperature versus the rest, after replacing the radiator, or draining and refilling the radiator on a Renix?

I have, I found 3 times in a row (once I figured out what was going on) that the bubble refused to come out, even if I stood on my head and begged!:soapbox:
My daughters 89 ran hot as hell for 3 months after doing a head job, and a complete new cooling system (hod to hot wire the e-fan, always on), then finally one day I noticed it dropped about 30 F, so it took about 3 months to get rid of the bubble, which I figured out in retrospect. She wiped out that new radiator a few months later (drunk telephone pole, LOL), and the air bubble was back with a new radiator.

If you leave the heater hose from the water pump loose/off (it bypasses the thermostat), and play games with filling the radiator with a fill hose Not the convoluted P trap hose), then swap hoses, while you leak antifreeze everywhere, you can get most of the bubble out, but it is way too messy, and pain full for me. I went with inline filler necks on mine, and I will never look back again.

 

[cruiser54]

Actually I've replaced radiators, done numerous coolant changes, motor swaps, water pumps, thermostats etc and never had an issue with overheating due to an air bubble after refill.

We never had an issue at the dealership from 1987 to 1992 doing the same. And there were 4 or 5 of us doing the services and repairs. I just recently adopted the habit of loosening the sender and I'm not sure why I have.

 

[Ecomike]

Actually I've replaced radiators, done numerous coolant changes, motor swaps, water pumps, thermostats etc and never had an issue with overheating due to an air bubble after refill.

We never had an issue at the dealership from 1987 to 1992 doing the same. And there were 4 or 5 of us doing the services and repairs. I just recently adopted the habit of loosening the sender and I'm not sure why I have.

Not sure that proves there is/was not an air bubble in the radiator!!!!

My daughters ran at 215-220 the first 2-3 months in the summer right after a major rebuild, then miraculously a few months later I discovered it was running 30 F cooler, even in the dead heat of the next summer with no hardware changes.

Only thing that made me figure it out, was the 87 Waggy, when I had tried everything under the sun to get it to run cooler than 235 F (it was suddenly overheating after 3-4 years of behaving itself), that was when I changed the very last part of the entire cooling system, for a 3 row brass CFS radiator, and it had zero effect versus the 3 year old cheap plastic/aluminum radiator, 1 row. I did everything I knew how to make sure the radiator was full, the engine block full, and so on. But the IR gauge, and finally my hand confirmed that the top 40% of the radiator still had air in it. So I went to the inline filler neck, which got the air out immediately. It still ran hotter than normal, but getting the air out of the radiator dropped the peak temp 30 F. A year later I discovered the exhaust donut seal, exh-manifold to down pipe flange was leaking, bad donut, and loose bolts. I fixed that and now it runs even cooler, about 20 F cooler. Now I may have a problem in the winter, LOL.

Therefore, it may be that Renix had enough OEM cooling capacity, to work OK, with a radiator half full of air while it took months for it to work its way out. IF you don't believe me go drain the radiator on your renix, refill your normal way, then check to see if there is not a significant air bubble in the top, and cold spot on the top 1/3 of it, even if it does not boil over.

 

[cruiser54]

The fact is they never ran hot afterwards. Always 205 to 210.

 

[Ecomike]

To me 205 to 210 is hot!!! LOL

Mine run at 200 F tops, idle in drive, parking brake on, for 30 minutes, with sun shining at 105 F ambient, 90% humidity, and AC on full blast!

On a routine day they operate 190 F at the thermostat housing!

 

[8Mud]

Not definitive but an indication, I've found when the radiator is partially plugged the top radiator hose swells and gets drum tight when the motor is up to temperature (thermostat open).. I've had mine get so hard it was hard, to impossible, to squeeze the top radiator hose closed with my hands (even a newer soft hose). I could actually see the top hose swell when I ran the RPM's up.

Air in the system, I check the same place, the top radiator hose. I squeeze it together a few times after the motor is up to temperature, You can feel it when you squeeze the hose together whether it is fluid or air. If there is air in there it usually bubbles up in the surge tank and then the coolant level in the surge tank will drop after a minute or two.

Most of my plugged radiators were worse by the outlet. A good flashlight and a dental mirror and you could look in the outlet and see ends of the lower crossover passages and see the buildup.

The radiators also leech copper on the inside and the dirt and pollen stuck to the outside make an acid that can eat them up on the outside. The copper can get pretty darned thin, in and on, the crossover passages. Sometimes flushing an old radiator springs leaks or makes it a lot weaker because the deposits were about the only thing holding it together in places.

Sometimes I've gotten away with not venting the air out of the cooling system, sometimes not. Seeing as the wife never has figured out what a temperature gauge is and won't stop driving until the something blows, I vent the system just in case. Not venting the system is one of those things you get away with, until you don't, then it gets critical fast.

If the vent in the cap on the surge tank is stuck shut, the air will likely never vent.