Is it possible to overfill a closed cooling system. Is it better to fill it to the top of the parallel part of the filling tube that comes parallel off the radiator before the tube turns upward to the fill cap, or is it better to leave some air in the system.
Is it possible to overfill a closed cooling system. Is it better to fill it to the top of the parallel part of the filling tube that comes parallel off the radiator before the tube turns upward to the fill cap, or is it better to leave some air in the system.
I just read you post. On this forum the "closed" system came on 87-90 XJ and some 91s. It has a radiator without a radiator cap. There is a plastic pressure bottle back on the fire wall just above the vent fan.
The "open" system has a "normal" radiator with a pressure cap. There is no plastic pressure bottle but there is a coolant overflow bottle to catch excess fluid. When the engine cools the coolant is sucked back into the radiator.
So if you have the "closed" system you can overfill; however, it will burp out anything excess coolant. It runs down can spray on your oil filter and possible starter.
Fill the pressure bottle when the engine is cold. There is a level marking in the bottle. If you look in the fill hole you will see what look like a chair. The coolant lever is to be over the round "seat". If it below that add coolant. You will also what look like the back of the chair sticking up around a 1/2 inch. The top of the back is the "cold full" line.
As long as the coolant is over the "seat" and below the top of the chair you will be just fine. I noticed with my new bottle when it burps is leaves some coolant on top of the bottle.
I had a leaking radiator tank which drove me nuts with constant topping off but no drips on the ground. The new radiator is working just fine and I am maintaning coolant level.
Coolant expands when it gets hot. The "closed" system MUST have expansion space. If you have no expansion bottle, your system must be dumping coolant every time you drive. And the "closed" system radiator doesn't have a pressure cap.
Sorry for the confusion. I have an OPEN system, I have a 90 xj with a 92 OPEN radiator-with a pressure cap - so my question is can I overfill this radiator, and how high can I fill it in relation to the tube that comes out from the radiator parallel to the ground and curves up to the pressure cap. Can I fill it to the bottom, middle or top of the tube that's parallel to the ground, or doesn't it matter.
I was confused about the terms open and closed, but my system is open.
I have an 90 xj with a radiator from a 92 xj OPEN system.
Is it possible to overfill a closed cooling system. Is it better to fill it to the top of the tube that comes out from the radiator parallel to the ground before it turns upward to the fill cap, or is it better to leave some air in the system.
I submitted an earlypost thinking this was a closed system--which it is not.
Back when I was an apprentice I didn't realize that there was a cracked head and I kept filling the radiator and consequently two cylinders and eventually the oil pan. Long story. :doh:
The best way to fill your cooling system is to do it when it is cold, remove the temp sender from the back of the head and fill the system until the coolant starts coming out of the sensor opening, place the sensor back in and then jack up the front so that the radiator opening is the highest point of the system and then add more. Start the engine, after the thermostat opens raise the idle speed and the level will drop as the water pump draws down. While keeping the idle speed up top off the radiator and immediately put the pressure cap on. DO NOT LET THE IDLE BACK DOWN UNTIL THE CAP IS SECURED or it will spew coolant onto the ground.
I thought you only had to go through all that trouble with a closed system. When I filled my 95 (open system) all I did was fill it as much as possible till the radiator was full, then filled the resevoir to the full mark. Then I ran the engine with the radiator cap off and the heater on until the thermostat opened. When the thermostat opens it'll take in more coolant. I add some till its full and then keep an eye on it for a few days to see if it takes in any more, it usually does take a little more, and I just add some to the resevoir and check to ensure that the radiator is full. Its always worked for me.
Are the 4.Os different? Am I doing something wrong? I'm not trying to hijack here sorry.
The "open" systems come with an overflow/recovery bottle stock, and if retrofitting from "closed" to "open" an overflow/recovery bottle should always be installed. The overflow bottle makes the system self-burping. As the coolant and air expand when the system is hot, the excess is pushed past the radiator cap and into the overflow bottle. Any air bubbles are released from the bottle to the atmosphere. When the system cools down after shutting off the engine, only coolant is pulled back into the radiator.
The radiator should be filled all the way to the neck, then the cap installed. The overflow bottle should normally be filled to the halfway mark when cold, but if you've just worked on the cooling system and there may be air trapped in it, 2/3 full might be a good starting point. Then watch the level over the next few days and refill as necessary when the system burps out air pockets. Once it has been burped, the radiator should always be completely full and the overflow bottle should be half full when cold.
It looks as if it's broken on the right side of the picture(front of the actual tank) is broken off. But it's smooth like it was manufactured like that.
that overflow tank is fine... where your coolant is going, i dont know. Make sure you check the oil! anything creamy looking is bad... That spout on the front is in case the coolant system boils over, this allows it to shoot out onto the ground... nice for the environment... hehe
~Joe~
Cool, thanks! Ya, i don't know where it's goin either,lol. Everytime i fill up to full, about 2days later it's gone :wave1: Oil is fine, i pulled the bottle, no leaks..hmmm. As far as pulling the temp sender in the rear of the head, DON'T! I had to change mine and now I have a broken brass sensor in my head an no temp guage. The cooling system takes care of itself. Just top her off!
