I just changed the upper and lower radiator hose on my 1995 XJ. I measured that I drained exactly 2 gallons of coolant before I did the hoses swap, including the reservoir tank, which I emptied as well.

Now I'm filling it up via the radiator, and it will ONLY TAKE HALF A GALLON!! It burped a little bit, I messaged the lower radiator hose to get a few more air bubbles to come up, and that's all it will take. No more air bubbles in the past 20 minutes or so. I even pulled the upper radiator hose where it attaches to the radiator, and coolant came out, so that tells me the radiator is full of coolant (right???). What gives?

If I was able to get in one-and-a-half gallons in, for example, I wouldn't worry. Just fill it up little by little via the reservior tank and keep an eye on it over the next few drives to ensure I get it all back in.

Should I start the engine it at this point? I'm just VERY CONCERNED that if I start the engine with only about one-quarter of the necessary coolant it should have, it will cause issues.

What are the next steps to get the rest of the 1.5 gallons of coolant back in????

I did this SAME exact hing on my former 1999 XJ with no issues. In that case, the coolant system took all of the coolant via the radiator on the first try.

 

You'll need to start it and add the coolant as needed...It should take more with just starting it, but the thermostat is probably completely closed and won't allow more to go in there at this point until it warms up a little..Don't forget to run the heater as you add the coolant..

 

Start the engine and see if the coolant level drops. Keep adding until you get it back to the same level as before. You can run an engine without coolant for this. Just be sure to shut it off if the gauge reads higher than normal, because it will overheat.

 

The engine is off and is cold now. Should I start the engine with radiator cap off and fill via radiator, or keep the radiator cap on and fill via reservoir tank? Or another way?

Also, the thermostat is above the water pump, right? So if I start the engine now, won't the water pump run for a while dry, with no coolant, until the thermostat opens?

 

What others above said.

Also, it helps to run it on an uphill. Maybe jack it up a little.

So yes, you have to run it to get the thermostat to open up and really get the coolant moving. Check the gauge, and if it gets high, turn it off. Let if cool off and coolant should get sucked back into the system from the reservoir.

You may need to do a few times.

Other possibilities is the thermostat is stuck or the water pump is dying. But try the easy things first.

 

Yep, ran it (with radiator cap on) for about 5 minutes, and it began to run hot, so turned it off. We'll see if it sucks fluid from the reservoir as it cools.

 

I've cycled the engine on and off about 5 times, each time staying on until the engine temp gets too high, then strut it off.

I'm thinking that the thermostat works OK and lets coolant flow, as the upper radiator hose gets pressurized when the engine is on. The water pump is relatively new, so I assume that is not the issue. The XJ is still about half a gallon short of the 2 gallons that drained out. I've the front end up on ramps to see if that helps. Any more ideas?

 

I ran the front tires up on ramps. That just may have done the trick. Thanks for your replies.

Yeesh. I've done this on another XJ, 2 Subaru Outbacks, and countless other cars. Never ran into this issue........

 

When I worked on these early xj's I would fill the engine with the upper radiator hose off at the thermostat and fill it until it was engine was full then install the hose start the engine fill the rest . I did this for a living so I didn't have a lot of time . so this is the fastest way and also the easiest way .

 

On Wednesday I fixed an upper radiator hose leak, lost some coolant I thought I had replaced. Well yesterday I drove up a multi level parking lot, and my coolant reservoir went down by 2/3s. I think the steep angle of the parking ramps burped out whatever air was left in the system.

 

By far the easiest way to get all the air out of the head is to remove the temp sensor, fill the radiator until it flows out the hole, replace the sensor, and continue filling. After a run up to temperature, you may need to top off with a quart or two.

 

IMO the easiest way is to buy the Lisle funnel.


I swap out my anti-freeze every 2 years so it is worth the investment to me.
Fill up the radiator all the way, put the level in the overflow tank where you like it, and start the Jeep.
Keep the idle around 1500 RPM and always make sure that you have some anti-freeze in the funnel.
30 to 45 minutes later usually good to go.
When I used to throttle by hand at about 1500 RPM it would be closer to a 1/2 hour.
But one of the reasons I installed an Ext Idle switch is for stuff like this.
At 1000 RPM closer to 45 minutes.