Sorry if I offend anyone but I must have read 50 posts on burping a cooling system, but now I am stumped. I just replaced the water pump on my 1999 Cherokee Sport 4.0. I followed all the instructions for burping the system especially the one with leaving the Tstat cap off but then all of the sudden Coolant started pouring out the cap hole when the jeep hit operating temp. So I shut it down, refilled it and also poured coolant into the heater intake hose. Took it for a drive and ran the heater. The air coming out never got hot and it started to overheat up to 230 so I took it home and when it idled it went back to 210. I let it idle for another 10 min and it stayed there at 210. When I felt the upper radiator hose it was hard as a rock and hot. The heater intake hose(out of tstat) was really hot but the outlet hose to the WP was cold. Any suggestions of what to do? My buddy said to pull the outlet hose and pour coolant through that to fill everything. The Tstat is new and was installed with the little ball pointing up, I feel like the Tstat isn't opening. Will air in the system cause that to happen? Any help ASAP would really be appreciated.

 

I'm going to presume the "tstat cap" is what u r calling the radiator cap. Let the motor idle with the radiator cap off AND keep the rad full while idling. When it "burps" air/coolant out, install a new rad cap. When the motor is cold, check coolant level in both the rad and bottle.

Always a good idea to test a stat prior to installing.

 

I'm sure most of the people with cooling system burp issues, are people with the older Renix era vehicles (with the pressure tank next to the firewall)


But certainly air in the cooling system will cause issues similar to what you are experiencing...........


Your heater core could also be plugged................That would explain the hot inlet hose, but cold outlet hose................(and no heat in the cab).


Low coolant level will also cause no-heat issues...........


Let the Jeep cool overnight, and look in the radiator cap in the morning................If you have to add a bunch more coolant in the morning then you probably had a trapped air pocket in the system somewhere.


If it sits idling for awhile at 210 degrees, then your thermostat is probably working fine.............Mine runs around 210 during normal stop/go driving around town...............


Also, I would remove both heater hoses at the engine, and hook a garden hose up to the heater outlet one (to backwards flush your heater core) and see if a bunch of gunk comes out..............




If you can...................Take a real close look at the radiator "Matrix"
Make sure all the core tubes look good, and that the "Zig-Zag" heat-sink media between them is intact........................I have seen cars with the heat-sink material half gone! (mostly in rust belt areas) and the cars would idle at an ok temperature, but as soon as you get them on the highway, the temperature would skyrocket..............

 

Renix or "closed" type cooling systems will start "burping" the moment the motor is started. "Open" type cooling systems will not "burp" 'til cooling system pressure reaches the rad cap rating......or when the rad cap is off.

Coolant levels in both the rad AND bottle should be checked when the motor is COLD.

 

Sorry about that. Yes I meant Radiator cap. I did run the engine with the cap off and kept the coolant level up, but like I said, when it hit operating temp the coolant started flooding out the radiator cap opening.

 

Radiator matrix looks pretty good, actually really good. My main concern on the temp was when I started accelerating the temp started to climb past the 210 to about 230. Slowed down and it went back to 210.

Also forgot to mention when I shut the engine off I popped the lid off the overflow bottle expecting pressure and heat but there wasnt any but there was air coming into the bottle as it was bubbling.

 

"Flooding out the radiator cap opening" means it's "burping". U may have closed it up a little too soon. Also, the cooling system MUST be filled VERY slowly. Check coolant levels in both the bottle and rad, motor COLD, for several days.

 

U have a "open" type cooling system which means the bottle is "open" to the atmosphere. If pressure forms in a "open" system bottle, something is wrong.

The "bubbling" is air "burping/bleeding" out of the cooling system.....perfectly normal.

The radiator cap is critical to a "open" system functioning correctly.....the rad cap has 2 valves and 3 sealing surfaces and all 5 components MUST function correctly.

 

Appreciate the help. The thing was is when I say flooded out it was gushing for about 30 seconds. probly lost half of what I put in.

 

Agreed..................You most likely closed the cap with more air still in there..............and Yes, make sure your overflow tank is filled to the proper level(the system will draw coolant back in from the overflow bottle as it cools, so if it's not at the proper level, you could draw air back into the system)


Air in the system will also cause the engine temperature to rise very quickly once you start going down the road..............
Sounds like the majority of your issue.........Trapped Air.......


The air expands rapidly when it heats up, and caused it to push a bunch of coolant out........................a solid fill of coolant will not expand that rapidly..........

 

It's impossible to fill a cooling system too slowly. Filling very slowly (1/2 gal at a time and stop) will allow most of the air to escape prior to starting the motor.

 

Also to add to this,

I just had to fill back my radiator after a failed replacement, a story for another pub trip, and a good amount of air will come out. Fill it up as a good steady stream. I made the mistake of pouring it in fast at one point and that section of coolant must of hit a pack of Bubbles cause a bunch came gushing back out. Just continued to fill slow again after that and all was well

 

So would it be safe to remove the cap tomorrow and reburb the system? I will probably try and clean/flush out the heater core before it do by running water through the outlet hose.

 

Also have the heater on high as you're idling. Just remember how m h air is actually there. Just like bleeding brakes after doing a new line, sometimes the air seems never ending

 

Just add additional coolant to the expansion tank as necessary to get to the "full hot" mark, the rest will take care of itself.