Jeep Enthusiast Forums banner

Don't think I'm going to like the answer to this

3K views 22 replies 14 participants last post by  mrese 
#1 ·
Alright, I have an '04 GC with the 4.7 and about 107K miles. When I bought it, the dealer said that it had an all-new bottom end due to a "noise" that it still has - probably either a timing chain tensioner or a valve "lifter" guide. Anyway, it has about 50 psi pressure.

So, it has air in the coolant system - when I start it when cold you can hear water rushing in the heater core. It "overheated" once when an air pocket hit the thermostat housing, but didn't go above 250, and was allowed to cool before hitting the "red" zone.

I've added coolant to both the bleeder screw and the radiator, as well as the overflow tank.

I've replaced the radiator cap.

The concern is this - it isn't sucking coolant from the overflow, and when it's cold and you remove the rad cap, it has pressure in the system. The rad cap is cold, regardless of engine temp. According to the factory temp gauge though, it never goes above 210, and hangs out below the 210 line (but barely - 205ish).

Generally, it runs fine, doesn't show any coolant in the oil or oil in the coolant, keeps temperature and oil pressure, and doesn't show erratic driving. It did stall once, but that was after I swapped from 92 octane to 87 on an empty (like .5 gallons left) tank. When cold, the exhaust smells like exhaust, not like antifreeze.


So, should I run a coolant CO test, or forget about it until it shows some noticeable issue? I'm worried about head gaskets, but I'm always anal about this kind of stuff.
 
See less See more
#3 ·
I've had the same "water rushing" sound around the heater core since the day I yanked my split radiator and replaced it. Sucks water from the overflow tank, never goes above the 210* center-line and I've burped it like three times to get any air out and it still does it...
 
#5 ·
So what about the pressure in the cold radiator? Don't worry about it?

I'd think if it was exhaust gas pushing in that it would blow coolant out of the purge tank (it doesn't) or severely overheat (which it doesn't overheat at all). Am I wrong in thinking like this?
 
#6 ·
sometime cooling systems will hold pressure even after its cold(this is why its not pulling from the overflow tank). I always vaccum bleed the cooling system after repairs but most people and shops cant do this. maybe someone could post the bleeding procedure from the shop manual. the procedure might be on wjjeeps.com.
 
#7 ·
I just park so my front tires are above the level of rear. Take off rad cap (when cool obviously). Turn on motor, turn heat all the way hot and set the blower fan to low. Then when the thermostat opens water goes through the heater core and any air pockets get pushed through until they reach the open cap.
 
#21 ·
This worked like a charm for me this morning. A few weeks ago my low coolant light came on and I filled from the expansion tank... oops. So it would almost over heat at idle and heard plenty of water rushing sounds under the dash.

There was a lot of air in there. Temps now stay under 210 and no more water sounds. All she needed was a good burping. :cheers2:

I.m guessing the I did not bleed the system well using the hex bleeder by the T-stat when I replaced the t-stat a few months ago.

Hope this helps anybody else.
 
#8 ·
14mpg said:
I just park so my front tires are above the level of rear. Take off rad cap (when cool obviously). Turn on motor, turn heat all the way hot and set the blower fan to low. Then when the thermostat opens water goes through the heater core and any air pockets get pushed through until they reach the open cap.
Well that's simple and brilliant. Never thought about it haha!
 
#9 ·
So what I'm getting is, don't worry about it.
 
#12 ·
Of course get the air out, but I'm wondering what could cause the pressure in the rad when cold. The air in the system?
 
#17 ·
Prerssure in the radiator when cold is not uncommon. Your radiator cap is designed to release pressure if the pressure in your radiator goes above the amount stamped or printed on the cap. So lets say the radiator cap is rated at 19 psi. (yours may be more or less). That means any pressure above 19 psi will be purged into the overflow tank. Now lets assume the pressure is less than 19 psi in your radiator, well thats the amount (the hiss) you are hearing when you release the cap. A cooling system that will hold pressure over night or until after the vehicle is cold is a good cooling system in my opinion.
 
#14 ·
50 psi oil pressure. My concern is positive pressure, evidenced by a hiss when the cold radiator is opened, as well as fluid not going from the like tank to the rad, despite a new rad cap.
 
#18 ·
Burp the coolant system.
 
#19 ·
Double E said:
Hows that tube from the radiator to the overflow?
It isn't plugged. When hot. If you burp the radiator cap it'll blow into the overflow.
 
#20 ·
I just did 14MPGs trick of burping the system with the heater cranked all the way up. Managed to get about 2/3 cup of air out (measured by the amount of coolant I needed to top it back off). Since I only get the waterfall sound on dead cold startup I guess I'll find out if this did the trick tomorrow morning...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top