TJ: bubbling coolant in overflow

[daniel_buck]

My TJ bubbles in the overflow tank after driving 20+ miles when I turn the motor off, has done this for a while now, the temperature has always been good, right smack on 210 (which I gather is perfectly normal for TJs) and the level in the overflow tank hasn't ever been low, so I didn't pay much attention to it.


Recently, it's started bubbling after just 4-5 miles. So, I figured it's probably the radiator cap that isn't holding pressure. Put on a new cap, and I noticed that even though the level in the overflow was "full", I didn't see any coolant in the radiator. I didn't have any coolant or distilled water with me, so I just drove home with the new cap. And no bubbling when I got home. The new cap has a release valve on it, so out of curiosity, I pulled the release valve as soon as I got home, and the same bubbling sound happened that used to happen with the old cap. So... I'm fairly certain that it was just the old cap that was not holding pressure.

However, since I didn't see any water in the radiator itself, I let the motor cool down, and then this morning I filled up the radiator until I could see water near the top. With all of that out of the way:



So my question is ---------> why would the overflow reservoir read "full" (after it sat overnight to cool down, which I assume is when the fluid would get sucked back into the radiator?), while the radiator itself wasn't full? I was able to put about 1.5 quarts into the radiator itself. Which I believe means the system was only about 90% full. Which might explain why the bubbling has recently started sooner than it used to with the old cap?


Preemptively, I'm going to order a thermostat and a waterpump to keep with me on long trips (I do drive across country once every year). My jeep has 140k miles on it (2006 Rubi 4.0L). As far as I know, the thermostat and pump have never been changed, and the radiator fluid has only been replaced once. Would it be a bad idea to just go ahead and preemptively replace the thermostat and waterpump and flush the cooling system now? or just wait until heating problems actually occur later on down the line?

[Lumpy Grits]

I'd be look'n at do'n a leak-down test, PDQ.
What's the engine oil look like?
LG

[daniel_buck]

I'm gonna be changing the oil this weekend most likely, I'll take a good look at it.

I tried to look for leaks last night, but since we actually got a little bit of rain, everything was wet I'll take a look tonight when I get home.

Thanks for the reply

[Lumpy Grits]

You need to do the leak down test-My bet is a die'n headgasket.
LG

[Russ Chung]

Dan,

I had the same problems at about the same mileage on my 'O5 TJ. Replacing the cap solved both problems.

I don't think that it is necessary to carry a spare thermostat or spare water pump with you. If the thermostat fails, just wait until the engine cools down, remove it and then drive to the nearest auto parts store to get a replacement. A water pump is not likely to fail suddenly; it will leak when the seal goes bad or the bearing will begin to make noise, or both. In both cases, it will give you some warning, so you can drive to an auto parts store and get a replacement. BTW, a couple of years ago I stopped in Mexicali for lunch enroute to Cabo San Lucas on a 108 degree F day when I noticed there was a small puddle on the ground under the engine. I determined that it was coolant coming from the water pump seal. Since I knew that there were few auto parts stores between Mexicali and Cabo, I paid 550 pesos for a water pump at Autozone (I was alarmed when the clerk rang it up on the register because I thought it was 550 dollars). But the coolant leak stopped and I still have the unused water pump in the box.

Russ

[daniel_buck]

LG, is a leak-down test something that I can perform myself? I'll do a search and get more info on that, thanks! Is that the same as a pressure test? I'll look at the oil too, it's time for an oil change anyway.





Thanks for the reply Russ

Next time It's light, I'll give the pump a good look, and see if it's leaking anywhere, I assume these have weep holes like most pumps do? I've not been noticing any puddles under the jeep. When I go offroading, sometimes some coolant will spill out, but I think that's spilling out from the overflow tank at off-camber angles.

Since the temperature gauge is reading normal, the thermostat and pump are probably fine, it was just the cap I guess. Well I'm glad I replaced that first, it was cheap and easy :-D I'll give the motor a good look over next time I take a decent drive and have enough light to see around in there, just to make sure there's not a leak somewhere in one of the hoses, or the pump, or something. As well as a pressure test.

[mrchips]

Pressure test the cooling system and the cap to look for exterior hose, fitting leaks.
Leak down test is using compressed air to put pressure in each cylinder at TDC to verify if you have valve, , piston ring blow-by or if you have a cyl head gasket leak. you can also use a special liquid from the auto parts stores to ck and see if you have combustion gases in the coolant, this will also tell if you have an internal coolant leak not visible..

[Lumpy Grits]

LG, is a leak-down test something that I can perform myself? I'll do a search and get more info on that, thanks! Is that the same as a pressure test? I'll look at the oil too, it's time for an oil change anyway.





Thanks for the reply Russ

Next time It's light, I'll give the pump a good look, and see if it's leaking anywhere, I assume these have weep holes like most pumps do? I've not been noticing any puddles under the jeep. When I go offroading, sometimes some coolant will spill out, but I think that's spilling out from the overflow tank at off-camber angles.

Since the temperature gauge is reading normal, the thermostat and pump are probably fine, it was just the cap I guess. Well I'm glad I replaced that first, it was cheap and easy :-D I'll give the motor a good look over next time I take a decent drive and have enough light to see around in there, just to make sure there's not a leak somewhere in one of the hoses, or the pump, or something. As well as a pressure test.

YES, you can do the test your self.
I would first pull the spark plugs and 'read' them. Mark what cyl they came from-You can also post pictures of the plugs here for us to help.
Listen to Chips. He's a good 'wrench'.
LG

[daniel_buck]

I didn't get a chance to do anything last weekend, a friend had his jeep over, so we were working on that.

BUT, I'm pretty sure it's the water pump. It puked out about a gallon or more to the concrete as I parked at work this morning. I can't actually see the leak, but It's not a hose, and it's leaking somewhere right above the crank pulley, so I'm pretty sure it's the water pump.

I'm gonna AAA it home tonight, and catch a ride from to work from a friend for the rest of the week, and then this weekend take the fan off and replace the pump.

I can't actually get my eyes on the source of the leak, but if it's leaking all over the crank pulley, and the top of the motor and the head is dry, it can't be anything else but the pump, right?

[Lumpy Grits]

It's a 'weep-hole'' in the WP.
Your WP impeller bearing is dying.
Go ahead and pull the WP off and take it with you to NAPA for match up.
LG

[daniel_buck]

That's what I figured, I just can't get my eye balls on it to get a look at it, but I'm 100% sure it's not leaking from anywhere else accept the bottom of the water pump.

I'll look it over tonight with a mirror and flashlight after the AAA truck drops me off at home, by then it shouldn't be puking water all over the place, and I should be able to get my head up in there

[daniel_buck]

Forgot to update this thread. Last saturday I put in the new waterpump (OEM Mopar) as well as a new lower radiator hose (old one looked crusty). Seems to be doing just fine.

Fast forward to this morning, I get to work (a few miles after the vehicle has fully warmed up) and I smell coolant again. I see coolant on the top of the radiator, I'm guessing it's cracked on the top. I'll have to look closer when everything is cold and dry (with the rain, it's a bit hard to tell), but it appears that the top of the radiator has a crack in it. I don't see any coolant coming from the hoses or hose connections.


So..... it looks like I'll be getting a new radiator I guess. I'm going to try and limp it home tonight, and if everything is dry on the roads, take a good look around there to see if anything else is leaking. It didn't actually overheat this morning, temperature was fine, hopefully I can make it home, it's about 6 miles.


At least this isn't all happening on a long road trip :-D

[daniel_buck]

So in looking for a replacement radiator, it seems that alot of people suggest sticking with OEM, the ones with the plastic top. But at the same I read everyone complaining about how much they leak. Is it worth it to try and go for an all metal radiator? or just pick up an OEM replacement that has a plastic top?


These are the brands that I see on RockAuto, I don't see an OEM/Mopar brand.

VISTA-PRO
TYC
PRO
SPECTRA PREMIUM / COOLING DEPOT

[Lumpy Grits]

Find the leak first--
I bet it's from the seam on the front of the top tank.
LG

[daniel_buck]

Find the leak first--
I bet it's from the seam on the front of the top tank.
LG

It's definitely more than just a sweating leak, it was streaming down onto the concrete. Once everything dries up and cools down, I'll take a look on my lunch break.