Any Mopar Tech's here - Grand cherokee 4.7 loosing coolant.

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MileHighDart

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So I was under the hood of my 05 Grand Cherokee yesterday, checking oil, etc.

I notice the radiator overflow tank is empty. Filled it back up to between the "add" and the "full" line. Pull the radiator cap, and add about a quart to get it back up to the top.
Drove it to church and dinner last night, maybe 40 minutes driving total.

This morning I go back out and check it, the overflow tank is completely empty, open the radiator and add about 2 quarts, then refill the overflow.

There is no sign of any leaks on the ground, or under the chassis that I can see. Not blowing any white smoke out the tailpipe, which should be happening if its got a blown head gasket and its burning antifreeze.
It's got to be going somewhere, but I'm lost
 
Most likely culprit is headgasket, very common on those motors.
 
In my opinion you need to do a cooling system pressure test (with the vehicle running and up to temp with a few revs while watching the gauge on the tester)
This will tell if it's getting compression into the cooling system, if the person doing the test knows how to do it and knows what they are seeing.

If you are positive there are no leaks then I'd bet that's what is going on.
Something is pushing the coolant out and then sucking the recovery dry when it cools down again.

Wouldn't be a bad idea to put a new cap on it in any case, as that can be a cheap fix for these kinds of problems as well.
 
Most 4.7L I have worked on have a combustion leak into the coolant system and push coolant out of the radiator into the overflow bottle.when it cools the coolant in the over flow empties back to the radiator....
Try starting it cold with overflow hose pinched or empty and the radiator cap off/
Let get to operating temperature and see if it pushes coolant out.
I will run a customer vehicle to operating temperature with cap off and sniff the gases coming out of the radiator for HC (FUEL) and I can confirm head gasket problem.
you can also purchase head gasket leak detection tool,blue fluid changes to yellow in a test tube that fits over radiator neck....
you could just top it off cold and run it up to temperature with the radiator cap on and feel your radiator hoses.if they become rock hard due to pressure,you got a blown head gasket.It is common on the 4.7L and if overheated badly the valve seat in the heads come loose...
 
MileHighDart said:
So I was under the hood of my 05 Grand Cherokee yesterday, checking oil, etc.

I notice the radiator overflow tank is empty. Filled it back up to between the "add" and the "full" line. Pull the radiator cap, and add about a quart to get it back up to the top.
Drove it to church and dinner last night, maybe 40 minutes driving total.

This morning I go back out and check it, the overflow tank is completely empty, open the radiator and add about 2 quarts, then refill the overflow.

There is no sign of any leaks on the ground, or under the chassis that I can see. Not blowing any white smoke out the tailpipe, which should be happening if its got a blown head gasket and its burning antifreeze.
It's got to be going somewhere, but I'm lost
Click to expand...
Yes, have replaced several 4.7 heads in the past, you could pull spark plugs and look for traces of coolant burn, also, did you check for heater core leaks( wetness under carpets) also check trans fluid as I have seen the radiators leak into the trans cooler lines also- just some of the leaks I have seen, also look for coolant from behind water pump pulley- hope it helps
 
Moparman1806 said:
Yes, have replaced several 4.7 heads in the past, you could pull spark plugs and look for traces of coolant burn, also, did you check for heater core leaks( wetness under carpets) also check trans fluid as I have seen the radiators leak into the trans cooler lines also- just some of the leaks I have seen, also look for coolant from behind water pump pulley- hope it helps
Click to expand...
My 02 ram did it when it was new, from day one. it was the rad. cap leaking. I made an additional gasket for it. -------15 yrs later , it doesn`t leak hardly any thing now (don`t even check it except when I change oil) , still the same coolant and cap. 'BRAKE PADS TOO !" 163,000 AND SOMETHING.
 
Well I tried a couple things you guys suggested. I took the rad cap off, clamped off the overflow tube. Started it up from cold and watched to see if it started pushing antifreeze out. Before it got 1/4 of the way warmed up it was pushing antifreeze out the top of the radiator.
So then I put the cap back on and waited for it to get up to temp, once it was warmed up, the upper radiator hose was very hard, maybe not rock hard, but much harder to squeeze that when it was cold.
So to me that's two indications that I might have a head gasket problem. Might go a step further and try the head gasket leak detection tool, or pull the plugs and look at them.
 
MileHighDart said:
Well I tried a couple things you guys suggested. I took the rad cap off, clamped off the overflow tube. Started it up from cold and watched to see if it started pushing antifreeze out. Before it got 1/4 of the way warmed up it was pushing antifreeze out the top of the radiator.
So then I put the cap back on and waited for it to get up to temp, once it was warmed up, the upper radiator hose was very hard, maybe not rock hard, but much harder to squeeze that when it was cold.
So to me that's two indications that I might have a head gasket problem. Might go a step further and try the head gasket leak detection tool, or pull the plugs and look at them.
Click to expand...

Usually a starting head gasket leak will pressurize the cooling system before the coolant starts going back into the motor because if it, so you are probably ok as far as the rest of the motor but it sure can't hurt to check the plugs.
The hoses will only pressurize to the point the cap doesn't hold it back any longer.
That is when you start loosing coolant and overflowing the recovery system.
When it cools down it creates a vacuum and pulls back what was in the recovery tank.
The recovery tank being empty is a good sign actually, because it hints that the leak is so small so far that it can still build a vacuum and pull coolant back into the radiator.
 
First check the radiator cap. If that is ok then do a block check. With the blue chemical that reacts to hydro carbons. if it turns green or yellowish you have a head or gasket problem.
 
Head gaskets are the usual culprit on the 3.7L and the 4.7L. But you may as well check the plastic side tanks of the radiator, that can be a problem area too. Most often the coolant will just steam away and not leave a puddle.
 
I have a 4.7 in a 2011 Ram 1500 and I was loosing coolant my problem was the water pump with only 75,000 miles the bearing was toast.
 
You can try some "steel seal" in a bottle. Drain the coolant. Remove the thermostat. Add new coolant with the "steel seal". start it and let it warm up. then put the thermostat back in and see if it does you anything, and drive very easy for the 1st 100 miles to let it work. If it works, change your coolant every 2 years and add another bottle. In fact, If you own a 4.7, you might want to put a bottle in every 3 years as a PM thing. last ditch effort before pulling out the $$$$$. And I agree with the above post.... 3.7 and 4.7 (and I'll throw in 2.7) are all bad news.
 
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