Coolant leak, but heat works fine, no overheat, no pressure/heat on the radiator cap - JeepForum.com
 
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post #1 of 6 Old 01-17-2020, 10:18 AM Thread Starter
ServiceGames
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Coolant leak, but heat works fine, no overheat, no pressure/heat on the radiator cap

So, I don't know exactly what's going on. Since I bought this Jeep about 5+ years ago, I've had coolant issues with it. Very first thing that had to be done was a water pump replacement.

Anyway, it's been treating me well especially since it's used as my daily driver (for road and city driving on the way to work every weekday). Last week or so, I noticed some steam coming out of the front of my hood. Not much steam, and being that it was a very foggy day, I almost didn't check. But, it seems that my reservoir was empty. Oddly enough, my radiator appeared to be full.

I knew this was true because I could take the radiator cap off. It was cool to the touch and wasn't under very much if any pressure after a 45 minute drive. I could squeeze the hose on the top side of the radiator, and it would raise the level of coolant under the radiator cap. But, again, the reservoir was empty. I had some extra water with me, so I filled up the reservoir and went on about my day.

That night, I checked it when I got back home, and I found the same issue. Radiator cap was cool, little to no pressure on the cap, reservoir near or completely empty, coolant right under the radiator cap that could be squeezed up through the radiator hose on top of the car.

To make this issue even more puzzling, the heat works just fine. The car doesn't overheat. It has a 190 degree thermostat in it. And, the car seems to stay between 190 and 200 (200 is when the electric fan kicks on). On the road, it sits right at 190 degrees and doesn't move at all. While sitting in traffic, it will go up, but never over 200.

Again, heat works just fine, it doesn't overheat, but coolant is definitely leaking or somehow under pressure in a different place causing a coolant blowoff to lower the pressure.

Thermostat was changed during the summer last year. Any advice would be great because I don't have any idea where to start on this one.

Thanks in advance!

SG

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post #2 of 6 Old 01-17-2020, 10:33 AM Thread Starter
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Sorry... should mention it's a 2004 Jeep Grand Cherokee Laredo

Thanks

SG
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post #3 of 6 Old 01-17-2020, 10:49 AM
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Seems a coolant pressure test would be the best place to start. It is a tool readily available to rent/loan at most auto parts stores. It will pressurize the whole cooling system while the engine is off, and simulate the pressurized situation you get when running down the road with the engine working. This tool will allow you to watch for leaks while you stand there looking under the hood with the engine off. Be very careful not to run it much unless you are certain that you dont have an air bubble trapped in the system somewhere. This happens alot with these jeeps, and can cause major engine damage. Which engine does your Jeep have?

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,4" short arm lift,JK'sW/32's
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post #4 of 6 Old 01-17-2020, 11:16 AM Thread Starter
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Quote:
Originally Posted by Bigrigr View Post
Seems a coolant pressure test would be the best place to start. It is a tool readily available to rent/loan at most auto parts stores. It will pressurize the whole cooling system while the engine is off, and simulate the pressurized situation you get when running down the road with the engine working. This tool will allow you to watch for leaks while you stand there looking under the hood with the engine off. Be very careful not to run it much unless you are certain that you dont have an air bubble trapped in the system somewhere. This happens alot with these jeeps, and can cause major engine damage. Which engine does your Jeep have?
First of all, thank you for the recommendation. And, I do plan to do a pressure test this weekend. Thankfully, my wife's father used to be a mechanic and happens to have a pressure tester that I can use. Would you recommend removing the bleed plug first to see if I can bleed any air out of the system before trying to run the pressure test?

And, please let me apologize for not putting the engine type in the original post. It's the 4.0L I6.

Thanks again for your help!

SG
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post #5 of 6 Old 01-20-2020, 07:00 AM Thread Starter
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With the help of my wonderful wife, we did a compression test on the car. Older tester, but we were able to get it to start leaking. Seemed to be coming from the Water Pump, dripping onto the Harmonic Balancer, and then to the ground. So, the next day we picked up a new water pump. Drained the radiator, pulled the old Water Pump, installed the new one, put everything back together, put coolant in the system, burped it using the upper radiator hose. Went for a test drive.

A few hundred yards away from our house, temp started going way up (got back home before it got into the red), steam started pouring out of the engine. Got back to the driveway, turned off the engine, popped the hood, and quickly found that the upper radiator hose had a tear in it that was spraying out steam. Opened the radiator cap, and the steam stopped as the system wasn't under pressure anymore.

So, back to the O'Reilly to get an upper radiator hose. I showed the guys at O'Reilly, and they told me that the hose was rotted anyway. So, installed the new hose, refilled the system, burped the system by starting the car and letting it run for a bit. Once we were both satisfied that the coolant had been burped properly, we put the radiator cap back on, and I went for a drive. Car started acting exactly like it should. Usually sitting around 190 and never going over 210 (when the electric fan comes on). But, usually sitting well below 210.

Checked yesterday, and the reservoir was empty (guessing the coolant settled into the system). Filled the reservoir back up to full, and took it for a longer test drive. Seemed to be working just fine. Checked it last night. Reservoir was still full, and when I opened the radiator cap, I could squeeze the upper radiator hose, and the coolant level would rise under the cap. No signs of any new leaks at all.

Drove the car into work this morning, and it performed great. Stayed usually around 190, but rarely got past the mid point between 190 and 210. When I got to work (45 min drive away), I pulled in without any steam coming from the engine bay. Popped the hood to double check, definitely no steam, reservoir was still at "Full," and while the Radiator Cap was still cold, when I unscrewed it and let a little pressure off, you could hear just a tiny bit of air come out of the system. I quickly closed it before any antifreeze started overflowing and spraying out. But, pressure in the system is better than no pressure in the system like it was last week.

Thank you all for your help! Looks like this issue is hopefully fixed

SG
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post #6 of 6 Old 01-20-2020, 09:17 AM
Bigrigr
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Glad you got it figured out. And thanks for letting us know what the results were. Happy Jeeping!

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,4" short arm lift,JK'sW/32's
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