Mystery Coolant Leak - JeepForum.com
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post #1 of 17 Old 09-26-2021, 04:01 PM Thread Starter
tecthom28
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Mystery Coolant Leak

Hey Everyone -

While driving home from a pretty long trip through the middle of nowhere, I noticed that the temp gauge was slowly creeping up. I tried pulling off somewhere but had about 12 miles till the nearest exit. I made it about 6 miles till every light on the dash went crazy and the temp gauge went off (just turned off the zero). Pulled off for about 45 min and finished the last half into a parking lot and had it towed home.

Once home, I found the leak in the radiator.. so I replaced the radiator, hoses, thermostat, and water pump since I know all of that overheating may have done some damage and also because I'm in there already with a truck at 150k mi.

The truck is now all put back and I put my 1st gal of coolant in with no problem. The issue is once I started pouring in my 2nd gal I can hear it all coming out the rear of the engine onto the garage floor. It's hard to trace but I can see it coming from the passenger side and dripping onto the top of the tranny. Not sure where in that area is the source of my leak. Could it be the heater hoses?

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post #2 of 17 Old 09-26-2021, 05:40 PM
ColdCase
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V6 or V8 or Diesel? Model year?
99SK04GTX and IDoMy0wnRacing like this.

I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #3 of 17 Old 09-27-2021, 11:28 AM
Bilko
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Do you have access to a lift or some ramps? You need to get under there and see what's going on. If you can hear the coolant flowing out it should be easy to spot the source. The other option is to place your phone or a GoPro under the Vehicle to spot the source.
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post #4 of 17 Old 09-27-2021, 11:56 AM Thread Starter
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Its a 2012 3.6L, 2WD

Current: 2012 Grand Cherokee Overland V6 2WD
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post #5 of 17 Old 09-27-2021, 12:03 PM Thread Starter
tecthom28
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Quote:
Originally Posted by Bilko View Post
Do you have access to a lift or some ramps? You need to get under there and see what's going on. If you can hear the coolant flowing out it should be easy to spot the source. The other option is to place your phone or a GoPro under the Vehicle to spot the source.
So when I get under the car, theres very little leaking until i fill up to almost 2 gals. It will almost feel like I overfilled the car based on the amount escaping with the engine off.

If I follow it with a camera and a light, it seems to escaping right over the oxygen sensor on the passenger side as it drips down the top of the transmission. I also see some dripping on the passenger side as well so I think it could be the Oil Coooler rather than the Coolant Temp Sensor or Heater Hose.

Would the oil cooler leak with the engine off? I was orignally thinking the ect sensor would be the culprit as I also originally got a P0117 error as it overheated.

Current: 2012 Grand Cherokee Overland V6 2WD
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post #6 of 17 Old 09-27-2021, 12:20 PM
ColdCase
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Yeah I was thinking oil cooler, its has o ring that could have blown out, or you have a serious crack in it. This will leak out of the "valley" under the intake onto the transmission. I haven't heard of one leaking just with water fill. On other engines, I've often heard of freeze plugs or head gaskets leaking coolant after overheat.

Edit: ... Coolant flows from the right cylinder block water jacket and from the left cylinder block water jacket into the housing (o ring seal). The coolant flows through the oil cooler and exits the housing from the rear hose nipple where it is returned to the water pump.

So the hose could be leaking or blown off.... but dunno.

I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #7 of 17 Old 09-28-2021, 10:41 AM Thread Starter
tecthom28
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Quote:
Originally Posted by ColdCase View Post
Yeah I was thinking oil cooler, its has o ring that could have blown out, or you have a serious crack in it. This will leak out of the "valley" under the intake onto the transmission. I haven't heard of one leaking just with water fill. On other engines, I've often heard of freeze plugs or head gaskets leaking coolant after overheat.

Edit: ... Coolant flows from the right cylinder block water jacket and from the left cylinder block water jacket into the housing (o ring seal). The coolant flows through the oil cooler and exits the housing from the rear hose nipple where it is returned to the water pump.

So the hose could be leaking or blown off.... but dunno.
That gives me the confidence to move forward with the plenum removal today to take a look. I'll update you tomorrow! Thanks @ColdCase !
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post #8 of 17 Old 09-28-2021, 11:39 PM Thread Starter
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Well, it looks like the mystery seems to be solved...

Pulled up the plenum (tilted it over as I was removing and saw some oil - or burned coolant leak out) and lower intake and found gunk and burnt coolant everywhere... I also see a pool of coolant toward the back of the cooler, which now would make sense to the leaking of coolant down the back of the engine. I'm going to also be doing a new oil change as well and cleaning out the plenum and lower intake.

Ordered the 2014+ Oil Cooler unit today and should have it by Monday to install.
  1. Should I be ordering any other hoses, o-rings, etc?
  2. should I clean out the throttle body after seeing a bit of oil (maybe coolant) behind the plate?
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post #9 of 17 Old 09-29-2021, 05:40 AM
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Sounds like you were getting more that the usual oil mist pushed/pulled through the PCV into the intake manifold where it pooled. May be normal at 150k miles but I dunno. Did you check compression?

I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #10 of 17 Old 09-29-2021, 04:03 PM
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That fitting is cracked, is it not replaceable? you had to buy the entire cooler assy?

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post #11 of 17 Old 09-30-2021, 11:21 AM Thread Starter
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tecthom28

Quote:
Originally Posted by RedTrex View Post
That fitting is cracked, is it not replaceable? you had to buy the entire cooler assy?
Yes sir. I'm replacing the entire cooler assembly and going with the 2014 assembly as well. I looked at the hose that goes out to the assembly and it seems to look ok. Does anyone think that should be replaced as well?

I heard I should also replace the knock sensors while I'm in there... is that something that would make sense to do?
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post #12 of 17 Old 09-30-2021, 11:37 AM
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If the hose feels a bit hard, and perhaps a bit swollen, I say replace it.

Bob N. 2011 Grand Cherokee Overland 5.7L, 1999 Cherokee XJ 4.0L (off-road enhanced)
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post #13 of 17 Old 10-01-2021, 09:48 AM Thread Starter
tecthom28
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Quote:
Originally Posted by OldPaint View Post
If the hose feels a bit hard, and perhaps a bit swollen, I say replace it.
Good idea, Ill check and order today!
Ill update next week when it all arrives!

Current: 2012 Grand Cherokee Overland V6 2WD
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post #14 of 17 Old 10-06-2021, 04:23 PM Thread Starter
tecthom28
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In prep for the new cooler, I started the process of removing the old cooler, draining out the old coolant and oil and installing new knock sensors (figured it was a good idea since I was in there).

Noticed that there are rubber gaskets on the engine still.. should those be there or is that maybe cause for the leak? The hose feeding the back of the cooler was in good shape.

Are the two gaskets needing to be removed and just melted to the engine?? They arent even truly centered. Attached two pics.
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post #15 of 17 Old 10-06-2021, 08:16 PM
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There is a Oil filter housing that bolts to the block and an oil cooler that bolts to the block through the housing. There are seals between the cooler and housing and between the housing and block. Are you are installing a new housing assembly that includes the cooler and housing, or reusing the housing?

In any case, you need to remove the old/used seals, wherever they are. Then install new seals. Always use new dry seals. Do not lubricate the seals between the cooler and housing. Lubricate the oil ring seals between the housing and block (your photo) with clean engine oil prior to installation. I think sometimes the cooler/housing comes with seals installed.

You install the sensors and attach the heater hose before positioning and attaching the housing to the block. There are 5 bolts to be tightened to 106 in lbs in the sequence below...

..
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I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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