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Unread 09-19-2012, 07:23 PM   #1
jhumphrey
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1998 XJ Cherokee 
 
Join Date: Nov 2010
Location: Middle, TN
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Radiator leak?

Hey All,

Today while I was trying to isolate a "pop" from my xj, I noticed a small amount of steam rising up from my upper radiator. It was about like a cigarette. It was near my fan on the passenger side. When I leaned over the steam, it had the faint smell of antifreeze, so I ran my finger along the top edge of the radiator (technically, I guess this is the bracket...) and when I removed my fingers, I saw a small amount of clear liquid on my finger tips. This liquid had no smell and had the consistency of water. It didnt "feel" like coolant, but the steam smelled like coolant.

The OP had replaced the radiator (and water pump, IIRC) with a new one just a few weeks before he sold the xj to me, so the radiator itself isnt old at all. The "rail" of the radiator at the top seemed to be wet for about 3" or so and only my finger tips were wet. Im thinking a pinhole leak, but need some suggestions on what else it could be. I did check out the hoses running along the radiator and they were dry, so its definitely the top of the radiator.

Im adding this to my "spend more money" list

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Unread 09-21-2012, 04:56 AM   #2
Reptile
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Start by replacing the rad cap. If the cap is faulty, pressure will build up and eventually release in the form of steam. One area where it is likely to release is through the water pump (there is some kind of pressure relief device in it). Make sure also you have a 50/50 coolant mix.
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Unread 09-21-2012, 07:42 AM   #3
Paradise XJ
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I'd look at the cap, as said. I'd also look at the overflow hose and the nipple it attaches to. Just a tiny crack can let out a bit of steam, or coolant, or both.
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Unread 09-21-2012, 08:22 AM   #4
jhumphrey
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Thanks. Ill replace the cap (good idea any way to do so).

I took the jeep to the radiator shop today. They hooked it up to a pressure test and loaded it to 16lbs. No leaks anywhere, but it did lose pressure (went down to 12 in about 20 mins or so). Im not losing coolant, but (obviously) am losing pressure somewhere. We couldnt find any symptoms of a leaking head gasket and the expansion system worked as it should. He said it could be seeping somewhere, but we couldnt locate it. Any suggestions as to what to do? Replace the head gasket anyway? Drive it until something happens? Flush it, refill it, and see if the pressure holds then (in case air was in the system somewhere)?

Im kinda at a loss for how to proceed from this point.
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Unread 09-22-2012, 02:25 PM   #5
jhumphrey
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So I did a compression test and found that the numbers were fairly equal, except cylinder #3. The numbers:

Cyl 1: 175
Cyl 2: 170
Cyl 3: 155
Cyl 4: 175
Cyl 5: 180 (between 175-180)
Cyl 6: 175

While I was out, I changed the cap and also put on the zj fan clutch as well as the fan shroud. About cyl 3, is that possibly a leaking exhaust valve (as the Internet says)? It a little over 10% difference. I've read that 10-15% is ok...
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Unread 09-22-2012, 02:44 PM   #6
Reptile
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Compressions are good, although a little high. Sounds like you're having some carbon deposit in your combustion chambers.

If you keep on having issues, check the coolant. You can find very inexpensive coolant testers. You coolant need to be at least 50% antifreeze. The boiling point start dropping fast as you go below that treshold. You did mention the liquid you found had a watery feel to it...
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Unread 09-22-2012, 02:52 PM   #7
jhumphrey
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Quote:
Originally Posted by Reptile
Compressions are good, although a little high. Sounds like you're having some carbon deposit in your combustion chambers.

If you keep on having issues, check the coolant. You can find very inexpensive coolant testers. You coolant need to be at least 50% antifreeze. The boiling point start dropping fast as you go below that treshold. You did mention the liquid you found had a watery feel to it...
So it sounds like I need to drain the cooling system and refill. Sorta like hitting a "reset" button, as I'm unsure what the PO used when the system was worked on...
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Unread 01-13-2013, 04:39 PM   #8
benni01
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Quote:
Originally Posted by Paradise XJ View Post
I'd look at the cap, as said. I'd also look at the overflow hose and the nipple it attaches to. Just a tiny crack can let out a bit of steam, or coolant, or both.
I have a 2001 cherokee. How would you fix the problem if the nipple was pretty much gone for the overflow hose? Does that mean radiator replacement? Also coolant comes out of my leak at the overflow attachment every time I drive no matter how long the engine runs. Could this mean the problem is in more than just the radiator nipple and the cap.
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