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  #1  
Old July 12th, 2019, 07:22
Tony the Liger Tony the Liger is offline
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Unexplained coolant loss, but mechanics thinks the head is fine. ???

Posted this in a couple other forums. Just wanted to get as many opinions as possible.

I have a '00 XJ @175k miles. I've owned it for a couple years now, but have barely driven it. Bet I haven't put 500 miles on it since I bought it. I'm losing coolant, but I can't figure out why. My immediate worry was the dreaded head issue, but aside from the coolant loss, nothing else suggests that I have a cracked head. Last winter, when I first noticed this, I checked the oil fill cap and did see some nasty looking foam. I was pretty convinced at the time that I had a head issue, all things considered, but I did some research, talked to some folks who are more knowledgable than me, and described what I was seeing to every mechanic who'd take the time to talk to me, and they all said that what I was seeing was condensation in the cold months, and not coolant mixing with the oil. FWIW, the oil I could see looked fine, I couldn't see a crack, and I haven't seen any of that foam/condensation since. Runs well, doesn't knock or rattle, stays cool, doesn't smoke or smell, exhaust looks normal. Last year, I had a coolant leak that I could see; I had it pressure and compression tested (to help find the leak and check on the head); didn't find any issues with the head at that time, but my water pump was leaking. I replaced the water pump, fan clutch, thermostat and radiator cap, and I haven't seen any leaks since. I haven't driven it much at all since then, so while I know crazier things have happened, the idea that I somehow developed a head crack after having it tested and little driving seems pretty wild to me. Still, I'm losing coolant somehow, so I took it to my mechanic last week. He ran another pressure test and couldn't find any leaks, but he says based on the way it runs, sounds, smells, etc., nothing makes him think there's a problem with the head.

So, where's the coolant going?
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Old July 12th, 2019, 07:42
RCP Phx RCP Phx is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

Have you tested for combustion gases in the radiator? When my 2000 did this it was a small leak in the head gasket. Just as yours, there was no visible signs other that using water.
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Old July 12th, 2019, 07:49
VAhasnoWAVES VAhasnoWAVES is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

the problematic head crack usually results in mixing. i wouldnt jump right to suspecting that.

if you are losing it but not seeing it... its burning off before you can see it. its either making its way into the cylinder or burning off the block. id suspect head gasket either way.
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Old July 12th, 2019, 07:51
Tony the Liger Tony the Liger is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

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Originally Posted by RCP Phx View Post
Have you tested for combustion gases in the radiator? When my 2000 did this it was a small leak in the head gasket. Just as yours, there was no visible signs other that using water.
Doing this today. Fingers crossed.
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Old July 12th, 2019, 07:52
Tony the Liger Tony the Liger is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

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Originally Posted by VAhasnoWAVES View Post
the problematic head crack usually results in mixing. i wouldnt jump right to suspecting that.

if you are losing it but not seeing it... its burning off before you can see it. its either making its way into the cylinder or burning off the block. id suspect head gasket either way.
I'm going to send an oil sample to Blackstone Labs, too, fwiw.
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  #6  
Old July 12th, 2019, 08:03
chickenbot chickenbot is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

how are your freeze plugs? there is one located inside the transmission bell housing as well
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  #7  
Old July 12th, 2019, 14:26
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8Mud 8Mud is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

I had a head gasket go and it leaked coolant into two cylinders. I did notice an excessive amount of water vapor coming out of the exhaust pipe, but a cold motor will spew out some moisture anyway, just water from the atmosphere. The real tip-off was when I held a white paper towel up to the exhaust after starting a cold motor and noticed the droplets of water had a blue tint, the color of my coolant.
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Old July 12th, 2019, 14:31
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8Mud 8Mud is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

I've also had tiny radiator leaks, where most of the leaking coolant would evaporate away and never leave a telltale drip under the XJ. But they would leave whitish deposits near the leak. Behind the fan shroud near the passengers side end tank is a likely spot.
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Old July 12th, 2019, 15:00
tech1001 tech1001 is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

I just got done changing the head on my 2001 , try pressurizing the coolant system then remove the oil cap and look in side the valve cover at the head , the head will crack under the oil cal cap you should be able to see the coolant coming though a crack in the head . It will put the coolant in to the oil and the engine will run good still but it could hurt the engine bearings .
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Old July 13th, 2019, 20:08
Jim Malcolm Jim Malcolm is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

Check the fluid in the transmission, assuming it's an auto. If it's milky pink like a strawberry milkshake, you have your answer...
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Old July 14th, 2019, 09:19
puredrive puredrive is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

Quote:
Originally Posted by Tony the Liger View Post
I'm going to send an oil sample to Blackstone Labs, too, fwiw.
Soon after I got my 2000 XJ, I started to notice a very small of coolant loss. I did the oil sample and sure enough I had coolant in the oil.

Keep us posted and good luck
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Old July 14th, 2019, 11:01
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

Replace the radiator cap
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Old July 14th, 2019, 11:05
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

How much coolant loss are we talking about over how much time?

And what sort of use is the vehicle seeing during this time?
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  #14  
Old July 14th, 2019, 14:16
Tony the Liger Tony the Liger is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

Quote:
Originally Posted by puredrive View Post
Soon after I got my 2000 XJ, I started to notice a very small of coolant loss. I did the oil sample and sure enough I had coolant in the oil.

Keep us posted and good luck
Will do. Hoping for the best but expecting the worst.
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  #15  
Old July 14th, 2019, 14:17
Tony the Liger Tony the Liger is offline
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Re: Unexplained coolant loss, but mechanics thinks the head is fine. ???

Quote:
Originally Posted by old_man View Post
Replace the radiator cap
I did that a while back. No leaks from that area.
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