Mysterious Coolant Leak

[2000YukonXL]

2000 Yukon XL 5.3L, with a mysterious coolant leak. Has been to 4 different shops and checks out fine, pressure checked the system (even over night) and its perfect... Low coolant light comes on after about a 30 min trip, no over heating, front heat works fine, rear heat is ice cold, but not showing any signs of leaking back there either. Maybe I'm looking in the wrong spot?? Been this way for 2 years!! HELP!!!

 

[LinuxMint]

Is it actually leaking, or are you just going off of the light?

 

[2000YukonXL]

Its definitely leaking! Runs the resevoir dry in a short amount of time, maybe 150 miles max on the freeway before you HAVE TO stop and fill it back up, but even when its low, it won't overheat. There's been speculation that it may be the head leaking into the exhaust, but nobody has proved it, and beings that its been 2 years I feel like something would have gone seriously wrong by now...

 

[bkboatnsleds]

Google "Castech Heads" Hope I',m wrong.

 

[04SS99Denali]

sounds like a head gasket issue if there is no visible leak. is it leaving a lake under the truck? do you smell it at all? from the way its leaking you should have a pretty hefty puddle under the truck if its actually leaking

 

[CEN2MENTAL95]

have you found any oil in coolant or coolant in the oil?

 

[2000YukonXL]

Coolant and Oil are not mixing, and other than the fact that it goes empty so fast there is absolutely no sign of the truck leaking. I've checked and rechecked the carpets, hoses and everything else I can find, nothing is wet or appears to be leaking. The only other thing that might be a sign is that when the truck is cold in the mornings, the exhaust steams some for a few minutes then stops, and the rear heat blows ice cold, thats why I was thinking possible rear heat related? Its been 2 years Its getting kinda old!! I'm going to go google those heads.....

 

[bottomline2000]

I have developed the same problem. no source of leak. no puddle under truck, no smoke out tailpipe, no coolant around engine no driveability issues. just missing coolant. I'm thinking I have the castech blues.. heads are stamped 700 I do believe.

 

[2000YukonXL]

Seriously, how long can one drive around with these castech heads spewing coolant into the oil before some serious happens? Something has to give!! We're talkin 40-50,000 miles! I actually took it from WA to SoCal, straight through both ways (except fuel) 2500 miles round trip, I'm baffled! If mine is a Castech head issue, I do have to say they're holding up pretty well lol. I was reading somewhere else from a Google search something about a guy with a similar problem, except he says his was pooling coolant in the intake manifold and blowing it out the exhaust.... I'm thinking that is a plastic or composite intake manifold?? Is it possible that the coolant is going in there? maybe cracked? I dunno, I'm just a chick on a mission

 

[bankswood]

OK I'm going to throw this out . I have a friend with a late 90's Honda. It was using more coolant than gas. Same symptoms as you. No leaks, no coolant in the oil, etc. Finally found out he had a bad 02 sensor. Never threw a code but a new sensor fixed the problem