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Old 12-06-2016, 10:09 AM   #5
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Join Date: May 2004
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Re: 2005 Yukon Denali slight coolant leak at Y connector

2005 Yukon, Dec. 2016: It's due for emission testing this month and the Check Engine light (the "submarine", according to Mrs. Cusser) appeared. I got this code read, there were three codes P0128 for failure to reach operating temperature fast enough, most likely a bad thermostat. Note that I did NOT replace the thermostat when I replaced the water pump either (on this, it fits into the water pump).

So I bought a new thermostat, one of the ones with the rubber gasket fitted to it, and it fits into the recess of the water outlet. At least repair was straightforward, pretty much just had to remove the black plastic air intake/fan guard thing, then two bolts to remove the water outlet from the water pump to get to the thermostat. I had jacked up the front, saved coolant that spilled out and re-used the coolant (about a gallon came out); coolant was just a few months old, and the check engine light did go off as Mrs. Cusser was driving it later, good.

If it ever gets to something real expensive that is not a driveability/wear/safety issue, Mrs. Cusser can always sell to me and then not have to worry about emissions.

Then over the weekend I noticed some some dried ATF on the metal lines running near the transmission on passenger side, and also noticed some ATF leaking (level was still above "Low"). So since the transmission was overhauled in April and still under warranty, it goes to the transmission shop today.
It's always something.
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