Losing coolant and is baffled

[Gmcgranttruck]

Helping out a friend. Not sure on all info
2005 gmc sav Over 160K gets hot and loss of coolant. If top off
It run fine till coolant level gets low again.
Had water pump replaced cause sometimes those damn fins rot away.
Problem still happens. Had pressure tested 15 psi above for hr and held whole time.
Checked for coolant for exhaust fumes. Nothing. Not leaking on the ground, no steam. It just disappears.
Any ideas. She run good. No missing.
Where is it going?
Thanks ahead of time for ur help.

 

[dirtclod]

Have you climbed underneath and looked at the bottom of the oil drain pan? You won't necessarily see any drips on the driveway. Forward motion and engine vibration may play a roll in masking a fluid leak.

 

[california roofer]

Check the dipstick and oil filler cap on top of the valve cover for CHOCOLATE MILK !!!

YOU MAY HAVE A CRACKED HEAD GASKET, OR CRACKED HEADS.

GM has had a few heads cracked heads so they posted this bulletin. Check this link out:

http://ww2.justanswer.com/uploads/Bluegorilla/2008-12-05_142924_Coolant_loss_5.3.pdf

Check this one out as well:

http://www.agcoauto.com/content/plugins/p2_news/printarticle.php?p2_articleid=148

Hope for the best

 

[california roofer]

Check the dipstick and oil filler cap on top of the valve cover for CHOCOLATE MILK !!!

YOU MAY HAVE A CRACKED HEAD GASKET, OR CRACKED HEADS.

GM has had a few heads cracked heads so they posted this bulletin. Check this link out:

http://ww2.justanswer.com/uploads/Bluegorilla/2008-12-05_142924_Coolant_loss_5.3.pdf

Check this one out as well:

http://www.agcoauto.com/content/plugins/p2_news/printarticle.php?p2_articleid=148

 

[california roofer]

Check your dip stick and oil filler cap on the valve cover for CHOCOLATE MILK.

You may have a cracked head gasket or even a cracked head.

GM had a problem with some of their heads cracking.

Search:

GM 06-06-01-019B Bulletin

http://ww2.justanswer.com/uploads/Bluegorilla/2008-12-05_142924_Coolant_loss_5.3.pdf

 

[california roofer]

You may have a cracked head gasket or a cracked head!

Check your dip stick or oil filler cap on the valve cover for CHOCOLATE MILK.

Do a search on GM 06-06-01-019b Bulletin.

Attached are some pictures of hairline cracks in the heads.