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Loosing coolant. When I crank car it leaks a lot of coolant, but stops when driving. If I fill the reserve up I can't see it leaking anywhere. As soon as I put it in drive it leaks like a faucet for a few seconds. Thinking a hose? Oil is clean.

  • Welcome to the site. When you say "it's leaking" ... what part of the engine is leaking? Does it come out the front or back of the engine? Maybe off one of the sides? Can you narrow down where you've looked? Does the engine run? What year of Yukon is this? Which engine? How many miles? Any other information you can impart? – Pᴀᴜʟsᴛᴇʀ2 Sep 3 '16 at 19:31
  • try renting a pressure testing kit or have someone crank the engine while you look for your leak – Ben Sep 3 '16 at 20:33
  • Verrrrry common for water pumps to go bad and start leaking on the Yukons. Not sure if they leak intermittently like you described but it could be a place to look. – Dalton D Sep 4 '16 at 2:45
  • VERY old question. But, dye kits are about $30 on Amazon. Get one, put some dye in your coolant. When it starts leaking, Get the blacklight and yellow goggles out of the dye kit, and you should be able to trace the leak very quickly. (Also works great for oil and AC leaks.) – 3Dave Apr 4 '18 at 19:02
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If it is not obvious from where it is leaking, your best bet is to go on a car wash, and clean the engine as much as you can. Leave the car dry, fill up the coolant, and then try to replicate the issue.

Also before you try to replicate the leak, it might be a good idea to remove any plastic covers from the top and the bottom of the engine.

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I had a similar problem and could not find the leak. I did the above recommendation (cleaning the engine) and the leak was the at the intake manifold gasket (right rear side).

I hope this helps.

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