Identifying cylinder with exhaust leak to coolant

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2 months 2 weeks ago #201804 by xsnrg
Hi, I have an '08 Sienna with 3.5L 2GR-FE engine. It's very apparent that there's an exhaust leak (presumably through HG) into the coolant, over pressurizing the coolant system. The van has 224k mi on it, so I'm not planning to replace the HG, I would most likely replace the engine or the van before that. I basically have little to lose trying Blue Devil HG sealant. The instructions to people with exhaust to coolant leaks involve removing the plug from the cylinder that has the leak. You replace the coolant with water and add the sealant while running (starting from cold) with the thermostat out and then let it idle for 50 min, assuring that the system gets above 150 degrees. The plug is removed to reduce the pressure coming through the leak to allow the magical unicorn blood to have a chance to plug the leak. Now my question ... how to determine which cylinder is leaking. They mention removing and inspecting the plugs to determine which cylinder is leaking. Apart from one that is different from the others, what am I looking for? If exhaust is leaking OUT of the cylinder, I wouldn't expect the inside of the cylinder or the plug to be all that different from the others. I don't seem to be leaking coolant into the cylinder unless it's happening just a little bit when the car is off. The system seems to hold pressure really really well, verified with a pressure test (and also by the fact that it's still very pressurized sometimes the next morning when completely cold). As you probably know, getting those back 3 plugs out is a real bear, requiring removal of the windshield wiper assembly and pan as well as the air intake manifold. I'd love to find the leak in the front three which are fully accessible.

disclaimer: I've read the stories, bad and good on using the different sealants. I know this is a roll of the dice and in most cases ill-advised. I've just decided to try it anyway before replacing the engine or the vehicle. if you don't have a tip for identifying the leaking cylinder and you just want to voice disapproval on trying the sealant, please save yourself the typing and me the reading. Thanks!

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2 months 1 week ago #201863 by sixteenacrewood
Replied by sixteenacrewood on topic Identifying cylinder with exhaust leak to coolant
I just watched a youtube video on this posted by "Oldskool funk" title "checking a blown head gasket with no specialized tools"
Basically take all the plugs out and start with cylinder #1 , put plug in, top off radiator with water disable coil so engine won't fire, turn over with starter, watch radiator with cap off. Test each cylinder, bad one will blow water up out of radiator.
watch the video, it was well done!
hope this helps

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2 months 1 week ago #201870 by relative4
For large leaks, the radiator geyser method is helpful. Otherwise a leakdown test is the proper way. Leakdown testers are inexpensive, or you can possibly borrow one from the auto parts store.

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