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EFV-8 Club Forum / General Ford Discussion / Exhaust gas leak

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Posted By Discussion Topic: Exhaust gas leak     Dustbowl 07-25-2012 @ 10:46 AM reply profile send p.m. Member Posts: 74 Joined: Feb 2011 Thanks for several suggestions in response to my recent post on "cylinder head removal". I got the heads off. The reason I took them off was to search for an apparent leak of exhaust gas into the cooling water system in my 36 Ford/21 stud engine. After removal, i cannot see any visually obvious source of leak/crack in head gaskets, cylinder heads, or cylinder walls. My question is what do I do next, and IN WHAT SEQUENCE? For example, should my next step consist of taking the heads somewhere for magnetic particle crack inspection? Thanks in advance for experience advice. supereal 07-25-2012 @ 2:38 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 It is really difficult to determine where, or if, there is a combustion leak after the heads have been removed. You can look carefully at the usual place for cracks, between the valve seat pockets and the cylinder wall. You can have the heads Magnafluxed at a good machine shop, but the block can't be done unless it is disassembled. What made you think that there was a ombustion leak into the water jacket in the first place? Overheating? Coolant in the oil? keith oh 07-26-2012 @ 11:07 AM reply profile send p.m. New Member Posts: 116 Joined: May 2010 I guess you must have had the coolant tested and found exhaust gas in it. Before going to the expense of a major teardown I would clean the head surface and block very well and replace the heads with a set of FelPro gaskets greased on both sides with chassis grease. (They can usually be reused if greased, if need be.) I then would put in a large bottle of liquid Barr's Stop Leak following their instructions. The most you would be out is some labor and the cost of the stop leak. 6lucky13 07-26-2012 @ 1:52 PM reply profile send p.m. Member Posts: 57 Joined: Jun 2011 In addition to having the heads magnafluxed, I would have them resurfaced before reinstalling. Jon Dustbowl 07-26-2012 @ 5:25 PM reply profile send p.m. Member Posts: 74 Joined: Feb 2011 In response to Supereal's question of why I think I have a leak of combustion/exhaust gas leakage into the cooling water circuit, I observe after driving awhile that significant water comes out radiator overflow pipe (which has a back pressure valve to 3#). The engine doesn't overheat and this overflow occurs when engine temp is 160F or less. The amount of "overflow" is more than might occur simply due to thermal expansion of the water. I have not had the radiator tested for presence of combustion gas. Does all these make sense? TomO 07-27-2012 @ 7:26 AM reply profile send p.m. Senior Posts: 7271 Joined: Oct 2009 Your assumptions make sense, but I would have used them to do some tests that would help to isolate the problem. Small cracks and head gasket leaks are hard to find when you have to look all over the 8 cylinders. Even if you know the general area of the failure, they can be hard to find. With the information that you have posted, my plan of action would be to have the heads resurfaced, get new head gaskets and reassemble the engine. If there is still coolant loss, with the radiator full, I would get the engine to operating temperature, remove the water pump belt, start the engine and look for bubbles in the radiator. You may have to operate the accelerator to make sure that the problem is not a crack or blown head gasket. If you see bubbles, then remove the upper hoses and with the coolant near the top of the opening, repeat the procedure to determine if the problem is on one or both sides. The next step would be to do a compression check on the failing side to see if you can isolate it to one cylinder. If the compression check does not isolate the problem, do a cylinder leak down test. Harbor Freight has an inexpensive leak down tester, or you can just try pressurizing one cylinder at a time by modifying a spark plug to accept a metal valve stem and then inserting the modified plug in one cylinder at a time, with the piston at TDC an applying air pressure to the spark plug, while looking for bubbles in the coolant. Tom supereal 07-27-2012 @ 7:36 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 As the overflow occurs when the engine is cool, and there isn't overheating, it is possible that the radiator core Is obstructed, causing the upper tank to be unable to handle the volume. A combustion leak almost always produces rapid and strong overheating, and some coolant in the oil. Pull the dipstick and hold a match under the end. If it sputters, there is coolant. It is also possible that the radiator cap is faulty, or incorrect for the filler neck, and does not seal properly. This message was edited by supereal on 7-27-12 @ 7:37 AM

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