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Mysterious Bronco coolant loss
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NaymzJaymz
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Aug 14, 2011, 5:51 PM
Post #1 of 7
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Mysterious Bronco coolant loss
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Hi folks. My vehicle is a "91 Ford Bronco 4x4 with a 5.0 litre engine. The vehicle has a brand new radiator, a new heater core, and all new hoses. My problem is that the engine is still losing coolant somehow. A friend who is an experienced mechanic attached as pressure tester on the radiator cap location and detected no pressure drop at all. I've popped the hood at night with the engine running at temperature and cannot (with a flashlight) see the slightest evidence of a leak anywhere on the engine or in the cab, as well as any smell of hot coolant that usually comes from even a slight leak. Despite having over 200k miles the rig smogged easily recently here in California, and the oil is absolutely clear. The compression appears fine(although I haven't checked it) since the Bronco runs fine and smogged fine. The AOD tranny shifts fine and has clear fluid too. I was devastated when I put all those new parts in and still lost coolant, although the loss is now rather gradual. The old radiator and heater core leaked noticeably. Again, the hoses are all new, but there is absolutely no sight of a leak any where, even when the engine is hot. Thanks for any help I can get on this one.
James
(This post was edited by NaymzJaymz on Aug 15, 2011, 1:39 AM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Aug 14, 2011, 5:54 PM
Post #2 of 7
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Re: Mysterius Bronco coolant loss
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Did he pressure test the engine when it was hot or cold? When you start it up in the mornings do you feel any misfires that go away after a few seconds? Did you look around the timing cover to block area for dampness or leaks? There is a gasket between the timing cover and block that deteriorates with age and can leak.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Aug 14, 2011, 5:57 PM)
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NaymzJaymz
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Aug 15, 2011, 1:36 AM
Post #3 of 7
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Re: Mysterius Bronco coolant loss
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The engine was reasonably warm. Obviously, it had to cool down some to put the pressure tester on. As for the timing cover area and gasket, I've checked the engine many time very carefully, but now that I've heard of this possibility I can pay particular attention to that area, as well as any other ideas someone else may have. I do notice what might be called a misfire during intial start up from time to time, but then the motor starts a few seconds later an runs fine. Thank you for taking time to answer.
James
(This post was edited by NaymzJaymz on Aug 15, 2011, 1:43 AM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Aug 16, 2011, 6:28 PM
Post #4 of 7
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Re: Mysterius Bronco coolant loss
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One thing you could try is to connect the pressure tester to the engine after it has cooled off and let it set on there overnight. Don't over pressurize the system, of course. The next morning or whenever, remove the spark plugs and crank the engine over with the distributor unplugged. If coolant spurts out any of the spark plug holes, there is your leak.
It's possibility that you could have coolant leaking into a combustion chamber after the engine sits. When you start the engine there is enough coolant in a combustion chamber to cause a misfire for a few seconds or until the coolant is burnt off.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Aug 16, 2011, 6:28 PM)
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NaymzJaymz
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Sep 3, 2011, 8:42 AM
Post #5 of 7
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Re: Mysterius Bronco coolant loss
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Thanks again for your advice, sir. Sorry it took so long for me to view this. The things you mention lead me to a few more questions. If this is the problem, where is the coolant coming from? Would it come from the block to head mating surface(head gasket) or would it be a crack? How is the liquid getting into the combustion chamber? If this is the problem, it sounds like a major engine problem that will require a rebuild. It is embarrassing for me to admit that I let the engine overheat a few years ago when the old radiator leaked. It has run fine since then and has smogged twice. Could the head have warped? If so, why would it run fine still? There is also an issue in which the rig briefly stalls after climbing a hill, and the mechanic I mentioned said that could be due to the overheat. On another forum a mechanic said that it could be a lifter issue brought on by overheating. Anyway, thanks for your help on these issues. Please let me know how you think that water could be getting into the cylinders. Thanks, my friend.
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Discretesignals
Ultimate Carjunky
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Sep 3, 2011, 1:55 PM
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Re: Mysterius Bronco coolant loss
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There is a coolant sleeve around the cylinders inside the block and ports for the water to flow from the block to the head. These ports are sealed between the cylinder head and the block deck by the head gasket. A breach in the head gasket between a coolant port and the cylinder firing ring can allow coolant to leak into the cylinder. The leak may be gradual (symptom of mysterious coolant loss) or could be fairly large resulting in white smoke pouring out the exhaust.
Cast iron heads can crack or warp if overheated. Cracks in the cylinder head or cylinder walls can allow coolant to get into the combustion chambers.
Head gasket do have a life span and that span can be shortened by massive or frequent overheating.
There is also a possibility that an intake gasket could be leaking coolant which could mimic a bad head gasket.
With the age of the vehicle and mileage it's possible it's time for head gasket replacement. It is usually wise to have the heads checked for cracks and valve train reconditioning done at the same time.
Don't wait too long because if the gasket fails big time you could end up with coolant in the engine oil which can destroy engine bearings.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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NaymzJaymz
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Sep 4, 2011, 3:52 PM
Post #7 of 7
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Re: Mysterius Bronco coolant loss
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Thanks again, my friend. I think you're right on this one. I'm learning as I go along, piece by piece. thanks for all of your help.
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