Odd cooling problem
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Senior User
Joined: Jan 2008
Posts: 105
Likes: 1
From: Issaquah, WA
Odd cooling problem
I recently removed the passenger side head to have some broken exhaust bolts removed on my '94 F250 7.5L. Everything is back together, and the truck runs great.
My problem is that the coolant level keeps dropping with no visible leaks. I performed a test for hydrocarbons in the radiator which was negative. The coolant looks perfectly clean. I performed a compression test on the passenger side which resulted in 135, 145, 145, 150 psi.
I ran the engine for 10-15 minutes prior to the hydrocarbon test. While waiting for the engine to cool back, the radiator cap released a bit of coolant. Basically burped coolant out of the radiator with the engine off. I tested the radiator cap, and it held 13 psi.
I'm really at a loss as to what might be causing these symptoms.
Any ideas?
My problem is that the coolant level keeps dropping with no visible leaks. I performed a test for hydrocarbons in the radiator which was negative. The coolant looks perfectly clean. I performed a compression test on the passenger side which resulted in 135, 145, 145, 150 psi.
I ran the engine for 10-15 minutes prior to the hydrocarbon test. While waiting for the engine to cool back, the radiator cap released a bit of coolant. Basically burped coolant out of the radiator with the engine off. I tested the radiator cap, and it held 13 psi.
I'm really at a loss as to what might be causing these symptoms.
Any ideas?
New User
Joined: Apr 2017
Posts: 7
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From: Raeford NC
Maybe an obvious statement but is it possible your coolant was low and it is still working out the air pockets as you continue to fill? Have you tried running the truck with heat on full blast to help work out those air pockets assuming that's what they are and not something else. I should probably also ask how much coolant you have added?
Senior User
Joined: Dec 2016
Posts: 290
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From: Philly
Does your pressure tester tell you anything about the rest of the system? I found I had forgotten a clamp on a heater hose, recently. When that was fixed a freeze plug started leaking. Can't be going too many places. How much is it dropping? Enough to form a puddle somewhere? Or does it hit the manifold and burn off?
Laughing Gas
Joined: Oct 2014
Posts: 1,227
Likes: 4
From: Washington
Coolant runs unobstructed through the heater core. Air baffles are what determine whether the heater is "on" or not.
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Senior User
Joined: Jan 2008
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From: Issaquah, WA
I've replaced a gallon of coolant until now. Each time I check it, the level in the radiator has dropped a few inches. Meaning, from the time the system seemed full, another gallon has gone in. No, I haven't run the heater because my understanding is that coolant is always running through the heater core. There are no visible leaks. No puddles, no evidence of burning off a manifold, etc. I think it should be done with burping by now. I've run/driven the truck at least 10 times. Although trapped air is certainly a possibility.
More Turbo
Joined: Jun 2003
Posts: 687
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We will assume the new head gasket hole pattern matched the old.
I guess i'd make another attempt to burp by parking facing up hill and running the engine with the radiator cap off, while feeding the radiator until full.
Did the bolts on the exhaust break while doing a manifold replacement?
I guess i'd make another attempt to burp by parking facing up hill and running the engine with the radiator cap off, while feeding the radiator until full.
Did the bolts on the exhaust break while doing a manifold replacement?
Thread Starter
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Senior User
Joined: Jan 2008
Posts: 105
Likes: 1
From: Issaquah, WA
We will assume the new head gasket hole pattern matched the old.
I guess i'd make another attempt to burp by parking facing up hill and running the engine with the radiator cap off, while feeding the radiator until full.
Did the bolts on the exhaust break while doing a manifold replacement?
I guess i'd make another attempt to burp by parking facing up hill and running the engine with the radiator cap off, while feeding the radiator until full.
Did the bolts on the exhaust break while doing a manifold replacement?
No, the exhaust bolts broke on their own. This whole started with an exhaust leak caused by 2 broken bolts on the passenger side manifold. I broke an EZ-out on one of the bolts which led to removing the head for a machinist to work on.
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Cargo Master
Joined: Jan 2004
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From: South Dakota
Does the truck have a coolant recovery tank?
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Blown gasket possibly lead.
I recently had a similar issue with my Ranger. I finally narrowed it down to a minor leak in the head gasket into the #5 cylinder (loss of 10 Psi compression and slight flash rust on spark plug) Not so much as to see the white smoke or even smell it - just a quart or so of coolant per week. Since the engine has 230+K miles, I decided to put in a can of copper based stop leak from Bar's Leak. No lost anti freeze for 6 months since.
Thread Starter
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Senior User
Joined: Jan 2008
Posts: 105
Likes: 1
From: Issaquah, WA
I recently had a similar issue with my Ranger. I finally narrowed it down to a minor leak in the head gasket into the #5 cylinder (loss of 10 Psi compression and slight flash rust on spark plug) Not so much as to see the white smoke or even smell it - just a quart or so of coolant per week. Since the engine has 230+K miles, I decided to put in a can of copper based stop leak from Bar's Leak. No lost anti freeze for 6 months since.
Thread Starter
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Senior User
Joined: Jan 2008
Posts: 105
Likes: 1
From: Issaquah, WA
My lowest compression was 135 psi. The radiator tested negative for hydrocarbons. I still think there's a decent chance of having an issue with the head gasket, but I don't have any evidence to support that. This weekend I'll park the truck uphill and let the engine run with the radiator cap off until it the coolant level stabilizes.
Is there any other test that can be done to determine if the head gasket is bad? The only other thing I know of is getting the oil tested to see if there's coolant in it.