Internal intake/coolant leak?
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Joined: Dec 2004
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Internal intake/coolant leak?
Hi All,
I've done a search on this, but I wanted to run my particular circumstances by you all.
1985 Coupe, Z51, 160,000 miles.
It's been losing about 2-3 pints of coolant per day since I cleaned the throttle body and IAC a week ago. It's pulling it out of the overflow tank when cold, and not overflowing it when hot. The radiator was a little wet around the bottom (I'll replace it this weekend) but not enough to account for the amount I'm losing. A little bit of white vapor from the exhaust, both banks, upon initial startup when cold, but it goes away in a minute or two. Pulled the plugs, and 7 of them looked ok, a light tan/brown. Number 7 was squeaky clean-hmmmm.
The car runs great, the oil is clean and not milky.
Yesterday morning on cold startup, a lifter was clattering loudly as if it wasn't pumped up, and continued to do so for about 3 minutes, despite 60 pounds of oil pressure, then the racket calmed down. Did the same thing when I started up after work 11 hours later, so I stopped and dumped some Valve Medic snake oil in it. This morning, the lifter clattered again, and again after work, for the same amount of time.
A friend said he had the same thing happen with his van, seems that his mechanic found an intake manifold gasket leak that allowed some coolant to get into the combustion chamber, and to also "wash out" a lifter, causing it to clatter like mine, for the same period of time.
I'm thinking that I'll replace the intake gaskets this weekend, and take a chance that the head gaskets are ok.
Any thoughts?
Many thanks in advance!
Mark
I've done a search on this, but I wanted to run my particular circumstances by you all.
1985 Coupe, Z51, 160,000 miles.
It's been losing about 2-3 pints of coolant per day since I cleaned the throttle body and IAC a week ago. It's pulling it out of the overflow tank when cold, and not overflowing it when hot. The radiator was a little wet around the bottom (I'll replace it this weekend) but not enough to account for the amount I'm losing. A little bit of white vapor from the exhaust, both banks, upon initial startup when cold, but it goes away in a minute or two. Pulled the plugs, and 7 of them looked ok, a light tan/brown. Number 7 was squeaky clean-hmmmm.
The car runs great, the oil is clean and not milky.
Yesterday morning on cold startup, a lifter was clattering loudly as if it wasn't pumped up, and continued to do so for about 3 minutes, despite 60 pounds of oil pressure, then the racket calmed down. Did the same thing when I started up after work 11 hours later, so I stopped and dumped some Valve Medic snake oil in it. This morning, the lifter clattered again, and again after work, for the same amount of time.
A friend said he had the same thing happen with his van, seems that his mechanic found an intake manifold gasket leak that allowed some coolant to get into the combustion chamber, and to also "wash out" a lifter, causing it to clatter like mine, for the same period of time.
I'm thinking that I'll replace the intake gaskets this weekend, and take a chance that the head gaskets are ok.
Any thoughts?
Many thanks in advance!
Mark
Drifting
Joined: May 2008
Posts: 1,694
Likes: 490
From: Denver, NC
Hi All,
I've done a search on this, but I wanted to run my particular circumstances by you all.
1985 Coupe, Z51, 160,000 miles.
It's been losing about 2-3 pints of coolant per day since I cleaned the throttle body and IAC a week ago. It's pulling it out of the overflow tank when cold, and not overflowing it when hot. The radiator was a little wet around the bottom (I'll replace it this weekend) but not enough to account for the amount I'm losing. A little bit of white vapor from the exhaust, both banks, upon initial startup when cold, but it goes away in a minute or two. Pulled the plugs, and 7 of them looked ok, a light tan/brown. Number 7 was squeaky clean-hmmmm.
The car runs great, the oil is clean and not milky.
Yesterday morning on cold startup, a lifter was clattering loudly as if it wasn't pumped up, and continued to do so for about 3 minutes, despite 60 pounds of oil pressure, then the racket calmed down. Did the same thing when I started up after work 11 hours later, so I stopped and dumped some Valve Medic snake oil in it. This morning, the lifter clattered again, and again after work, for the same amount of time.
A friend said he had the same thing happen with his van, seems that his mechanic found an intake manifold gasket leak that allowed some coolant to get into the combustion chamber, and to also "wash out" a lifter, causing it to clatter like mine, for the same period of time.
I'm thinking that I'll replace the intake gaskets this weekend, and take a chance that the head gaskets are ok.
Any thoughts?
Many thanks in advance!
Mark
I've done a search on this, but I wanted to run my particular circumstances by you all.
1985 Coupe, Z51, 160,000 miles.
It's been losing about 2-3 pints of coolant per day since I cleaned the throttle body and IAC a week ago. It's pulling it out of the overflow tank when cold, and not overflowing it when hot. The radiator was a little wet around the bottom (I'll replace it this weekend) but not enough to account for the amount I'm losing. A little bit of white vapor from the exhaust, both banks, upon initial startup when cold, but it goes away in a minute or two. Pulled the plugs, and 7 of them looked ok, a light tan/brown. Number 7 was squeaky clean-hmmmm.
The car runs great, the oil is clean and not milky.
Yesterday morning on cold startup, a lifter was clattering loudly as if it wasn't pumped up, and continued to do so for about 3 minutes, despite 60 pounds of oil pressure, then the racket calmed down. Did the same thing when I started up after work 11 hours later, so I stopped and dumped some Valve Medic snake oil in it. This morning, the lifter clattered again, and again after work, for the same amount of time.
A friend said he had the same thing happen with his van, seems that his mechanic found an intake manifold gasket leak that allowed some coolant to get into the combustion chamber, and to also "wash out" a lifter, causing it to clatter like mine, for the same period of time.
I'm thinking that I'll replace the intake gaskets this weekend, and take a chance that the head gaskets are ok.
Any thoughts?
Many thanks in advance!
Mark
Before you start guessing at gaskets, do a compression and leakdown test. If you have low compression in the cylinder with the clean plug you may have a coolant leak between the cylinder and the coolant via the head gasket. A leakdown test will tell you if it is the head gasket because the air pressure will escape into the coolant and bubble in the radiator.
You could also pressure test the cooling system. If the pressure keeps dropping, you have a leak. If you don't see the leak externally, it is internal.
You should repair all known leaks and check all hose connections prior to motor disassembly if possible in order to properly diagnose.
A coolant leak into the intake will not show up when pressurizing the cylinder because it is in the intake before the cylinder.
