1998 5.7 Vortec lower intake manifold leaking coolant after the gaskets were replaced.

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1998_K1500_Sub

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The specs for the last of of the 3rd torqueing the bolts are 12lb.

Were they torqued with a suitable wrench? With a 12lbft specification, I would use an appropriately rated torque wrench, e.g., 20-200lbin, to do the job. Note that 12lbft = 144lbin.

For comparison, I wouldn't use a wrench rated for 10-75lbft.
 

SAATR

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the truck is parked up hill, the anti freeze is running down the joint of the head and intake to the back of the engine. I would assume while driving the wind blows it to the back of the engine, the back side of the trans. starter are wet..

Absolutely, because that is the lowest resistance path to the ground. You have coolant around the head of the bolt, and what could be a little bit of coolant on the boss that the heater quick connect fitting screws into. I'm asking if you are absolutely, positively sure that the coolant isn't running down from the heater quick connect threads or from the area around the intake bolt, and then following the channel between the head and intake manifold to the rear of the engine? Those two possible leak paths are much easier to test, and to repair, than pulling the intake manifold again.
 

Wilecoyote

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Absolutely, because that is the lowest resistance path to the ground. You have coolant around the head of the bolt, and what could be a little bit of coolant on the boss that the heater quick connect fitting screws into. I'm asking if you are absolutely, positively sure that the coolant isn't running down from the heater quick connect threads or from the area around the intake bolt, and then following the channel between the head and intake manifold to the rear of the engine? Those two possible leak paths are much easier to test, and to repair, than pulling the intake manifold again.
The truck has been sitting since I found out it was leaking. Last night after work I looked at it w flashlight and felt the threads on the connector it was dry reached under the boss in the intake and it was wet. Looked at the tape on the threads and saw about 1/2" tape above the boss. This morning I turned the connector 3 whole turns and fired it up before I took shower. Came back out bout 20 mins later and it was hot and dry. Apperantly the connector was only hand tight and not snugged down. Drove to work and it's still dry.
 
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SAATR

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The truck has been sitting since I found out it was leaking. Last night after work I looked at it w flashlight and felt the threads on the connector it was dry reached under to boss in the intake and it was wet. Looked at the tape on the threads and saw about 1/2" above the boss. This morning I turned the connector 3 whole turns and fired it up before I took shower. Came back out bout 20 mins later and it was hot and dry. Apperantly the connector was only hand tight and not snugged down. Drove to work and it's still dry.

Glad to hear it was an easy fix.
 

Frank Enstein

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The truck has been sitting since I found out it was leaking. Last night after work I looked at it w flashlight and felt the threads on the connector it was dry reached under to boss in the intake and it was wet. Looked at the tape on the threads and saw about 1/2" above the boss. This morning I turned the connector 3 whole turns and fired it up before I took shower. Came back out bout 20 mins later and it was hot and dry. Apperantly the connector was only hand tight and not snugged down. Drove to work and it's still dry.
Woo Hoo! Easy and cheap fix!
 

TylerG

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Absolutely, because that is the lowest resistance path to the ground. You have coolant around the head of the bolt, and what could be a little bit of coolant on the boss that the heater quick connect fitting screws into. I'm asking if you are absolutely, positively sure that the coolant isn't running down from the heater quick connect threads or from the area around the intake bolt, and then following the channel between the head and intake manifold to the rear of the engine? Those two possible leak paths are much easier to test, and to repair, than pulling the intake manifold again.
I’ve got the same problem on my 98 5.7 vortec. I just rebuilt the engine 12 months ago and installed the Fel-pro lower inlet manifold gasket. My machinist checked the intake manifold for cracks and flatness. I closely followed the three step torque procedure with loc-tite on the threads.

I noticed a small drop in coolant a few months ago and found it dripping off the starter, transmission cooler lines and transmission bell housing. Also some drips on the passenger side motor mount.

I found leaks around the thermostat housing and replaced the housing and thermostat. Also found a leaking clamp on the heater coil hose at the water pump. No more leaks there. (The heater hose connection had also leaked right after the rebuild and I immediately cemented it in place. Definitely no visible leaks there.)

However, I just put a radiator tester on at 13 psi and see a small leak at the lower intake manifold between the front two bolts on the passenger side. Makes sense, since the coolant would run along the channel and down the back of the engine. The pressure tester drops to 12 psi and stays steady for over 3 hours.

Can I loosen, reseal and retorque the front two bolts, or do I need to pull and reinstall the entire intake manifold? (I don’t remember if I used my 20-150 in-lb or 10-150 ft-lb wrench for the third pass, but knew the smaller would be more accurate.)
 

SAATR

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I’ve got the same problem on my 98 5.7 vortec. I just rebuilt the engine 12 months ago and installed the Fel-pro lower inlet manifold gasket. My machinist checked the intake manifold for cracks and flatness. I closely followed the three step torque procedure with loc-tite on the threads.

I noticed a small drop in coolant a few months ago and found it dripping off the starter, transmission cooler lines and transmission bell housing. Also some drips on the passenger side motor mount.

I found leaks around the thermostat housing and replaced the housing and thermostat. Also found a leaking clamp on the heater coil hose at the water pump. No more leaks there. (The heater hose connection had also leaked right after the rebuild and I immediately cemented it in place. Definitely no visible leaks there.)

However, I just put a radiator tester on at 13 psi and see a small leak at the lower intake manifold between the front two bolts on the passenger side. Makes sense, since the coolant would run along the channel and down the back of the engine. The pressure tester drops to 12 psi and stays steady for over 3 hours.

Can I loosen, reseal and retorque the front two bolts, or do I need to pull and reinstall the entire intake manifold? (I don’t remember if I used my 20-150 in-lb or 10-150 ft-lb wrench for the third pass, but knew the smaller would be more accurate.)
You'll want to drain the coolant out of the truck first, but you can absolutely pull and reseal those bolts without pulling the manifold.
 
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