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350 mag mpi rebuild antifreeze dumping into oil pan

tobyyost

New member
Hi all. I just finished a rebuild on a 350 mag mpi. Block was cracked so found a machine shop that had extra 880 blocks. I took them everything to check out and got the new block back bored 30 over. Had them check intake and all the manifolds and risers and they said all looked good. Keep in mind that the engine ran just fine. But the block was cracked on the exterior. Was not even any signs of water in the oil. While out I also installed a freshwater cooling system a mfh-5320. Just put engine back in boat and began filling the heat exchanger. It took over 3 gallons of antifreeze which I thought was odd. I then ran out. So I figured I had enough in to try to turn the engine over. Before I did I checked the oil again and the oil was all of a sudden way high. So I sucked some out and sure enough all that antifreeze went straight into the oil pan. Any idea how this could be happening? Either I or the machine shop missed something dramatic for all that antifreeze to flow right into the oil pan in literally a few minutes. I’m not sure where to start to try to track this down so any advice would be greatly appreciated. Thanks.
 
Prior to installation the machine shop checked the intake and I also did right at the time I put it on. Did not see any issues. Everything matched up on the head gasket and intake gasket. Now even if there was a problem with a gasket I doubt it would leak this fast. Does anyone have any ideas on how I could try to do some tests to see where the leak is coming from prior to just tearing everything apart? I’m certain I’ll have to tear some stuff apart but would like to go into this with some sort of plan to try to keep the redo minimal. Any thoughts are appreciated. Thanks.
 
You need to drain the oil thoroughly then fill the motor with water and pressurize the block with air. If the block is cracked--probably--you'll see right away.

Good luck.

Jeff
 
As Fastjeff suggests,

Get a hold of a radiator pressure checker and see if you can pressurize the system to determine leak location.

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If the AF drops that fast into the oil pan I dont think pressurizing will help.
Pull the therm housing and fill intake with water, should hold water
Pull the intake and inspect it again with the gaskets.
With the intake off you can introduce water directly into the heads

If you still cant hold a water level then suspect a cracked block
 
I can't seem to upload the pictures or video that I have, but after removing the distributor and putting a scope in, it seems like I am getting water running for all 4 corners of my head gasket. Wish I could figure out how to upload the pics, but if your familiar with a 350, you know how the head gaskets have those two raised points on each side, it looks like the water is running out of there, but with no water running, you don't physically see any gaps. Is it running down from intake maybe and just looking like it is coming out of there? Any thoughts? or directions on how to upload the pics?
 
head gaskets have no raised points, thre flat. or do you mean intake gaskets, Doubt you can actually see the head gasket corners
 
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[FONT=&quot]So I took the intake manifold off and to my surprise I am not seeing any issue with it or the gasket. So I started filling a hose with water and sure enough the leak appears between the head and block almost like it’s coming out where the gasket is. Happening on all 4 corners even when just pouring water down the head ports. Has to be cracked heads now wouldn’t you think? From talking to the machine shop the other day sounds like they didn’t pressure test them. Isn’t that a normal part of the process to pressure test the heads? Especially when they knew the block was cracked. Just getting disgusted here. If I would have known all this I would have just got a new long block. Any thoughts / recommendations at this point. [/FONT]
 
Yep. Was the wrong head gasket. Stupid mistake on my end. I even looked them over good prior to install. But there was a little spot in each corner that wasn’t right and it allowed the water to just run right down. Thank you all foryour help with this.
 
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