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  #1  
Old 10-20-2010, 06:57 PM
73tomsawyer 73tomsawyer is offline
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Water in oil - How do you test for an internally cracked engine block. GM straight 6

My straight 6 runs good, but I am getting water in the engine oil. How do I check for leaks in the block?
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  #2  
Old 10-20-2010, 07:45 PM
wardd wardd is offline
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pressurize the cylinders?
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Old 10-20-2010, 09:34 PM
73tomsawyer 73tomsawyer is offline
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I checked the pressure of the cylinders all around 150, which I believe is right on with the age of engine. Specifically the engine is a 1973 GM 4.1 liter straight 6. Used in Chevy C-10 trucks.
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Old 10-20-2010, 10:10 PM
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troy2000 troy2000 is offline
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A more likely culprit is your head gasket; that's a lot more common than a cracked head or block.

It also might just be condensation, especially if you make short trips -- or if your scavenger hose is blocked.
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Old 10-21-2010, 11:11 AM
73tomsawyer 73tomsawyer is offline
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I have replaced the cylinder head and head gasket with brand new ones.
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Old 10-21-2010, 02:58 PM
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If you have an oil cooler check it too.

Dino
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Old 10-21-2010, 05:18 PM
73tomsawyer 73tomsawyer is offline
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I am almost positive this engine does not have an oil cooler, although I am not exactly sure what you would be describing. I can check if you can tell me where to look. Thanks for the ideas guys, hope to hear more!
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Old 10-21-2010, 09:35 PM
Petros Petros is offline
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There is a dye you can get to put in the water to see if and where it is leaking. If it is coolant getting in your oil than you will see the dye in the water mixed with the oil. Check with auto parts stores, perhaps NAPA, might have such a dye.

You also might put some stop-leak in the coolant, it will fix, at least temporarily, and small cracks or leaky gaskets that allow coolant into the oil. The stop-leak is cheap and will not harm the engine. It will tell you if it is indeed coolant getting into the oil, or just condensation.
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  #9  
Old 10-22-2010, 03:04 AM
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pistnbroke pistnbroke is offline
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bring each cylinder up to TDC and apply compressed air to the plug hole via an adaptor.. if you have leakage into the water jacket you will get bubbles in the water /water loss ....if its leakage from a water gallery to a oilway its most likley its in the head gasket ...was this a problem before you did the head gasket??
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Old 10-22-2010, 04:24 AM
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gonzo gonzo is offline
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You are needing to pressure the the water jacket and not the cylinders. Plug the the water hoses (inlets and outlets) Use a plumbing pressure test setup, which is a tire type air valve and a pressure gauge. If the pressure goes down there is a leak.
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  #11  
Old 01-22-2011, 03:15 PM
73tomsawyer 73tomsawyer is offline
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*THE BLOCK IS CRACKED*

The engine runs decently, but does take on about 4 quarts of water in 3 hours of boating. How long do you think I can run it pulling skiers and such? I have a short stretch of river and could go upstream in a small area and be pretty safe with engine failure.

Previously I was changing the oil every run, which is horrible for the environment, and not something I can live with. If I filled the engine with fresh oil once, and ran it until it died, I think I could get the most out of it.

As posted earlier, I did install a brand new cylinder head so it could possibly be worth parting out instead. What would most likely be the first failure? Am I in any danger of a fire (the engine always ran fairly cool)? Does anyone have experience with running an engine with these problems until their just ain't nothing left? Thanks in advance, and your help is much appreciated to a young gun who will carry this knowledge and pass on the joy of tooling and boating.
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Old 01-22-2011, 09:00 PM
Capt Ram Capt Ram is offline
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4 quarts in 3 hours says your lucky to go 1 mile-
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  #13  
Old 01-23-2011, 08:53 AM
WickedGood
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I had that same Sraight Six in a 71 Chevy pickup truck.

Ran it over 500,000 miles.

I would say that the engine has given more than its lifespan and you can go pick up a Chevy 350 at a junkyard for a couple hundred bucks and just swap out the engine if the boats in good condition.

dont bother trying to get a chevy V6 as they were junk.


a Jeep straight 6, 4.0 ltr would be perfect
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  #14  
Old 01-23-2011, 09:12 AM
mark775
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"The Joy of Tooling And Boating"

- Chapter one
"running an engine with these problems until their just ain't nothing left"
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  #15  
Old 01-23-2011, 11:10 AM
73tomsawyer 73tomsawyer is offline
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Do I risk doing damage to the cylinder head? I have thought about a new block from a junkyard.A couple hundred dollars ain't bad. I would want it rebuilt if I wanted it to last for longer than just trying to sell the boat off. I guess that would cost me too. BTW how would you go about removing an engine block from a junkyard, just start wrenching and throwing **** in the truck bed? Then get a dolly or fork truck and lift it out?
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