mercruiser 140 closed cooling system probelm

[bigblackcat]

So this 76 reinell i just got started has a closed cooling on a mercruiser 140. The boat has been sitting for
years. I recently got the boat to fire up after diagnosing crank no start problem. I put water in the resivior tank and
when the engine fired off, water came out of the exhaust/prop. I hadnt hooked up the hose to the lower unit at that
time. The engine ran for just a 5 seconds.
My question is, is this normal if its a closed system or is there a cracked manifold allowing water to get to the
exhaust side? Also should i use a special coolant?

 

[Bondo]

Re: mercruiser 140 closed cooling system probelm

Nope,... That ain't normal,.... 'course, neither is closed coolin' on a 3.0l....

Got some Pictures,..?? could be cracks in alota places, especially the heat exchanger...

Do a pressure test for starters...

Have ya replaced the impeller yet,..??

 

[bigblackcat]

Re: mercruiser 140 closed cooling system probelm

Well i took off the heat exchanger today and ran water in it to see if there were any internal leaks;none found. So
my thinking is that it could be the manifold??? Or could it have a bad head gasket or cracked head? The engine oil
looks clean and not milk shaked, but could there be a crack on the exhaust side and cause coolant to come out the
sterndrive exhaust? could I do a leak down test on each cylinder and pin point the problem?

 

[achris]

Re: mercruiser 140 closed cooling system probelm

Put the closed cooling system all back together and get a standard automotive radiator pressure tester.... pressure test the system and chase down the leaks as you would a car... Cylinder leak down test might also help, if the problem is a cracked head... But if it's the manifold or elbow gasket, that test will tell you nothing...

 

[Don S]

Re: mercruiser 140 closed cooling system probelm

If you still have the heat exchanger off, remove the end caps from the raw water side of the HE, block off the ports to the antifreeze side and pressurize the antifreeze side. Put it in a tub of water and see if you get bubble out of the raw water side. If no leaks, then put it back on and test as Chris recommends.

 

[bigblackcat]

Re: mercruiser 140 closed cooling system probelm

well I took off the intake/exhaust manifold and found to have coolant on the exhaust ports. Is this normal?

 

[achris]

Re: mercruiser 140 closed cooling system probelm

well I took off the intake/exhaust manifold and found to have coolant on the exhaust ports. Is this normal?

No. Sounds like maybe a hole in the manifold somewhere???....

 

[bigblackcat]

Re: mercruiser 140 closed cooling system probelm

Can someone explain the water flow circulation
On this engine, or is there a diagram that someone
can share?

 

[Fishermark]

Re: mercruiser 140 closed cooling system probelm

Are you sure you have a 140 (3 liter) and not a 170 or 470?

 

[Don S]

Re: mercruiser 140 closed cooling system probelm

When you are around salt water, closed cooling is quite common on 3.0L engines.

This diagram shows how it works.

 

[bigblackcat]

Re: mercruiser 140 closed cooling system probelm

got home today after work and pressure tested the heat exchanger and found no leaks. poured fresh water into the coolant side of the exhaust manifold and found no leaks. Removed the valve cover and inspected for residual coolant sitting in the rockers; none found. In
fact the upper end looks very clean, almost new. Oh and I'm starting to wonder if this engine is a 140??
the serial number I found is #4462913. Could it be a 120????

 

[bigblackcat]

Re: mercruiser 140 closed cooling system probelm

Okay I found something!!!! Upon looking at the riser on the manifold i found a large 2 inch hairline crack on it. Could there be a
larger internal crack causing coolant to come out of the stern exhaust???? God I hope so...

 

[bigblackcat]

Re: mercruiser 140 closed cooling system probelm

Got the manifold off and separated the riser from the mount plate. Found that the water passages where
plugged up with rust, also found that the water passages though the mounting plate was plugged with a
hard plastic substance. Also the gasket under the plate covered the
water passage to the manifold. I'm assuming it is not supposed to be
this way. Any thoughts?

 

[achris]

Re: mercruiser 140 closed cooling system probelm

You have closed cooling, that gasket is there to close the end of the manifold off... It's a special gasket, and needs to be replaced with the right one... If you have the genuine manual you can go to the cooling system section and have a look at the water flow diagrams....

Chris......

 

[bigblackcat]

Re: mercruiser 140 closed cooling system probelm

Thanks. But I have no manual.

 

[Don S]

Re: mercruiser 140 closed cooling system probelm

Thanks. But I have no manual.

You do now, click here

 

[tormrod]

Re: mercruiser 140 closed cooling system probelm

I have this same issue with my 140 closed cooling. Rust and corrosion everywhere but fortunately no holes. Just had to replace the end cap on the exhaust manifold. Thanks for the pic of the cooling system and the Mercruiser manual. Great help.