1987 merc cruiser 170hp 4 cylinder coolant leak

[southwest395]

Hi everyone. My name is jason new to the merc 170 hp motors. The problem iam having is. When i fill up my coolant resivor my coolant drips out my outdrive as soon as i poor it in. Now if i run the motor it blows it out. I know the impeller is bad on the lower unit. Does that affect he coolant leak. I pulled the cap of my 4" heat excahnger and it lost a gallon of coolant. I checked to see if its missing with the oil its not. Its not leaking anywhere in my hull from like hoses or gasket. Just out my outdrive from what i can see. Any idea anyone or is going to be a nightmare

 

[fmalott]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

there is only suppose to be raw water pumping out your outdrive regardless if the impeller is good or bad. i'm not an expert but you will get help from them. i would take a wild guess and say your heat exchanger has a leak, the antifreeze goes threw tubes in the exhanger and gets cooled from the raw water surrounding the tubes then the raw water gets pumped back out the outdrive and the antifreeze just circulates in the motor from the water pump

 

[southwest395]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

there is only suppose to be raw water pumping out your outdrive regardless if the impeller is good or bad. i'm not an expert but you will get help from them. i would take a wild guess and say your heat exchanger has a leak, the antifreeze goes threw tubes in the exhanger and gets cooled from the raw water surrounding the tubes then the raw water gets pumped back out the outdrive and the antifreeze just circulates in the motor from the water pump

so if I understand this correct. The tubes are what suppose to hold the coolant. And the cylinder that holdes the tubes are suppose to be fresh water

 

[achris]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

The other possibility is that you have a bad exhaust elbow or its separator plate gaskets. You need to remove the elbow and check it. If it's ok, then replace it, with a new gaskets and pressure test the system to see where the communication between the closed and seawater cooling system is... Here's a flow diagram to help you....

Chris..........

 

[southwest395]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

The other possibility is that you have a bad exhaust elbow or its separator plate gaskets. You need to remove the elbow and check it. If it's ok, then replace it, with a new gaskets and pressure test the system to see where the communication between the closed and seawater cooling system is... Here's a flow diagram to help you....

Chris..........

I think the exhaust billow and gasket would make more sence to replace first. Cause when i pulled the cover plate off the heat exchanger it dump a gallon of radiator fluid in the hull of my boat. If if the motor is runing or not it was driping out the the outdrive. When its runing it blows it out the outdrive with amater 3 mins after i fill the resvior up.

 

[achris]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

If you drop the caps off the heater exchanger and got coolant come out, it's the heat exchanger. The cavities covered by the caps should only contain seawater....

 

[southwest395]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

If you drop the caps off the heater exchanger and got coolant come out, it's the heat exchanger. The cavities covered by the caps should only contain seawater....

i only drop the front cap with gasket. It draind nothing but coolant. so that would be the heat exchanger bad then. instead of the seperator gasket. when i first bought boat it was full and ran it when i bought then. it sat for two months ran it again and again. The coolants was still full then just recent it started to drip out the outdrive why it was just siting there

 

[achris]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

Remove the heat exchanger and have it checked and repaired by a normal radiator shop. Then, when that's done and the exchanger back in place, pressure test the whole system.

 

[fmalott]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

If you drop the caps off the heater exchanger and got coolant come out, it's the heat exchanger. The cavities covered by the caps should only contain seawater....

my thought exactly

 

[southwest395]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

my thought exactly

Is there away to pressure test it at home. New to NY dont know a radiator repair shop is here. So the heat exchanger is not suppose to have coolant at all.

 

[achris]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

Yes it is, but only around the outside of the tubes, not in the end caps... You have a tube leaking or a cracked weldment.... You don't need to pressure test it, it's leaking! Use the internet or a phone book and find a radiator shop...

 

[southwest395]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

Yes it is, but only around the outside of the tubes, not in the end caps... You have a tube leaking or a cracked weldment.... You don't need to pressure test it, it's leaking! Use the internet or a phone book and find a radiator shop...

ok so how does a heat exchanger work. what part of it gets coolant and what part does get coolant in a heat exchanger

 

[RogersJetboat454]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

ok so how does a heat exchanger work. what part of it gets coolant and what part does get coolant in a heat exchanger

Take a look at the picture achris posted. The unshaded or white arrows is the raw water coming in from the drive, going through the exchanger, and back out the exhaust. The shaded, or black arrows are the coolant, and the places it flows. The heat exchanger works like the radiator in your car, only instead of air cooling down the coolant, cold raw water from the outside is cooling down the coolant. Hence why it's a problem to have a busted impeller in your outdrive. The coolant and water in the exchanger are separated by a series of sealed tubes to prevent the two from mixing as each respective liquid flows through the cooler. If there is a break in the system, coolant can enter the water, or water can enter the coolant.

 

[achris]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

ok so how does a heat exchanger work. ...

Just like a radiator in a car. The water inside the radiator gets hot from cooling the engine and the air flowing through it cools the water.
A marine heat exchanger has engine coolant flowing around the outside of the internal tubes and seawater (in place of the air) flowing through the those internal tubes.

Why all the questions? Your heat exchanger is faulty, get it fixed....

 

[southwest395]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

Just like a radiator in a car. The water inside the radiator gets hot from cooling the engine and the air flowing through it cools the water.
A marine heat exchanger has engine coolant flowing around the outside of the internal tubes and seawater (in place of the air) flowing through the those internal tubes.

Why all the questions? Your heat exchanger is faulty, get it fixed....

it is geting fixed. just didnt understand what part of it got coolant and what part got water. iam new to coolant cooled motors

 

[achris]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

.... iam new to coolant cooled motors

Worked on cars? They are all 'coolant cooled engines'...

 

[RogersJetboat454]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

Worked on cars? They are all 'coolant cooled engines'...

Maybe he's a air cooled guy who's exclusive to old VW's and Corvairs?

 

[stonyloam]

Re: 1987 merc cruiser 170hp 4 cylinder coolant leak

so if I understand this correct. The tubes are what suppose to hold the coolant. And the cylinder that holdes the tubes are suppose to be fresh water

That is exactly WRONG! The raw water flows through the tubes and the coolant (antifreeze) flows around the tubes inside the jacket. When you remove the end cap, ONLY RAW WATER should come out. If antifreeze comes out you have a leak between the coolant side and the raw water side.
Like this, the green is the raw water and the lt blue is the antifreeze: http://en.wikipedia.org/wiki/Shell_and_tube_heat_exchanger yours is actually a three pass exchanger, where the water goes back and forth 3 times, the cold water enters the front tube and exits the rear tube.