Coolant exiting my exhaust

[slowjoe]

120 Lehman when I start up I get coolant coming out exhaust .. just at startup it’s visible...at rest there is small amount that it’s lost in the expansion tank ... I removed exhaust elbow and I think it’s the gasket .. has anyone had this before ?

[timb]

Originally Posted by slowjoe

120 Lehman when I start up I get coolant coming out exhaust .. just at startup it’s visible...at rest there is small amount that it’s lost in the expansion tank ... I removed exhaust elbow and I think it’s the gasket .. has anyone had this before ?

it could be the heat exchanger and the raw water pushes it out at start up. Unless it is a dry exhaust

[O C Diver]

Hsve you pressure tested the coolant loop with a radiator tester to see if the heat exchanger is leaking?


Ted

[slowjoe]

I heard the heat exchanger has pressure the other way ... I would get raw water in my fresh system

[slowjoe]

There is a gasket behind the exhaust elbow that closes the fresh water in exhaust manifold from going in to elbow ..

[Xsbank]

How do you know there is coolant coming out the exhaust? That sounds improbable to me...

[Lepke]

Coolant is usually at 15 psi or more. Salt water is not really under pressure, but has a high flow rate. When the engine shuts down and coolant no longer circulates, the coolant next to the cylinders gets overheated and causes the pressure to rise at a time where there is zero pressure on the salt water side. So the common source for coolant in the exhaust is a small leak between the coolant and salt water in the heat exchanger. Typically it would be seen at startup.

[kchace]

Originally Posted by Lepke

Coolant is usually at 15 psi or more. Salt water is not really under pressure, but has a high flow rate. When the engine shuts down and coolant no longer circulates, the coolant next to the cylinders gets overheated and causes the pressure to rise at a time where there is zero pressure on the salt water side. So the common source for coolant in the exhaust is a small leak between the coolant and salt water in the heat exchanger. Typically it would be seen at startup.

[Xsbank]

I still want to know how you can see it?

[Simi 60]

Originally Posted by Xsbank

I still want to know how you can see it?

First time i roded out our heat exchanger i pinched the oring putting it back together.
Shot a load of bright green coolant out the exhaust on start.
Water for about 1 metre back was fluoro green.

[psneeld]

Lehman pressure caps are pretty low, 7psi or so IIRC.

But after sgutdown, the fresh water is still under pressure and the raw water isn't.

But which way would the leak go, I am not sure, or if it ultimately goes to both sides of the exchanger.

I replaced the gasket when I installed a new elbow, but not because of a leak.

[slowjoe]

I’m going to change the gasket behind the exhaust elbow which seemed bad and go from there

[Ski in NC]

Take zinc out of sea water side of heat exchanger and see if any coolant drips out once sea water finishes draining.

[slowjoe]

But what would that tell me .. I think my leak is before the exchanger..

[Ski in NC]

It would tell you if there is an internal leak in the heat exchanger.

[slowjoe]

I will be taking off the exchanger and sending it for cleaning and inspection..will let u no what happened... thanks everybody

[slowjoe]

Talked to AMD they said most probably is elbow gasket or leak in exchanger

[Tator]

Where did your leak turn out to be at?

Tator

[slowjoe]

I changed the elbow gasket & had my heat changer cleaned and tested ... all installed but waiting to put boat in water .. at least another month yet ... hopefully it should be fine ...can’t really be anything else ... I no head gasket is good .. what else is left ??

[what_barnacles]

Possible internal crack in the exhaust manifold from heat and corrosion. Also the gasket between the manifold and the elbow. Some manifolds allow for raw water cooling, and need to be blocked off when using coolant.