Coolant being replaced by sea water?

[hamishmcduff]

165hp inline 6 with san juan heat exchanger.

I had noticed my temps slowly getting higher and higher at cruising speed over an extended period of time.
at one point it had reached 190*+.
I replaced the impeller and its housing and my mechanic replaced a seal at the top of the water tube.
Temps suddenly dropped to 160ish at cruise, has never run better.
Started to notice a blackish water in the coolant overflow tank?
decided to drain the coolant and replace with new.
Fluid that came out was not 50/50 mixed coolant.
Replaced anyway with new mixture.
Next trip out the temp rises back up to 190ish after about 45 min.
coolant overflow tank is overflowing into bilge with hot fluid.
It would return to 160+ at idle but I could only get it on plane and sustain it for 20 min before the temp would shoot up again.
Checked the fluid in the system and it was sea water again?
Could this be the heat exchanger?
I could use some direction on where to start on this matter, my year for boating is finished now, and I would like to get things in order for next year.

 

[tpenfield]

Re: Coolant being replaced by sea water?

Yes, time to do a pressure test of the cooling system. clearly, there is a leak of some sort, now it is time to find it.

 

[Don S]

Re: Coolant being replaced by sea water?

Could this be the heat exchanger?

Absolutely, that is the only place the coolant and sea water meet.

 

[FreeBeeTony]

Re: Coolant being replaced by sea water?

Could also be the gasket between the manifold and elbow..........if it's a full system.

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

Could also be the gasket between the manifold and elbow..........if it's a full system.

I was told this was a possibility but that it would be highly irregular.
I will start at the heat exchanger and go from there.

But now that my season is over I will do a compression check on the engine and see if it's time to rebuild and if so I will replace the elbow and any sketchy components.

Thanks for the guidance everyone.

 

[FreeBeeTony]

Re: Coolant being replaced by sea water?

I had the exact problem w/ my V8 and found I installed the wrong gaskets between the elbows and manifolds, I had salt water in the overflow. Originally thought it was th H/E.......just because the fresh water side doesn't hold presure doesn't neccessarily point to the H/E!!

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

Well I am thinking about removing it and replacing it anyway, so I'll share the results.
But I would like to know how to pressure test the heat exchanger?
What is the recommended max pressure to the heat exchanger anyways?
I am thinking about pressurizing the raw water side and observing the leak down time.
But I would need a setpoint to start from.

 

[stonyloam]

Re: Coolant being replaced by sea water?

It seems that you have an unusual problem here, under normal conditions the system is pressurized and if you had a leak in the exchanger you would expect the coolant to leak out, rather than the raw water leaking in. It probably has a 14psi radiator cap on the system. You can borrow a cooling system pressure test kit from Autozone.

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

It seems that you have an unusual problem here, under normal conditions the system is pressurized and if you had a leak in the exchanger you would expect the coolant to leak out, rather than the raw water leaking in. It probably has a 14psi radiator cap on the system. You can borrow a cooling system pressure test kit from Autozone.

You're right it is a 14psi cap.
But how much pressure does that impellor produce?
I had the whole unit replaced top,bottom,seals and impellor could it provide enough pressure to force it's way into the closed system?
Basically it "looks" like it displaced all the cooling fluid into the overflow tank and into the bilge.
The closed side was filled to the top with sea water?
If it could produce more than 14psi and push its way into the closed side then that could explain the reservoir and bilge being full of an unknown liquid.

And 1 question still baffles me? How did it overheat?
Either way I will first be looking at testing that heat exchanger.
I would love to know how much pressure it is capable or designed to handle.
It is a San Juan unit and I cannot get any info on it.
Does any one know?

 

[stonyloam]

Re: Coolant being replaced by sea water?

IMHO there is no way that the impeller SHOULD produce that much pressure, after all the raw water just flows through the system, and there should be no restriction, so should be very little backpressure. Have to think about it some LOL.

 

[stonyloam]

Re: Coolant being replaced by sea water?

Normally the engine coolant will flow throughout the engine then through the internal tubes in the exchanger be cooled by the raw water flowing around the exchanger tubes. The coolant side should be pressurized and if the exchanger tubes failed the coolant would leak out, not raw water in. So is there any chance that the exchanger hoses could have gotten mixed up? In other words the raw inlet on the coolant inlet, and visa versa? That would account for the raw water in the engine and the overheating, because that would restrict the coolant flow. I would suggest that you very carefully check and make sure the engine coolant and raw water hoses on the exchanger are hooked up properly. All I can think of except for a complete failure of the exchanger internally.

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

I would suggest that you very carefully check and make sure the engine coolant and raw water hoses on the exchanger are hooked up properly. All I can think of except for a complete failure of the exchanger internally.[/QUOTE]

The hose sizes are completely different, and I took pics with my cell phone before I disassembled the system.

 

[stonyloam]

Re: Coolant being replaced by sea water?

Yeah I kind of thought it was a long shot. If the raw water exits the exchanger directly to the exhaust, then I guess the only thing left is a major failure of the exchanger internally. Time to pull it and have it checked out.

 

[FreeBeeTony]

Re: Coolant being replaced by sea water?

Is it a full system?
Is the manifold included in the FWC'd side?

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

Is it a full system?
Is the manifold included in the FWC'd side?

I don't know what that means?
I have a heat exchanger that takes in raw water and it exits out into the elbow above the exhaust.

The only manifold I can think of is the intake manifold where the engine coolant circulates through.
Is this what you are talking about?
please elaborate for me.

 

[Technorunner]

Re: Coolant being replaced by sea water?

A little thought here. I mabye ovetthinking this one. If the H/E is leaking the coolant would be leaking out into the seawaterside of the H/E. When you start the engine there might be to little coolant in the engine making the internal water pump draw seawater in until it starts building pressure again. Then it would leak out and draw new water in if this is the case it would go in cycles. The coolant would then be replaced by seawater. But as i stated in the begining i may be over thinking this one. Easiest to do a pressure test.You dont need that much pressure to see ( or hear) the leakage. 10 psi would probably enough!

 

[FreeBeeTony]

Re: Coolant being replaced by sea water?

Would it be possible for you to post some pics?
Might make things alot easier to describe......

 

[twiggy2cents]

Re: Coolant being replaced by sea water?

So if it wasnt spewing coolant before but is now, I would think you had an air pocket trapped in the block from when you drained the coolant. Did you do anything to purge the air from the system when you changed the coolant?

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

So if it wasnt spewing coolant before but is now, I would think you had an air pocket trapped in the block from when you drained the coolant. Did you do anything to purge the air from the system when you changed the coolant?

Actually no I didn't.
I ran it on the muffs and then checked it the next day and topped up the level.

 

[twiggy2cents]

Re: Coolant being replaced by sea water?

Air easily gets trapped in the block due to the thermostat and if you dont let it out it will over heat and also air expands more than liquid does from heat, so that can cause your burp of coolant out the cap. Also I dont know how old your boat is but normal green coolant is 30,000 miles, I dont know hour use but I know that it gets grody looking when it is time to be changed due to it picking up aluminum and steel partilcles in the cooling system over its life.