Crusader 6.1 coolant loss mystery

[JohnEasley]

Good Morning,

I'm hoping the experienced minds here can come up with some ideas. He's what's happening and what we did for diagnostics.

My friend has a 2006 36' Silverton with Crusader 6.1 engines. He's had it about a year and a half. At first, it would run fine on multi-day trips. In the last few months, the port engine started running hot on the second or third day. Each time the temp alarm went off, he would check the coolant reservoir and find it empty so he would top it up with coolant and it would be fine for another day or two. Yesterday, we attempted to track down the leak.

Armed with a pressure tester, we topped up the coolant tank using a two-cup measuring cup. It took two of these to top it up. As soon as we applied pressure using the tester, the coolant tank was dry again. Refill, repeat, dry again. Repeat, repeat, repeat. The tester would pump up to 15-17 psi but wouldn't hold it. It would slowly start to leak down. Within a couple of minutes, it would be down to 10 psi.

Over the span of a couple of hours, we probably poured close to three gallons into the reservoir tank. We never found any leaks around any hose fittings, the thermostat housing, the gaskets on the manifolds, spacers, or risers. We took the end cap off of the heat exchanger and pressurized the system again but nothing dripped out. We removed the exhaust hoses coming from the risers and pressurized the system, no drips. However, by listening closely, we could hear what can only be described as gurgling coming from the exhaust opening of the risers.

The engine starts easily and runs smoothly. There is no excess fluid in the crankcase and the oil is not milky or foamy. There is no sheen on the water near the exhaust when that engine is running; however, the owner reports what appears to be a small amount of steam from that exhaust when running at temperature.

We know a lot about where there is not a leak but we have yet to definitively identify where all of that coolant is going.

Anyone run into this before? What did it turn out to be? Any suggestions or ideas would be greatly appreciated.

Thanks,

John

 

[sunchaser]

How long since the risers were changed out? They are throw away items every 5 to 7 years. Mercruisers fail a bit earlier than Crusaders.

 

[tiltrider1]

Risers typically handle raw water, when they fail the engine gets hydrolocked. Exhaust manifolds are typically fresh water cooled and there is a block off plate between them and the riser that could have failed but not likely. This just leaves the heat exchanger with the coolant possibly filling up the raw water system. Pull the raw water hoses off the heat exchanger and try again.

 

[DavidM]

Something doesn't add up. How are you pressurizing your system with the test kit? If you are using the filler cap that test cap should block the overflow drain and you shouldn't lose any coolant there.

If you are using some other port to pressurize, maybe a coolant drain valve, then maybe the pressure is too high for the cap or the cap is relieving before its rated pressure. Try swapping the cap with the good engine and see what happens or pressure up the good engine and see what happens.

David

 

[Tolly Roger]

Check the transmission fluid and level.
It may be the transmission cooler has failed.

There is a very good crusader forum you can post the question on as well:
Crusader Marine Engine Forum

 

[JohnEasley]

How long since the risers were changed out? They are throw away items every 5 to 7 years. Mercruisers fail a bit earlier than Crusaders.

They're most likely the originals from 2006.

 

[JohnEasley]

Risers typically handle raw water, when they fail the engine gets hydrolocked. Exhaust manifolds are typically fresh water cooled and there is a block off plate between them and the riser that could have failed but not likely. This just leaves the heat exchanger with the coolant possibly filling up the raw water system. Pull the raw water hoses off the heat exchanger and try again.

Good suggestion. We might be able to do that this weekend.

 

[JohnEasley]

Try swapping the cap with the good engine and see what happens or pressure up the good engine and see what happens.

Thanks, David. Interesting idea. We can give that a try.

 

[JohnEasley]

Check the transmission fluid and level.
It may be the transmission cooler has failed.

There is a very good crusader forum you can post the question on as well:
Crusader Marine Engine Forum

Oh, hadn't thought of checking the transmission fluid. Good idea.

Thanks for the link. I posted the situation over there, too.

 

[C lectric]

Risers typically handle raw water, when they fail the engine gets hydrolocked. Exhaust manifolds are typically fresh water cooled and there is a block off plate between them and the riser that could have failed but not likely. This just leaves the heat exchanger with the coolant possibly filling up the raw water system. Pull the raw water hoses off the heat exchanger and try again.

I've seen that happen. DOn't know specifically about your case. A friend had a similar problem and traced it to the rotted out separator plate between the exhaust manifold and the exhaust elbow. THat plate separates the raw water and the coolant. If it breaches you will have a leak of coolant.

Check it out. At least think about it and do not ignore.

 

[sunchaser]

On several occasions I've neard the plate/block fail at about the same time as the riser. On both Crusaders and Mercruisers they both should be replaced as a PM item, especially if in salt water.

Some don't worry about the plate too much if you boat in fresh water and do not have a coolant loop. That was my case in 4 different vessels.