Removing/Bypassing Heat Exchanger

[390Express]

Source of the post You really shouldn't lose any antifreeze at all discoing the water heater. You'll lose a few cupfuls when you remove the hose but you should be able to get the other hose (the loop) on pretty quick and stop the loss. Then, you could blow air into one of the hoses going to the water heater heat exchanger and recover all that coolant out the other side. Use that to top off whatever you lost in the engine.

But, that said, getting back to your original question... 'how would you do it'? We'd have to know the exact model and year of your engines to find out. Then it would just be looking at some parts lists to figure it out.

IIRC, you have some 454 Crusaders. Below are some water flow diagrams for both the freshwater flow and raw water flow and you can see the differences. There's a different thermostat housing so that the raw water goes there first, then down to the water pump, rather than to the heat exchanger. There's also a blockoff plate (not shown) between the manifolds and the risers on the freshwater cooled so that the antifreeze in the manifolds doesn't get to the risers. In the raw water version, that blockoff plate is replaced with a gasket, with the hole in the gasket towards the top.

You'd need to plug off the holes for hoses on the risers and the ones at the back of the manifolds (I actually have the plugs for this if you need/want them.. they are really large)

You should also change the thermostats, because the raw water versions used a 143F, whereas the freshwater used a higher one (160F, 170F or 180F). 210F is WAY TOO high and should never get that high unless there's a problem and a little leak wouldn't be that problem unless it was running out of water.

Crusader_fresh_water_flow.jpg

Crusader_raw_water_flow.jpg

Thanks KM

Source of the post Thought of a better way to bypass the water heater without losing virtually ANY coolant.

First, open the cap from coolant system on the engine to relieve any pressure in the system. Then put it back in place.

A foot or two from the engine, use two clamps (like wood clamps) on each hose to pinch them shut about an inch apart. Cut the hoses between the clamps. Raise the two coming from the engine above the highest point on the engine or heat exchanger and remove the clamps. Use a bronze barbed fitting to connect these two hoses and clamp tight. No loss of coolant (Ok, maybe a FEW drops). Put one of the ends of the hoses coming from the water heater into a bucket and remove its clamp. Raise the other hose coming from the water heater and remove its clamp and blow air into this hose. The remaining coolant in the hot water heat exchanger should be blown out into the bucket. Save that coolant for later use.

A leak could absolutely cause a high temp situation. The closed coolant side runs off of pressure. If the system isn’t making 19lbs (or whatever the radiator cap is rated for), the t-stat won’t open properly, and it will run hot.

The reservoir is the highest point of the system, followed by the heat exchanger. I’m guessing that once I open the HW loop, it’s going to shoot out of there like a rocket.

Do you happen to know what size hose it is, that goes to the HW system. Seems like it’s about a 3/4” ID, but there’s going to be no good way to measure it while it’s shooting out everywhere.

These engines have a horrible design for draining the coolant out of them.

[390Express]

Source of the post Thought of a better way to bypass the water heater without losing virtually ANY coolant.

First, open the cap from coolant system on the engine to relieve any pressure in the system. Then put it back in place.

A foot or two from the engine, use two clamps (like wood clamps) on each hose to pinch them shut about an inch apart. Cut the hoses between the clamps. Raise the two coming from the engine above the highest point on the engine or heat exchanger and remove the clamps. Use a bronze barbed fitting to connect these two hoses and clamp tight. No loss of coolant (Ok, maybe a FEW drops). Put one of the ends of the hoses coming from the water heater into a bucket and remove its clamp. Raise the other hose coming from the water heater and remove its clamp and blow air into this hose. The remaining coolant in the hot water heat exchanger should be blown out into the bucket. Save that coolant for later use.

If you open the rad cap, about a quart or more comes gushing out.

[km1125]

RE: "If the system isn’t making 19lbs (or whatever the radiator cap is rated for), the t-stat won’t open properly, and it will run hot."
I don't think that's true at all. The thermostat should be opening at whatever it's rated for. The coolant should not boil for well over 212, so as long as no point in the system is hitting 212, you don't need ANY pressure in the system. That pressure is really designed around localized hotspots, that could get beyond 212 (or up to 240 with a coolant mix), which might boil, forcing coolant out of the system. This is especially true when the engine is shutdown and no cooling is taking place.

Where is your "radiator" cap located on the engine, if not the reservoir or the heat exchanger?

[390Express]

Source of the post RE: "If the system isn’t making 19lbs (or whatever the radiator cap is rated for), the t-stat won’t open properly, and it will run hot."
I don't think that's true at all. The thermostat should be opening at whatever it's rated for. The coolant should not boil for well over 212, so as long as no point in the system is hitting 212, you don't need ANY pressure in the system. That pressure is really designed around localized hotspots, that could get beyond 212 (or up to 240 with a coolant mix), which might boil, forcing coolant out of the system. This is especially true when the engine is shutdown and no cooling is taking place.

Where is your "radiator" cap located on the engine, if not the reservoir or the heat exchanger?

Radiator cap is on the t-stat housing.

Design is horrible.

[390Express]

Source of the post RE: "If the system isn’t making 19lbs (or whatever the radiator cap is rated for), the t-stat won’t open properly, and it will run hot."
I don't think that's true at all. The thermostat should be opening at whatever it's rated for. The coolant should not boil for well over 212, so as long as no point in the system is hitting 212, you don't need ANY pressure in the system. That pressure is really designed around localized hotspots, that could get beyond 212 (or up to 240 with a coolant mix), which might boil, forcing coolant out of the system. This is especially true when the engine is shutdown and no cooling is taking place.

Where is your "radiator" cap located on the engine, if not the reservoir or the heat exchanger?

It has to be true.

The system is full of coolant, there are no blockages, the raw water side is doing its job, it has all new gaskets and a brand new 180 T-stat, and it’s running hot.

[bud37]

Thermostats open and close on temp......the only time the opening can be affected is if you were to have a high flow water circulating pump, which in this case does not apply.

Now it is possible to have a bad new thermostat....as for the design, consider the other engine is fine.

Verify the temps with an IR temp gun first, and pressure test the cooling system. Now if this engine has been hot all along the water passages in the exchanger could be restricted and the heat exchanger in need of replacement based on the temps you are saying and the loss of coolant....just like an old rad on your car....no difference. Overheating the fresh cooling water going thru the exchanger will cause build up.

One other item to consider might be the engine circulating pump....

Actually if memory serves me....did you not resolve this problem after the valve job ?

[km1125]

Went back and re-read some of your old threads. Seems like this engine has had a hosts of issues over many of the last years related to overheating or high temp issues. Does this only occur at slow speeds or idle or do you have issues at higher speeds as well?

What's really different about this engine than your starboard engine? What temp does that one run at? Have you taken an IR gun and compared readings across both motors when they're both running? Seems like you could narrow down if this is a raw or fresh water problem like that. I'd even be tempted to swap some parts (like heat exchanger) between engines to troubleshoot it.

I'm also curious how much coolant you have in the reserve tank on each engine. There really should be very little, as it's really an overflow tank and should accept a bit of coolant as the engine warms up and expands the coolant, but that gets sucked in when it cools. There should only be enough in that tank so you know the level is dropping if you're consuming coolant somehow.

[390Express]

Went back and re-read some of your old threads. Seems like this engine has had a hosts of issues over many of the last years related to overheating or high temp issues. Does this only occur at slow speeds or idle or do you have issues at higher speeds as well?

What's really different about this engine than your starboard engine? What temp does that one run at? Have you taken an IR gun and compared readings across both motors when they're both running? Seems like you could narrow down if this is a raw or fresh water problem like that. I'd even be tempted to swap some parts (like heat exchanger) between engines to troubleshoot it.

I'm also curious how much coolant you have in the reserve tank on each engine. There really should be very little, as it's really an overflow tank and should accept a bit of coolant as the engine warms up and expands the coolant, but that gets sucked in when it cools. There should only be enough in that tank so you know the level is dropping if you're consuming coolant somehow.

Port engine has had a consistent history of running hot, and losing coolant. New valve job and gaskets changed nothing, no signs of anything wrong with the heads, block, intake or exhaust system.

The raw water side works great. New impeller, backflushed, no missing pieces, no clogs, raw water side runs perfect; perfect flow, passes 5 gallon test, passes temp test before and after the heat exchanger, etc.

The issue appears to be either the Hw heater, or heat exchanger, which, again, is why I want to delete both, and convert the engine to raw water cooled.

[390Express]

Runs hot at all speeds, lower and higher rpms.

The coolant reserve tank only holds approx 2 quarts. Generally it’s stored with it about 2/3 full per the recommended fill line on the bottle.

Despite filling it repeatedly, the reserve vessel is frequently empty when I check on it at a later date.

The stbd engine operates at temp, right at 180, no issues.

IR temp gun confirms that the port engine is running 20-30 degrees warmer than the stbd engine. IR temp gun confirms that raw water side remains cold, and similar comparative temps to stbd, entire fw side runs hot, no discernible culprit.

[km1125]

When I say " taken an IR gun and compared readings across both motors", I mean comparing very specific points on both motors. For example, taking the IR readings on the input and output of the heat exchanger on both the raw and fresh water flows (4 readings on each engine), and other parts like below and above the thermostat housing, and before and after the manifolds, etc. Things like this would help narrow down why and where that engine temp is getting out of control.

With the history on that motor, I would certainly take the hot water tank out of the picture. I don't know if those are 3/4 or 5/8 hoses offhand, but I would bypass that and eliminate it from the equation totally. If you do this when it's been a while since the engine has run, you can skip the "remove the radiator cap step" as the system shouldn't have any pressure in it.

Until you solve the problem, you don't NEED to run a coolant mix in there. The engine will run fine and should not overheat with a 180F thermostat, especially if you have pressure in the system (~15PSI is all you need). You could drain whatever coolant you have now and save it and just run tests with just water, so if you spill anything or need to refill it's not a big deal. Of course ultimately you'd want to have the coolant mix back in there (unless you do actually just convert to a raw water system). Once you get the actual problems solved (both overheating and losing coolant) then you could drain and refill with the proper coolant mix so you don't have to worry about winterization of that part, and it would protect the internal metals from corrosion like it's supposed to do.

It's going to be a lot of parts and time to convert to raw. You might still end up wanting to do that if you find you have a bad heat exchanger but that should be a decision for later.