Coolant Resevoir Keeps Filling Up.

If you take the rad cap off the heat exchanger and you get bubbles yourhead gasketis probably gone.
 
Start with cold engine do not take rad cap off with hot engine. As engine warms up you will over flow a bit. Wear protective glasses and cloths as you watch.
 
Try swapping the heat exchanger cap from the other engine (the metal ones with the spring on the bottom).
Maybe the cap isn't sealing with the filler neck on the heat exchanger??
Look inside the filler neck for some crud.
Maybe swap heat exchangers side to side (PITA but, easy).

Also, get a radiator pressure tester from an auto parts store.
Most loan them for a small fee or free (Auto Zone) and follow the instructions it comes with.
This tool can help diagnose a failed head gasket.

Hope it not as bad as it might be,

Best,

Mark.
 
I have switched caps and done a pressure test. If I have a cracked block does that mean new engine?
 
bigpursuit said:
I have switched caps and done a pressure test. If I have a cracked block does that mean new engine?
Click to expand...

During the pressure test with the engine running did pressure rise and hold or was the pressure gauge bouncing around??
It should be steady.
Just testing to see if it holds pressure with the motor off is only part of the test..

If it turn out you need a new engine...you could try "Blue Devil Engine and Cooling Sealant".
I know there are many reasons not to use a sealant like this but, a friend used it in an old trawler with coolant system leaks and that was YEARS ago!
No more leaks and that boat has gone down to Florida and back since.
I dont like magic in a bottle but, that stuff worked for him.
 
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I tested the air in the resevoir with one of those test kits that test for combustion gas. It proved to be negative. While the engine was running @ 3400 rpm I went below with an IR Heat gun and checked every part of both engine I could get a read on. everything on both engines was around 160 except the port side exhaust manifold on the engine with the problem. That manifold read 240! After all this messing with the heads and gaskets it appears the bubbles were boiling fluid and not combustion gas. The engine never overheated because the blockage kept the hot liquid from getting to the rest of the engine.

I believe problem solved! I am going to replace manifolds on both sides.​
 
Yes, I am very interested to know if this resolved your issue.

I took mine out on Monday and temp on Port engine was fine while running and at idle. I took a look in the bilge when we got back because I had a slow water leak coming from the strut screws which I had re-caulked and wanted to see if I had any water in the bilge. No water but some antifreeze from the port motor. I filled the overflow container to cool line before we left and it was almost empty when we got back. I did not have much time to troubleshoot, but felt some fluid around the one of the hoses where it connects to the pump. In the past the belt would squeel on that motor until it was under load or warmed up, so I am wondering if the bearings in the pump are bad. The strange think is it looked like most of the fluid was below the overflow tank and I did not see it splatter all over the place like it got on the belt. I was told there is a bleeder hole or something like that in the pump which allows fluid to come out when something is not working right. I am not talking about the raw water pump. All this headgasket and cracked block talk has got me very nervous. I will be down at the marina troubleshooting more this weekend. I hope it is something somewhat minor.

I just had to put a new tranny in last fall which was not very cheap. She ran great other than that.
 
Problem is not fixed! After changing the manifolds and elbows on both sides I still get air bubble in the coolant resevoir. So far I have changed the heads, manifolds, elbows, thermostat, hoses, radiator cap, impellar. The other day I switch the heat exchanger from one boat to the other to see if that did anything and the problem still occurs.
The I took several test runs and made the following observations:
1: The coolant resevoir will bubble after going a mile or 2 with the boat @ 3400 rpm
2: The bubbles only appear as the boat slows down to idle. As I am running all looks normal. As the resevoir bubbles the tank fills some with fluid. It eventually fills up.
3: AFTER the several start stops the left manifold heats up to 240. This only happens after the resevoir is somewhat full.
4: The boat itself never overheats and runs fine. The temp gauge at the dash shows normal temperature.

I don't believe my problem is combustion gas in the system. I tested the bubbles using one of those suction type testers and the result is negative.

I am starting to believe air is just introduced into the system somewhere at higher rpm's. Is it possible the water pump on the enclosed side is sucking air through a bad seal? Any input would be greatly appreciated.
 
Wait a min..
Will the engine now over heat or will it run at normal temp.
It is normal for the engine to push some fluid into the res. when it gets hot and pull some back in while cooling....maybe we are chasing a ghost and all is ok??
 
The boat has never overheated. The amount of fluid that gets pushed into the resevoir and the bubbling is not the normal function of the overflow res. I have posted a video on a previous post if you want to see it. There is also a foaming of the fluid when this happens. When compared to the other engine it's dramatically different. If I don't stop the exhaust manifold warms up to 240.
 
Great video. I love a good mystery. What are the pressure readings you recorded when you pressure tested the system (how high did you pressurize it) and for how long did it hold pressure (both engines)?


The air being injected into the cooling system is displacing the fluid and bubbling the resevoir. Air injection on deceleration is odd. Normally a cracked block/head/leaking head gasket blows bubbles on acceleration not deceleration. In fact, deceleration is usually when the fluid is sucked into places it shouldn't go. Supercharged engines have a history of leaking air into the water jackets because the plenum is under constant pressure. In your case, the plenum is under vacuum which largely rules out the intake side of the engine. That leaves the combustion chamber and the manifolds which you say are new. So, a few answers (beyond the pressure readings) would help:

1) Has anything changed which would have increased exhaust back pressure?
2) Is the bubble rate the same as before you had all the work done?
3) Was the water pump replaced?

The next step I would recommend to track down the exact issue is to temporarily replace the existing closed cooling hoses with clear hoses to see what side of the engine the bubbles are coming from. Sorry for being so late to the thread .....I know this is frustrating,

-John
 
John,

Thanks for jumping in! I tested the pressure with one of those guages you attach in place of the radiator cap. The cap is rated for 7 pounds so I pumped just past 7. I left it there for awhile and nothing happened. I started the engine with it on and still nothing happened, pressure remained constant. I never pressure tested the other engine.


The water pump has not been replaced but I just ordered one and it is getiing installed next week. I figure it's the last thing left so what the hell it's not that much money. The mechanic is going to install the pump and take for a test ride. If the problem still exists he is installing clear hoses and going that route.

I'm not exactly sure if the bubbling is the same as before. I didn't notice bubbling at first, the symptom was really the resevoir spewing coolant while I was running. It doesn't really do that now, it instead fill the resevoir some every time I slow down after going hard for a mile or so. So the resevoir fills but it takes longer. The bubbling on the video was taken before the manifolds were replace that is the same as before. I am better at noticing symptoms now than I was when this first noticed an issue.

The boat runs on lake Michigan so it is fresh water. It is stored inside heated. I have a hard time believing the problem is combustion gas since the heads have been completely replaced and it's hard for me to believe I some how cracked a block with a closed system stored inside heated. I bought the boat brand new in 2000. Everything was fine until last year.

So for the sake of conversation if it is not the water pump what can it be? Everything else has been replace or tested.

Thanks again to anyone who reads this and gives some input!
 
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You have done all the right things. I seriously doubt the water pump is cavitating enough to cause this but it is a mystery. I do know that putting clear hoses on the engine will show which side has an issue.


In regards to the pressure test..... If you attach the pressure gauge and do not pump it up.....I'm wondering what pressure it actually sees as the engine warms up and you accelerate/decelerate. It should rise beyond 7 pounds since bubbles and fluid are getting past the cap.....if it doesn't let me know. Shut the engine off if it reaches 8 pounds and be careful releasing the pressure.

-John
 
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From what I've read, the Crusader fresh water cooling system is a "full" system vs Merc's "1/2" system. On my 8.1's coolant flows through the engine block and head, through the heat exchanger, then back to the engine. The only other part of the system with coolant is the resevoir tank (on the top of the engine - placed above all other coolant parts). Yours has an additional part of the cooling system - the exhaust manifolds. Correct me if I'm wrong, but unlike Merc's, yours are cooled with coolant - not seawater like mine.

When you said that the one exhaust manifold heats up to 240 AND that the bubbles were actually coolant boiling and not combustion air, it got me thinking. Could the issue be something involving a restriction of coolant flow to or from that exhaust manifold? I'm not familiar with the plumbing used in conjunction with the exhaust manifolds, but you may want to consider the possibility of some kind of blockage. It is common for the exhaust manifolds to heat up upon deceleration since the coolant flow drops. Could the coolant get hot enough to boil, and if so could the resulting bubbles work their way to the resevoir??

Anyone have a diagram of Crusader's coolant system??
 
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Just an observation. I have 7.4 Mercs with full fwc systems. The specified pressure for the cooling system is 16 PSI. Most automotive cooling systems use 13 or 14 and I find it really strange that Crusader use only 7 but that is what appears in their parts manual http://www.crusaderengines.com/manuals/L510008.pdf so it has to be right.

Again I don't know anything about Crusaders but merc manifolds have short hot sections that run from the exhaust port on the head, before it enters the water cooled manifolds. I check the temps along the outside of the manifolds, well away from the exhaust port entry side of the manifolds.

I posted earlier in the thread and recounted how I had the exact same problem with my port engine. It turned out to be the heat exchanger leaking between the raw water and closed chambers. What happened was the coolant would expand normally and flow into the recovery tank. When the coolant contracted in the system after I stopped the engine it drew air in through the leaks in the exchanger instead of coolant out of the recovery tank. When the sea water pump stops the exchanger slowly empties of raw water and fills with air - so by the time the coolant contracted it was easier to draw in air than lift coolant out of the tank.

When I checked the coolant level in the exchanger before use or after it had cooled down it would be low and the recovery tank full. If I topped off the exchanger then it simply overflowed out of the recovery tank once operating temps were reached again.

If I did not top off the exchanger the recovery tank did not flow back into the exchanger because there wasn't a pressure deficit (due to air entering). When up to temp again there were bubbles appearing in the recovery tank due to air being pressurized and expanding from being heated by the hot water in the system. Air expands much more than water so cold air entering the exchanger and being heated meant bubbles in the tank every time but they would peter out when the air had reached maximum expansion (a slow process).

I did not leave the level low except when experimenting as I was worried about air pockets getting drawn into the engine cooling passages.

As for your compression tests, I think they are normal or at least they are for medium to high hour engines with center exit merc manifolds. Condensation, aerosol droplets from vacuum pulses and the like cause rust on the valve seats and lower the compression on the middle cylinders. I can't see Crusaders being completely immune to this even if they do have better reversion protection than merc exhausts. My compression was similar to yours and came back up to with 5% after some good high speed runs at 75% of max rpm. Obviously too much corrosion on the valve seats can't be cured this way.

By the way, I spent thousands fixing this cooling issue because none of the normal diagnostics picked up these tiny leaks. Pressure testing the cooling system with the exchanger filled covered the leaks with coolant and they were so small water hardly flowed out. So it passed the pressure test (but an overnight test would have shown some drop, alas we didn't do one overnight). When the exchanger was partially empty it showed up more readily as water wasn't covering all the leaks.

Hope this helps.
 
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I'm fairly sure the hot manifold on the engine is the source of the bubbles but the clear hose test will prove it one way or another. There are a couple of things that can cause it and a likely candidate is the hose that feeds the manifold water. Some FWC configurations use poppet style balls in a t fitting to feed water to the manifolds. Sometimes these things get stuck and cut/restrict water to the manifold. Just checking the water flow of that manifold's hose may help solve the issue.

Diagnosing these things without being able to see them work is always a bit of a challenge.
 
Thanks everyone for time you have taken to think things over and respond. Couple things:
The left manifold that gets hot is brand new as is the hoses going to and from the manifold. We checked all fitting and the path to the manifold since I was also convinced that was the source of the problem. I have since noticed the manifold is not hot when I first detect the bubbling. The manifolds only appear to get hot once there is air in the system from the bubbling. When I check the temp of the manifold with an IR gun while under way the temp is normal(170),
The heat exchanger I switched from the other engine so it is not the heat exchanger.

So what is left? The water pump is the only thing I haven't changed. I googled "Failed water pump seal admitting air " and found a forum where people had trouble with cars that sounded like mine and it was the water pump sucking air(not cavitation).

The only other thing would be blockage in the block itself(the boat never over heats so I doubt that) or a cracked block. I believe I have elimnated all other sources.

Please chime in with thoughts!
 
Most boaters keep a pump like this on hand to aid clean up and transfer. Plugging the degas hose and connecting the pump intake to the closed system should pull far more negitive pressure/vacum than the system pump is capable of. If the pump removes much coolant,there must be air comeing in to replace the coolant. Kind of a pressure test in reverse.
 
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Like I said.....it is hard to get facts that don't change over the web.

It is possible that a bad seal on the suction side of the water pump could have an issue. When they do, they usually leak antifreeze when you pressurize them or switch a hot engine off. This is really not a hard problem to trace. Changing a few hoses will show where the air is coming from. The air is a symptom not the systemic problem. If you check the hose that feeds the manifold that eventually gets hot....my bet is that you will find air heading into the manifold which is why it gets hot.

You and your mechanic need to deal with this before you replace the water pump. The water pump is an educated guess. The clear hoses will tell you where the air is coming from.

-John
 
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