Need closed cooling system help

[yeller]

I've been having trouble getting my motor to run cool. It will overheat after a few minutes of driving. It uses a closed cooling system that I put together with some used heat exchangers, but I did get the HE's tested before installing. The engine HE is a 4" x 22" unit. I believe I get good enough raw water flow through the system. I base this on the fact that my exhaust header tubes do not get hot.

To rule out the thermostat, I removed it, but no luck. Engine still overheats.

My next step was to test the circulating pump. I am using an electric pump (that I did not test prior to install). I removed the hose from the manifold thermostat housing to the HE and replaced it with a clear hose so I could watch the water flow. At first, I had a large air pocket in the hose and circulation seemed very low. When I crimped off the tstat bypass hose, I could tell right away the pump was pulling a lot more water through the HE and I was/am hoping I found the problem. With the hose crimped off, the pump seemed to pull more water from the reservoir and the air pocket diminished. With the air pocket virtually gone, the circulation through the HE seems to be good regardless of whether the tstat bypass hose is crimped or not.

I haven't fired the motor back up because I don't have water where it is currently stored. I hope to fire it tomorrow.

I am vaguely hopeful that there was an air lock in the system and the pump was circulating the water through the tstat bypass instead. If the motor still overheats...which I'm afraid it will, I can only point the finger at the HE.

I'd hate to spend a grand on a new HE and still overheat. I was confident the one I have would be big enough. It's bigger than the one I had on my procharged HO and that motor never ran hot. This new motor will overheat in less than 10 minutes idling on the hose.

Is there anything else that might be missing?

[gcarter]

One of the key features of the remote system I installed is the vent line from the top of the thermostat housing to the expansion tank. The literature "demands" that this tube runs uphill from the housing to the tank. If your housing is cast, you could drill and tap it to add the vent line.
Well anyway, maybe the schematic will help.

[yeller]

Mine is plumbed that way George. I did find it interesting that a small amount of water continually dumped into the expansion tank from that hose. It got pulled back into the system through the bottom hose on the tank but I had expected that water would only enter the tank as the water heated and expanded. I don't have a tstat in the system right now, so as long as the pump is running, water flows into the tank, and then back into the system, even when the water is cold.


My whole system is plumbed as per your drawing, except my tstat is in the manifold housing and not at the HE, so (as per the drawing) I don't have the labelled "tstat bypass" and basically the labelled "fixed bypass" is my tstat bypass because the hose connects below the tstat.
I am curious as to the purpose of the two bypasses in the drawing. I can understand the tstat bypass, but then what is the purpose of the fixed bypass?

[yeller]

Not super easy to see, but the arrow in this pic points at the overflow hose going from my tstat housing to the top of my expansion tank.
Overflow hose.jpg


This pic shows the fill hose going from the bottom of the expansion tank to the inlet hose for the circulating pump.
Fill.jpg


....and for those that are curious. That lovely expansion tank was taken out of a VW.

[Morgan's Cloud]

Just a thought . You said that you had the exchangers tested , but were they dipped and cleaned ?
If they've got crusty scale on the tubes it can greatly reduce their ability to 'exchange' that heat.

[gcarter]

I am curious as to the purpose of the two bypasses in the drawing. I can understand the tstat bypass, but then what is the purpose of the fixed bypass?

The small bypass is to help bleed air out also, as far as I can tell.

+1 on what Steve said.

[BUIZILLA]

it sounds to me like the left bank/right bank water flow is deadheading against each other

[gcarter]

it sounds to me like the left bank/right bank water flow is deadheading against each other

I'm not sure that can happen Jim.
I don't know about glen's HE, but ,I'd assume, all HEs of that size are multi pass, and the two outlets going to the exhaust water manifolds are on different passes.
At least mine are.
Another potential thing to investigate is circ pump water flow. On the largest version (1,100 HP) of my system, it calls for 120 GPM.
My HE (good for 500 HP) , and my circ pump is 55 GPM. I'm assuming mine is sufficient, but I don't really know yet.
Your's would fall into the intermediate size (700 HP).

[yeller]

Just a thought . You said that you had the exchangers tested , but were they dipped and cleaned ?

Yes had them professionally dipped, cleaned and pressure tested.

it sounds to me like the left bank/right bank water flow is deadheading against each other

Sorry if I'm asking dumb questions, but:
Are you talking about the closed cooling side internally in the motor? How would that would be possible?
Or are you talking about the raw water side? I am getting good flow out the exhaust. Headers stay nice and cool.
Or are you talking about the HE? I have one inlet and one outlet for both the raw water and the closed cooling water, so I don't know how it could deadhead.

[yeller]

Another potential thing to investigate is circ pump water flow. On the largest version (1,100 HP) of my system, it calls for 120 GPM.
My HE (good for 500 HP) , and my circ pump is 55 GPM. I'm assuming mine is sufficient, but I don't really know yet.
Your's would fall into the intermediate size (700 HP).

I believe my circ pump is 55 GPM. I have no idea what the HE is rated for. I've done several different google searches, but can't find any company that lists HP ratings for their HE's. But even if I'm undersized, I wouldn't think I would overheat in a matter of minutes when just idling??

[Morgan's Cloud]

** A disclaimer , please don't interpret my posts/suggestions as coming from someone who knows anything **

Is this a new problem or did it happen as soon as you installed the closed system ?

Does the raw water dumping out of the tailpipes even feel a weenie bit warm or is it still very cool , like it hasn't interacted with a HE that has a hot side ?

I think that the only reason I ask that is because I'm wondering if the circulating pump is not somehow able to pump the fresh water into and through the HE.

[gcarter]

Glen, could you explain, point by point, the hook up in the picture w/no engine?
How're you splitting the raw water flow to the two manifolds?
Where would the circ pump be?

[yeller]

MC, this is a new system. Water is definitely going through the HE.

George, I attached a pdf labelling every hose in that pic. I don't have an easy jpg editor, so I had do it in my pdf editor.
Raw water flow exits the HE and goes to a T-fitting, and then to the two headers.
I am using a crank driven raw water pump. (Same one you are using).
I have an electric circulation pump and it mounts to the block like a conventional pump.

[XABICHIN]

Had a Nordic 25 with 496 mag that would start to overheat and go into limp mode or shut down. Finally found the water supply hose to the pump would collapse and restrict water flow. Changed the hose and the problem went away. Just a thought....

[gcarter]

Glen, it looks correct. The only thing I might have done differently would have been to include the oil cooler in the run from the strainer to the raw water pump inlet and eliminated the long run around the transom. But I'm reasonably sure that's not your problem.
The only things I can think of are:
the size, the Monitor system for 700 HP is 4-1/8" X 32", the 600 HP version is 4-1/8" X 29". So, is it big enough?
http://www.perfprotech.com/high-perf.../category/1511
You were correct that it should cool at idle, which brings up my next question, how many passes is it? You may already know, the dividers are visible when the end caps are off. If it's a single pass (doubtful) it probably wouldn't cool.
Of course, you haven't run it since you did the purge exercise, so this discussion may be simply academic.