07 5.7 mpi separating coolant fitting

[Bman03878]

It’s the fitting under the right side of the exhaust manifold. It’s metal with a plastic fitting that pushes on it. Has a plastic ball inside I’m assuming some kind of check valve. Running the boat at higher rpm it boat keeps separating this fitting. Changed it twice. Is there some kind of flapper or check valve in the manifold or exhaust that’s not opening restricting the flow causing this to separate from pressure. Any info would be greatly appreciated. Thanks again.

 

[Bt Doctur]

Remove it and the rest of the "Quick Crack" system of plumbing and install regular drain fittings with blue plugs

 

[Bman03878]

Remove it and the rest of the "Quick Crack" system of plumbing and install regular drain fittings with blue plugs

My problem with that is I don’t know what the problem is. I’ve had this boat since new and this has never happened so really I’d like to know why. Is there some kind of valve or flapper that isn’t opening completely allow the increased pressure to blow it off

 

[Bman03878]

Here’s another question. Where it comes apart has a ball in it like a check valve. Is that line supposed to pump water? When it blows off the water doesn’t come out of the manifold it pumps out of this hose

 

[alldodge]

You have replaced it twice?
Didn't know it came apart, does it unscrew or just pop apart?

If its the pic then it doesn't pump water, it just keeps water from flowing back

 

[Bman03878]

You have replaced it twice?
Didn't know it came apart, does it unscrew or just pop apart?

If its the pic then it doesn't pump water, it just keeps water from flowing back

 

[Bman03878]

This is the part. When it comes apart the water is pumping up towards the manifold. The threaded part goes into the bottom of the manifold

 

[alldodge]

ok
It is a check ball and has 2 functions
Keep water from passing up into the manifold when boat is running
Drain water out during winterization

The check valve I posted is there to help keep the mans full once the motor stops.

Yours should not just pop open when running. It should take a screw driver placed between the 2 parts where the slot is and pried open. If its a OEM part and is doing that I would contact Merc Tech support and see what they say

I the short term, take a heavy tie wrap or piece of copper wire and hose clamp. Loop the wire over the top of the upper tube and run back on both sides. Then place the hose clamp over the wire and around the lower section. This should keep it from popping off for the short term

 

[achris]

That's the drain on the bottom of the manifold, not the check valve... Likely you have a blocked manifold or elbow on that side...

Chris....

 

[Bman03878]

ok
It is a check ball and has 2 functions
Keep water from passing up into the manifold when boat is running
Drain water out during winterization

The check valve I posted is there to help keep the mans full once the motor stops.

Yours should not just pop open when running. It should take a screw driver placed between the 2 parts where the slot is and pried open. If its a OEM part and is doing that I would contact Merc Tech support and see what they say

I the short term, take a heavy tie wrap or piece of copper wire and hose clamp. Loop the wire over the top of the upper tube and run back on both sides. Then place the hose clamp over the wire and around the lower section. This should keep it from popping off for the short term

Right that’s why I say some kind of pressure is popping it off like a blockage somewhere. When it comes apart it is pumping water out of it towards the manifold. Which from what you stated the ball stops that. But it builds enough pressure to pop it apart. Why would the “drain” line be pumping water thru it? Thanks for your insight

 

[Bman03878]

That's the drain on the bottom of the manifold, not the check valve... Likely you have a blocked manifold or elbow on that side...

Chris....

Is there a flapper or valve in the manifold? I also was thinking maybe a blocked exhaust. When I run it on a hose water does come out but maybe something stopping it fully. This motor is in an inboard ski boat

 

[alldodge]

It should not pop off. The pump might produce 30 psi at the most at high rpm, and that shouldn't cause the issue

You have a 3 point drain system, so things are both fill and drain
Pic is for 4.3 but works the same. Color scheme Green drain, Red raw water, Blue bypass when thermostat is closed

 

[Bman03878]

It should not pop off. The pump might produce 30 psi at the most at high rpm, and that shouldn't cause the issue

You have a 3 point drain system, so things are both fill and drain
Pic is for 4.3 but works the same. Color scheme Green drain, Red raw water, Blue bypass when thermostat is closed


View attachment 365977

Yeah I don’t understand why it keeps popping. It’s fine at lower rpm but seems over 3500 and it pops apart. Same side. That’s why I wonder if there is something in the manifold or exhaust that’s not letting all the water out. I don’t want to take it apart if I don’t have to. Thanks again

 

[alldodge]

First law of hydraulics is, pressure exerted on a confined liquid is transmitted with equal force on all areas. So pressure on one side is exactly the same as the other.

To prove, move that one to the other side and see if it still pops same side

 

[Bman03878]

First law of hydraulics is, pressure exerted on a confined liquid is transmitted with equal force on all areas. So pressure on one side is exactly the same as the other.

To prove, move that one to the other side and see if it still pops same side

I was thinking same to see if it pops off. Since two have popped on the same side I think it would be unlikely

 

[achris]

First law of hydraulics is, pressure exerted on a confined liquid is transmitted with equal force on all areas. So pressure on one side is exactly the same as the other.

But the pressure differential isn't internal, it's between the inside and the outside.. That's why is breaking apart.

OP. No valves inside the manifold or elbow. What you may have is rust building up and restricting water flow. As well as pressure, that will cause very hot water to linger in the fitting, softening the plastic and allowing it to pop apart...

Chris ..

 

[alldodge]

Ya know if the drain side of the fitting is clogged, then there will be water pressure above the check ball but not as much below. If it wasn't clogged then pressure above and below would be about the same

Remove the lower end hose from the fitting (drain side) and blow air thru it. Maybe remove the entire hose and see if it or the drain manifold below manifold is clogged up

 

[achris]

That fitting is both a drain (to the drain manifold) and the fitting that takes hot water from the thermostat housing. It's plastic and I believe it's getting too hot...

 

[Bman03878]

That fitting is both a drain (to the drain manifold) and the fitting that takes hot water from the thermostat housing. It's plastic and I believe it's getting too hot...

The water that comes thru it I can grab the fitting while the boat is running and it doesn’t burn my hands. Even the manifold I can put my hand on and not get burned. If I put it back together without the check ball am I hurting anything. Here’s also a question if the exhaust and water go thru the same manifold what stops the water going back thru the manifold and into the valve train. These answers are great and I’ll try anything that’s suggested

 

[achris]

Just replace the blown fitting with a standard brass 90 degree fitting. Connect the hose from the thermostat housing to the new fitting and block off the other hose.

Resembling and refitting with the check ball missing may allow hot water back into the circulatory system with unknown consequences...

Chris...