Antifreeze filling up over flow bottle when running. **UPDATE**

[rick3452]

Hi guys, I just finished doing my new impeller job on my 2000 5.0 Bravo 3 everything went fine? So I toped off the heat exchanger to the proper level and with nothing in the plastic overflow bottle I took it out for about an hour this evening. I had my wife drive so I could take a peek in the engine compartment. I noticed a slight but steady stream of antifreeze/water coming out of the top of the overflow tank!! What the heck?? Temp was a perfect 160, elbows nice and cool. and when I just got back the overflow bottle is totally full. I did not open pressure cap.

What would make the water fill up the overflow???
Thanks a bunch.
Rick

PS there were no pieces of the old impeller missing

 

[alldodge]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

Hi guys, I just finished doing my new impeller job on my 2000 5.0 Bravo 3 everything went fine… So I toped off the heat exchanger to the proper level and with nothing in the plastic overflow bottle I took it out for about an hour this evening. I had my wife drive so I could take a peek in the engine compartment. I noticed a slight but steady stream of antifreeze/water coming out of the top of the overflow tank!! What the heck?? Temp was a perfect 160, elbows nice and cool. and when I just got back the overflow bottle is totally full. I did not open pressure cap.

What would make the water fill up the overflow???
Thanks a bunch.
Rick

PS there were no pieces of the old impeller missing

OK dumb question maybe; You said you didn't remove the cap, but was the cap on tight, as in all the way on?

 

[rick3452]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

yes, ran with cap on as normal, I'm assuming that tomorrow morning when I go out there the water will have been sucked back in the exchanger….

 

[thumpar]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

Are you getting any bubbles?

 

[phillyg]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

I'm guessing the cap has a weak spring or is frozen in the open position, or possibly the thermostat is bad.

 

[alldodge]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

It could be you fine, and if the antifreeze goes back in check the cap for a defective seal.

 

[thumpar]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

Did it do this before the impeller change? Is the impeller change the only thing that was done?

 

[stonyloam]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

Some coolant should go into the expansion tank, but not that much. As thumpar mentioned, with the cap off look for bubbles in the coolant.

 

[rick3452]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

It could be you fine, and if the antifreeze goes back in check the cap for a defective seal.

I did notice recently that there was some antifreeze that escaped from the cap, would a bad seal on the cap allow the water to flow to the expansion tank?????

 

[thumpar]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

I did notice recently that there was some antifreeze that escaped from the cap, would a bad seal on the cap allow the water to flow to the expansion tank?????

A bad seal or spring could cause it. The system is meant to run under pressure as it heats up.

 

[rick3452]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

does anyone have the part # and pressure rating for my 5.0 for a new cap? Ser # omo12817
Thanks…..Rick

 

[stonyloam]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

I did notice recently that there was some antifreeze that escaped from the cap, would a bad seal on the cap allow the water to flow to the expansion tank?????

Ideally your system should be full or nearly full of coolant. Maybe a little air in the space below the cap. You should have a hose going from the cap neck to the bottom of the expansion tank, with the tank filled to the "full cold" line. When you start your engine the coolant heats up and expands creating pressure in the system. When the pressure exceeds the cap rating (14-16psi or so) the cap seal with the neck is broken and coolant or trapped air flows out into the tank until the pressure drops and the cap reseals (tank should be at "full hot" level). Once up to operating temperature no more coolant should flow into the tank. Once you shut down the coolant cools and contracts drawing some of the coolant back from the tank into the system. The tank should never overflow if the system is working correctly. If there is a lot of air in the system it might push more coolant out, or if air is being introduced into the system by a bad head gasket for example it could push coolant out. See how much the tank level goes down when it cools and when it is cool (never pull the cap hot) pull the cap, start the engine and look down to see if there are bubbles in the coolant. Something is not right here.

 

[rick3452]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

Thanks Terry, and everyone else, I will replace the cap tomorrow , fill correctly and run….

 

[Fun Times]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

does anyone have the part # and pressure rating for my 5.0 for a new cap? Ser # 0M012817
Thanks…..Rick

Hi Rick, Your cap PSI rating is 16 PSI. Mercruiser part number 36-8148791

For the filling procedure, either check your notification inbox on the other boating forum you frequent as I resent it liked you asked or this should help you out better, http://boatinfo.no/lib/mercruiser/manuals/mercruiser24.html#/750

You've been busy with this cooling system over the last year and a half haven't you? I sent you that back on 09-04-2012.

 

[rick3452]

Re: Antifreeze filling up over flow bottle when running. UPDATE***

Re: Antifreeze filling up over flow bottle when running. UPDATE***

Hi Rick, Your cap PSI rating is 16 PSI. Mercruiser part number 36-8148791

For the filling procedure, either check your notification inbox on the other boating forum you frequent as I resent it liked you asked or this should help you out better, Boatinfo - Mercruiser Service Manual nr. 24 - 1998-2001 - Engines GM V8 305 & 350 CID

You've been busy with this cooling system over the last year and a half haven't you? I sent you that back on 09-04-2012.

A million thanks Fun Times!! Actually since the problem with the HE back then Iv'e had no issues at all?. 1000 Hours in three years and I'm still having a blast with this boat.
Rick

 

[Scott Danforth]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

your cap is actually purchased from stant when installed on the HX prior to it being shipped to Mercruiser.

the overflow bottle is there because the system does not have enough expansion volume in the top tank. it is a design consession to keep the height low. if you fill the system completely when cold, you will get about 6% of the system volume overflowing into the bottle when warm

 

[rick3452]

Re: Antifreeze filling up over flow bottle when running.

Re: Antifreeze filling up over flow bottle when running.

****UPDATE**** So after all the great information I went out this am and saw that the FULL bottle had returned back to the system..
So I went to boat supply place and picked up a new pressure cap (14), could not find a 16. Bought new correct coolant, drained the HE, refilled according to mercruiser method, started it up and went for a cruise down the inter coastal about 1200 RPM's the whole time.
Within 20 min. to a half hour it was apparent that the bottle was once again filling. and by 45 Min. it was coming out the overfull on the bottle. So turn around head back to the dock, ( by the way TEMP was always a perfect 165) but I was concerned that eventually I would be low on coolant and overheat as it continued to pee out the top of the bottle. (never budged of 165) So here's what I observed, while my wife was driving I felt all around the H.E the top near the cap was hot, and most of the top was hot, but the end caps were almost cool to the touch as well as the bottom. I did pull the two end caps off just to see if there was a blockage and there was nothing. I just can't figure out why the coolant is being forced out the over flow hose. 1.5 years ago I did have the H.E repaired for leaking tubes but it has been good since. By the way NO BUBBLES and engine is running perfect. Thermostat opens properly and the hoses on either side of T stat are equally hot. Thanks for the help I really appreciate it. Rick

 

[Scott Danforth]

Re: Antifreeze filling up over flow bottle when running. **UPDATE**

the top tank and cap along with all but the last 1.2-2" of the heat exchanger will be hot because that is the glycol side.
the end caps are cool because that is where the raw water turn around passages are. that is also where you clean out the tubes of the HX when they get clogged by rocks and debris that make it past the inlet strainer and the impeller in the raw water pump.

it is over-flowing the bottle for two reasons.

A - too much coolant in the bottle in the first place. remember the 6% volumetric expansion
B - you have a leak in your system and raw water is being introduced to the glycol side of the system

it should stop over-filling at some point if the issue is A when the 50/50 mix stop expanding due to heat. it will continue to over-fill if the issue is B.

 

[alldodge]

Re: Antifreeze filling up over flow bottle when running. **UPDATE**

While you should have a 16 pound cap, a 2 pound less cap should not cause the issue. Your engine is running at normal temps "at the thermostat housing", I think somewhere it is overheating. My first guess is the exhaust manifold and elbows. Check to make sure the sealing surface on your heat exchanger has a smooth sealing surface for the cap. If the surface is smooth, then get an IR temp gauge. With the admiral driving on plane, start taking readings.

 

[thumpar]

Re: Antifreeze filling up over flow bottle when running. **UPDATE**

You could try pressurizing the cooling system and listen to hear if there is a leak into the raw water side.