closed cooling system check

[NC State Guy]

1980 mercruiser 470 ser#5520896

I'm not sure if my circulating pump is working or if I may have clogged passages in my cooling system. I can feel air pockets in the hoses is the presence of any air in the system not normal? Is there a way to check the circ pump with out removal?

I have a new impellar on the sterndrive.

Thanks

 

[Eric 3.7LX Alpha 1]

Re: closed cooling system check

Welcome to the 470 club and iboats, I usually just fill it up and wait a while with the cap off then keep topping it off. I usually see air bubbles burp the system out the cap opening. The level goes down a bit and I keep adding till the air seems to be out. Sometimes I start the engine with the cap off while everything is cold, and hopefully the water pump will push what ever air is in there out the cap opening. Air wants to go the highest spot because it is lighter than water, as the water gets warm it expands and begins to overflow out the open cap, thats when I close the cap.

Are you having any problems with running warm? (over 160'F) with a 160'F t-stat?
Good luck,
Eric

 

[NC State Guy]

Re: closed cooling system check

Yeah I'm having probs with running hot. My temp gauge is the yellow-green-red, usually gets to the edge of green/red. I used an IR therm and got some readings around 190F on the block and ex manifold. the head was 220F, Shut things down right away. I think my circ pump is not working b/c the coolant tube that runs from the aft of the heat exchanger to the fore end of the exhaust man is empty? no fluid in this hose. Think I'm going to start taking off hoses and look for blockages, maybe previous implellar failure frags. If I don't see blockages I wonder if the circ pump is bad. As of right now I'm not losing coolant anywhere..

I have good venting to the motor and I run the blower all the time while underway. I'm thinking of adding scoops where cup holders are on the doghouse.

I did remove my thermosat and checked it in 160-170F hot water it is functioning normal.



Thanks

 

[Don S]

Re: closed cooling system check

When you are filling the cooling system, you need the front of the engine slightly higher than the back so the air bubbles will come out of the back of the block.

 

[stonyloam]

Re: closed cooling system check

the coolant tube that runs from the aft of the heat exchanger to the fore end of the exhaust man is empty? no fluid in this hose.
Thanks

If you have the manual (if you don't Adults only, #9, Manual #8) check out cooling systems page 6A-13. That shows the aft hose as carrying seawater, sounds like you are not getting water from the impeller to the exchanger. Maybe kinked or leaking hose? 470's forever

 

[Eric 3.7LX Alpha 1]

Re: closed cooling system check

The impeller can not get into the engine coolant, it is on the seawater side of the system. Check out the manual link above and you will see how everything flows.

I am not a big fan of a temp gauge that does not read numbers. Unless you know exactly where on the gauge certain temps are. Mr Gasket sells a thermocap, which is a radiator cap with a built in thermometer on it. They sell them in different pressure ratings as well. Would be an easy add on to let you know what the temp of the coolant in the engine is:

http://cgi.ebay.com/ebaymotors/THER...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

I keep my original with me in the tool box just in case.

 

[NC State Guy]

Re: closed cooling system check

Yes I actually bought the clymer shop manual for this motor. The hose that I was describing shows coolant flows down to the aft of heat exchanger from the fore end of the ex man. There is another hose directly aft to this one for seawater.

I will get a real time therm intalled.

Don, when I refill the coolant, will raising the trailer jack fully be sufficient to tilt the motor back? I could prob get 20 degree tilt. I plan on filling with the reservoir off until ex man and block and head are full, then attach reservoir and fill it. then start motor and top off as needed.

Thanks 4 yalls help so far..

 

[Don S]

Re: closed cooling system check

Yes I actually bought the clymer shop manual for this motor.

Great, kind of expensive for knee pads though. That's about all those things are good for.
Download the OEM manual here. Then you will have the proper information, not hit and miss from aftermarket manuals.

will raising the trailer jack fully be sufficient to tilt the motor back?

I have no idea, look at it. IF it's nose down, it will get an airlock and overheat. This isn't rocket science, you want the front of the motor a bit higher than the back so the air moves forward out of the back of the block, and put it together then put the coolant in.

 

[NC State Guy]

Re: closed cooling system check

Ok thanks Don. I did download the manual you linked too, much much better info/pics. Now to craigslist to sell the clymers kneepad......