HELP im loosing coolant????

[donkey206]

I have a 1988 Freedom 220F and I love it. I have the famous 3.7l 470 merc and an alpha 1 outdrive. I just rebuilt the motor because of a head gasket. The problem all started when I started losing coolant slowly and wasn?t sure where it was going. My oil never looked bad at all; I did have milky oil under my valve cover but never on my dip stick. When I would go for a 20 min boat ride I would lose about 1gal of coolant. We would troll for about 4hours or so and I would fill it back up and we would head make to the marina. The boat never over heated, and I NEVER added water to it when it was hot/warm. I replaced the exhaust elbow/reservoir cause it was corroded bad, the boat has a fresh water cooling system with a 4" heat exchanger. Now that the boat is at home and out of the water I have rebuilt the engine and it runs amazing. When I start the boat I can smell coolant from the exhaust, and it?s a little white in color, after the boat running for about 5 min or so the coolant reservoir is low, about half a gallon. I?m really lost and will not take the boat to a rip off shop to have someone tell me to buy 5k in parts. The exhaust manifold looked pretty bad were the exhaust elbow/reservoir bolts on. Could coolant be leaking were they meet together? Could I try some gasket sealer there? If anyone has changed the exhaust elbow/ reservoir there are four small holes and a big on were the exhaust flows out. The gasket has one open and the other three are closed off. Is it supposed to go on a special way? Could water be leaking out threw the heat exchanger? That would make too much sense because I wouldn?t be able to smell it right?

Any help or input would really really be appreciated. Thank you so much in advance for any help.

 

[Eric 3.7LX Alpha 1]

Re: HELP im loosing coolant????

Sounds like a possible leak in the heat exchanger. One of the tubes may be cracked and leaking out the coolant. It happens when the sea water side is not drained out correctly and temps get below freezing. Open up the end covers on the exchanger and have a look with a light (or) disconnect each end of the coolant connections on the exchanger. cap off one side and pressure test it with a psi gauge. Not too much psi though, maybe 10-15 psi same as what radiator cap is rated for, see if it holds

If damaged can be repaired by a radiator shop, they can solder that tube closed if necessary.

 

[zbnutcase]

Re: HELP im loosing coolant????

Or yes could be a leak at manifold/riser joint.

 

[Don S]

Re: HELP im loosing coolant????

I have the famous 3.7l 460 merc

That is a 470 style, not a 460. It does use the Ford 460 head, but the engine was originally know as the 470.

I would drain the coolant from the engine and heat exchanger and pressure check it to see what is leaking. Isolate the heat exchanger from the engine and pressure test seperately.

 

[stonyloam]

Re: HELP im loosing coolant????

Drain a little fresh water out of the exchanger (aft plug) and see if there is antifreeze mixed in with it. If so probably bad leak in coolant tubes. If OK next most likely place is the exhaust manifold. If it is the exchanger, I would not mess around trying to fix it, you loose cooling capacity when you block off the tubes. These guys have brand new: http://marineengineparts.com/shopsite_sc/store/html/page246.html Good luck.

 

[donkey206]

Re: HELP im loosing coolant????

Thank you for all the help, im gonna test the heat exchanger tomorrow. If it was leaking threw the heat exchanger would i smell coolant threw the exhaust?

 

[legoman67]

Re: HELP im loosing coolant????

yes, because the coolant leaks into the raw system, which is then pumped out the exhaust with the rest of the raw water, 1 gallon in 20 min seems a litte exessive to be the heat exchanger, i would look at your manifold/riser.

 

[Rocky_Road]

Re: HELP im loosing coolant????

My book shows a "SEPERATION PLATE (NON-VENTED)" between the exhaust elbow and the exhaust manifold...meaning that the 3 small ports are blocked off.

Happy boating!

 

[legoman67]

Re: HELP im loosing coolant????

"SEPERATION PLATE (NON-VENTED)"

yup, my boat has them too, for any boat where the manifold is on the closed cooling loop, and the riser gets the raw water. if that plate got damaged or bent then this could be the cause of your problems, or you are lacking the plate all together.... should look something like this: (pic stolen from google images)

 

[Bifflefan]

Re: HELP im loosing coolant????

Leaking heat exchanger

This is what I did to fix mine:
Remove the heat exchanger from the boat and put it on a bench.
Remove both end caps. Drain all the water/coolant from it and let it dry over night.
Get a metal coat hanger and straighten it out. Put something under one end of the heat exc. so it is about 1/2 inch higher than the other end.
Pour acetone in the coolant section (center) of the exchanger and watch the lower end to see if it runs out. It will if you have a bad tube.
Put a light on the bench at the lower end and look through the raised end through each tube until you find the one (or ones) that are leaking. You will see the acetone bubbling inside the tube. Shove the coat hanger through that tube so you know which one it is on both ends.
Bend the hanger over so it wont fall out and repeat as needed till you find all the leaking tubes.
drain out all the acetone and store it back in the jug and let the exchanger dry again.
Here is the part you have options: I did this one,
Stand the exch on one end and mark the hole with the hanger, shove the hanger down the hole so it is about 2 inches down the tube.
Take something and rough up the inside of the bad tube. I used a rat tail file.
Take a tube of RTV and squeeze some down the the tube so it is about an inch down the tube, and then take some J-B stick weld or 2 part epoxy and plug the end of the tube.
Repeat on all the tubes on this end.
Flip the exchanger over and repeat on the other end. this time removing the coat hangers one at a time until all the tubs with holes are plugged. I let mine sit for a couple days and then retested it with straight anti freeze (not acetone) this time and reinstalled it.

Good luck.....

 

[boat_chick]

Re: HELP im loosing coolant????

Same thing happened to me! Replaced the riser gasket. Nothing. Had a little coolant in the exhaust manifold, so I pulled the head and replaced the head gasket. Fixed the problem. For a few months.... This spring I started losing coolant again. I thought, not again!! I started the engine and pulled the pressure cap and watched the coolant rise and overflow out the top. Then a big air bubble came out. So, I pulled the head again. I had 3 mechanics look at it and no one could see where the gasket was blown. Finally some one told me that I had a water leak somewhere. Then we saw the marks on the exhaust side of the block where coolant was leaking out of the water jackets. I had the head and block checked for warpage, and it was a little off in that area. I found a diesel shop that could machine it with the engine intact. It was a little off.... they had to take .005 off the block and .003 off the head!! wow! It should run like a beast now. Almost got it back in. I would look for signs off water leakage and maybe have the head and block checked. I'm glad I did!

 

[donkey206]

Re: HELP im loosing coolant????

Ok so I pulled the raw water outlet hose off of the exhaust ellbow and with the earmuffs hooked up I started the engine, there was no coolant coming out of the heat exchanger just clean hose water. Then I took the exhaust elbow off and there was coolant in the exhaust manifold.

I do not have that plate, however the gasket that I got does block off all the holes but the back one. I think im gonna try and use some gasket maker between the elbow and manifold. If it works than I know I need a new manifold.

 

[legoman67]

Re: HELP im loosing coolant????

is your manifold on the closed cooling loop? if so that hole is definitely your problem! i wouldnt trust gasket maker to keep the hole plugged up, i wouldnt even trust the gasket either, go to your local mercruiser dealer and they should be able to order the correct plate for you if they dont have it in stock. remember you need a gasket on both sides of the plate when you put it back together, so make sure you order enough gaskets when you order the plate.