Mercruiser 470 static antifreeze loss

"I have Mercruiser 470 engines

"I have Mercruiser 470 engines. One of my engines loses antifreeze when the system is not pressurized. Some days I go to my boat and find the bilge with approximately a quart of antifreeze in it, some days the engine has not lost any antifreeze.

The engine runs great with a temperature range between 160-180 dependent upon how hard it is being run. When running, the engine does not lose antifreeze.

I warmed the engine up and pressurized it as the engine was cooling and lost no pressure. I pressurized the system the following day, when it was cool and it had lost antifreeze, to 14 PSI and it lost no pressure in a 2 hour period. It seems to happen after the engine has cooled and set overnight.

I have been unable to locate any indication of where the antifreeze is exiting the engine. It is not going out through the overflow container.

Any suggestions? It gets old frequently cleaning a bilge and purchasing antifreeze."

"Place several sheets of newsp

"Place several sheets of newspaper under the engine. It will show the location it's coming from. If it is hard to determine the origin, put a packet of dye in the antifreeze, run it awhile then place the newspaper in place to find the leak. Use a black light to check the engine. The light will show the origin. I'm betting the engine circulating impeller seals are giving out."

"Funny you should say that. I

"Funny you should say that. I went down again today and was approximately one quart low on antifreeze. I refilled the antifreeze and ran the engine up to temperature. After I shut down, I placed white terry cloth towels under the heat exchanger, water pump and exhaust elbow and reservoir.

It appears that the only antifreeze I am losing is what is in the reservoir assembly.

In a couple of days, I will go back and see what this yields."

"Jeff, you say that the reserv

"Jeff, you say that the reserve antifreeze container is not leaking, but how about the connecting hose to the rad filler area? The filler should only be open when the system is pressurized, so you may either have a bad connection, or a rad cap that is not holding pressure and is somehow letting the extra fluid leak out."

I thought about the radiator c

I thought about the radiator cap and had swapped it with my other engine with no change. I have also capped off my overfill hose and still lost antifreeze. I think this rules out those items.

I went down yesterday to check where I had placed my towels. There was no sign of antifreeze on any of them and yet I was a quart low again. Another afternoon cleaning out the bilge.

What is weird is I only lose what is in the reservoir on top of my exhaust manifold and it only does it when the engine is cold.

I still need to confirm my connections to my heat exchanger are not leaking externally. Today I will be warming up the engine again and placing towels around all of the connections to the heat exchanger.

"Have you used a radiator pres

"Have you used a radiator pressure checker yet?

You can do this cold.

It may be the only way to find the leak.

One like this.........

http://www.sears.com/shc/s/p_10153_12605_00915510000P?vName=Tools&cName=Auto&Mec hanicsTools&sName=Auto%20Specialty%20Tools&psid=FROOGLE01&sid=IDx20070921x00003a"

"I warmed the engine up and pr

"I warmed the engine up and pressurized it as the engine was cooling and lost no pressure. I pressurized the system the following day, when it was cool and it had lost antifreeze, to 14 PSI and it lost no pressure in a 2 hour period."

go higher say 16 -18 psi and

go higher say 16 -18 psi and try to force it a bit.

Also can see any residue trails left anywhere from the antifreeze?

it may have something to do with the elbow block off blate??

I am also confused as you said you needed to clean up the bildge? what did you have to clean up? If antifreeze then you should be able to find its source.

I know this sounds like a long shot but maybe try to find some florecent dye that a black light will illuminate and put it in the antifreeze and retest and maybe you will be able to find the source. Maybe at a arts and craft store???

"The bilge clean up was in reg

"The bilge clean up was in regards to the antifreeze I am losing. It is exiting the engine, but I have not been able to trace where.

I haven't been able to find a residue trail, but there are places I am not able to see well under the engine. This is the reason I am placing white towels around the engine parts to see if I can determine where it is coming out.

Today, I went down to the boat and there was no antifreeze loss. I ran the engine again to get it up to temperature and then placed white towels around the fittings and the heat exchanger. I'll go look at it again tomorrow to see if there is any evidence of leaking."

Looks like you are going to ha

Looks like you are going to have to pull an all nighter to see when the leak starts. I had a van once that would do the same thing. I put some dye in the antifreeze and found the leak the next day; water circulating pump was the culprit. You can get the dye at any auto parts store.

"Jeffrey Wisner, as the other

"Jeffrey Wisner, as the other guys stated the leak could be coming from anywhere! But there is a small hole on the front lower part of timing cover that will leak coolant when the front seal on your 470 engine is shot. This is an indicator that you should not run engine because if the second inside cam seal goes it could possibly let coolant into the crankcase. If you find that the leak is at this location then you will have to replace the two cam seals behind water circulator and while you are at it replace the crankshaft oil seal. Also, you will probably have to install a jiffy sleeve on camshaft end because of grooving."

"I placed a white towel below

"I placed a white towel below the timing cover weep hole previously and had no indication of leaking from there.

Today, I went back and had lost no antifreeze for the second day in a row."

"I am glad to hear that Jeffre

"I am glad to hear that Jeffrey, maybe you will get lucky and its a bad hose or something.
It could be anything! best of luck, Tom"