Antifreeze Disappearing

[anchorman]

The antifreeze in the overflow bottle keeps going down to the add line. It doesn't make any difference if the engine (Universal M35) is running or not. There isn't any antifreeze in bilge. Have change overflow bottle, had a hole in it, but didn't solve problem. Whenever I check fluid in engine it is full.

[Paul L]

Put a white engine diaper under the entire engine. You will likely see some drops after awhile.

[anchorman]

If that happenes where is it coming from?

[Bleemus]

Are you seeing signs of water or coolant in the oil? Does your exhaust smell sweet?

[macman4190]

In my case, I tightened every single hose clamp on the engine.

[belizesailor]

Originally Posted by Bleemus

Are you seeing signs of water or coolant in the oil? Does your exhaust smell sweet?

^^ This is the highest priority path...eliminate the possibility of internal leaks before you worry about external.

[hellosailor]

if it isn't leaking externally, you really want to eliminate the question of where the internal leak is. Especially the head gasket.

[meridian28]

Does it continue to go below the add line? If not you should be ok.

[Suijin]

Another avenue to check is your heat exchanger. If the tubes corrode your coolant will mix with sea water and adios coolant hello corrosion. If you can’t find any other leak pull the exchanger and pressure test it (easy). You can’t find leaks through visual inspection.

Has the zinc in the exchanger been inspected/replaced regularly, like every three months? If not then dollars to donuts on an old Universal you’re looking at a new exchanger.

[Jd1]

I had the same issue with an M35B engine. Took quite a bit of time to find the culprit - an old hose. I had checked and tightened all the hose clamps but as it turned out, the 'sort of' hard hose just couldn't seal properly around a hose barb no matter how tight the hose clamps were.
I did see a tiny leak but on my engine the reservoir is maybe a litre and it would take two or three weeks to loose enough water to cause an issue.

[Peregrine1983]

Wait until night. Get a flashlight. Turn off all the lights.

Search around the engine and bilge with the flashlight. Green antifreeze will pop right out to your eye in these conditions and you'll find the leak.

Good luck