MCM 470 Coolant leakage

[GaetanfromAnnecy]

I recently did the rehab of the waterpump gasket on my mercruiser 470. (water pump on top of the camshaft).
I did also change all gastket on the exhaust manifold side.
I do not see any leakage on the hoses.
The engine is 1983, with low mileage (300 hours)

Nevertheless I did restart the engine a couple of times and after I still have to refill the coolant (a small quantity (200 ml) but everytime I need to refill. I believe the coolant is leaking down in the bottom of the cale but I'm not 100% sure of that.
Any thoughts ?

 

[alldodge]

Re: MCM 470 Coolant leakage

No 470 expert here but my comment may be noticed by others. My understanding is the water pump has a seal which if damaged can leak coolant into the raw water system and this could be causing your issue.

 

[stonyloam]

Re: MCM 470 Coolant leakage

I believe the coolant is leaking down in the bottom of the cale but I'm not 100% sure of that.

cale???? Do you have the hose from the reservoir properly hooked up to the expansion tank? Is the expansion tank filled to the "fill line"?

 

[Eric 3.7LX Alpha 1]

Re: MCM 470 Coolant leakage

You have plenty of experts here... and plenty of us 470 owners here as well.. :facepalm:

Exactly where do you see coolant leaking from??

If you replaced a gasket..... thinking that was the leak near the water circulating pump on the engine... take a closer look and see if the leak may be coming from this spot on the front cover:


Oh yeah welcome to Iboats... and the 470 club.. :facepalm: :facepalm:

 

[GaetanfromAnnecy]

Re: MCM 470 Coolant leakage

Terry,

Thanks for your reply. Actually no, the expansion reservoir is not filled. Should I fill it ? I thought this was just working as an overflow ?

 

[stonyloam]

Re: MCM 470 Coolant leakage

It works just like in your car. When the antifreeze in the cooling system heats up it expands and has to go somewhere, so as the pressure builds to about 14 PSI the spring in the cap releases and the excess coolant flows out, through the tube into the expansion tank. Then when it cools it is sucked back into the reservoir. If it is set up properly it will keep the system full. So you will want to keep the tank about half full (there is a line on the tank) so the coolant can go back and forth. If the hose is not on or leaks the coolant will flow out and be lost. You might want to do a compression check and cooling system pressure check ( borrow the tools from Autozone). Pull the plugs and take a look at the insulators, should be tan or brown, if white may indicate coolant leaking into cylinder.