Yanmar 2GM20F, No coolant reservoir?

[paulg222]

I have a Yanmar 2GM20F 1982 era in my boat (Hunter 33). I'm fairly new to this boat (got it this year). I noticed it has no coolant expansion tank/reservoir. Is that normal?

Won't coolant just come out of the hole where a tube is normally present that runs from the coolant fill to the expansion tank (yes there is a spot for the tube to attach although I haven't verified that the hole is actually open).

Also, lol, I tried opening coolant fill top for first time recently (yes engine was cool) and while it did turn and seem to come looser, I could not lift it off the tank. Didn't want to force it, not sure if there is some other trick, is it normal for these to stick even if you are able to rotate them to what seems to be the open position?

[zemurray]

Mine has a coolant reservoir.

[Wotname]

Originally Posted by paulg222

I have a Yanmar 2GM20F 1982 era in my boat (Hunter 33). I'm fairly new to this boat (got it this year). I noticed it has no coolant expansion tank/reservoir. Is that normal?

Won't coolant just come out of the hole where a tube is normally present that runs from the coolant fill to the expansion tank (yes there is a spot for the tube to attach although I haven't verified that the hole is actually open).

..........?

Normal - yes and no!

Yanmar highly recommends the fitting of an expansion tank but it does not mandate it.

Is it a good idea - yes.
Is it essential - no.

From the manual.

[Fore and Aft]

I have the exact same motor and got my coolant tank off eBay. It seems to work well.
https://www.ebay.com.au/i/2831933459...hoCDOYQAvD_BwE
Cheers

[stormalong]

I have had three diesels on two boats and none of them had expansion tanks. I add one to my present engine. You can (could) find them at many autoparts stores.

[Mike Banks]

They all have coolant reservoirs unless very old--anything where the tank is not connected directly to the water pump or thermosiphon will need a reservoir. It looks as though your hoses are stretching to compensate for the expansion--at best temporarily--or your coolant is going into the bilge--assuming your engine thermostat has not been removed and tossed into the drink--

[bstreep]

Just add one from fleabay or amazon. Easy to do, and good to do. Our generator, same basic engine, didn't have one.

[Boatyarddog]

Originally Posted by paulg222

I have a Yanmar 2GM20F 1982 era in my boat (Hunter 33). I'm fairly new to this boat (got it this year). I noticed it has no coolant expansion tank/reservoir. Is that normal?

Won't coolant just come out of the hole where a tube is normally present that runs from the coolant fill to the expansion tank (yes there is a spot for the tube to attach although I haven't verified that the hole is actually open).

Also, lol, I tried opening coolant fill top for first time recently (yes engine was cool) and while it did turn and seem to come looser, I could not lift it off the tank. Didn't want to force it, not sure if there is some other trick, is it normal for these to stick even if you are able to rotate them to what seems to be the open position?

Probably just push down hard while turning to remove the cap.
Did you say you had no tank? The cap should be on the coolant tank.
Was the tank removed for some reason?
2gm20f is a fresh water(block surrounded with antifreeze) cooled engine.
Was yours converted to a raw water cooled engine?
Or it came with a remote mounted tank? Or no tank.
Confused,
SV Cloud Duster

[paulg222]

Originally Posted by Boatyarddog

Probably just push down hard while turning to remove the cap.
Did you say you had no tank? The cap should be on the coolant tank.
Was the tank removed for some reason?
2gm20f is a fresh water(block surrounded with antifreeze) cooled engine.
Was yours converted to a raw water cooled engine?
Or it came with a remote mounted tank? Or no tank.
Confused,
SV Cloud Duster

It has no plastic expansion tank (or whatever that is called, perhaps "recovery tank"). It has a main coolant tank and is fresh water cooled but there is no hose leading from the main coolant tank to an expansion/recovery tank, although there is a spot for a hose just below the coolant cap. I will try pushing down while turning technique, thanks.

[paulg222]

Originally Posted by Mike Banks

They all have coolant reservoirs unless very old--anything where the tank is not connected directly to the water pump or thermosiphon will need a reservoir. It looks as though your hoses are stretching to compensate for the expansion--at best temporarily--or your coolant is going into the bilge--assuming your engine thermostat has not been removed and tossed into the drink--

It has a main coolant tank, but no plastic recovery/expansion tank. It is from 1982 so that is pretty old. Previous owners had boat for 16 years and unless they removed this expansion tank it has been running like this for a while. I should probably ask them how often they topped up the coolant.

Assuming that nothing is jammed in the mechanism, once the coolant reaches the pressure rating of the cap, coolant would flow out of the hole that is just below the cap (with no hose attached), and yes into the bilge. Unclear if this would actually be in vaporized form or liquid. If vaporized form at least it won't be leaking down on other parts of the engine directly (but condensing somewhere and then to bilge). Buy yeah if that mechanism isn't working then I suppose the hoses would take the load (bad, but hey at least not losing coolant).

[kevincook]

My father had a 3QM30 and the cap on the heat exchanger was difficult to remove, you had to press down on the cap much harder than a typical automotive radiator.

Also, the boat did not originally have an expansion tank, the fitting for the overflow was simply capped off. We added a small expansion tank.

[Wotname]

Originally Posted by paulg222

....... once the coolant reaches the pressure rating of the cap, coolant would flow out of the hole that is just below the cap (with no hose attached), and yes into the bilge. Unclear if this would actually be in vaporized form or liquid. .........

Unless the engine was badly overheating, any escape from the cap would be liquid.

[Boatyarddog]

Originally Posted by paulg222

It has no plastic expansion tank (or whatever that is called, perhaps "recovery tank"). It has a main coolant tank and is fresh water cooled but there is no hose leading from the main coolant tank to an expansion/recovery tank, although there is a spot for a hose just below the coolant cap. I will try pushing down while turning technique, thanks.

Sorry for my confusion.
That is a recovery overflow tank.
The coolant tank is the metal one.
Those caps can be a bugger to get off.
Thanks for the update.
Cheers,SV Cloud Duster