Adding a coolant recovery tank/bottle

[Steve DAntonio]

My MD2030 does not have a coolant recovery tank. There is an overflow hose that runs to the bilge; the radiator cap appears to be a standard cap rated for 13 psi. I would like add a tank, so I can more easily monitor my coolant level. Volvo Penta sells a setup that includes a tank, modified cap with hose nipples, and clamps (see pics). Unfortunately, the package costs over $300 (minus the electronic monitoring system)!

Is there an alternative product I can use? I am a little confused regarding how this set-up works. I assume there must be a pressure release valve in this modified cap. If not, how does it maintain pressure to avoid boiling?

Thank you for your help!

I believe the tank shown here, and the diagram depict, a remote expansion tank, rather than a coolant recovery tank. Expansion tanks are pressurized, as this one appears to be, recovery tanks are not.

You could ad a recovery tank provided the pressure cap you now have uses two rubber gaskets, rather than one metal and one rubber, the second rubber gasket is needed to allow the engine to develop a vacuum when shut down cooling, to draw fluid back into the cooling system. You'd only need to replace the cap to use a recovery tank, if the one you have does not include the second upper rubber gasket.

This short article explains the concept in detail. https://stevedmarineconsulting.com/the-benefits-of-coolant-recovery-bottles/

Remote expansion tanks are often used to accommodate an engine-heated water heater whose heat exchanger is located above the engine's pressure cap. Those are discussed in this article https://stevedmarineconsulting.com/water-heater-primer/

 

[Vashon_Trawler]

I believe you nailed it, Steve. The Volvo Penta tank does indeed look like a remote expansion tank. It does appear pressurized--this makes perfect sense now. Paying over $300 for a cap and a pressurized plastic tank that could crack/fail over time is not a consideration. The electronic level sensor alam is no longer available.

Given all the information, I will simply purchase a recovery bottle to use with my new cap. I really appreciate everyone's help. This has been an interesting thread!

Chris

 

[Sammy_Mariner]

Coolant Recovery

Hi,
In the automotive world, especially the classics, I advocate coolant recovery systems. Not sure about your particular setup and maybe you have already pinned it down. The radiator's (RAD) cap is made for use in a "recovery" system. The overflow from the "RAD" neck goes to the Coolant container's inlet side. There is an overflow side to the container for when it fills beyond capacity.

For those that may not know the science behind their use.....

When the engine is in use there is a certain level of coolant expansion. If this expansion is great enough, it forces the inner seal of the RAD cap off it's "perch", thereby, allowing the coolant to flow into the recovery container. Later, when moored, perhaps over-nite, as the engine and coolant cool down, there is a negative pressure created within the engine and RAD. This negative pressure pulls/sucks the coolant back and into the RAD (if all is working correctly). Over time,this repeated expansion and contraction replaces any air caught in the cooling system (mostly the block) and replaces it with coolant. One can tell if the system is working as designed, when the system is cooled to the point, one can remove the RAD cap, the coolant level should be right at the level occupied by the cap's seal.
Hopefully this is useful to some.

 

[Dave_E]

Greetings,
Mr. VT. On a previous Lehman we owned I did just that and yes, it WAS one way but it allowed me to monitor how much coolant was spewed out with a quick glance. Every so often, I would simply empty the remote tank back into the coolant reservoir. Not a big deal to do during the morning ER checks. At that time I was unaware of the coolant recovery tank available from AD for the Lehmans.

Bump.