Coolant Recovery

[Red Herring]

Hi All,

A quick question. I have a new to me boat with a Universal 5424. I did a full service on the motor last weekend including a coolant change, and noticed that the PO had a 14 pound cap on the manifold, stock is 7, and there was also no coolant recovery system.

So my question is... are coolant recovery systems - hose and reservoir - not standard on marine diesels? I have looked at a number of diagrams, and not seem one depicted. I have ordered a kit off amazon, and will install it next weekend.

Thanks!

Steve

[Wotname]

Originally Posted by Red Herring

Hi All,

A quick question. I have a new to me boat with a Universal 5424. I did a full service on the motor last weekend including a coolant change, and noticed that the PO had a 14 pound cap on the manifold, stock is 7, and there was also no coolant recovery system.

So my question is... are coolant recovery systems - hose and reservoir - not standard on marine diesels? I have looked at a number of diagrams, and not seem one depicted. I have ordered a kit off amazon, and will install it next weekend.

Thanks!

Steve

Dunno about most marine diesels but Yanmar only provided them as an optional extra on their earlier coolant cooled engines.

I have seen many aftermarket ones fitted and just as many without!

[Red Herring]

Ha. Thanks for that. I kind of figured as much. I noticed coolant venting after changing the coolant last weekend, and thought it was weird that there was nothing to catch it. I'm going to install one regardless!

[Cat36Mahalo]

You’ll need to change the cap to be a coolant recovery style. I added a recovery tank to my Universal M25 and it didn’t work. That’s when I found out the recovery system need a different cap (not pressure related).

[tkeithlu]

You can deal with excess heat by increasing the boiling point with a pressure cap or deal with it by coolant recovery. Older engines (my main and my Universal M25 genset) do it with pressure. If your engine has a pressure cap and 14# to boot, and is still over-pressuring the system and spilling coolant, I'd suggest you clean your heat exchanger, check your raw water temperature, and generally make sure that you are adequately cooling the engine.

[Red Herring]

Originally Posted by tkeithlu

You can deal with excess heat by increasing the boiling point with a pressure cap or deal with it by coolant recovery. Older engines (my main and my Universal M25 genset) do it with pressure. If your engine has a pressure cap and 14# to boot, and is still over-pressuring the system and spilling coolant, I'd suggest you clean your heat exchanger, check your raw water temperature, and generally make sure that you are adequately cooling the engine.

Thank you. I replaced the cap with a modern 7# and later read in an original parts manual that the last owner had it right with a 14#, which didn't vent, and had no issues with coolant loss. I might be chasing my tail here, and will reinstall the original 14# cap and leave it at that.

[Bill O]

Many years ago coolant recovery tanks were not in all cars, but they are now. I added one to our Perkins 4.236 when I got the boat and replaced the cap at the same time to avoid coolant loss issues.

I think the coolant recovery tanks are a good way to monitor the coolant levels better and possibly detect leaks/coolant loss before it becomes a problem. Also if you need to add coolant to the hot motor w/the pressurized system it can be a big safety issue. People were scalded/steam burned when they attempted to add coolant to an overheated car engine before it cooled down. Just for the safety issue its worth adding the expansion tank.


Bill O.

[Uncle Bob]

Originally Posted by Red Herring

Thank you. I replaced the cap with a modern 7# and later read in an original parts manual that the last owner had it right with a 14#, which didn't vent, and had no issues with coolant loss. I might be chasing my tail here, and will reinstall the original 14# cap and leave it at that.

Just to reinforce the point already made, the cap you need has two seals not just the one that is found on a system without recovery tank. The second seal is directly under the cap itself, in addition to the seal on the spring loaded relief valve.

[a64pilot]

The whole idea of an overflow tank is so that the cooling system can remain totally full of liquid and not have any air, the reason is air contains oxygen, and oxygen causes corrosion of course.
If you have a system that is 100% full of liquid it’s going to expand from heat and since liquid isn’t compressible it’s going to overflow, if you don’t have a tank then when it cools it’s bringing air back into the system, with enough air space then you have some compressible air and of course room for the liquid to expand, that is why in old cooling systems you don’t fill to the top, you need some air space.

So an overflow tank system will be exchanging fluid every heat cycle.

This is not to be confused with an expansion tank, that’s a completely different animal, and isn’t the kind of thing you add later.

The cap needed for an overflow tank is easy to determine, if you hold it level it will have a washer like piece of metal hanging loose in the center of the rubber gasket that is just hanging there, that is a one way valve that will open if there is ever even a tiny amount of vacuum in the system and will of course allow liquid back in from the tank. When the engine is running it will quickly build pressure due to heat and when the cap hits its pressure setting, it will open and allow air if there is any and liquid if there isn’t to flow into the tank, that is how an overflow tank system will automatically over time purge any air in the system.