Coolant level on 2010 R25 Classic with Yanmar 150

[AlanSutton]

We have and R25 with the Yanmar 150 engine. Does anyone know how to check the coolant level since the cap is under the cabin bulkhead? Our marina has asked the question.
Last season we had an overheating problem, and I wanted to check the coolant level. I added coolant to the overflow reservoir and as the engine cooled it flowed into the engine. There are no signs of antifreeze leakage in the bilge.
Thanks for any thoughts.
Alan Sutton

 

[scross]

Yes, the cap is under the bulkhead. It still can be removed. Remove only when engine and coolant are cold. Removing the cap is the only reliable way to correctly check the coolant level. You need coolant right to the top until ithe fluid starts to overflow. Trying to completely fill the coolant by only filling and refilling the overflow container will not do the trick.
After a coolant change you need to fill to top, run engine for 5-10 minutes, let cool down, remove cap again and refill to the top again. This is sometimes called “burping” the coolant.
A flat radiator cap wrench tool makes it easier to remove and replace the cap.
Low coolant levels will definitely cause an overheating problem on the 4BY2 engines.

 

[CaspersCruiser]

We have and R25 with the Yanmar 150 engine….. I wanted to check the coolant level. I added coolant to the overflow reservoir and as the engine cooled it flowed into the engine….

Your engine is the 4BY2-150. I have the 180 HP version of that engine. It’s the same block.

I learned the hard way on my engine that the overflow tank is not the way to add or check the coolant level, even though it is marked as such. When my engine was running hot, the owner of another 4BY2 powered Ranger Tug suggested checking the coolant level. I showed them the overflow tank had a perfect level. He said, “Oh, you can’t go by that,” in a tone of voice like I should have known that. We removed the coolant cap on the engine and saw that coolant wasn’t even visible.

So even if that coolant cap is located in a poor position, apparently the only reliable way to check the coolant level on the 4BY2 is to remove coolant cap an see what the coolant level is.

 

[AlanSutton]

Thanks for the replies.
It is probable that my coolant level has been low for some time, since I can't get at the filler cap. I'll look for a "flat radiator cap wrench" because I can't get it off by hand.
Then how to add fluid. It sure isn't accessible.
Thanks again!
Alan

 

[glider4]

The radiator cap wrench came with our 2009 R-25 Classic so I don’t know where it was obtained. I included it when we sold the boat. Kinda looked like this but much smaller.
https://a.co/d/2VKo1pd

I was told by another R-25 Classic owner that he had tried adjustable pliers and had twisted the caps mounting flange by yanking on the pliers too hard. He liked our wrench and ended up making a dual position one like ours out of a 3/8” thick piece of UHMW plastic using a spare cap as a template and a jig saw to do the cutting.

 

[AlanSutton]

Thanks for the information on the filler cap wrench. I'll see where I might find one. Maybe our marina has an idea.
But after the cap is removed, do you check the coolant level by feel? And then how did you add coolant? With a hose and funnel?
Thanks again. This information is really helpful.
Alan Sutton

 

[scross]

Funnel with Tygon tubing to reach into fill area. Either pour coolant very slowly until it starts running over top, check by feel or some comb of both. Much easier to do with two people involved. You want the coolant right at the very top!
And if it takes a lot of coolant to fill it (say more than a pint) then I would burp it by running the engine for 5-10 minutes, letting it cool down then fill again.