3YM30 compatible Radiator Cap

[dave777]

Has anyone had success with a compatible Radiator Cap for the 3YM30?

[dave777]

Originally Posted by dave777

Has anyone had success with a compatible Radiator Cap for the 3YM30?

Noone else?

[chris in SG]

I've replaced mine with regular auto caps, rated at 1.4kg/cm2. Not sure this is the correct pressure, but I've overheated occasionally and the cap opens a little earlier than the temperature alarm.

My engines are 3YM30 too, but surely the 'radiator cap' size and design is an auto standard which is also adopted by marine engine manufacturers?

[dave777]

Originally Posted by chris in SG

My engines are 3YM30 too, but surely the 'radiator cap' size and design is an auto standard which is also adopted by marine engine manufacturers?

I've heard that the cap is very important to the working of the overflow system, which opens at one temperature, and uses suction when cooling to draw back from the overflow. Don't recall seeing this in any car, maybe diesel's, tractors etc. use a similar system. But the official Y----- price on an official cap is crazy, there's got to be an OEM substitute, because Yanmar most likely doesn't make the caps anyway.

[chris in SG]

Seems to me the system is similar to this auto standard:

https://mechanicbase.com/coolant/how...k%20Necessary?

[dave777]

Originally Posted by chris in SG

Seems to me the system is similar to this auto standard:

https://mechanicbase.com/coolant/how...k%20Necessary?

Great explanation.


So the question remains, for the 3YM30, which widely available radiator caps would function as per the engines design

[Island Time O25]

On a tractor forum they're saying that most Yanmars have 13psi cap. But I've seen figures as high as 17.5psi and as low as 7psi.

[chris in SG]

I must admit, until you raised the question, I had assumed the cap dimensions were an industry standard. After googling, I now realize there are a variety of dimensions, mainly diameter of the external cap; diameter of the spring-loaded seal; and depth of the spring-loaded seal below the cap.

I suggest you take the old one to a well-stocked auto supply shop or radiator repair shop and measure carefully.