Yanmar / Barrus coolant leak. 4TNV88-D

[frlrubett]

Yanmar 4TNV88-D Engine. Had a coolant leak which was presumed to be from an old coolant hose. Replaced coolant hose, cleaned up the joint and added new jubilee clip. 3 months later, there is still a coolant leak, each time I run for an hour there is two sheets of kitchen towel to mop up.

Have investigated further, cannot tell exactly where the leak is coming from but it seems to originate from the same area as before. If we assume the new pipe is doing the job, where else could be leaking?
 

In the pictures attached, is there a gasket on the green arrow? If you look closely, it seems like the gasket at these points (or something similar) has been pushed out of this joint. What is this part called and could this be causing a leak?
 

If the above theory is not possible, where else could this leak be coming from (if we assume the new pipe is fine). If you look at the picture you can see there is some tissue paper underneath this joint, this paper becomes saturated with coolant. I have other bits of paper in other areas below and around this which have not taken on coolant, so I am confident this is where the leak is. Any ideas?

[Tony Brooks]

I would call it the coolant engine header tank and a gasket failed there is likely to leak. New gasket, clean up the faces and I would give both sides of the gasket a smear of grease before fitting, but some would use a thin spread of a gasket sealer (don't know the brand manes these days but Hylomar was good.

[Eeyore]

Looks more like one of Barrus’s dual thermostat housings. The lower temperature thermostat is in the standard position below the black block. The higher temperature thermostat is beneath the cover you are pointing to. The gasket is probably the best that could be found last time it was changed, hence the “hanging out” appearance. It can be quite challenging to stop the stat from dropping a little during assembly; over tightening can then  cause the cover to distort. A little grease can be used to hold the stat in place. Check the cover on a flat surface, typically a piece of glass (the smooth underside of a glass chopping board will do). Use a sheet of emery cloth on the glass to rub away until flat again. Don’t try bending it back as this usually makes things worse!

Edited to add:

They actually look like the tabs you sometimes find on gaskets.

Follow @Tony Brooks advice re grease or sealant on any new gasket. 

Edited February 25, 2023 by Eeyore

[frlrubett]

18 hours ago, Tony Brooks said:

I would call it the coolant engine header tank and a gasket failed there is likely to leak. New gasket, clean up the faces and I would give both sides of the gasket a smear of grease before fitting, but some would use a thin spread of a gasket sealer (don't know the brand manes these days but Hylomar was good.

Thanks for this,

Is there an OEM gasket available for this ?

[Tony Brooks]

I am sure there is, from E P Barrus of Bicester.

[Tracy D'arth]

Rather than wait for an expensive gasket, corn flake carton and grease works every time.

[Eeyore]

Last document on this page

https://www.barrus.co.uk/divisions/marine/diesel/shire/downloads/shire-parts/?p=1

Bottom of page 16.

Your engine is a Barrus 40, build code 05. Normal format in the parts book is Shire 05 40