Assessing a used Yanmar 8HP diesel engine

[HorseshoeBay]

Bought a torque wrench at Repco today.


Please see the screenshot of advice about gaskets.


https://ssch.com.au/warning-on-the-use-of-hylomar/

[skipperpete]

No problem , don’t use Hylomar then.

[HorseshoeBay]

The head was put on and a torque wrench was used to gradually tighten the head bolts.

The engine was manually cranked and produced and held compression.

The starter motor was used to crank the engine for a few seconds.

The valve rocker arms and pushrods were installed.

A feeler gauge was used to set the timing gaps to 0.2mm.

The rocker cover was installed.

Yanmar oil was added.


The next challenge is to setup the high pressure pipe from the injection pump to the injection valve.

On the injection pump, there are two nuts on the high pressure pipe.

Does anyone know the correct way of manipulating these two nuts to align the pipe with the injection valve.

The high pressure pipe is BRITTLE!

[Wotname]

Originally Posted by HorseshoeBay

...........
The next challenge is to setup the high pressure pipe from the injection pump to the injection valve.

On the injection pump, there are two nuts on the high pressure pipe.

Does anyone know the correct way of manipulating these two nuts to align the pipe with the injection valve.

The high pressure pipe is BRITTLE!

Whoa -

The high pressure pipe has a captive flare nut on each end - see blue arrows. Position the high pressure pipe between the injection pump and the injection valve (it only goes one way). Wiggle it a bit to get the flared ends into place and finger tighten the flare nuts. When nicely aligned, torque up the flare nut on each end.

The 'nut' on the injection pump is the 'delivery valve spring holder' and should not be undone or removed unless you are disassembling the injection pump. See red circle and arrow.

The high pressure pipe is HARD but not brittle. It is heavy walled steel pipe about 6mm outer diameter and a 2mm inner diameter i.e it has a 2mm wall thickness. It is pretty hard to break.

[HorseshoeBay]

The Air Bleeding Bolt and washer don’t tighten down and seal against fuel, which leaks.

Fuel does flow down to the Fuel Injection Pump, however, fuel doesn’t come out of the Fuel Injection pump when the engine is manually cranked.

Months ago, on the Fuel Injection Pump, I loosend the Delivery Valve Spring Holder and the whole pump out of curiosity.

[HorseshoeBay]

Recall, on the Air Bleeding Bolt, there was some kind of material wrapped around the threads.

It was loose, so I pulled it off.

Wonder what could replace that material, or would a new bolt be a better option?

[Wotname]

The thread of air bleeding bolt on the fuel filter is notorious for being stripped. The alloy housing is soft and everyone over tightens the bolt, especially after the copper sealing washer work hardens with use and needs more torque to seal properly.

The stuff around the thread is probably thread sealing tape and is a very poor 'fix'. Plenty of opportunity for small broken strands of tape to get into the injection pump.

A better fix is to drill it out and tap a new thread the next size up (or fit a helicoil) You must keep the new thread perpendicular to sealing surface on the housing.

Then toss away the copper washer and use a fibre washer for sealing as it uses far less torque to achieve a seal. Some years ago, Yanmar recognised the problem and replace the copper washer with a fibre washer.

You can buy a new housing but the price might shock you or replace it with a aftermarket filter.

[Compass790]

Originally Posted by HorseshoeBay

Bought a torque wrench at Repco today.


Please see the screenshot of advice about gaskets.


https://ssch.com.au/warning-on-the-use-of-hylomar/

Ok thanks for posting. Thats interesting but in my experience & that of my customers with ys 8 Yanmars you have much less trouble with head gasket leaks if loctite 515 or 518 is used. I posted about permatex 51813 as I believe it is a cheaper equivalent of Loctite 518. But accept it's your choice. I havent actually used Hylomar.
Good choice buying a torque wrench.

[HorseshoeBay]

Compass790,
Do you have experience with the air bleeding bolt on the fuel filter being stripped? Please see Wotname's post.

[Compass790]

Originally Posted by HorseshoeBay

Compass790,
Do you have experience with the air bleeding bolt on the fuel filter being stripped? Please see Wotname's post.

Yes I do but I got rid of the whole setup & just have a different fuel filter.
What Wotname said is good advice if you want to retain Yanmar one & I would if you are fixing for resale.

[HorseshoeBay]

The Air Bleeding Bolt is a banjo bolt isn’t it?

Looking for the size of the original bolt and then one size up?

Must the new bolt be a banjo bolt?

Also need a matching fibre washer.

[Compass790]

yep go 1 size up, easier to bleed if it's a banjo but can get away without it. Nylon washers work too but fibre better probably

Take skipperpetes advice & retorque head after the motor has run hot too.

[HorseshoeBay]

Looking for sizes of new one size up bolt and washer.

[Wotname]

Originally Posted by HorseshoeBay

The Air Bleeding Bolt is a banjo bolt isn’t it?

Looking for the size of the original bolt and then one size up?

Must the new bolt be a banjo bolt?

Also need a matching fibre washer.

Why don't you look at the existing air bleed bolt or the diagram you posted upthread. This will tell you quick smart what kind of bolt it is and far faster than posting on CF.

[HorseshoeBay]

Learning by mistakes: drilled a 1/4 hole for a thread tap marked 1/4!

Had a 5/16 W18 tap, which worked in the 1/4 hole.

Now need to locate an appropriate bolt and washer.


Rewinding: the washer that was on the original nut looks like nylon?


The fuel filter housing will be disassembled and thoroughly cleaned so nothing, such as a small chip of aluminium, goes a damages the injection pump.

Wonder how many people cruising remotely have had a Yanmar incapacitated by the Air Bleeding Nut leaking fuel?

The engine certainly has design/material weaknesses.