Assessing a used Yanmar 8HP diesel engine

[HorseshoeBay]

I am also wondering about assessing the injector?

With the head off and the piston out, would this be done by turning the water pump pulley by hand and seeing what happens at the end of the metal injector pipe?

[mcpusc]

Originally Posted by HorseshoeBay

I am also wondering about assessing the injector?

With the head off and the piston out, would this be done by turning the water pump pulley by hand and seeing what happens at the end of the metal injector pipe?

do you have the YSM or YSB/YSE? the injection pump is the part that is really different between them. the YSB type pump is unique among diesels and very sensitive to misadjustment in the linkage, if it's not adjusted to close the needle valve fully as described in the manual you'll get no injection. bleeding the thing can be a bit of a job as well, you may need to bleed at the delivery valve holder if there's an air bubble trapped in the pump. the manual is your friend here, follow the linkage adjustment and bleeding process to the letter. OTOH the YSM injection pump is a more common type and much better behaved, but any adjustments must go to an injection shop.



either way the injection pumps run off a cam on the camshaft. you'll need to set the throttle to max and then crank at more than a minimum speed, then you'll get a dribble of fuel from the HP fuel pipe. you can crudely test the injector by connecting it as described in the manual, but i'd reccomend taking it to a diesel injector shop and having them check it if you have any concerns.



also please pardon me, but are you familiar with the dangers of high-pressure hydraulics? the pressures developed in the injection system can cause devastating injuries and the injector and piping need to be handled with extreme care while troubleshooting! especially if you choose to test the injector off the head keep flesh well away from the business end

[Wotname]

Originally Posted by HorseshoeBay

The interna, walls have a red coating that doesn’t appear to be rust..........

It is a type of paint which Yanmar applied at manufacture.

[HorseshoeBay]

The piston and conrod have been separated.

The riser mixer was examined using a headlamp and a long screwdriver, looking at internal rust, which didn’t seem too deep.

That just could be chipped away, leaving hard material/metal.

Finally, a hose was used to put a decent stream of water into the cooling water inlet.

None of that water drained down the exhaust inlet, instead all flowed out the exhaust hose.

I am considering cleaning the rusted threads and connecting it to the new SS exhaust elbow, which has arrived, in order to test the engine running.

Replacing the existing riser/mixer with a SS part would be another investment.

The valves have been reseated using coarse and fine grinding compounds.

One of the next challenges is the REMOVAL OF THE CYLINDER LINER.

ADVICE WELCOME!

I don’t have a special liner removing tool.

Would putting crushed ice inside the liner help?

Any TIPS?

[Wotname]

Originally Posted by HorseshoeBay

..........ding compounds.

One of the next challenges is the REMOVAL OF THE CYLINDER LINER.

ADVICE WELCOME!

I don’t have a special liner removing tool.

Would putting crushed ice inside the liner help?

Any TIPS?

First bit of advice - don't remove it unless you have to. Inspect for scoring, glazing and wear. The manual gives wear limits and measuring points. You are unlikely to have a bore micrometer but you can do a rough and ready measurement by using the existing piston (rings removed) and feeler gauges. Measure piston diameter with a standard micrometer and insert into liner (upside down) and use feeler gauges to measure the gap between liner wall and piston. Add the two measurements and you have a rough indication of the bore diameter. If it is inside the wear limit and there are no other imperfections, leave it alone.

To remove liner you will need some tooling. See section 14 of the manual for a picture of what Yanmar suggests and then make something similar. I used 1" RHS and long bolt. Basically you need something to pull the liner out and the only purchase you have is the bottom end of the liner.

It is not an interference fit and it is only corrosion that is keeping it in place. Once the corrosion 'seal' is broken, it comes out easily. The new one is refitted by hand without any undue force necessary. Follow all the cautions in the manual.

[Compass790]

You are in good hands with Wotname.
My advice if you want to pull the liner ( but MEASURE I.D. first) is to fill the block with CLR or hydrochloric acid & leave overnight for CLR & Wotname can tell you about hydrochloric. You need to remove thermostat & block drain that is brass or bronze & plug with steel before using hydrochloric. I pulled liner without doing this & it was a helluva battle. Had maximum force on 12mm ss threaded rod & had to beat liner btm with 4lb mallet. Would use 16 or 20mm threaded rod if I did it again.
Yes ice might help but corrosion removal the best way I suspect.
You need to check oil pressure on these engines as oil pump wear can be a problem.

[HorseshoeBay]

The liner doesn’t appear to have much scoring, though there is much varnish-like glazing.

How detrimental is glazing?


Will consider CLR if I pull the liner.

[Compass790]

Originally Posted by HorseshoeBay

The liner doesn’t appear to have much scoring, though there is much varnish-like glazing.

How detrimental is glazing?


Will consider CLR if I pull the liner.

Not sure about the glazing but a honing will strip that off. .
Measure it the way Wotname described to see if bore wear is in the ballpark. But if you are getting a new liner in your rebuild kit I would just replace it anyway.

[HorseshoeBay]

The received rebuild kit includes a liner.

Removing the existing liner has its challenges to properly overcome.

To fill the block with CLR, would it be advisable to attach to head and crank case cover?

[Compass790]

Originally Posted by HorseshoeBay

The received rebuild kit includes a liner.

Removing the existing liner has its challenges to properly overcome.

To fill the block with CLR, would it be advisable to attach to head and crank case cover?

No you dont need the head or crankcase cover, Just need to fill up cooling water galleries & block any holes. Just experiment with fresh water first. Remember remove thermostat & any bronze plugs.

Well if removing the liner is going to be a challenge yes measure first & see if its necessary.

[HorseshoeBay]

As the existing liner has much glazing and the rebuild kit included a new liner, I will look at replacing the liner.

If CLR is used, what’s the best way to block the holes so the CLR can soak in?

How about the lower fixture on the liner extractor?

Would a RHS crossbar suffice?

[Wotname]

Originally Posted by HorseshoeBay

As the existing liner has much glazing and the rebuild kit included a new liner, I will look at replacing the liner.

If CLR is used, what’s the best way to block the holes so the CLR can soak in?

How about the lower fixture on the liner extractor?

Would a RHS crossbar suffice?

I used 1" RHS and shaped it to fit the liner (see attached simple drawing). Use your new liner to size the rounded ends and the lip cut out. If you want to get fancy, make a crosspiece using the RHS and a couple of welds.

Try silicone to seal the holes, it worked for me.

[Island Time O25]

A few years back ordered the mixing elbow for 2qm15 from this guy. His price was more than 1/2 off of Yanmar authorized dealer. He ships internationally as well.

https://exhaustelbow.com/

[HorseshoeBay]

The thermostat and brass drain plug have been removed.

Have Sikaflex? to seal the water holes.

Should the CLR be used a full strength or diluted?

CLR says “do not use on cast iron”.

Any precautions?

[Wotname]

Originally Posted by HorseshoeBay

................

Should the CLR be used a full strength or diluted?

CLR says “do not use on cast iron”.

Any precautions?

Yes, lots of precautions, most of which should be common sense but nevertheless ...

Keep the stuff out of your eyes!!!!!!!
Keep the stuff out of your nose (and lungs)!!!!!!!
Keep the stuff out of your mouth (and stomach)!!!!!!!
Keep the stuff off your skin as much as possible.

That said, CLR is a mild(ish) acid type cleaner and most people use it safely and regularly. Start off with some dilution but if it isn't working fast enough, up the concentration as you see fit.

Disclaimer - I have never used CLR in a cast iron Yanmar block, I use hydrochloric acid (muriatic acid, HCl, brick/concrete cleaner etc) BUT that is far more aggressive than CLR. Unless you are very confident and have some experience with using stronger acids I would NOT suggest using hydrochloric acid.

All (or most) acids are problematic on cast iron as the surface of cast iron is somewhat porous and flushing it out takes time. My guess is the disclaimer with CLR for cast iron is a CYA thing and providing you rinse it extremely well, it should OK. It may discolour a decorative cast iron surface but inside an engine - well not much of a problem. The red coating will likely provide reasonable protection.

At the end of the day, salt water is not good for cast iron but the engine has used it for 40 years. A bit of CLR for a few hours is not a big deal, rinse well, did I say rinse well!

Still, it remains your choice!!!!