Over heating Yanmar 3TNE68

[Rob65]

I’ve got a Yanmar 3TNE68 engine in an old 10kva Arcgen generator which is overheating so the safety cut out stops it.

When it stops I have let it cool for half an hr and it only takes about a pint or two of water at most to fill it back up.

It generally only gets run for short periods but today I had it on for about 30 mins and it stopped and then after cooling would run for about 15 mins.

I’ve taken the rad out and reverse flushed it. Not much muck came out and it flows as fast as my garden hose runs so I don’t think it’s blocked internally. The fins are in good condition and if held up to the light I can see through the fins. Have blown the fins clean with workshop airline and not much came out.

Thermostat opens when blown with hot air gun and infrared thermometer said it was at about 70 deg c after it opened.

It’s got about 3000hrs on but the rest of the machine works so I’d like to get to the bottom of this and not have to spend too much cash.

Before I go jumping into this with both feet ithas anyone got any words of wisdom such as known issues with these engines?

Thanks.

 

[Shovelhands]

Not specific to that engine, but have you checked the water pump? Sounds like could be lack of circulation?

The water you are adding, is it spitting it out when it overheats? Or is it consuming it elsewhere?

 

[Rob65]

Not specific to that engine, but have you checked the water pump? Sounds like could be lack of circulation?

The water you are adding, is it spitting it out when it overheats? Or is it consuming it elsewhere?

The water gets blown into the expansion bottle.

 

[V8Druid]

as James says ... water pump not circulating the H2O rapidly enough .. 'praps the impeller is letting go of its shaft when it gets hot(ter) and slowing down/not pumping as it should ??

 

[Rob65]

as James says ... water pump not circulating the H2O rapidly enough .. 'praps the impeller is letting go of its shaft when it gets hot(ter) and slowing down/not pumping as it should ??

Yes, water pump was going to be my next line of investigation unless someone comes up with a better suggestion.

I was a bit reluctant to go for it as to do so means stripping more of the tin work off it and the bolts usually shear off in the rivnuts due to being so rusty. Looks like I’d better get a 5mm drill and M6 taps out ready.

 

[JD450A]

I have two of those engines suffering that fault atm due to worn fanbelts...... As the engine gets to temp the water pump seems to stop... Engine boils.

Dip the revs on the digger and let the pump pick back up nae bother

 

[Rob65]

I have two of those engines suffering that fault atm due to worn fanbelts...... As the engine gets to temp the water pump seems to stop... Engine boils.

Dip the revs on the digger and let the pump pick back up nae bother

Thanks Rory, this is the sort of ‘Inside information’ I was hoping for. I’m busy tomorrow but I’ll find a few mins to check the belt.

When the belts wear are they stretching or are they old and hardened so they don’t grip the pulley?

 

[JD450A]

Thanks Rory, this is the sort of ‘Inside information’ I was hoping for. I’m busy tomorrow but I’ll find a few mins to check the belt.

When the belts wear are they stretching or are they old and hardened so they don’t grip the pulley?

Think it's a bit of both Rob, but the digger is on 4000hrs, and the Other on 3000hrs.... so I'd look at that first.

Has taken a bit of headscratching to find.... Only clocked it was that after taking the cab off the mini digger for a job, having it run into the read on the gauge.... looked down at the fan and saw it was stopped dead.

 

[V8Druid]

the Vee belts lose their section's width as they age and it's the sides of the vee that do the driving ... 's a bloody good shout that Rory ... had to change JakieB's some time ago as although it was tight, it wasn't driving the alternator and fan properly ... not wide enough to fill the pulley's width and merely driving on the flat inside of the belt ... new one cured it no prob.s

 

[Mick-the-fitter]

Is the engine actually steaming hot or is it shutting down on temp switch?

 

[V8Druid]

Is the engine actually steaming hot or is it shutting down on temp switch?

It's pushing a couple of pints into the expansion so i'd guess it's getting close to boiling/steaming to pressurise the coolant into the header/expansion Mick

 

[Mick-the-fitter]

Like the boys have said, go for pump, or head gasket, if it’s got very hot once, the gasket may then leak there after.

 

[Rob65]

I quickly pulled the belt off it today. I’ve seen worse but it’s hard and shiny on the sides. Doesn’t look like the bottom face has been in contact with the bottom of the vee’s in the pulleys.

If the belt had been very bad I might have been tempted to stick it all back together with a new one and see how it went. Given that I’m not totally convinced it’s the culprit I think that since I’m in to it this far I may as well go in a bit deeper and look at the water pump.

It will not be straight forward as the bolts that hold the sheet metal together are very rusty so likely to break at best and possibly will twist some of the already rusted thin panels.

Thanks for all the advice. It will probably be the weekend before I get time on this again now.

 

[Canal Navvy]

Something I've noticed on small engines is that trouble can start when a "cogged" belt is replaced by a plain belt. The plain belts don't seem to cope as well round small diameter pulleys. Probably more likely to result in short life rather than overheating though

 

[Tacitus]

One easy way to find if the belt is your problem, short of replacing it, is to spray a bit of resin on the old belt. This will give it temporarily more grip and stop any slippage if there is any. If this cures your overheating, you know you are in for new belt/s. Not permanent solution but it works instantly.

CRC - Belt Grip 400G

CRC Belt Grip provides a temporary, synthetic treatment for worn belts to extend its life. Reduces slippage, hardening, glazing, dirt build-up and friction Helps eliminate annoying squeaks and squeals Can be used on leather, rubber, canvas, or fabric, and is ideally suited for flat, round and...

www.automegastore.com.au

 

[V8Druid]

....... possibly will twist some of the already rusted thin panels.

disc the heads off, first as last and drill/tap 'em out, as you're expecting to have to do anyway, without doing any further damage Rob

 

[Gecko]

Doesn’t look like the bottom face has been in contact with the bottom of the vee’s in the pulleys.

The belt should never touch the bottom of the Vee - it get its grip from wedging into the Vee itself.
If the current belt is hard and shiny, it's due to be replaced.

The common method of compensating for an old belt is just to keep increasing the tension until it stops slipping, but this can easily overload the pump or alternator bearings.

 

[Rob65]

Right, since the belt looked ok took the water pump off. That looks ok also. Have held the drive flange on the vice and no movement on the impeller when gripped with slip joint pliers.
Did notice someone has been in here before though as the spigot at the back of the pump had red gasket sealing compound all over the o ring.

Having found nothing conclusive I figured in for a penny so in for a pound and pulled the head.

The gasket was a bit delaminated but that might have happened when I lifted the head. Photos of the thing are attached. Can anyone see anything obvious wrong.

I’ll clean everything up and check it for flatness and if nothing is wrong all I can do is put it back together with new gaskets etc and hope.

 

[V8Druid]

Right, since the belt looked ok took the water pump off. That looks ok also. Have held the drive flange on the vice and no movement on the impeller when gripped with slip joint pliers.
Did notice someone has been in here before though as the spigot at the back of the pump had red gasket sealing compound all over the o ring.

Having found nothing conclusive I figured in for a penny so in for a pound and pulled the head.

The gasket was a bit delaminated but that might have happened when I lifted the head. Photos of the thing are attached. Can anyone see anything obvious wrong.

I’ll clean everything up and check it for flatness and if nothing is wrong all I can do is put it back together with new gaskets etc and hope.

how were the bolts, coming out Rob? all dog tight?

 

[Tacitus]

Looks like blown gasket to me, between 2 and 3 ... or is it 1? the one at the bottom of the picture..
Clean it all up and look for cracks in the head. Hopefully none. Use a flat surface like thick glass pane and fine sandpaper on it to check for flatness. Best of course is to take to a shop for machining flat. .
Buy new bolts to mount back and give the correct tension.
The blowing in the water bottle is compression blowing in the water jacket once it heats up and opens the gap..