Yanmar 3GM(F) Water Heater Performance

[zds]

Yes, but mine takes longer than that. The issue is I can't figure out why.

I've always suspected my engine "runs cool" and that the thermostat doesn't need to open up until I've done some serious motoring. This would stop coolant from circulating.

Can anyone show me how to route the lines so that they're both on the pump side of the thermostat, ideally with a picture?

 

[petersea]

ZDS, your set up (at least at the engine) is all ready bypassing the thermostat. The thermostat also all ready has a bypass built in to it when it is manufactures (small hole just to relieve pressure) Remember not all engine have a heater or hot water unit to go to. The stat sits in the block and your return line is above it. The supply line is on the pump and will pump to the hot water heater any time it is turning. Your system while it is slightly different then Kloudie 1 set up should still work. I still think you need to take the return line off and verify it is in fact the return and that it is not crossed at the water heater. The only thing I noticed is that your may take a longer time to heat up the engine because the return line is entering cooled water back into the engine but it should still work after the engine is hot and you say your will get hot fairly quickly. You also said you think your engine runs cool so I am confused as to why it get hot so that it is "untouchable". Are you sure you have a thermostat ?? have you every taken the housing off and verified it is there and the correct one ? Sort of all that if you look at Klodie 1 picture and you will see his water temp sender is mounted on the front of the engine below the thermostat while your is below on the side. The significance is that his return is where you sender unit is. That will not really change anything but could account for a slightly longer time heating things up but very marginal. I think you need to verify that the lines are not switched on the hot water heater and that the return is in fact flowing good. If you engine water pump is not working correctly this could also explain some of your issues. Did you every verify that you have good circulation after the thermostat opens and how long it takes to open (the water will be visible flowing once the stat is open with the cap off should not be more then 10 mins under load from a cold start). The return line from the heater will have a flow similar to a water hose at about half volume. What confuses me is you think your engine is running cool but get untouchable in 15 min again I am talking about the engine heat exchanger and you will be able to hold you hand exhaust elbow after where the water enter on a normal water temp). I still think your engine water pump may be bad (impeller slipping while this is not common it does happen) or the lines a crossed or blocked somewhere. keep us posted as I for one am curious what the problem is .

 

[zds]

Pete-

Thanks. When I say it gets untouchable, I mean the engine and the coolant loop lines near the engine. However, this doesn't seem to circulate for a long time, though it does eventually circulate, and I can't figure out why.

As for removing the "radiator" cap, I'm pretty sure mine pressurizes when it gets hot... won't leaving it open cause an overflow?

 

[petersea]

No remove cold and leave off just to test.......a small amount may overflow if system is overfilled but the level will remain at the neck if everything is working correctly. test at a high idle (1000 rpm)

edit to add; DO NOT remove a hot pressue cap ! !

 

[zds]

OK, just returned from testing and can confirm the following:

1. It's not a problem at the water heater, either a blockage or the tempering valve (I confirmed flow and bypassed the valve).

2. There are two water pump designs: old and new. Old, which I have, has the coolant SEND above the thermostat, meaning that nothing goes TO the heater until the thermostat opens. The new style has the send below the thermostat.

3. With the engine running at 2,000 and cold, there's nothing coming out of either of the heater coolant lines.

4. When the thermostat opens (verified by the warming of the hose between the thermostat and the reservoir, and of the reservoir itself), there's still no significant flow to the heater.

5. Eventually, once everything gets good and hot, there's flow. I suspect it takes this long because the coolant flows past the bypass outlet, and takes the less-restrictive route through the cooling system.

So, I either need to buy a new pump (not thrilled about this) or figure out a workaround.

 

[kloudie1]

Reverse the positions of the temp switch and the heater outlet pipe like Dan's engine picture shows and it will work MUCH better. The thermostat creates a pressure drop even when open that will force much more water through the water heater. The engines before serial # 5548 didn't have the extra tapped hole. That is in the pump body bracket. My engine (6897) apparently has an extra threaded hole on the front side of the pump body bracket (thermostat housing), which ya can see in the picture.. Good luck with it, ZDS ..

 

[kloudie1]

Yanmar 3 GMF Water Heater

"Nother note.. here is a picture of the front of my engine. You can see that where your "out" to the heater is, on my motor is plugged and the switch and the heater connection are both in the pump "body bracket", below the thermostat. The downside of putting the temp switch downstream of the thermostat is that if the thermostat fails closed, you will overheat and not get an alarm. Thermostats normally fail open. Lots of folks suspect that they may have failed closed but it is VERY rare. I have experienced three fail open on cars and not one fail closed in the 44 years that I've been working on 'em. Yes, I did change the one in my 3 GMF two years ago.. it was operating properly when I tested it .. but I found stuff in my heat exchanger..

 

[Dan Johnson]

More Yanmar-Water Heater...

Confirmed--have the older Yannie 3GM30F - SN 2123.

Claude - I did have a thermostat fail closed on my '67 Malibu heading down I-95 just north of Daytona, in the middle of the night, on Spring Break in 1970. Hit a thuderstorm-torrential rain-idiot light went on, pulled to the side and sat until it cooled enough to check the coolant. Had a little loss-ran until the light came on again, shut it off and coasted to the side. Took all night to get to an exit with a gas station that could replace the thermosat. Only redemption was to hear a Ferrarri come past me at full song at well over a buck MPH--heard it for over two minutes going away--amazing Doppler!

 

[kloudie1]

Dan, Yeah, I have heard that does happen, but thankfully, it is not often.. Interesting reminiscence.. The good thing is that on that car, it is a really short job to change out! I guess that, on your Yanmar, they depend on the weep hole to eventually sound the alarm ?? It will be late but eventually, it should sound.
Good to hear the V-12 singing !! There was a grad student in engineering who'd brought a very nice California (68 ish?) bach from overseas military duty.. I used to walk out to hear him start it and drive off! Good stuff!

HEY ! ZDS !?? Have ya changed that connection yet? Come on man! that lady wants some hot water !

 

[Dan Johnson]

Couldn't tell what engine the Ferrarri had, but no doubt it was one--just a red streak fastback in the black of night. Every time I hear one I get pangs of envy!

 

[zds]

I broke the electrical connection on the thermostat trying to disconnect it in advanceof the move. Total bitch. But, I'm now thinking of replacing it with a guage sender in a tee, if I can find one with the right threads.

 

[kloudie1]

ZDS, pretty sure that the fittings are 3/8 Pipe Thread.. surprisingly not metric.

 

[kloudie1]

The new temp sender switch is part # 127610-91360 .. The thing turns on at about 220 F and off at about 205 F.. color of the cap is brown..

 

[zds]

It's 3/8 Japan pipe thread, not 3/8 NPT, I believe.

 

[zds]

Re: Yanmar 3 GMF Water Heater

Claude-

Got a picture from the top of your engine looking down?

Thanks.

 

[kloudie1]

Already posted.. Page one #6 on this thread..

 

[kloudie1]

Looking straight down on the thermostat housing. You can see the hose that comes over the alternator (upper one of the pair) is going in where your temp alarm switch is located.. and on Dan's picture, you can see that his temp switch is in the outlet elbow, downstream of the thermostat.. My return hose is in the same place as yours is, on the water pump suction. Dan's is there too.

 

[kloudie1]

K, 'nother note and I'll stop.. Notice how Dan and my hoses do not rise any significant distance over the hose fitting elevation. I see yours have a good bit of vertical loop in 'em. It would be good to get those things to lie flat so ya don't have big air traps in the hose.. The pump might be having a hard time getting the water over the hump initially.. The engine needs to be spun to around 3000 RPM for a few seconds (like 10..) to get enough pressure to blow all the air out of the heater and hoses.. I think you'll be happy with the heater after ya get the hoses corrected.(The major problem is the fitting location, I think, and the hose loops aren't helping) Good luck with the work, ZDS

 

[zds]

Claude-

On the pictures, up until now I hadn't noticed that hose running over the alternator. Now I get it! You have the "new style" housing.

On the loop, I have a coupling in the send side of my loop near the engine to help with bleeding. I disconnected the hose at the coupling during my test the other day. No flow, even when held below the level of the engine.

I think this explains why they redesigned the housing.

The plan now is to replace the broken temp sensor with another of the same type (for the dummy light), but to reinstall it above the thermostat. The heater loop will go in the space the sensor occupies now, with a T fitting and a dial sensor. That gives me a dummy light and a gauge.

I just wish the whole thing wasn't in an exotic thread size...

 

[zds]

Yanmar Service Manual Excerpt

As a public service, I'm posting a scan of the relevant section from Chapter 15 of the Yanmar Service Manual. A combination of this manual and the comments in this post have helped me figure out this situation.