1GM10 Overheating -- where's the thermostat

[AJ Miceli]

I have 10 year old 1GM10 with 500 hours on it. It's been overheating for the past 3 weeks. I have cleaned the intake to the pump and changed out the impeller on the pump. Water is flowing fine on the intake side.

But it's still overheating. I removed the hose leading to the mixing elbow and it's bone dry, so obviously no water is exiting the block. Now I suspect the thermostat, but the manual is not clear on where it is. Is this the thermostat cover??

Thanks in advance!

 

[JumbleDuck]

But it's still overheating. I removed the hose leading to the mixing elbow and it's bone dry, so obviously no water is exiting the block. Now I suspect the thermostat, but the manual is not clear on where it is. Is this the thermostat cover??

Yes. I don't understand the bronze-y coloured thing on top of it. Mine had a hose coming out the top.

 

[AJ Miceli]

Thanks! I had already removed the hose that feeds the mixing elbow. That's the color of the part before they sprayed the whole engine silver. You can kind of see into the middle of the outlet and it's completely dry. So the blockage has to be somewhere between the inlet to the pump and that outlet. So it's ok to remove that cover, right?

 

[Topcat47]

Yes. The thermostat often gets clogged with salt deposits, droop it into a cup of vinegar and it should all bubble off. When it's clean, drop it into a saucepan of water and check it's operating. It looks as if the outlet pipe in the photograph is blocked, that it with vinegar too. Check the water pipe from the pump as the water should by-pass the thermostat when the engine is cold.

After that, it's going to be a pump removal and refurb. it's easier to remove the pump in it's entirety than do it in situ and I"d fit new seals if i were doing that. It's not rocket science, just treat it carefully. BTW the bolts supplied with the engine are "cheese" headed, so use a well fitting socket, preferably with a true hex head.

 

[JumbleDuck]

Thanks! I had already removed the hose that feeds the mixing elbow. That's the color of the part before they sprayed the whole engine silver. You can kind of see into the middle of the outlet and it's completely dry. So the blockage has to be somewhere between the inlet to the pump and that outlet. So it's ok to remove that cover, right?

Ah right, see what you mean. I was seeing it as a bronze-coloured thing attached to the housing. As Topcat47 says, everything needs de-salted. On mine the pipe below the thermostat was almost completely blocked with salt too.

If you haven't had any, or much, flow through the head, that's likely to be blocked up with salt too. I'd be tempted to attach a hose from the tap to the bottom of the thermostat housing, block the top, remove the thermostat and just blast fresh water through the head for an hour or two to dissolve salt out. If you do that, don't feed the water coming out into the elbow, as it will back-fill the engine. Disconnect the outlet hose too and drain elsewhere.

When I rebuilt my engine I found it very hard to get a good detailed diagram, but the dealer in the US (much cheaper, but you need a friend to receive and bring the stuff here) send me a couple of pages from their parts manual which helped a lot. If you'd like them, PM me an email address.

 

[Spyro]

.As the thermostat opens it closes off the path to the lower hose that is still attached and pushes water through the block and thermostat housing and out via the outlet that has the hose removed You say water is flowing fine on the intake side so it has to be flowing somewhere. If you have a thermostat problem water will flow either through the block or straight out the bypass circuit depending on whether is stuck shut or open. Is water coming out of the exhaust? No water flow at all sounds like a pump problem or the system loosing prime and not being able to suck water in.

 

[Tranona]

First thing to check is that short vertical hose as it gets blocked easily. Access to the thermostat is by removing the cover with the water pipes on it. as already suggested it may well be worth descaling the whole system. another access point is the cover with the anode it (have you ever changed the anode?) on the block behind the alternator if there is sludge visible there that is a sure sign the waterways need cleaning. Replacing the anode regularly reduces the amount of sludging, as does running the engine hard every time you use it. They dislike running at low revs because they don't get hot enough.

 

[AJ Miceli]

Thanks very much. These comments are all very helpful. Just one thing: At least it's unlikely to be salt because I'm on Lake Erie and the boat has never left the Great Lakes But it could be other deposits. In fact, I have suspected that it might be zebra mussels which are a big problem in our area.

I'll check the short vertical hose next. But since there's no water at all coming out of the exhaust I'm beginning to suspect the pump.

How do I check the pump? Is it OK to close the sea cock, remove the cover and the impeller from the pump, and turn it over a few times to see if the impeller shaft is spinning?

 

[Appledore]

" But it could be other deposits. In fact, I have suspected that it might be zebra mussels which are a big problem in our area."

Have you actually checked the water inlet cock (through-hull) and the strainer? If, as you suspect, it might be zebra mussels, the strainer might be blocked, hence no water reaching the water pump.

 

[AJ Miceli]

Yes, the water is flowing freely TO the pump. I pulled the boat and cleaned the sail drive. I disconnected the inlet hose from the pump and let the water flow freely. Bonus I got to check my bilge pump (it's working!)...

 

[pete]

Crank the engine with the decompresser engaged and the pump outlet disconnected if you get water there reconnect and move on to next connection.

 

[Appledore]

" But it could be other deposits. In fact, I have suspected that it might be zebra mussels which are a big problem in our area."

The next step is to remove the pipe on the outlet side of the water pump, if you haven't done it. Turn the engine over to spin the pump, and see if water comes out. If you use your decompressor, the engine won't start, but will still spin the pump of course.

 

[Appledore]

Crank the engine with the decompresser engaged and the pump outlet disconnected if you get water there reconnect and move on to next connection.

Sorry, you beat me to it - my 'phone rang!!

 

[Tranona]

The water pump impeller needs careful inspection. first, as suggested check whether there is output from the pump. If not then the impeller is probably faulty - either blades broken or the rubber has parted company with the bronze hub. You can inspect this by removing the cover and as suggested turning the engine over using the handle with the decompressor lever raised.

 

[AJ Miceli]

Update:

First, thanks to everyone for your wisdom. Every suggestion was helpful, and made me feel more comfortable with the repair.

It took a long time, but I finally got access to every part of the 1GM10 water system. There were actually multiple problems. There were still a couple zebra mussels on the intake side of the pump. The pump and the impeller were fine. Then there was a clog in the "T" feeding the block and the bypass. That was also some zebra mussels and some unknown green substance. Then when I got to the thermostat I found it stuck in the open position (however no water had been going through the block due to the blockage in the "T") -- see picture below. After getting a new thermostat I thoroughly flushed the block and any pathways I could access. Then I reassembled and water is flowing again. However, the pump oil seals were very old and cracking, so now I have some dripping out of the weep hole. I've ordered seals and will replace those.

For further reference: The hardest thing to do was to get the hoses off. All had been clamped tightly for 11 years. I'd say that I spent 8 hours getting the two hardest short hoses off (not counting the trip to Harbor Freight to buy a set of picks) using a combination of moderate heat (hair dryer), picks, and scraped and bleeding hands. The trickiest thing was getting the thermostat out. In order to do that I had to remove the hard fuel line and move it carefully away from the block. I hate messing with those thin tubes.

So -- Thanks much! Now I'll be able to help others if they face this problem.

AJ Miceli
Erie, PA

 

[RichardS]

The hardest thing to do was to get the hoses off. All had been clamped tightly for 11 years. I'd say that I spent 8 hours getting the two hardest short hoses off (

Getting hoses off the spigots on cars and boats can be a real pain in the proverbials. Before now I have just given up the battle and cut the water hose with a sharp blade and, after doing whatever work was needed, joined the two ends back together with a double-ended spigot hose joiner. :ambivalence:

When replacing hoses I always smear the spigot / hose with silicone grease as this makes removal next time much easier.

Richard

 

[JumbleDuck]

However, the pump oil seals were very old and cracking, so now I have some dripping out of the weep hole.

See those pipes that the drips are dipping on? Thos are oil pipes and they are (a) essential and (b) mild steel. It maybe doesn't matter as much on fresh water, but replacing them with flexible rubber hoses is a piece of cake, My local Pirtek (UK hydraulic franchise) made me up a pair in ten minutes for thirty pounds. Well worth doing if you are working on the engine again sometime.

And congratulations on sorting so many problems. It's the same with old cars - there is rarely just one thing wrong, but a combination of minor faults.

 

[Appledore]

See those pipes that the drips are dipping on? Thos are oil pipes and they are (a) essential and (b) mild steel. It maybe doesn't matter as much on fresh water, but replacing them with flexible rubber hoses is a piece of cake, My local Pirtek (UK hydraulic franchise) made me up a pair in ten minutes for thirty pounds. Well worth doing if you are working on the engine again sometime.

And congratulations on sorting so many problems. It's the same with old cars - there is rarely just one thing wrong, but a combination of minor faults.

Essential to replace those two oil pipelines! As JD says, get them made from your local hydraulic outlet for much less than the Yanmar ones! And they will last longe too. I kept the old steel ones as 'just in case' I might need them!

 

[nemodreams]

The water pump is actually quite easy to remove. Much easier to work on for impellor etc. Just be careful the first time you hit the original bolts. There is no gasket involved, just a large rubber o ring which is re-used. Just the timing case behind - no big deal.
I always do the impelllor with the pump off. Changed the bolts to stainless - so I know the heads are good. The one behind the crankpully is awkward - but its only a 5 min job.

Stubborn hoses release easily if wrapped with kitchen roll or similar - and pour on boiling water. Leave a minute to or so and they slip off.

the manual for free is here -
http://www.motoren.ath.cx/menus/yanmar.php

 

[JumbleDuck]

I always do the impelllor with the pump off. Changed the bolts to stainless - so I know the heads are good. The one behind the crankpully is awkward - but its only a 5 min job.

I had a speedseal, which made access quite a lot easier. By a happy coincidence, I have a 1GM10 speedseal for sale. Cheap.