Well the engine is a universal M18. I do have what seems to be plenty of water coming out. I can run the enine for about a half hour then it seems to overheat up to 200. I am not sure where to start so I figured I would eliminate the thermostat and sending unit by replacing them. Sometimes if I let it idle in neautral it will start to run hot but when I increase the rpms to about 1500 still in neautral the temp comes right down.
Any help is appreciated.
thermostat engine info
Moderator: Jim Walsh
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Chris Reinke
- Posts: 179
- Joined: Apr 14th, '05, 14:59
- Location: CD330 - Innisfail (Gaelic for "A Little Bit Of Heaven on Earth"), Onset, MA
My humble $0.02 worth....which I offer as a catalyst for the more knowledgable board members to modify/correct/advise against.
It sounds like a pretty routine overheating problem. Since you have plenty of water coming out of the exhaust I would conclude that the problem is within the closed coolant loop, including the heat exchanger. I would start by checking the thermostat by the methods already suggested. The next step would be to clean the heat exchanger. You can clean the heat exchanger with a mixture of muriatic acid 50/50 with water....or just take it to a local radiator shop and ask them to do it for you.
Do you have a water heater attached to the heat exchanger? If you do, the hoses that go from the heat exchanger to and from the water heater could be restricted. If you have something compressing the hose (like an anchor in the locker) or sediment in the hose the flow could be hindered.
One should keep in mind that in addition to the heat exchanger and thermostat there are other components and areas of the engine's cooling system that could cause or contribute to high operating temperatures and overheating. These are:
1. Supply hose to the raw water pump. Hose should be wire reinforced (to keep from collapsing) and routed to avoid sharp bends. It sounds like this is not your problem due to the "high" flow of exhaust water.
2. The raw water supply hose inside diameter should be as large as a standard hose nipple will allow the raw water pump to accept without bushing up. i.e. pump inlet 1/2" npt standard nipple will accept 3/4" ID hose.
3. Raw water pump internal wear and impeller fatigue.
4. Reduced flow of raw water and/or fresh water through the heat exchanger due to corrosion, scale or debris inside the exchanger (cleaning method posted above).
5. Internal corrosion of the water injected exhaust elbow causing raw water flow restrictions. The elbow can also be cleaned with the 50/50 acid mixture.
6. Domestic hot water heater improperly plumbed into the engines cooling circuit. The new thought is that the heater should be connected to the Thermostat by-pass circuit at the thermostat housing, and not off the heat exchanger return. (I have pictures that illustrate the conversion...but have no clue how to post on this site)
It sounds like a pretty routine overheating problem. Since you have plenty of water coming out of the exhaust I would conclude that the problem is within the closed coolant loop, including the heat exchanger. I would start by checking the thermostat by the methods already suggested. The next step would be to clean the heat exchanger. You can clean the heat exchanger with a mixture of muriatic acid 50/50 with water....or just take it to a local radiator shop and ask them to do it for you.
Do you have a water heater attached to the heat exchanger? If you do, the hoses that go from the heat exchanger to and from the water heater could be restricted. If you have something compressing the hose (like an anchor in the locker) or sediment in the hose the flow could be hindered.
One should keep in mind that in addition to the heat exchanger and thermostat there are other components and areas of the engine's cooling system that could cause or contribute to high operating temperatures and overheating. These are:
1. Supply hose to the raw water pump. Hose should be wire reinforced (to keep from collapsing) and routed to avoid sharp bends. It sounds like this is not your problem due to the "high" flow of exhaust water.
2. The raw water supply hose inside diameter should be as large as a standard hose nipple will allow the raw water pump to accept without bushing up. i.e. pump inlet 1/2" npt standard nipple will accept 3/4" ID hose.
3. Raw water pump internal wear and impeller fatigue.
4. Reduced flow of raw water and/or fresh water through the heat exchanger due to corrosion, scale or debris inside the exchanger (cleaning method posted above).
5. Internal corrosion of the water injected exhaust elbow causing raw water flow restrictions. The elbow can also be cleaned with the 50/50 acid mixture.
6. Domestic hot water heater improperly plumbed into the engines cooling circuit. The new thought is that the heater should be connected to the Thermostat by-pass circuit at the thermostat housing, and not off the heat exchanger return. (I have pictures that illustrate the conversion...but have no clue how to post on this site)
water heater
The hot water heater has been removed, however the hoses to and from the hot water tank have just been spliced to together.