G5200 clogged block?

[BruceP]

UPDATE: to see if the water pump had failed, I temporarily replaced the upper radiator hose with a clear one and removed the thermostat. The coolant was NOT flowing. Does this mean the water pump is bad OR will coolant not flow right away after start up? I left it idling a minute or two and NO flow...

I would suggest that is not a valid test.
Without thermostat, the coolant is free to flow ANY direction it wants..... the direction of least resistance is thru the 'bypass' pipe back into the engine. (thus bypassing the radiator)

QUESTION: With that clear section of pipe TOTALLY FULL of liquid... how could you tell if there is any flow anyway?? .... you are not expecting the waterpump to 'lift' coolant up the pipe into the radiator, are you?
(the waterpump is designed to MOVE liquid in a totally-full system... it is not really capable of 'lifting' uphill)

With thermostat installed, it is often possible to leave the radiator-cap off and see the flow as slight ripples The fluid in the radiator will do pretty-much nothing until the the thermostat starts to open... then you should see some flow.
.... but using 'point-n-shoot' thermometer gives you more information.

DO NOT remove radiator cap with hot engine without first squeezing top hose to validate there is no pressure.

 

[TexanNB]

Thanks again. So I'm looking at ordering the Genuine Kubota part but I'm finding very different prices. One is from Coleman Equipment for $128, another from Messicks at $205, Kubota Generators Direct at $141, and $255 from my local dealer.

Has anyone had any experience from any of these places? I assume these are all OEM, if so then I'd like to go with the lowest price but wanted to make sure. Thanks!


Coleman: https://www.colemanequip.com/parts/details/KubotaEngineParts/Kubota-Water-Pump-Assembly/15852-73036/

Messicks: https://www.messicks.com/parts/kubota/15852-73036

Kubota Generators Direct: https://kubotageneratorsdirect.com/product/15852-73036/

 

[TexanNB]

I would suggest that is not a valid test.
Without thermostat, the coolant is free to flow ANY direction it wants..... the direction of least resistance is thru the 'bypass' pipe back into the engine. (thus bypassing the radiator)

QUESTION: With that clear section of pipe TOTALLY FULL of liquid... how could you tell if there is any flow anyway?? .... you are not expecting the waterpump to 'lift' coolant up the pipe into the radiator, are you?
(the waterpump is designed to MOVE liquid in a totally-full system... it is not really capable of 'lifting' uphill)

With thermostat installed, it is often possible to leave the radiator-cap off and see the flow as slight ripples The fluid in the radiator will do pretty-much nothing until the the thermostat starts to open... then you should see some flow.
.... but using 'point-n-shoot' thermometer gives you more information.

DO NOT remove radiator cap with hot engine without first squeezing top hose to validate there is no pressure.

I suppose I was assuming it would cause the coolant to flow to the radiator (I really have no idea how this thing is plumbed. I'd really like to understand where coolant flows within and into and out of the block...). The engine was getting too hot when I had the thermostat installed, top of radiator getting up to 240-250F.
Can you explain why coolant would not flow to the radiator without the thermostat? Could I plug the bypass tube to test if water pump is working? How else could I test the water pump? Fill the system to the brim so that the upper tube is completely full? Thanks again for the advice.

 

[BruceP]

I'd really like to understand where coolant flows within and into and out of the block..

I will attempt to explain: (this is AFTER the thermostat has started to regulate..... the WARM UP flow essentially bypasses the radiator and RECIRCULATES back into the engine)

• Rotary waterpump is bolted to front-plate of engine and (like all other rotary pumps) SUCKS coolant into its center and PUSHES towards the perimeter of the rotor.
• Most of the SUCK side of the pump is from the lower radiator hose.
  • but can be from the BYPASS pipe based on thermostat position.
• The PUSH side of the pump is always INTO THE ENGINE thru a hole in the plate which the pump is mounted.

HOWEVER: As the thermostat opens/closes, it CHANGES THE DIRECTION of hot coolant coming out of the engine. The thermostat has the ability to BYPASS the radiator (quicker warmup) and then as it opens...sends the hottest fluid into the top of radiator.

LOOK CLOSELY... you can see the little hose between the water-flange and the pump....this is the "bypass" we have been talking about which feeds some portion of the flow back into the engine WITHOUT going thru radiator.

QUESTION FOR YOU: Can we assume you have performed the standard test to validate thermostat operation. You should ALWAYS test brand-new one before installing. (it is handy to have a pair of needlenose pliers in your hand so you can reach in and grab the thermostat to inspect its position)

1. Take note of temperature is marked on thermostat.
2. Put thermostat in sauce-pan of water.
3. Heat on stove
4. Use accurate thermometer to monitor water temperature
5. It should be just reaching full OPEN position as the marked temp. is approached.

 

[TexanNB]

I will attempt to explain: (this is AFTER the thermostat has started to regulate..... the WARM UP flow essentially bypasses the radiator and RECIRCULATES back into the engine)

• Rotary waterpump is bolted to front-plate of engine and (like all other rotary pumps) SUCKS coolant into its center and PUSHES towards the perimeter of the rotor.
• Most of the SUCK side of the pump is from the lower radiator hose.
  • but can be from the BYPASS pipe based on thermostat position.
• The PUSH side of the pump is always INTO THE ENGINE thru a hole in the plate which the pump is mounted.

HOWEVER: As the thermostat opens/closes, it CHANGES THE DIRECTION of hot coolant coming out of the engine. The thermostat has the ability to BYPASS the radiator (quicker warmup) and then as it opens...sends the hottest fluid into the top of radiator.

LOOK CLOSELY... you can see the little hose between the water-flange and the pump....this is the "bypass" we have been talking about which feeds some portion of the flow back into the engine WITHOUT going thru radiator.

QUESTION FOR YOU: Can we assume you have performed the standard test to validate thermostat operation. You should ALWAYS test brand-new one before installing. (it is handy to have a pair of needlenose pliers in your hand so you can reach in and grab the thermostat to inspect its position)

1. Take note of temperature is marked on thermostat.
2. Put thermostat in sauce-pan of water.
3. Heat on stove
4. Use accurate thermometer to monitor water temperature
5. It should be just reaching full OPEN position as the marked temp. is approached.

Thank you for the explanation of coolant flow. That's very helpful.
Based on this, if the bypass pipe were blocked off/plugged so that coolant couldn't flow from the water flange back down to the pump, would coolant then be pumped up into the upper radiator hose, therefore confirming that the water pump is indeed working correctly?

Answer about thermostat:
I did check the thermostat on the stove as you described (was one of the first things I checked) and it opened at 81C which was marked on the T-stat.

 

[TexanNB]

I will attempt to explain: (this is AFTER the thermostat has started to regulate..... the WARM UP flow essentially bypasses the radiator and RECIRCULATES back into the engine)

• Rotary waterpump is bolted to front-plate of engine and (like all other rotary pumps) SUCKS coolant into its center and PUSHES towards the perimeter of the rotor.
• Most of the SUCK side of the pump is from the lower radiator hose.
  • but can be from the BYPASS pipe based on thermostat position.
• The PUSH side of the pump is always INTO THE ENGINE thru a hole in the plate which the pump is mounted.

HOWEVER: As the thermostat opens/closes, it CHANGES THE DIRECTION of hot coolant coming out of the engine. The thermostat has the ability to BYPASS the radiator (quicker warmup) and then as it opens...sends the hottest fluid into the top of radiator.

LOOK CLOSELY... you can see the little hose between the water-flange and the pump....this is the "bypass" we have been talking about which feeds some portion of the flow back into the engine WITHOUT going thru radiator.

QUESTION FOR YOU: Can we assume you have performed the standard test to validate thermostat operation. You should ALWAYS test brand-new one before installing. (it is handy to have a pair of needlenose pliers in your hand so you can reach in and grab the thermostat to inspect its position)

1. Take note of temperature is marked on thermostat.
2. Put thermostat in sauce-pan of water.
3. Heat on stove
4. Use accurate thermometer to monitor water temperature
5. It should be just reaching full OPEN position as the marked temp. is approached.

UPDATE: I put a C-clamp on the bypass tube to force the water pump to pump up to the radiator. I got pulsing flow that had bubbles in it. My diagnosis is that the water pump is working at least somewhat and that it has a bad head gasket.

Any opinions?

 

[BruceP]

My diagnosis is that the water pump is working at least somewhat and that it has a bad head gasket.

Any opinions?

There are some 'tests' for head-gasket failure:

• check antifreeze for combustion-gas content
  • There are test-strips which you simply dip in the antifreeze and check the color-change
• leak-down test
  • Replace radiator-cap with hand-pump to pressurize/measure how well the system maintains pressure.
  • Most autoparts stores will loan-out leak-down tester kit.

 

[lmichael]

Get yourself one of these before you needlessly tear an engine apart Amazon.com: Block Tester BT-500 Head Gasket Combustion Leak Test Kit - Made in USA : Automotive

 

[TexanNB]

Get yourself one of these before you needlessly tear an engine apart Amazon.com: Block Tester BT-500 Head Gasket Combustion Leak Test Kit - Made in USA : Automotive

Ordered. Should be here by tomorrow. I'll update y'all with results soon. Thanks.