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tab a 04-14-2019 01:59 AM

F725 with FD590V 20Hp overheating
 
I asked about this almost 2 years ago :tango_face_smile: , and at that time hadn't seen any coolant loss. Didn't make time to work on it last year, just mowed for 15-20 minutes until it would overheat, let it cool, and continue. Would prefer not to do that this summer. :tango_face_wink:

Cam broke in past, and was replaced. Overheating MIGHT have started shortly after that (wasn't mine then).

Am not seeing bubbles in overflow tank but am definitely losing small amounts of coolant, which is very slowly getting worse with time. Am thinking 2 major possibilities are head gasket or water pump internal leak.

If so, how would you suggest best narrowing it down? Coolant pressure test, looking for coolant in cylinders? I have a pressure tester but no adapter that fits rad neck.

Thanks!

burned300 04-14-2019 12:33 PM

Re: F725 with FD590V 20Hp overheating
 
Wonder if cam was timed correctly


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tab a 04-14-2019 02:22 PM

Re: F725 with FD590V 20Hp overheating
 
When I first noticed it, I wondered about that too. But since I now know it's losing coolant I think it less likely.

Thanks.

bruceatlam 04-14-2019 06:22 PM

Re: F725 with FD590V 20Hp overheating
 
The implication in your description of the problem is that after it overheats, it cools without the addition of any water/coolant. Is that true? If so, the water level isn't low when it overheats. Therefore, it's over heating because the water isn't circulating or there's no air flow through the radiator to cool the water flowing through it. Tells me that the water pump is shot or the radiator is plugged either internally or externally. Is the thermostat opening??

tab a 04-14-2019 10:49 PM

Re: F725 with FD590V 20Hp overheating
 
No, I have to add coolant, nearly every time after 15 minutes of mowing, then cooling.

Previously checked rad flow and thermostat: ok.

Thanks.

dave_r 04-15-2019 12:38 AM

Re: F725 with FD590V 20Hp overheating
 
If it's the water pump, then you should see it leaking on the outside of the motor. Head gasket, it's either going out the exhaust or going into the engine oil.

tab a 04-15-2019 07:28 AM

Re: F725 with FD590V 20Hp overheating
 
Don't know how true it is but my research found some that say this motor not uncommonly has a water pump that leaks INTERNALLY.

Which is why I asked the original question.

Don't really want to change the head gasket if it's just the water pump.

Thanks.

bruceatlam 04-15-2019 11:04 AM

Re: F725 with FD590V 20Hp overheating
 
If the water pump leaks internally, the water has to go somewhere. If it's leaking that much water internally you should see evidence in the crankcase. The oil should really be milky and the level should be increasing. If that's not the case (and I'm guessing it's not) then the water pump isn't leaking internally. I think that you're left with the head gaskets. Just for grins, have you checked the compression?

tab a 04-15-2019 10:17 PM

Re: F725 with FD590V 20Hp overheating
 
No I haven't. Good idea.

HeyYou 04-16-2019 07:56 PM

Re: F725 with FD590V 20Hp overheating
 
Take a close look at the radiator as well. On my mowing tractor, (radiator in the very front, with a mid-mount belly deck) I have to clean the radiator out after each mowing, else it clogs up with clippings. It develops a nice mat on the front, and you can peel it off like a rug......

That wouldn't account for coolant loss though.... Now, the overheating *may* be due to the fact that the system isn't reaching its designed pressure. Higher pressure raises the boiling point of the fluid.....

I *think* you can get adapters for cooling system pressure testers, that will fit the radiator on the tractor. Local auto parts store might be able to help you out with that. (and even rent you the tool.....) The also have test kits, to see if you are getting combustion gases into the coolant. (a sure indicator of a blown head gasket.)


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