Oil Cooler Thermostat

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Jul 28, 2011 | 10:31 AM

dougbk

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From: Greater St Louis, MO

Oil Cooler Thermostat

How would you check to make sure the thermostat is opening on a HD oil cooler?

I noticed the oil temps on my bike are quite a bit higher this year than usual and suspect that the internal thermostat on the cooler may not be functioning right.

Jul 28, 2011 | 11:02 AM

journeyman

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From: SE Wisconsin

The foolproof way is remove it and lower it into a pot of boiling water.
Then hope the wife understands.

Jul 28, 2011 | 11:57 AM

fabrik8r

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From: earth

Yep, do the boiling water thing, if you can hold it between the blades of a measuring caliper and then dip it in the hot water you will be able to see the plunger movement. STM, start to move temperature is 185F, fully stroked occurs at 220F.

Jul 28, 2011 | 12:36 PM

dougbk

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From: Greater St Louis, MO

I thought about boiling water, like you would a regular thermostat, but I didn't know if you could see it.

Jul 28, 2011 | 12:50 PM

07RoadHawg

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From: Here

Hate ask an obvious question here, but why not just go for a ride and put your hand on the cooler? If it's hot, the t-stat is opening. Or do you think it's not opening all the way?

Jul 28, 2011 | 01:02 PM

dougbk

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From: Greater St Louis, MO

I suspect it is not opening due to the additional heat I am getting. I thought maybe the temp gauge went bad, but noticed it dropped right down when I was riding in the rain, so I sort of ruled it out.

I am not sure but doesn't the oil still circulate through the hoses and not enter the cooler when the thermostat is closed? If that is the case then it would still get hot, just not as hot.

If it does not circulate through the hoses but stops at the thermostat then the touch method would work. I will try it and see.

Jul 28, 2011 | 05:24 PM

fabrik8r

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From: earth

You have to understand how the tstat works, it is nothing like a traditional automotive thermostat that most folks are familiar with. A car thermostat colapese and rebounds, the oil cooler thermostat expands and rebounds.The oil cooler adapter thermostat is actualy a simple thermal actuator, aka wax motor. when it gets hot the piston pushes out aganst the cap, and the body moves to block the direct port to the oil filter, then the oil is redirected to the port that leads to the heat exchanger. The oil takes the path of least resistance, the HD adapter filters after the cooler, since the filter provides more resistance than the cooler, some of the oil can flow to the cooler long before the thermostat actuates. So the cooler will feel hot even before the thermostat actuates. With a Jagg adapter it filters the oil first and then sends it to the cooler when the thermostat actuates.

Last edited by fabrik8r; Jul 28, 2011 at 06:02 PM. Reason: unnecessecary word