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Can a Thermostat occasionally stick open?

479 Views 5 Replies 4 Participants Last post by  Candubrain
2016 V6 3.6 with 115,000 Kms, Canadian Model

The orange check engine light was on

Took it to an independent mechanic, the scan codes showed low coolant temperature, and misfiring on some cylinders.

It's a 20km drive to the mechanics shop, all highway speeds. I didn't notice anything unusual as far as a rough running engine, but I did see the coolant temperature was hovering around 70C and didn't get up to full normal temps of 90C until the last 5Kms or so. I hadn't noticed low coolant temps prior to this, but I wasn't looking for it.

The mechanic cleared the codes and has ordered a new thermostat and waiting for it to arrive.

Since then I've done several trips in town and on the highway, but have not had the error code since and the vehicle appears to come up to full temperature as normal. Average outdoor temps -2C to 5C.

Can a thermostat occasionally stick open? I thought once they failed, thats it.

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Yes, they can be intermittent like that. They will begin to stick more and more often if you continue to drive with it. The sticking can happen either open or closed, and you are lucky that it is happening on the open side for now.
Is it an electronic or purely mechanical thermostat?
If the former, then it might be more complex to diag. If the latter, then replace and be done with it.

Get VCDS and stop relying on what the garage tells you. It will quickly pay off.
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thanks for the replies and helpful information
115,000Kms. Thermostat replaced, it had stepped ridges on the sliding surfaces, which probably was the cause of it occasionally sticking open. The replacement from VW has a slightly different design which may prevent this type of wear.
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