thermostat or sensor

[Sasquatch]

2001 V70XC 5 cylinder turbo engine

Got a check engine light last week.

Took it to Autozone, and they said it either needs coolant (doesn't seem to), or is a thermostat or coolant sensor. Had it on the highway last week before the Nor' Easter, and it had the temp gauge at about 1/4 when it should have been at about 1/2 way. I saw the temp gauge thing before I had it checked, so pulled off highway to see make sure I didn't burst a hose or something. Seemed fine, and temp came up (not moving through cold wet weather), so continued on my way.

So, long story short:
Does this sound like a bad thermostat to you guys? The kid at Autozone said the failure mode on the Volvo ones is to fail open, so they flow cold all the time, which seems to back up why it was 1/4 on the highway.

Has anyone here done the thermostat on one of these pigs? Is it pretty straight forward? Is the thermostat under the gooseneck right where the hose goes into the block? Is there an easy way to drain coolant to put it back, or should I just let it wash away, and refill?

What and where is this sensor?

How might I diagnose if it is a sensor or the thermostat?

Which one to get? I see a 160,180, and 195 degree here:
http://www.autopartswarehouse.com/se...+Components%29

The price isn't too bad at $16-18 or so, but there are a lot of different choices, all looking the same.

Thanks for any help you can offer.

[Julien]

The thermostat comes as a complete assembly, with the sensor included. You cannot buy a gasket for the housing, so it is not servicable. I haven't changed one out myself so I can't give you any tips there. Make sure you order a base gasket for it as well.
Here's an example.... http://www.ipdusa.com/products/7007/...sembly-housing

[Sasquatch]

You're kidding me, right? We just jumped from $16 to $116? The thermostat is NOT SERVICEABLE? These are one of the most basic serviceable parts in any car! You undo two to four bolts, pop out the old t-stat, scrape gasket off, put on new gasket, insert new t-stat, and put it all back together.

So now what? Unbolt the whole thing, and bolt a new one in? To the tune of $116?

This car HAS to go.

[Julien]

Volvo don't sell a gasket for it. My Indie mechanic made one out of gasket paper, but it hasn't stayed water tight. You could give it a try, you might have more success.

[Julien]

Just checked, IPD, looks like the one for your car is different to mine, and you'll get away with it for much cheaper. A win for you.

[guymon]

What? Go to your volvo dealer and get a new thermostat for your 01 for $35. It replaces just like any other thermostat. You might want to check what kind of coolant is in your system. I picked up coolant from the dealer to top off what would spill out. That was as much as the thermostat!

[wgriswold]

I seem to remember that at some point Volvo went from a simple thermostat replacement to replacing the housing as well with a corresponding large price increase. I don't remember the year that the design changed, maybe 2003?

[JRL]

Yes, 2.5ts

[howardc64]

01 thermostat is trivial. 2 torx head bolts and the housing comes off. New t-stat comes with rubber o-ring. I had low temp once (reading 1/4 on dial instead of 1/2). It was the t-stat.

Cooler temp t-stat is for the turbos. Check various websites. Its pretty clearly spelled out. $15 online.

http://www.fcpgroton.com/category-ex...464/by_year/51

[Xheart]

The temp gauge needle reaches 11, not 12.
Freezing weather, is this OK?