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Discussion Starter · #1 ·
'98 S70 T5M 180K

Last night on the way home the temp. gauge went above 3:00. Not quite to red, but the top of the white marks. By blasting the heat and driving mellow the 1 mile or so home, the temp. gauge dropped to near normal. It's always been rock solid on 3:00 until last night.

Let it idle in the driveway this morning and after 10-15 minutes the gauge climbed above normal.

Coolant looked good. Not boiling. Right color. Newer expansion tank cap is on there and holding pressure.

Oil looked fine.

No major signs of coolant leakage or blown hoses. No coolant smells in cabin.

New OEM radiator installed 5/25/11.

Fans seem to be kicking on as they should.

Upper radiator hose gets hot, but lower is cold.

Any thoughts on next steps to take? Water pump?
 

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DO NOT CONTINUE TO DRIVE IT
until the problem is found.
These engine can overheat quite easily and make life quite diffucult for you ($$$$$)!
 

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If only one hose is getting hot, I'd say the thermostat is sticking.

Ever replace it? It's very easy, start there. Will only set you back a few bucks.

The water pump has a metal impeller, so it would be making a hell of a lot of noise if the fins broke off and weren't circulating water. You'd know.

If there are no obvious leaks, go for a new thermostat.
 

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+1 on new thermostat to start.
 

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I had a similar issue with my 98, & it was the temp sender that had failed. I replaced it, & the thermostat together.
 

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I'd start at the thermostat.

Then I'd move to the water pump. As for the impeller coming off and making noise, mine made NO NOISE. The impeller was lying in the block and the car was trying to overheat.
 

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I'd start at the thermostat.

Then I'd move to the water pump. As for the impeller coming off and making noise, mine made NO NOISE. The impeller was lying in the block and the car was trying to overheat.
Dear god! I guess anything can fail, even in ways you'd never expect.
 

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Discussion Starter · #8 ·
OK. I'll try the t-stat. Based on other vehicles I've owned, I'm more accustomed to them failing open rather than shut. I purchased this car a little over a year ago from another forum member who maintained it very well and kept excellent records. Unless a receipt is missing, it looks like the t-stat was purchased and installed in Dec. 2002.

I've read a few posts where people recommend using only a Wahler thermostat, which I assume I'll have to order or buy at a Volvo dealer.
 
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