Thermostat or water pump bad?

Post by **gnalan** » 26 May 2021, 11:02

My temp guage pegged today while idling before I was getting ready to leave. Temp outside is almost 90F. I shut it off, popped the hood, and let it cool off. I did notice the upper radiator hose was extremely hot and the lower radiator hose was still cold.

My question is would this be the water pump, thermostat, or possibly something else? Even if the thermostat didn't open wouldn't there still be heat in the lower radiator hose? Any help would be greatly appreciated.

cleven · Post by **cleven** » 26 May 2021, 13:14

Best bet is change the thermostat first, burp the system and go from there.

Post by **gnalan** » 26 May 2021, 13:25

Sounds easy enough to do. Is there a way to keep from losing too much coolant when I swap the thermostat?

Post by **gnalan** » 26 May 2021, 13:32

I see the stock Volvo one is set at 90C, Vaico is set at 87C, and Mahle is set at 92C, all from FCPEuro. Has anyone tried any of the other two besides the Volvo one, or a different one from anywhere else? If so did you notice any difference in gas mileage, or engine performance?

Azik09 · Post by **Azik09** » 26 May 2021, 13:39

Let the engine get warm at idle and turn on the heater (yes, and don't look at 90F outside). If you get HOT air, then water pump is OK and thermostat is the prime suspect. But not the only.

Post by **gnalan** » 26 May 2021, 13:48

The temp guage pegs as soon as I start it. The engine is cold and the hoses are cold. Could it be a bad sensor? Where is it located at?

chris11211 · Post by **chris11211** » 26 May 2021, 14:12

You stated that one hose is hotter that the other right? That could be a sign that your radiator has hit the end of it's life.

Here's the right radiator for your model, and they also have a cheaper one for $105

https://www.fcpeuro.com/products/volvo- ... 0-31319056

I think the best course of action is to let a dedicated independent volvo mechanic take a look; they should tell you what's going on.

Post by **oragex** » 26 May 2021, 14:18

Look closer at the two wires going to the coolant temp sensor connector on the stat housing. Or maybe the sensor is shot

Post by **gnalan** » 26 May 2021, 14:39

This is with the engine cold, and not running. The key is in position 2. Looks more like a sensor or wiring issue. I'm in the process of replacing my starter, and removed the two rear nuts holding the starter to the bracket on the engine block. I didn't have a problem before that, and I was removing the nuts with my arm wedged in between the power steering line and the intake manifold. I'm assuming from looking at the wiring that it runs along the block under the intake manifold and connects around the starter? Maybe I bumped something loose, or one or both of the wires are grounding out on the block causing the needle to peg. Any thoughts? I'd rather not pull the intake manifold off, but I'll have more access when the starter is removed probably this weekend. It's raining right now, and if there's a problem other than the sensor I don't want to drive it into the barn to work on it out of the rain. I really don't want to blow the engine.

93SCMax · Post by **93SCMax** » 26 May 2021, 14:56

You've got a sensor or sensor wiring issue.

This video may help.

https://www.bing.com/videos/search?q=20 ... &FORM=VIRE