WInter showed up in Philly finally. The Volvo (245, 88) is not putting out the same heat that it did last winter. I've noticed that the temp gauge has been showing a little low, don't know if that has any bearing on the issue at hand. The gauge now shows at about 1/4. Used to run at 1/2, right on the money. Heat is lukewarm, not HOT like it used to be. Open to any ideas.

THANKS!

 

The first thing to check is coolant level...often overlooked as a cause of poor heat. Given the temp readings, it's possible the thermostat is stuck open...but my experience has been Brick heaters will still run you out...just takes a bit longer. Heater valve sticking is always a possibility.I'd lean towards the thermostat. If you replace it, pay a few $'s more for a Wahler...it's worth it.

 

Just noticed tonight that there is a rather loud hissing noise when I shut the car off. Sounds like it's coming from the passenger side under the dash. Heater core?

 

OK...NEVER mention heater core...got it? Try not to even think it! It's ok to surreptitiously feel the carpet for coolant...but don't let the car see you do it. I find night works best. Honestly, As soon as I think heater core, even though it isn't, they fail within a month! Has happened personally twice.
When heater cores go, they leak coolant and it goes somewhere. Usually into the passenger side footwell but sometimes outthe condensation drains onto the pavement. Hard to miss the aroma too. More likely, the hissing is a vacuum leak. Your vac canister is behind the center console kick panels...I'd look there first. Vac doesn't enter into the direct alteration of heater temps except with regards to fresh/recirc. If it is bitter cold, that could be an issue too. Still...given the symptoms, I'd think thermostat to be the main culprit.

 

I agree with Swift. The hissing sound is most likely due to a failure of the vacuum check valve on the intake manifold. When you shut the engine off, all of the vacuum in the canister under the dash is leaking out through the check valve and making the hissing sound.

I have had a stuck open thermostat and when outside temp is below freezing, it takes forever to get good heat in the car. That's what I would check first.

 

Interesting. Sounds like a combo of both things. How hard is replacing that check-valve? I'll replace the thermostat since it hasn't been replaced yet, is easy and cheap. Then I'll look into the vacuum valve issue.

act1292, it has been VERY cold here lately. Definitely could be the issue.

Thanks for the help. (Don't tell my Heater core that I'm suspicious)

 

Very easy to test and replace the check valve. It is located right on top of the intake manifold. Open the hood and look for a black & white plastic cylindrical shaped object with a hose on each end. One hose connects to the intake manifold while the other goes through the firewall on the passenger side of the car. Disconnect it from the hoses and try blowing through each end. If it allows air to pass through from both ends, then it is bad.

Pretty easy to replace the thermostat as well. Like Swift said, try to get a Wahler.

Don't know how it is today where you're at but it is supposed to be pretty warm here today in Chicago (50+). Good weather for getting this kind of stuff done

 

Just checked the check-valve looks, like it works fine, although when I blow softly, it will pass air both ways. Will only pass air in one direction (towards the engine) when I give it a good puff though. Any other ideas? This noise only happens when it's very cold outside when the car is shut off, sounds like a all the air is leaking out from behind the dash.

Also lately, and probably unrelated, the car has a noise similar to a spring being plucked when the car is acceleration. Can't seem to pinpoint that noice, and only makes the noise while in gear and accelerating, mostly 1st and 2nd gear. Worse when it's cold as well. exhaust? leaking air?

 

Check compression and do a leakdown test on all cylinders....lol, I've been noticing lately that people dont do these checks and itmay help....thought my car was just fine mechanically....started trying to find electrical powertrain issues and never needed to, it was all mechanical for me....just check them, it gives good peace of mind at least