Below is a message I sent to my Volvo dealer along with pictures of the dash (did not attach pics but could if you want them) documenting an issue with my car warming up slowly when the temperature gets down around 0F. The car is a 2011 S40 with the T5 engine. The dealer confirmed that the issue I describe is happening but say they checked another 2011 S40 they had on the lot and it did the same thing. I find it really strange that it takes 20 min plus on the highway to reach operating temperature and that if you stop and run the heater at full the engine temperature drops. They gave me an 2013 S60 with the T5 engine while my car was in the shop over night and on my drive to work with temperatures below 0 this car was up to operating temperature within 5 minutes. They stated that the T5 engine in the S60 is a “different”…looked the same to me.
“When I drove my S40, with the heat on full trying to defrost it, after its visit to your shop for the throttle body replacement the temperature issue really showed up . Attached 5 pictures of the dash tell the story about the heat/thermostat not working properly:
- Start home see time/miles
- 7 miles 13 minutes car not up to temp, still running heat high
- Sat running in driveway for another 10 min, still not up to temp
- Turn off heat and let run for another 5 min, comes up to normal temp.
- Turn heat back on (air now much warmer than before) engine temp drops again
I know you tested it and did not see an issue but did you test it out in the cold or in the shop? This is only really noticeable during cold spells like we have been having. Driving the S60 with the exact same engine showed me the warm up time is NOT normal. I’m worried that driving the car while cold all the time is going to damage it/ cause engine wear.
Pls discuss with your service guy and let me know what can be done (weak thermostat??)”
Dealers recommendation is to put a block heater in it………
Please give me your opinion on this issue.
I have put duct tape over the grill in front of the radiator to see if this will help….car is silver so it doesn’t look schlocky as it sounds :o)
This does sound a lot like a thermostat kind of issue. The thermostat is supposed to be closed with the coolant temp lower than about 190 degrees or so. That means that at a cold start the thermostat should be closed and coolant only circulates through the engine block and heater core. At about 190 or so, it should open and then run through the radiator. If it’s really cold and driving cools it a lot the thermostat should close back up somewhere under the ~190 or so. So ~190 is about the bottom limit when the car is up and running.
What that actually means is that you can more or less look into a thermostat issue pretty easily yourself. You’ll just need a little patience. Start the car from cold and pop the hood. Then just stand around and wait…and wait…as the car warms up while keeping tabs on what the upper radiator hose feels like. It should stay pretty cool all the way through warm up. Do note that it will warm up some just from heat transfer at the engine block. But once the car finally gets to temp, all of a sudden it should get very hot - because the thermostat hits the ~190 and opens up. If the upper hose warms up very gradually with no cool period followed by a sudden hot period then this points to an open / leaky thermostat. Just picture it in your mind - if the car is cold there’s just cold and stagnant fluid in the hose (warming just a little from radiant heating). When the thermostat opens it’s like opening up a spigot full of hot water.
The part about the heat cooling the engine makes perfect sense, btw. Your heat comes from what is essentially a min-radiator. If you crank it up, this is pulling heat out of the coolant.
I agree with @cigroller 100%. This sounds exactly like a stuck open thermostat problem, and cooler temps would exaggerate the problem. With a properly working thermostat, it will hold the cold coolant in the engine until it warmed up fully. With a stuck open thermostat, coolant would flow between the engine and radiator constantly, letting the radiator cool the coolant as the engine struggles to warm it on these really cold mornings. This would make it really hard to get the engine fully warmed up. And it would be even worse at highway speeds. I’ll bet the used S40 on the lot had the exact same problem. Maybe a batch of bad thermostats that failed early?
As far as the duct tape on the grille, NASCAR racers use this trick all the time. Paint a large ‘8’ on the doors, and call it your track qualifier! 
Yes everyone says replace the thermostat, how hard could that be. So I went to do that and guess what? Thermostatis not where it was on previous model. I talked to independant Volvo repair shop and now I know why Volvo won’t replace it. $300 labor on this particular car and that’s not at Stealership rates!!! Yep got to remove air box and jack up the engine don’t ya know…Nice guy at repair shop is going to check the function of a couple of S40’s he will be working and let me know if they do what mine is doing. Not going to spend $300 if it is not a sure fix.
I suppose that if a couple of other S40s do things similarly that could mean…well, it’s not really clear what that would mean.
Did you do the thing with the upper radiator hose? The fact is that if that hose warms all the way up to temp gradually with everything else…then the thermostat is stuck open. If it stays mostly cool for a long time, and then suddenly heats up about when the car hits normal operating temp - then the thermostat is behaving itself. Anyone with an IR thermometer and a little patience could actually tell you at about what temp the thermostat does open. So there’s really no need to make guesses about your car based on the operation of other cars.
Testing if it does the same thing on other versions of the same model makes sense to me. Could just be a problem with the design. You’d think the Swedish company Volvo would know how to design a car that would produce ample passenger heat in cold weather though … lol …
But if all the other versions of the car do it, why waste money on testing the thermostat idea.
Some folks here have mentioned that they place a piece of cardboard to block part of the radiator in really cold weather to solve this kind of problem. I think I recall reading that same suggestion in the Popular Mechanics Car Repair book too.
Yes sounds like a simple test and I may do it but I don’t think it will convince Volvo of anything. OBDII reader shows the temp goes from 195 down to 160F when heat on fully. Will probably just drive with the OBDII showing live data to see if there is an opening of the thermostat phenomena occurs rather than stand around with my arm in the engine…there is no top hose, its a bottom and mid hose.
The coolant temp sensor is almost certainly before the thermostat, so the OBDII scanner won’t work for this.
Disagree. When cold fluid runs into engine it will lower the temp. Typically see this if you watch your temp guage as car warms up. It drops when the thermostat opens.
I’ve monitored temp gauges and scanned data on CTS’s. You will not see a lot of temperature fluctuation with a good working thermostat. The temperatures through the whole system will normalize and stay there. With a faulty thermostat, the temperatures WILL fluctuate slowly and typically stay below normal if everything else in the cooling system is running properly. If, once you get it warmed up, then turn the heater to full blast and watch the temp data. If it drops off noticeably and fails to recover, the that is an indication thermostat is bad.