Cooling system round 3?

i want to at least attempt to fix my car before i sell it. 2007 equinox 3.4
NEW water pump. New thermostat. Both rad hoses are hot and not collapsed. cooling fans WORK. heatercore is flushed and works fine. good heat.
coolant level is fine. motor has never overheated in 2 years.
vents will blow cool after 2-3 min at idle. i do not “think” reving motor helps heat issue
in summer, with ac working great, and car stopped, the dash temp rises. it will drop if i rev motor to 1500rpm.
do i have a clogged radiator issue? i dont think it is a head gasket issue. how can i drive for 2 years and not use a drop of coolant? heat works great on the highway. flow issue?
cold vents at idle in winter. warm motor in summer. ONLY at idle. whats the connection?

Definitely sounds like a flow issue to me. Check the thermostat for proper opening (or just replace it, it’s cheap) and make sure the lower radiator hose isn’t collapsed for starters.

Did you do a pressure test?

I have a slight whiff of coolant in suv with heat set to hot. No smell with setting at cold. HC is always hot. Blend door just bypasses vent air. My carpet is dry. No coolant drips on carpet in 2 yrs. so, a pressure test may show a loss of pressure? So, Cooling system is never at cap 15psi?
Heat is fine on hwy with low system pressure. But no heat at idle with low system pressure?

I flushed system. Am using code reader for ECT and looking at dash. Needle sits at normal. Reader says 200 or so. Goes to 212 at idle and fans kick on. Yet dash needle is still saying normal. It’s like the dash needle is responding much slower or not at all while reader says temp is changing. Before, the needle would move to 1/2 way point on dash while now it does not. Motor never seemed hot before and now gauge agrees?

I think the big clue is you don’t get big heat out the heater vents quickly during warm-up in the winter. Your car probably uses a bypass type theormostat, and those are designed to provide heat quickly to the passenger compartment. During warm up the coolant is supposed to be redirected back into the engine, none going to the radiator. Suggest to check that. Perhaps the the little valve that prevents flow to the radiator during warm-up is leaking. Air in the heater core loop could contribute to this also. Place the front wheels on ramps etc so the pressure cap is high as possible, then open the pressure cap and idle the engine with the heater on high. Do you notice during warm-up any air-burps coming up through the coolant? If all else fails I’d probably just remove the radiator and reverse flush it in the driveway, relatively easy to do and might help.

Did this problem of no warm air at idle during winter start AFTER replacing the water pump or BEFORE. If it was after, I suspect you got the wrong water pump. IIRC, there are two water pumps that are identical on the outside, will interchange with no problem, but the vanes flow the water in different directions. Something to do with whether the drive belt goes over the top of the pulley or under it.

Good idea above by @keith . Never experienced this myself, but I’ve heard that it is possible to get the water pump belt routing mixed up, causing the water pump impellers to turn the wrong direction. Probably worth the effort to double check the water pump is turning the correct direction.

I guess the problem with cooling system diagnosis is there are so many potential failure modes. On the surface it seems pretty simple, the pump pushed coolant around in a circle, some of which goes to the radiator, and everything is under a little pressure. What could possibly go wrong? But there’s a lot that can go wrong apparently.

Let me add something. I think that the water pump that has the belt go over the top has grooves in the pulley. Those that are used where the belt goes under have smooth pulley.

I recently (well, within the past year) replaced the water pump on my Corolla. The replacement part contains the impeller but is only half of the water pump, the other half has no moving parts & is just re-used. I double checked the impellers on the new one were oriented the same way as the old, but it would be pretty easy to not notice it.

It’s our 3rd car so it sat a lot. I never go to drive thru situation so I never saw no heat issue. It sat last 6 months in garage. No use at all. The wp pulley is smooth. So back of belt drives it. Pretty much impossible to route it wrong. So, I drive it, temp is 200. Dash temp gauge says normal. Sit in driveway, code reader says it is 212. Dash needle moves .010”? Easily nowhere near “middle” of gauge like before. Fans run, code reader says temp is dropping and dash gauge is still at normal. Why would flushing system seem to make gauge not move from normal? Wp is upper right. Has very little belt contact actually. Less than 1/4 dia

I wonder if the dash gauge reading and code reader are measuring at different locations? That’s the way it work on my Corolla, the computer measures the temperature at a different spot in the coolant path than the dash gauge. If so the discrepancy may have something to do w/that, perhaps some obstruction has developed in the coolant path.

I know the thermostat is new, but it probably makes sense to remove it and watch what happens when you heat it up in a pot of water on the stove. I had a problem w/my VW Rabbit years ago where the thermostat opened at the correct temperature, but didn’t open as wide as it should.

I’d certainly be able to get that belt routing wrong, but if it were wrong it seems like the belt tension would be so far off that it would be impossible not to notice.

2007 was also a bad year for stepper motors for the gauges. If you have never had the stepper motors replaced with the upgraded versions, you might consider that, also have the lights replaced and the resistors reflowed in the gauge cluster.

I just drove it. Temp gauge actually reads cooler now. About a tick over the 1/4 mark. I replaced cluster 2 yrs ago for bad tach. Maybe temp gauge is flaky now? But, that doesn’t explain cool vents at idle last year. The vent seems hot/ok now so maybe the system flush helped. I did flush heater core last fall. And highway heat has always been good.
Scan tool says temp is good. 200-205f

From what I’m seeing
The PCM commands the fan to turn on

  • 208°F for Low
  • 216°F for High

Temp below 210°F** , fans go from low to off.

Are you noticing the fans switch speed from low to high and visa versa?

You could place a scientific mercury thermometer into the coolant and see if it reads the same temperature as your scan tool.

Both fans run at about 214f. I have never noticed a speed change from hi/lo on the 4-5 equinoxes/torrents I’ve owned. The fans both shut off when temp drops to 208f approx. both fans run at same speed when I turn on ac. So, today dash temp gauge decides to be flaky? And was fine in the last year? Odd
I do have a digital thermo with thermocouple. Somewhere.

You might be able to use an engine-test strobe light to determine if the fans are switching speeds like they should. I would have guessed you could hear the speed difference. If they are on high when they should be on low, a possible explanation.