Any harm in running the heater on high in this hot weather after a coolant change?

[atikovi]

The harm would be to you if your sitting in the car

Ain't no worst than driving around Palm Springs with no a/c.

 

[zzyzzx]

Only harm I can see is you sweating all over the seats and it getting it absorbed into the cushion. Might want to consider lining the seat with a few towels to absorb all of that.

 

[paulo57509]

Just my take; some vehicles, the reservoirs are actually remote mounted, radiator side/top tanks. These have a pressure caps.

Coolant line on the left runs to the radiator; hose under the cap is an overflow to ground.

I think the contents of the reservoirs with pressure caps will mix pretty quickly. Reservoirs with non-pressure caps will mix during several hot/cold coolant cycles.

 

[Exhaustgases]

Maybe cooking your brain is the only damage I can think of.

 

[Jetronic]

Is this true? That that you have a heater core radiating heat out under your dash even in summer when the a/c is on?

Yes in some you can feel it.

 

[PontiacHO]

Probably said already but there has been in the past (I’m old) a valve in the heater hose that stops coolant flow to the core when AC is on.

 

[wander2039]

On the trip to Cali I turned on the heat climbing the mountain passes in the RV. Helps keep the temps at 210 no how hard it's churning. I've been doing this for years and no issues.

 

[Lubener]

Yet nobody seems to know how the coolant from the reservoir flows, hence my propensity to drive the car with full heat for a half hour or two to ensure it gets thoroughly mixed.

Not all vehicles are plumbed the same.. If in doubt, run it. You are making a mountain out of a mole hill.

 

[Snagglefoot]

Most vehicles circulate through the heater core 100% of the time. They use a flapper door to direct the air flow through the core (or not). There may be exceptions but the days of shutting off the coolant flow with a valve are long gone. My 74 Datsun had one.

 

[windeye]

But until the thermostat opens, the coolant doesn't flow everywhere.

Not true.

 

[atikovi]

Not true.

I can drive my Honda 10 miles and one radiator hose will be stone cold while the gauge is in the middle.

 

[Number_35]

I can drive my Honda 10 miles and one radiator hose will be stone cold while the gauge is in the middle.

That's pretty normal - the thermostat limits flow to the radiator until the coolant on the engine side of the thermostat is hot enough to cause the thermostat to open.

However, both heater hoses should be hot long before that.

 

[eljefino]

I did, 6 quarts, so I added 3 quarts of concentrate and the rest water, but see it's only good to -12°F. Now I have to drain a little and add more coolant, drive it around until it's all mixed to check it again.

Based on what, a little floaty ball tester? Those are garbage. Mix up 4 oz of virgin 50/50 and see what that gizmo tells you. Or draw a sample of your car's well-mixed antifreeze, dilute it a measurable amount more, and put it in a 0'F freezer to test it.

Math doesn't lie and your capacity is well documented. If you did the job right, and I think you did, you're good to go.

 

[atikovi]

Based on a refractometer.

 

[SHOZ]

Here's an odd one. My Hyundai Accent. The AC didn't work, no pressure so I never used it. But used defrost and the defrost floor setting quite a bit.

I was on the interstate in 90F wearther and backed up for construction. I have a constant OBDII reader showing coolant temp. It started to climb as expected and at 204F the fans were suppose to come on. I put it in defrost and high speed fan but the temp still rose. Ended up pulling over when it hit 220F and shut it off for a few minutes.

But found out the Accent has a separate fan relay for the condenser fan. And a low and high speed cooling fan relays. In Hyundai's wisdom if you have the controls in a defrost or AC mode then the cooling fans and the coolant temp are ignored. If I would have had it in vent or floor then the fan comes on at 204F.

I ended up jumpering the grounds on the condenser and low speed fan relays so if one comes on the other does too.

 

[The motor guy]

I routinely run the heat in the summer to dry out the AC system. Have done this for 30 plus years with no issues.

come again? You know you can just shut the compressor off and leave the fan on for the last few minutes before pulling into your driveway. I don't ever remember to do it, but it definitely allows the evaporator to dry out a bit.

 

[Number_35]

I routinely run the heat in the summer to dry out the AC system. Have done this for 30 plus years with no issues.

I've done that too. I hate the stale smell that results from water condensing in the ducts.

 

[The motor guy]

I've done that too. I hate the stale smell that results from water condensing in the ducts.

I've actualy never had the musty smell problem. Is this something that occurs on vehicles that aren't driven everyday?

 

[Number_35]

I've actually never had the musty smell problem. Is this something that occurs on vehicles that aren't driven everyday?

Good question. I'm not sure. Part of it might be that our summers are often quite humid. With high RH, the ducts are less likely to dry out properly when the car sits.

 

[The motor guy]

Good question. I'm not sure. Part of it might be that our summers are often quite humid. With high RH, the ducts are less likely to dry out properly when the car sits.

Probably system design too. Some are more prone to clogging up and such. Some vehicles, you have to unclog the drain tube occassionally otherwise it starts dripping on the floor