replaced t-stat, now slow to reach operating point

[mrbacardi]

Hello all!

I was getting annoyed by the lack of heat i was getting out of the camry during cold winter days (-30°F). I thought that since i've never changed the coolant since i got the car (about 6 years ago) or the thermostat, i might as well change both.

So i drained the radiator and coolant from the hose containing the thermostat and took the old one out and put the new one in with a new gasket. Refilled the radiator and system with new glycol (not pre-mixed, i mixed it with water)

Now the vehicle takes longer to reach the operating point! A lot longer, almost double the time. What i was thinking is that when i refilled the system, did i add too much glycol to water percentage? I was thinking of draining the radiator a bit and adding in some straight water. Like drain 1 Litre and then add 1 Litre of water.

What are all your thoughts?

[davemac2]

The coolant mix should not affect the warmup period much at all. I'm assuming when you say it takes longer to warm up, you mean it takes longer to get heat from your heater core into the cabin. You may have had a different thermostat in the car previously that opened up earlier at a lower temp. Your problem though is likely a plugged heater core from crud buildup in the system if you never changed the coolant over 6 years. You don't mention the model/year of your vehicle, but another thing to check would be the heater bypass valve in the engine bay near the firewall and its associated cable to the heater control if you have manual HVAC controls in the cabin. As well, you may have a weak water pump. This will need to be diagnosed properly by checking the coolant temp directly when the engine warms up to normal temps after 15 min, and inspecting the items already mentioned. If it is a plugged heater core, you can try an aggresive scale remover in the system to see if it helps.

dave mc

[toyomoho]

The T-stat responds to coolant temp doubt coolant mix ratio would cause much diff in heating rate.

Did you replace the T-stat with one of the same temp rating? And position of the hole or rivet in the flange upright. Did the old T-stat have this hole, larger hole, etc.

[mrbacardi]

i think ya'll are right with the coolant/water ratio being a non-issue.

The old t-stat was 180°F.
The new t-stat is 192°F.

The vehicle is toyota camry 1992, 248xxx kms.

Toyomoho what you mean by:

"And position of the hole or rivet in the flange upright"?

[Hajoca]

Rivet = Jiggle pin, that lets the entrapped air escape and vent in the system.

[DFBonnett]

OP,
Also note that, while unusual, it is not unheard of for a thermostat or any other part to be defective right out of the box.

[dz63]

Originally Posted by davemac2

The coolant mix should not affect the warmup period much at all. I'm assuming when you say it takes longer to warm up, you mean it takes longer to get heat from your heater core into the cabin. You may have had a different thermostat in the car previously that opened up earlier at a lower temp. Your problem though is likely a plugged heater core from crud buildup in the system if you never changed the coolant over 6 years. You don't mention the model/year of your vehicle, but another thing to check would be the heater bypass valve in the engine bay near the firewall and its associated cable to the heater control if you have manual HVAC controls in the cabin. As well, you may have a weak water pump. This will need to be diagnosed properly by checking the coolant temp directly when the engine warms up to normal temps after 15 min, and inspecting the items already mentioned. If it is a plugged heater core, you can try an aggresive scale remover in the system to see if it helps.
dave mc

What do you mean by "weak" water pump and how does one go about isolating this as the problem?

[davemac2]

dz63,

I mentioned a weak water pump as a possibility, but thinking about it more, it is not likely in this case. A heater core cable, valve, or plugged core are much more likely. A weak water pump would be one where the impeller is corroding away and reducing coolant circulation. You could potentially check for this without removing the pump by removing the thermostat and trying to check coolant flow rate out of the top hose. A weak pump would probably affect engine cooling more at higher loads such as highway driving and cause overheating. Not sure what effect it would have at lower speeds or at idle, but in combination with a partially blocked heater core, ??

dave mc

[mrbacardi]

ok leave the heater core out of the picture. The main question i'm asking is that why is the temperature of the coolant rising slower than before i changed it? i.e. the temperature gauge takes longer to reach operating temperature (just under halfway). The only thing i changed was the thermostat (old one was 180°F new one is 192°F, i even got a replacement 192°F thermostat and put it in only to find it not fixing the issue) and the coolant.

The new coolant i put in is the prestone yellow long life coolant. I don't know what colour the old coolant was, i never bothered to check (it was most likely the toyota red coolant, since the previous owner always serviced it at the dealership).

Is it possible that the new prestone coolant just takes longer to heat up vs. the toyota red coolant?

[Hajoca]

I doubt that it is the coolant, by adjusting the concentration you will change heat rtansfer rate (more water better heat transfer) but that should not cause what you are describing.

Is T-stat made for your car? is an aftermarket fail safe style that always bypass some coolant? It seems to me that the coolant is circulating through the rad all the time.

[Hajoca]

Get a coolant tester (gravity type with floating balls at Ctire)

[mrbacardi]

Originally Posted by Hajoca

I doubt that it is the coolant, by adjusting the concentration you will change heat rtansfer rate (more water better heat transfer) but that should not cause what you are describing.

Is T-stat made for your car? is an aftermarket fail safe style that always bypass some coolant? It seems to me that the coolant is circulating through the rad all the time.

The hose containing the thermostat is quite cold to the touch until it has reached operating point.

[davemac2]

The gauge sensor is upstream of the tstat is it not? I can only assume that there is none or very little coolant circulation until the tstat starts to open. Therefore, the coolant around the sensor will take longer to heat up potentially. You're in Winnepeg in the middle of January. What do you expect?

dave mc

[mrbacardi]

Originally Posted by davemac2

The gauge sensor is upstream of the tstat is it not? I can only assume that there is none or very little coolant circulation until the tstat starts to open. Therefore, the coolant around the sensor will take longer to heat up potentially. You're in Winnepeg in the middle of January. What do you expect?

dave mc

before the t-stat and coolant change it was fairly cold here. Below -25°C during the daytime. After leaving the vehicle plugged in overnight and starting the vehicle and reaching work, the coolant would be at operating temperature (just under half-way on the gauge).

after t-stat change and coolant change: average temperature about -8°C. After leaving vehicle plugged in overnight, starting the vehicle and reaching work, the coolant temperature would only be at 1/4 on the temperature gauge.

You know it would be interesting to know where exactly the temperature sensor is for the temperature gauge beside the speedometer. If it is on the radiator-side of the t-stat, then it's most likely reading exactly what it's supposed to be reading and this whole problem would be solved...never thought to look that up, i just assumed the temperature sensor would be on the engine side of the t-stat.