Is it normal for a car's coolant temp go 3/4 of the way up when in traffic?

[coolgraymemo]

I recently changed Water Pump, Timing Belt, Thermostat and Coolant on my 1.8T AEB.

My cars coolant temp, goes up a little past the half way point (just past the half line), when driving normally on the street or freeway. I think that's normal.

But when I'm in traffic, it goes 1 or 2 lines past the half way point (5/8 - 6/8), but cools down to the half way point when speeding up. Also, when I stop to make a quick trip into a store, (15-20 minutes) and get back into my car, the temp goes 3/4's of the way, but then cools down.

I have the proper mix of 50/50 coolant to water.


BTW its around 100 degrees here in Nor-Cal.


What can be my problem?

[coolgraymemo]

While searching I found it can be:

Faulty TStat.
Coolant Temp. Sensor.
A fan.

Or can it just be because it is really hot here in Sacramento?

[walky_talky20]

Coolant temp gauge should rise to the middle and stay there, period. It is NOT normal for it to go any higher (or lower) than the center of the gauge while the car is running. If it is hot and you shut it off, the coolant temp will rise slightly. In this case the needle may rise maybe 1 or 2 needle-widths above center, but should return soon after the engine is started, probably within 1 minute.

If the gauge is going higher than the center, you should verify that the electric fan is running on high speed during that time. If not, the fan, fan switch, fuse, or wiring is faulty. The other possibility is the gauge is just lying to you. You should probably just change the Coolant temp sensor first to be sure. They are very cheap. If CTS and fan operation is good, you should make sure the system is properly bled of all air.

Our cooling systems should be quite adequate at even 100F with the A/C on if everything is working properly.

[coolgraymemo]

To get air out of the system you turn the car on with coolant tank cap off right?

[djwimbo]

To get air out of the system you turn the car on with coolant tank cap off right?

there's a bleed hole in the hose coming out of the heater core, loosen the clamp, run the engine up to temp. Crank the heat inside the car, pull that hose back and let the air bubbles come out, but don't pull the hose all the way off.

Have you checked if both your fans are working???

The coolant temperature WILL rise if you shut the car off, the nature of the beast is that the pressure inside the system increases the boiling temp of the coolant/water mixture. When you shut the engine off, the heat inside the engine block will transfer to the cooling system, and since there's no airflow, the heat sinks into everything. Once you're driving again, or at least the cooling fans are running, the temp SHOULD come down quickly.

[EuRo_KiD]

^^^ But does running the car with the coolant tank cap off bleed the system too? Also, do you have a pic of said hose? /Threadjack

[coolgraymemo]

LOL.

Well yea, both fans turn on. One is on when the car is on; the other turns on when the a/c is turned on.


And for the system bleed. I did some research and another AZ'er said that taking the cap off the expansion tank while running is the same a bleeding the system.

[nunya]

To get air out of the system you turn the car on with coolant tank cap off right?

http://wiki.quattroworld.com/index.p...dCoolingSystem

[walky_talky20]

No, you can still have air trapped. You should bleed the system the proper way using the bleed hole. Actually, the *official* procedure is to elevate the coolant reservoir while using the bleed hole, but I've never found that to be necessary as long as the car is on level ground.

The electric fan should turn on on it's own without the A/C on. Just turning the A/C on and seeing the fan spin isn't checking the "dual thermal fan switch". That is what engages the fan on low or hi speed based on coolant temperature at the radiator outlet.

[djwimbo]

^^^ But does running the car with the coolant tank cap off bleed the system too? Also, do you have a pic of said hose? /Threadjack

Nope.

See the link in post #8

[JEmm]

Only read the first post, I'm saying heat soak. Just really hot and the stock smic isn't cutting it in the heat during traffic because it's not getting the airflow that you get while driving normally (for obvious reasons).

[walky_talky20]

Hmm. What does the intercooler have to do with engine coolant temperature? Engine cooling is done by the radiator.

[djwimbo]

Hmm. What does the intercooler have to do with engine coolant temperature? Engine cooling is done by the radiator.

... I wasn't going to say anything, but yes, you are correct sir.

[JEmm]

Hmm. What does the intercooler have to do with engine coolant temperature? Engine cooling is done by the radiator.

... I wasn't going to say anything, but yes, you are correct sir.

I honestly just skimmed through, saw he said he was running hot in traffic and thought heat soak immediately... My bad haha

But, would the lack of air flow over the radiator cause the coolant temps to run hotter? I mean, it seems odd that every time he stops or isn't moving it is hotter than when he's actually driving...

[walky_talky20]

But, would the lack of air flow over the radiator cause the coolant temps to run hotter? I mean, it seems odd that every time he stops or isn't moving it is hotter than when he's actually driving...

Yep. It could be his fan switch is dead and it never turns the electric cooling fan on.

[coolgraymemo]

Yep. It could be his fan switch is dead and it never turns the electric cooling fan on.

Where is the fan switch located?

[walky_talky20]

There is 2 different spots for the fan switch. I believe the switch-over was in 99.5, so it depends if you have a 99.0 or 99.5. Anyway, early B5's have a 3 prong, gray-colored switch screwed directly into the radiator end tank, just above the lower rad hose outlet. Later B5's have a 4-pin blue-colored fan switch mounted directly in the lower rad hose itself, and held in with a plastic clip. The switch resembles the green coolant temp sensor in size and shape, but is indeed different in function.

You would want to test to see if it is working before replacement. You can watch coolant temp in vag-com for comparison. Above about 95C, the low speed should kick in. Above about 102C, the high speed should kick in. While in vag-com you can verify your gauge cluster and ECU temp agree.