Heat loss at idle, temperature gauge climbs slowly

[Tippey764]

Exactly as the title states, when I pull up to a traffic light sometimes my heat will go away and the temperature gauge will slowly climb up. If i rev the engine up to 2k or start driving the temperature goes back to normal and my heat returns

I did just replace the thermostat recently and used the correct coolant. I'm pretty sure I bleed it correctly by letting it run for a bit with the cap off since there isn't a bleeder valve for the later model coolant system ( correct me if I'm wrong of course )

The car is a 1990 325is

[digger]

there is a bleeder valve on the t-stat housing, try and bleed it

http://www.rtsauto.com/articleimages/bleederscrew.jpg

[Tippey764]

I was told that you only use that bleeder on early year cars with the expansion tank on the right of the engine bay but later year cars with the expansion tank in the front left corner do not need it.

[LJ851]

My '89 has a bleeder valve and i have to use it to bleed the system.

[Tippey764]

Well regardless of that you would think any bubble in the cooling system would work its way out in 500-700 miles wouldn't you?

[digger]

there is an easy way to find out...

[3vilE30]

Well regardless of that you would think any bubble in the cooling system would work its way out in 500-700 miles wouldn't you?

False, I've had low heat for over 1000 miles. It took a straight 2hr long trip for it to start to get back to normal. Crack the bleeder and see if you get any bubbles. If you're getting a nice stream out the bleeder, close it and leave the filler cap open on the expansion tank and let it self bleed.

[digger]

also turn heater on etc when bleeding

[Tippey764]

Alright I'll take a look at it again today. My commute to work sucked, it's all highway and I started to lose heat and regain it randomly, also the temperature gauge was slightly higher than normal. I'm wondering if I'm low on coolant now, the check control hasn't said anything but maybe it's broken like everything else

[3vilE30]

also turn heater on etc when bleeding

Aha yeah! And don't forget to do it on an incline or jack up the front.

[Tippey764]

So after letting it sit all day at work for about 10 hours I came out to try to bleed it

Upon removing the cap a huge pressure relived itself and coolant gushed out although the car had been sitting for hours

I opened the bleeder until coolant flowed continuously and then closed it. I started the car and kept periodically opening the bleeder screw for about 15 minutes until I stopped getting any air. I finally regained heat inside the car at idle and couldn't get any more coolant into the car so I put the expansion tank cap on.

I have nice heat while driving but still at idle it cools down a bit and the gauge goes up a tick. What gives?

[digger]

if temp goes up when idling then the clutch fan may not be working as efficiently as it should be

[Tippey764]

If thats the case I should still have heat in the interior and it should be even warmer if anything.

[3vilE30]

Where does your temp needle stay around?
It's supposed to be a little cooler when idle because coolant isn't flowing as much, but it shouldn't be a drastic difference. You might still have air I had the same problem. It would be toasty while driving but once you came to a light it went away and took forever to get back up to normal heat.

[Tippey764]

Typically it never goes above the half mark when it's working right.

When the heat goes away the temperature gauge will reach 3/4