2005 Impala - Cabin Heat takes forever

[jim-milwaukee]

On my 2005 Impala, it takes a super long time for the cabin heater to blow hot air - 20 minutes even when it is warm out side. The temperature gauge says the engine is up to temp within a normal time; but, it seems like the heater core does not get any heat for a long time. Any advise?

When I start the car, my temp gauge shows that the coolant at the block heats-up pretty quick. After a few minutes of running, I can see the temperature drop about 20­ deg (from 220 to 200) then level off. I thought this was the thermostat opening-up.

I have until October before the first frost ... can't affort to wait 20 minutes every morning to defog the windshied!

[taillight]

It sounds like the flow through your heater core is blocked. Pull the hoses off and try flushing with a garden hose.

[jim-milwaukee]

Thanks. I'll see if I can flush the lines as well as the heater core. One of the guys here at work said there may also be a "heater core control valve" or bypass which could restrict flow to the heater core. I did a quick look and it looks like the feed/discharge lines from the block (above the thermostat housing/back into the block) are uninterrupted to the firewall. Does anyone know if there is a valve of this sort, or is it the case that once the thermostat opens up, the heater core has flow all the time?

[INF3RN0666]

If you car warms up to 1/3 of the gauge in about 4 minutes, then you're fine. I had the same problem, but my car would take forever to warm up. I pulled out the thermostat to find out it was stuck open.

[taillight]

There is a flow comtrol valve.

[jim-milwaukee]

Thanks guys. I did get to the root of the issue. When I was driving home from work, the car would not hold temperature. The gauge was fluctuating wildly between 175 and 240 degrees. I ripped out the themostat and found that it was getting stuck both open and closed. There are 2 springs on the therostat. The first (bigger) one is simply an open close valve set at 195 deg. The second spring is lighter and has a disk attached and is operated by thermal pressure. As the block gets hotter, there is more pressure due to expanding coolant and the disk allows more coolant to flow through the radiator. When cooler, the disk settles back to restrict the flow a bit. The disk moves up and down on a brass shaft. I could tell by the drag marks on the brass shaft that the disk was binding instead of free flowing.

My car took so long for the heat to come on because the disk was bound-up in the open position. Later on it bound-up more closed and I almost overheated.

I do not think there is any other flow restrictor than the disk in the thermostat unless it is burried in the dash. I think that 100% of the time there is full flow through the heater core.

Tip for anyone replacing a thermostat on a 3.4L Chevy ..... the bottom bolt for the thermostat housing (the one that is a real pain to get at) does not need to be fully removed, only loosened. The thermostat housing has a slotted hole on the bottom location. Not knowing this will cause you to rip out a lot of pieces which look like they are in the way!

[INF3RN0666]

Just so you know: Not removing the bolt is not the best idea. Thermostat housings have a gasket. So if you don't remove the bolt, you can't install a new one. Even if you wanted to keep the old one, not removing the bolt will cause you to tear the old gasket. I have a 3800, so I dont suffer from restricted access to the thermostat housing.

[wishnman]

My 2005 impala had the same problem. Here's the answer. The heater core is plugging up. When you sit idling, the fluid movement is slow, therefore the junk settles in the heater core, still allowing enough fluid to get through to heat. When you drive it, the fluid movement is much faster, therefore sending the junk into the heater core, plugging it up. To check for this problem: Get engine temp up to normal, feel both heater hoses. If one is hot and the other one is cooler, fluid is not passing through. Take off both heater hoses at the top of the engine, blow out fluid with low pressure.(5 or 10 lbs.) Fill both hoses with the right radiator flush. (Some engines are aluminum) Let stand for 4 hours. Flush with new antifreeze. (I used a garden sprayer) Stick the sprayer end in the heater hose and tape tight. My vent temp WAS 100 degrees. After fix was 152!!