Heat Issues

[theknight571]

Now that it's cold here I've discovered that I have heat issues with my 2008 Nissan Altima (2.5s). I had the car through last winter and did not have any issues.

So you know where I'm coming from, I am not a big DIY guy when it comes to cars. I've been learning more, but I am still not 100% comfortable with it.

Last Thursday I was driving and after awhile realized that I had left the defrosters on full blast and my face was not melting like it normally would be. (I know this, because this was a running joke between me and my son, as our faces would start to melt on the way to school. )

So... not knowing a lot about cars, I took it to the shop. $240 later they had backflushed the coolant system, and the heat was beautiful.

Everything was fine until yesterday (4 days after the shop) I noticed I was not getting much heat.

Doing some troubleshooting, I noticed that at idle, I got very little to no heat. However, at freeway speed I had heat... not as nice as right after they fixed it, but I at least didn't freeze on the way home.

Similar situation this morning. No heat at idle/slow speed. Some heat at speed.

I have checked the coolant level in the overflow. Last night before leaving work (cold engine) it was a little above the "min" level on the overflow tank. This morning after getting to work (hot engine) I checked again and the level in the overflow hadn't changed much. (I check at work because the parking structure has better lighting than the parking lot at my apartment complex.)

If it makes a difference the Engine Temp gauge gets to just below the center of the gauge. So it appears the that cooling system is at least keeping the engine properly cooled.

I've done some Googling and have some ideas on what might be happening, but I was wondering what the AT Garage might have to say before I do anything.

Thanks in advance.

 

[mvbighead]

I had something eerily similar with an 07 Impala. Ended up being low coolant. At stop lights, the heat would go cold. While running it was semi normal.

If it was working 4 days ago and not now, you may have a leak. I suppose your heater core could be plugged up, but if it works fine at operating speed I would doubt it.

 

[Squeetard]

Head gasket or thermostat could cause this.

 

[LTC8K6]

The water pump may be failing. Pumping poorly at low speeds?

 

[Scarpozzi]

My first guess would be that your coolant is low. The heater core is typically located near the top of the engine and fluid levels need to be near max before you get 100% heat. A quart of fluid can make a big difference.

Backflushing your system is what would have suggested had you not done it already. When they put the system under pressure and replace the coolant, it will fix most issues if things get gummed up...ie, junk in the system clogging radiator/heater core or any of the plumbing between your primary system and the heater core since it typically has smaller lines going to and from it.

Resolution: Definitely try adding more coolant to the system and watch for any leaks or try to notice if you smell any coolant. Check your exhaust and see if it appears to be more white than usual. If you don't see any leaks, get a spark plug wrench and back those out. Look for signs of anything weird...

Water pump could be an issue, but a blown head gasket could also be a root cause for leaks. Both of those would be the worst possible outcome (most costly to repair) so I suggest checking for any drips/leaks, etc...anything that could explain loss of coolant.

If you saw them backflush your system, make sure they tightened the hoses appropriately and that they're properly sealed when under pressure... If you have someone rev the engine while you watch with the hood up, you may see fluid or steam.

BTW...if you didn't see them flush it, they probably only disconnected 1 hose from the system at the top of the radiator. Make sure it's on good.

 

[bruceb]

Thermostat could be stuck in the open position or you could have air in the cooling system. Also check the pressure cap. If the engine temperatures are correct, could be the air doors are not moving properly.