Heat from vents not hot enough

[mug23]

Hello:

I have an issue with the heat coming out of the vents that's seems to be not hot enough even though I turn the temps all the way up. Here's the detail:

Engine warm up. If I keep the engine revving while stopped or the car is being driven, the heat from the vent is hotter. If I just let it idle, I can almost immediately feel the air coming from the vent to be cooler and not as warm. Could this be an issue with the water pump not spinning fast enough to recirculate the water through the heater core? Could the heater core somewhat have a blockage?

I have already done the how-to unclog heater core twice and each time right after the process, the air blows very hot which is what i want . But after a while, the air from the vent is not as hot as it was initially when unclogged.

I'm stuck and not sure on what to do to get a constant hot air from the vent when I turn up the heat. Please help as it's getting very very cold here in the Northeast!

[bmos]

Engine warm up. If I keep the engine revving while stopped or the car is being driven, the heat from the vent is hotter. If I just let it idle, I can almost immediately feel the air coming from the vent to be cooler and not as warm. Could this be an issue with the water pump not spinning fast enough to recirculate the water through the heater core? Could the heater core somewhat have a blockage?

I have already done the how-to unclog heater core twice and each time right after the process, the air blows very hot which is what i want . But after a while, the air from the vent is not as hot as it was initially when unclogged.

I'm stuck and not sure on what to do to get a constant hot air from the vent when I turn up the heat. Please help as it's getting very very cold here in the Northeast!

It sounds like you may be dislodging the blockage but not fully removing it. Are you flushing the core in both directions?

[mug23]

It sounds like you may be dislodging the blockage but not fully removing it. Are you flushing the core in both directions?

Yes, I have done it in both directions and it did clear out some stuff but not much. Again, the strange part is that at the time of the heater core being unclogged, once I refill the coolant, the heat is pretty hot.

I'm pretty sure the system is bleed of air as the car does not over heat or anything like that.

[maxiz1]

Did you get 90 degC (194F) coolant temperature? Is the thermostat ok?

[DarthWinja]

Try using compressed air with the water. I was having similar issues until I flushed it like that.

Rose: B5S4, Judith: Stage III B5A4 daily.

[bmos]

Try using compressed air with the water. I was having similar issues until I flushed it like that.

Rose: B5S4, Judith: Stage III B5A4 daily.

Careful when using compressed air, you don't want to much pressure as the hoses and core can only take so much.

[nynoah]

Anyone ever tried soaking the inner core with something like CLR to get the crud out? I would think that would help.

[Wrath And Tears]

Inside the heater core are plastic tubes that can break if you have too much water pressure or if you use a corrosive material.

[nynoah]

I thought the inside of the heater core was aluminum? Sure the top tank portion is plastic. But I would think the plastic would not have an issue with CLR. Well vinegar would do the same thing too and it might be less hard. Sometimes just flushing with water will not break the blockage material.

[Wrath And Tears]

The tubes are to help slow down the coolant so that the aluminum fins can suck out all that heat. Thats how my coworker described it to me. When the plastic breaks and crumbles it can clog up the heater core too badly to be flushed. Not saying that's what happened here, but what could happen in rare situations.

[noob5]

In case you have to do the replacement there is an all-metal heater core available from the B5 Passat (Part#8D1819031C). Ask me how I know: http://www.audizine.com/forum/showth...e-from-passat)

[A4Moby]

Take the core to a radiator shop? A heater core is just a small radiator. They deal with plastic tanks. Have them flush, pressure test and repair or replace as needed. Of course, these shops are harder and harder to find these days.

[down_n_dapper]

Take the core to a radiator shop? A heater core is just a small radiator. They deal with plastic tanks. Have them flush, pressure test and repair or replace as needed. Of course, these shops are harder and harder to find these days.

have you ever removed the heater core to just "take the core to a radiator shop"? its no small task in a B5 lol

[A4Moby]

Yeah, everything sucks to get to on a b5 I used my experience replacing all of my control arms and trying to torque all the bolts correctly as an excuse to upgrade to a long handle, flex head torque wrench. Which I love. So it all works out.

[nynoah]

Honestly I have not found one car I have ever worked on where the inside heater core was easy to get to.

[crazyquik22023]

You can verify water pump output by removing the expansion tank cap, then the small hose on the expansion tank and hold it over a bottle. Then have someone rev the engine to 2500 or so rpms. You should see a thick steady stream of coolant flowing out. And when you let off the throttle there should be a small "trickle" at idle. Your problem sounds more like your heater core is still clogged or there is still air in it. Carefully remove the hose with the hole going to the heater core and make sure a steady stream comes out of the hole. Then you know for sure all the air is out of the heater core.