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Heater issues?

Tiny
CHRIST CHEN
  • MEMBER
  • 2010 VOLKSWAGEN GOLF
  • 2.0L
  • 4 CYL
  • 2WD
  • MANUAL
  • 95,100 MILES
First, my car is Canadian Golf City 2010, manual 5 speed, 2lt engine, with 153 108 km.
My issue is that when I start the car in morning (cold start) even if I let it idle for 1hour,
{{All the hoses and engine radiator are coming warm/hot, the needle gauge is at operating temperature}} there is no heat coming out the vents until I "rev" the engine up to 1,500 RPMs (then heat start to come out).
Can it be a pump lack of circulation or the system pulling in air by a not big enough opening to lose coolant?

Christian
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Saturday, August 17th, 2024 AT 11:23 AM

13 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

The idea that you have to rev the engine to gain heat indicates either low coolant or air in the system.

Has the system been drained recently? Is the coolant level full?

Let me know.

Joe
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Saturday, August 17th, 2024 AT 7:24 PM
Tiny
CHRIST CHEN
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  • 36 POSTS
Hi Joe,

I didn't drain the system.
From time to time, let say every 3 months or so, I have to refill the ball tank with 1cup of coolant to keep it at minimum level but there is no obvious leak marks on the engine or ground, and there is always a coolant smell between the radiator and the engine on the transmission side.
Christian
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Sunday, August 18th, 2024 AT 6:26 AM
Tiny
JACOBANDNICKOLAS
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Hi,

If you smell it, there must be something leaking that you just can't see. What I would recommend is to pressure test it to locate the leak. You need a pressure tester, but most parts stores will lend one to you.

Here is a link that shows how it's done:

https://www.2carpros.com/articles/radiator-pressure-test

Next, when you say after starting and allowing it to warm up all hoses are hot, are you including the heater core hoses? Are both sides hot (supply and return)?

Joe
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Sunday, August 18th, 2024 AT 7:35 PM
Tiny
CHRISTIAN CHENARD
  • MEMBER
  • 6 POSTS
Hi Joe,

Yes, all hoses get warm/hot including heater core's, even the radiator gets warm top to bottom.

About the pressure test, where I live (Quebec, Canada), auto parts stores don't lend or rent tools (well, not in my region anyway).
But I'll try to find one.
Is the dye in the coolant and black light do the job?

Christian
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Monday, August 19th, 2024 AT 1:34 PM
Tiny
CHRIST CHEN
  • MEMBER
  • 36 POSTS
Sorry I made a mistake, before I "rev" the engine, only the inlet heater core hose gets fully warm and the outlet hose get warm near the engine only.
Christian
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Monday, August 19th, 2024 AT 5:45 PM
Tiny
CHRIST CHEN
  • MEMBER
  • 36 POSTS
Hi Joe,

Where I live, auto parts stores do not lend or rent tools, but i'll try to find a pressure tester.
Is the dye in coolant and black light do the job?
Christian
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Monday, August 19th, 2024 AT 5:49 PM
Tiny
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Hi,

Yes, if you have added dye and have a black light, you should be able to find it.

Let me know.

Joe
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Tuesday, August 20th, 2024 AT 5:36 PM
Tiny
CHRIST CHEN
  • MEMBER
  • 36 POSTS
Hi Joe,

Sorry for the delay, I had a hard time finding proper material.
I did try the dye (see on photo), drove for about 70 miles and can't see any leaks (bright yellow dye spots) anywhere even under the timing belt cover, but the smell was still there only between radiator and engine (transmission side). No smell inside the car, so it's surely not the heater core at this point, I'm confused.
Can it be the radiator itself but doesn't show significant leaks?
Christian
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Sunday, August 25th, 2024 AT 12:51 PM
Tiny
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Hi,

If you smell it but see no leaks, the only thing I can think of to do at this point would be a pressure test.

Now, I reread through our conversations. You noted that the supply hose for the heater gets hot, but the return doesn't. It sounds like the heater core itself is partially clogged.

This is where I may run into trouble. I know this is a Canadian Golf. The only 2.0L I show is a diesel. I don't think that is what you have, correct?

Let me know. I may need you to disconnect the supply hose to the heater core and spray water through it to see if the water comes out the return hose.

Let me know.

Joe
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Sunday, August 25th, 2024 AT 7:34 PM
Tiny
CHRIST CHEN
  • MEMBER
  • 36 POSTS
*You are right, it has a gas engine not diesel.
*Once I "rev" the engine, the return hose get hot.
*My golf city is basically built on the golf generation 1999-2005 platform.
*Next weekend, I will flush the heather core and see what's in it as dirt.
*I don't think the pressure test will show anything more, because you can't pressurize the system more than 15-18pound without the risk of blowing a seal.
Christian
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Monday, August 26th, 2024 AT 3:08 PM
Tiny
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Hi,

Sounds like a plan. Let me know what you find.

Take care,

Joe
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Monday, August 26th, 2024 AT 5:54 PM
Tiny
CHRIST CHEN
  • MEMBER
  • 36 POSTS
Hi Joe,

On the pic, it shows how much coolant there was in the heater core (i don't know how much there supposed to be) and there was no obstruction in heater core.
I used a garden hose to flush it both ways(inlet, outlet).
Still same issue.
I start to think it's the engine radiator itself or there is some exhaust getting in the system by head gasket.
Christian
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Saturday, August 31st, 2024 AT 8:35 AM
Tiny
JACOBANDNICKOLAS
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Hi,

I would think there should be more, but anything is possible. Here is a link that explains how to flush the system. I don't know if you need it or not.

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

Also, here is a link that explains how to check for a head gasket issue:

https://www.2carpros.com/articles/head-gasket-blown-test

Let me know what you find.

Joe
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Saturday, August 31st, 2024 AT 6:35 PM

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