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Overheating?

Tiny
BHAMDOC1973
  • MEMBER
  • 2012 VOLKSWAGEN PASSAT
  • 2.5L
  • 5 CYL
  • 2WD
  • AUTOMATIC
  • 172,000 MILES
No codes. If I leave it running it will climb to the middle and stay there for a while then go up a notch. If I drive it I notice it starts to climb. No leaks. Reservoir starts to boil. Pressure on radiator hose is okay. Is it possible the thermostat or a weak water pump?
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Monday, July 22nd, 2024 AT 10:33 AM

30 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

Will it overheat if you are driving at highway speeds, or does it seem to happen in stop and go traffic?

Also, do you hear the cooling fan turn on once it goes over the midway point on the gauge? Does the fan turn on with the A/C turned on?

Let me know.

Joe
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Monday, July 22nd, 2024 AT 8:37 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Yes, fans come on. I can't drive it far enough to know if its highway speed. Doesn't matter if stop and go or driving constant speed it still overheats.
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Tuesday, July 23rd, 2024 AT 5:03 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

The first thing I would do is replace the thermostat. If the coolant is full and there is no air in it, the thermostat is likely sticking. If you want to remove it, it can be checked by placing it into boiling water to see if it fully opens.

Now, on this engine, the intake manifold needs to be removed to access the thermostat. Not an easy job.

If you look below, I added the directions specific to the thermostat. At the end of those directions, I added the removal instructions for the intake.

Let me know if this helps.

Take care,

Joe

See pics below. Note: Make sure to have the required tools before you begin.
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Tuesday, July 23rd, 2024 AT 7:39 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Removed thermostat and it has some rust on it but installed it in boiling water and I only see it partially open does it open gradually? Or is this all it opens? If you zoom you can see it a bit open.
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Thursday, July 25th, 2024 AT 11:17 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Unfortunately, a new one didn't solve it. Moving to the water pump.
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Thursday, July 25th, 2024 AT 6:06 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

When you installed the new one, did the vehicle still act the same as the with the old one in it? Also, have you already replaced the pump? If not, let me know and I'll get you the directions if you need them.

Let me know.
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Thursday, July 25th, 2024 AT 8:53 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Did not replace the pump yet. Still stayed in the middle and with time when it started to overheat fans came on and she started to climb.
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Friday, July 26th, 2024 AT 6:45 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Replaced it. Did not look bad but who knows maybe with high speed it acts up. Had to remove the engine and transmission mounts to be able to jack up the motor side just enough to be able to remove the water pump. Put everything together and now it starts and dies. Similar to say a no or weak fuel pump or same as if the MAF is disconnected. Starts, runs a second, and shuts off. Very strange. Checked all I disconnected and all is connected. Didn't really have to do much except to remove battery to get to the mount. Am stumped, ugh.
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Saturday, July 27th, 2024 AT 8:50 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
And whenever I try to scan it I get a linking error. Used 2 different scanners. Can't even get the code to what is wrong or maybe disconnected.
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Saturday, July 27th, 2024 AT 8:52 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Am sure it's an immobilizer issue.
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Saturday, July 27th, 2024 AT 9:09 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
I left ignition on for a while to see if it will reset and it did not. Also when it starts the rpm needle does not move up. Is this controlled by the crank position sensor? I may have bumped a sensor or something off while jacking up motor. Can you tell me where it is located?
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Saturday, July 27th, 2024 AT 10:11 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Here.
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Saturday, July 27th, 2024 AT 10:25 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Removed battery cables, touched them for 10 seconds, put them back, turned ignition on for 30 seconds and it worked. I'll check if it overheats now.
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Saturday, July 27th, 2024 AT 11:01 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Is there a bleeding procedure for this car? In case I need it?
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Saturday, July 27th, 2024 AT 2:08 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Same results. 10-15 minutes running with full ac and no issues needle in the middle, then needle starts to climb and trmp from 220 to 235, then I rev it up and it chokes down to the middle then goes back up again. I have no heat or barely any heat from vents. Am almost sure there is a bubble or air in the system. I don't see a bleeder valve. Any help is appreciated.
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Saturday, July 27th, 2024 AT 5:09 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Also, if the heater core is clogged up and causing no heat will the water still circulate in the engine or will it stop it from doing so?
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Saturday, July 27th, 2024 AT 5:28 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Hardly any heat, very little on driver side, no heat just lukewarm heat on passenger side.
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Saturday, July 27th, 2024 AT 5:37 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

It sounds like you may simply have an air blockage. I went back to the manual, and it provides two ways of bleeding the system. The first one includes the use of a cooling system charge kit, (VAS 6096).

At the end of those directions are how to do it without the kit. Take a look and let me know your thoughts.

Joe

See pics below.
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Saturday, July 27th, 2024 AT 9:19 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
I did that and let it idle until the fans came on and it stayed in the middle for a while. But I went under the car and the lower radiator hose is cold.
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Sunday, July 28th, 2024 AT 2:08 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,575 POSTS
Then I turned the heat on and at first it was good on the driver's side but a lot of air. Once I turn the blower high the air becomes cold. Am suspicious of this cold hose under the radiator.
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Sunday, July 28th, 2024 AT 2:15 PM

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