Author Topic: OverheaTTing....  (Read 1961 times)

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CAs

  • Posts: 126
OverheaTTing....
« on: Jul 14, 13, 11:57 »
Hello crew,

I've stumbled into a pretty serious cooling issue with my 2001 TT and was curious if anyone else in the mk4 1.8t platform has experienced the same pitfalls as I have.

Coolant Temperture Sender - Brand New
Thermostat - Verified as good
Fans - Replaced Large diameter fan, not root cause of overheating, but noticed it had died (apparently pretty common failure)
Fan Control Module - Verified working correctly. Air conditioning turns low speed fans on.
Water Pump - Verified metal impeller and tried to spin it on its shaft to see if it has come loose. It has not.
Radiator Fan Switch - Jumped pins on plug to verify high and low speed operation. Both speeds working.

Watching my Temperature through the climatronic system I can see it climb well into 110+ degrees after idling for a while and my radiator fans do not come on.

Could it be that the Radiator Fan Switch has crapped the bed? Anyone else run into this issue?

Thanks  :thumbup:

cpa93

  • Posts: 440
Re: OverheaTTing....
« Reply #1 on: Jul 14, 13, 12:13 »
I would try to bypass and get the fans to run directly and work your way back from there

Old Dude

  • Posts: 72
Re: OverheaTTing....
« Reply #2 on: Jul 14, 13, 17:40 »
If the rad is getting hot, check inlet and outlet,....then fan switch is probably shot.
If rad is not hot , or just warm, you probably have a head gasket going.
When combustion gases from a leaking head gasket enter the cooling system, the normal flow is changed and
overheating can quickly follow.

Radvr6t

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Re: OverheaTTing....
« Reply #3 on: Jul 14, 13, 18:37 »

Does mk4 have FCM -- fan control module?

Also check oil cooler could be pootched causing a rise of temps

I Don't "Build" Cars I Just Make Em Ƥʀὄῥἔʀ
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CAs

  • Posts: 126
Re: OverheaTTing....
« Reply #4 on: Jul 14, 13, 19:25 »
Does mk4 have FCM -- fan control module?

Also check oil cooler could be pootched causing a rise of temps


Yes it has an FCM, replaced it. Its working as it should.

Rad is indeed getting hot.

Im pointing my fingers at a bad thermostat out of the box or a Thermoswitch
« Last Edit: Jul 14, 13, 19:25 by CAs »

Old Dude

  • Posts: 72
Re: OverheaTTing....
« Reply #5 on: Jul 14, 13, 20:29 »
If the rad is getting hot that means the thermostat is opening. Take cpa93's advice and manually run the fan by bypassing the fan switch and see if that works. These switches are easy and cheap to replace.

CAs

  • Posts: 126
Re: OverheaTTing....
« Reply #6 on: Jul 14, 13, 20:44 »
In my original post I mentioned that the fans run fine on both speeds when jumped at the thermoswitch.

will be replacing that tuesday!

the bartender

  • Posts: 5832
  • I control the horizontal, and the vertical
Re: OverheaTTing....
« Reply #7 on: Jul 14, 13, 20:45 »
leaking overflow bottle isnt holding pressure. just a hunch.

Old Dude

  • Posts: 72
Re: OverheaTTing....
« Reply #8 on: Jul 15, 13, 08:53 »
In my original post I mentioned that the fans run fine on both speeds when jumped at the thermoswitch.

will be replacing that tuesday!

Go for a drive with the fans jumped. If car does not overheat then replace the fan switch.
Good luck.Overheating is a royal pain.

CAs

  • Posts: 126
Re: OverheaTTing....
« Reply #9 on: Jul 16, 13, 19:24 »
PSA from CAs....

Purchase your Coolant Temperature Sensors from the dealer or oem part supplier.... That is all.

Gerg

  • Posts: 4564
Re: OverheaTTing....
« Reply #10 on: Jul 16, 13, 19:57 »
Been down that road before  :(
'92 GTI VRT - '93.5 Corrado VR6  - '04 R32 - '01 GTI 24V

CAs

  • Posts: 126
Re: OverheaTTing....
« Reply #11 on: Jul 16, 13, 21:08 »
Been down that road before  :(

So much wasted time diagnosing issues when it was TWO faulty aftermarket sensors...